Image-based phenotyping of cassava roots for diversity studies and carotenoids prediction

Fenotipagem baseada em imagens de raízes de mandioca para estudos de diversidade e previsão de carotenoides

CARVALHO, R. R. B. de; CORTES, D. F. M.; SOUSA, M. B. e; OLIVEIRA, L. A. de; OLIVEIRA, E. J. de. Image-based phenotyping of cassava roots for diversity studies and carotenoids prediction. PLoS One, v.17, n.1, e0263326, January, 2022.

Significado e impacto:
Um estudo que usou imagens digitais para extrair informações sobre a cor da polpa de raízes de mandioca e estimar correlações com o Teor Total de Carotenoides se concentrou na seleção de modelos preditivos para TCC usando índices, mostrou-se uma alternativa econômica, rápida, eficiente e com excelente capacidade preditiva para TCC em raízes de mandioca

Abstract:
Phenotyping to quantify the total carotenoids content (TCC) is sensitive, time-consuming, tedious, and costly. The development of high-throughput phenotyping tools is essential for screening hundreds of cassava genotypes in a short period of time in the biofortification program. This study aimed to (i) use digital images to extract information on the pulp color of cassava roots and estimate correlations with TCC, and (ii) select predictive models for TCC using colorimetric indices. Red, green and blue images were captured in root samples from 228 biofortified genotypes and the difference in color was analyzed using L*, a*, b*, hue and chroma indices from the International Commission on Illumination (CIELAB) color system and lightness. Colorimetric data were used for principal component analysis (PCA), correlation and for developing prediction models for TCC based on regression and machine learning. A high positive correlation between TCC and the variables b* (r = 0.90) and chroma (r = 0.89) was identified, while the other correlations were median and negative, and the L* parameter did not present a significant correlation with TCC. In general, the accuracy of most prediction models (with all variables and only the most important ones) was high (R2 ranging from 0.81 to 0.94). However, the artificial neural network prediction model presented the best predictive ability (R2 = 0.94), associated with the smallest error in the TCC estimates (root-mean-square error of 0.24). The structure of the studied population revealed
five groups and high genetic variability based on PCA regarding colorimetric indices and TCC. Our results demonstrated that the use of data obtained from digital image analysis is an economical, fast, and effective alternative for the development of TCC phenotyping tools in cassava roots with high predictive ability.

Instituições parceiras:
Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Estudo de associação genômica e seleção para resistência de campo à podridão radicular da mandioca e características produtivas

Genome-wide association study and selection for field resistance to cassava root rot disease and productive traits

HOHENFELD, C. S.; PASSOS, A. R.; CARVALHO, H. W. L. de; OLIVEIRA, S. A. S. de; OLIVEIRA, E. J. de. Genome-wide association study and selection for field resistance to cassava root rot disease and productive traits. PLos One, v. 17, n. 6, e0270020, June, 2022.

Significado e impacto:
A podridão radicular da mandioca (CRRD) é causada por um complexo de patógenos do solo e pode levar a uma redução no rendimento. A doença é persistente na área de cultivo, mesmo na ausência de um hospedeiro. Programas de melhoramento visam selecionar variedades resistentes, mas é importante identificar os patógenos presentes na área de seleção para estabelecer ampla resistência porque diferentes regiões genômicas estão associadas à resistência a diferentes espécies de patógenos. Alguns SNPs (polimorfismos de nucleotídeo único, que são o tipo mais comum de variação genética) significativos foram identificados para produção de raízes frescas sob condições de estresse biótico. Análises e validações adicionais ajudarão a entender os mecanismos moleculares da resistência à podridão radicular da mandioca.

Abstract:
Cassava root rot disease is caused by a complex of soil-borne pathogens and has high economic impacts because it directly affects the tuberous roots, which are the main commercial product. This study aimed to evaluate cassava genotypes for resistance to root rot disease in a field with a previous history of high disease incidence. It also aimed to identify possible genomic regions associated with field resistance based on genome-wide association studies. A total of 148 genotypes from Embrapa Mandioca and Fruticultura were evaluated over two years, including improved materials and curated germplasms. Analysis of phenotypic data was conducted, as well as a genomic association analysis, based on the general linear model, mixed linear model, and fixed and random model circulating probability unification. The observed high disease index  was directly correlated with genotype survival, affecting plant height, shoot yield, and fresh root yield. The genotypes were grouped into five clusters, which were classified according to level of root rot resistance (i.e., extremely susceptible, susceptible, moderately susceptible, moderately resistant, and resistant). The 10 genotypes with the best performance in the field were selected as potential progenitors for the development of segregating progenies. Estimates of genomic kinship between these genotypes ranged from -0.183 to 0.671. The genotypes BGM-1171 and BGM-1190 showed the lowest degree of kinship with the other selected sources of resistance. The genotypes BGM-0209, BGM-0398, and BGM-0659 showed negative kinship values with most elite varieties, while BGM-0659 presented negative kinship with all landraces. A genome-wide association analysis detected five significant single nucleotide polymorphisms related to defense mechanisms against biotic and abiotic stresses, with putative association with fresh root yield in soil infested with root rot pathogens. These findings can be utilized to develop molecular selection for root rot resistance in cassava.

Instituições parceiras:
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES; Fundação de Amparo à Pesquisa do Estado da Bahia, FAPESB; UK’s Foreign, Commonwealth & Development Office, FCDO; Bill & Melinda Gates Foundation.

Cultivar de mandioca de maturidade precoce para produção de farinha e amido, adaptada ao plantio direto e à mecanização

Early maturity cassava cultivar for production of flour and starch, adapted to no till planting and mechanization

RANGEL, M. A. S.; RINGENBERG, R.; VIEIRA, E. A.; FIALHO, J. de F.; SANTOS, V. da S.; FEY, E. BRS 420: Early maturity cassava cultivar for production of flour and starch, adapted to no till planting and mechanization.   Crop Breeding and Applied Biotechnology, v.22, n.2: e36962224, 2022.

Significado e impacto:

A cultivar de mandioca BRS 420 é uma opção para a cadeia de produção industrial de mandioca do Paraná e Mato Grosso do Sul devido ao maior rendimento de amido em comparação com as cultivares de controle, tanto no sistema de plantio convencional quanto no sistema de plantio direto, em colheitas de um e dois ciclos, é registrada e protegida pelo Ministério da Agricultura, Pecuária e Abastecimento (MAPA). A produção da planta base e o licenciamento de estacas para plantio são de responsabilidade da Secretaria de Inovação e Negócios da Embrapa - Escritório de Brasília. Como a mandioca é uma planta semiperene, os licenciados devem ter material para comercialização a partir de agosto de 2021. A lista das empresas que comercializarão as estacas de BRS 420 foi divulgada em 23/07/2019.

Abstract:
The cultivar BRS 420 has superior starch yields in early and late harvest, moderate resistance to the main diseases of the crop, adaptation to mechanized planting and to the no-till system, as well as rapid formation of soil cover (which assists in weed control). It represents an alternative for cassava growers in Paraná and Mato Grosso do Sul.

Instituições parceiras:
Embrapa Mandioca e Fruticultura Tropical; Embrapa Cerrados; Universidade Estadual do Oeste do Paraná, Unioeste.

Estudo de associação genômica das propriedades da pasta de fécula de mandioca

Genome-wide association study of cassava starch paste properties

SANTOS, C. S. DOS; SOUSA, M. B.; BRITO, A. C.; OLIVEIRA, L. A. de; CARVALHO, C. W. P. de; OLIVEIRA, E. J. de. Genome-wide association study of cassava starch paste properties. PLoS ONE, v. 17, n. 1, e0262888, 2022.

Significado e impacto:
Os resultados do estudo indicam que a genética determinante das propriedades da pasta de amido de mandioca (CSPP:Cassava starch paste Properties) é controlada por vários genes, atuando de forma que a contribuição de cada gene é independente das demais. Isso significa que é possível selecionar clones de mandioca com amidos de alto valor, combinando clones com SNPs (Single nucleotide polymorphism, ou polimorfismo de um único nucleotídeo, uma variação no DNA que ocorre quando um único nucleotídeo é diferente entre dois indivíduos) que sejam favoráveis para as diferentes propriedades, obtendo assim  clones de mandioca com amidos de alto valor em  programas de melhoramento genético.

Abstract:
An understanding of cassava starch paste properties (CSPP) can contribute to the selection of clones with differentiated starches. This study aimed to identify genomic regions associated with CSPP using different genome-wide association study (GWAS) methods (MLM, MLMM, and Farm-CPU). The GWAS was performed using 23,078 single-nucleotide polymorphisms (SNPs). The rapid viscoanalyzer (RVA) parameters were pasting temperature (PastTemp), peak viscosity (PeakVisc), hot-paste viscosity (Hot-PVisc), cool-paste viscosity (Cold-PVisc), final viscosity (FinalVis), breakdown (BreDow), and setback (Setback). Broad phenotypic and molecular diversity was identified based on the genomic kinship matrix. The broad-sense heritability estimates (h2) ranged from moderate to high magnitudes (0.66 to 0.76). The linkage disequilibrium (LD) declined to between 0.3 and 2.0 Mb (r2 <0.1) for most chromosomes, except chromosome 17, which exhibited an extensive LD. Thirteen SNPs were found to be significantly associated with CSPP, on chromosomes 3, 8, 17, and 18. Only the BreDow trait had no associated SNPs. The regional marker-trait associations on chromosome 18 indicate a LD block between 2907312 and 3567816 bp and that SNP S18_3081635 was associated with SetBack, FinalVis, and Cold-PVisc (all three GWAS methods) and with Hot-PVisc (MLM), indicating that this SNP can track these four traits simultaneously. The variance explained by the SNPs ranged from 0.13 to 0.18 for SetBack, FinalVis, and Cold-PVisc and from 0.06 to 0.09 for PeakVisc and Hot-PVisc. The results indicated additive effects of the genetic control of Cold-PVisc, FinalVis, Hot-PVisc, and SetBack, especially on the large LD block on chromosome 18. One transcript encoding the glycosyl hydrolase family 35 enzymes on chromosome 17 and one encoding the mannose-p-dolichol utilization defect 1 protein on chromosome 18 were the most likely candidate genes for the regulation of CSPP. These results underline the potential for the assisted selection of high-value starches to improve cassava root quality through breeding programs.

Instituições parceiras:
Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Agroindústria de Alimentos; Embrapa Mandioca e Fruticultura.

BRS 429 é uma cultivar de mandioca doce com polpa amarela e qualidades tecnológicas
BRS 429: sweet cassava with yellow pulp and high technological and sensory qualities

VIEIRA, E. A.; RANGEL, M. A. S.; FIALHO, J. de F.; RINGENBERG, R.; ROMANO, M. R.; RINALDI, M. M.; OLIVEIRA, C. M. de; ANTONINI, J. C. dos A. BRS 429: sweet cassava with yellow pulp and high technological and sensory qualities. Crop Breeding and Applied Biotechnology, v. 22, n. 4, e43402243, 2022.  6 p.

Significado e impacto:
A BRS 429 é uma cultivar de mandioca doce com polpa amarela e qualidades tecnológicas (alto rendimento radicular, maturidade precoce e arquitetura de planta favorável) e qualidades sensoriais (curto tempo de cozimento, pouca fibra e textura macia) que a tornam uma excelente opção para cultivo no Distrito Federal, Paraná e São Paulo, Brasil. Tem registro, (nº 42613) e protegida (nº 20200145) pelo Ministério da Agricultura e Pecuária (MAPA) e  proteção, plantas básicas e licenciamento de produtores de estacas-semente). A produção de plantas básicas e o licenciamento de produtores de estacas-sementes são de responsabilidade da Secretaria de Inovação e Negócios da Embrapa.

Abstract:
BRS 429 is a sweet cassava cultivar with yellow pulp and technological qualities (high root yield, early maturity, and favorable plant architecture) and sensory qualities (short cooking time, little fiber, and soft texture) that make it an excellent option for cultivation in the Distrito Federal, Paraná, and São Paulo, Brazil.

Instituições parceiras:
Embrapa Cerrados; Embrapa Mandioca e Fruticultura.

Lixiviação do ouro com mandioca: uma opção para eliminar o uso do mercúrio na mineração artesanal de ouro.

Leaching gold with cassava: an option to eliminate mercury use in artisanal gold mining.

Significado e impacto:

A mineração artesanal de ouro tradicional utiliza mercúrio como agente de separação e é responsável pela maior parte da poluição por mercúrio no mundo. A manipueira, subproduto do processamento da mandioca, pode ser usada como alternativa no processo de lixiviação. O método inédito e promissor descrito nesta oportunidade representa um avanço em direção à sustentabilidade ambiental da atividade, com a capacidade de separação de 50% do conteúdo de ouro dos demais minerais em 24h.

TORKAMAN, P.; VEIGA, M. M.; LIMA, L. R. P. de ANDRADE; OLIVEIRA, L. A. de; MOTTA, J. da S.; JESUS, J. L. de; LAVKULICH, L. M. Leaching gold with cassava: an option to eliminate mercury use in artisanal gold mining. Journal of Cleaner Production, v. 311, 2021.

Abstract:

Mercury pollution from artisanal gold mining causes severe environmental and health problems, especially to operators and people living around the processing facilities. Over 2000 tonnes/a of mercury is released to the environment by the artisanal miners which is the largest man-made source of mercury pollution. Here we present a novel method using a local plant, cassava, common in many artisanal mining areas in Latin America, Africa, and Asia, to dissolve gold from ores. In our experiments, we used a liquid by-product of cassava flour manufacturing, “manipueira” to leach gold from the gold ore. It contains hydrogen cyanide, generating from the hydrolysis of cyanogenic glycosides in the cassava plant. The results were very promising to replace the use of mercury, as approximately 50% of the gold content was extracted from the ore in 24 h.

Instituições parceiras:

University of British Columbia, UBC; Universidade Federal da Bahia, UFBA; Embrapa Mandioca e Fruticultura, CNPMF.

Avaliação de resistência a bacteriose e relações doença-rendimento em germoplasma brasileiro de mandioca.

Evaluation of resistance to bacterial blight in Brazilian cassava germoplasm and disease-yield relationships.

Significado e impacto:

A mandioca é uma das fontes mais importante de amido em países em desenvolvimento. Dentre as pragas que podem afligir a mandioca, está a bacteriose. Visando identificar resistência para fins de seleção e melhoramento genético, 83 genótipos de mandioca foram inoculados com a bactéria Xanthomonas phaseoli, responsável pela doença. Após 3 anos de avaliação, foram identificados 16 genótipos considerados moderadamente resistentes. A seleção dos 10 acessos com a melhor performance pode representar um aumento no rendimento de até 114,64%.

TEIXEIRA, J. H. dos S.; GUIMARÃES, M. A. S.; CARDOSO, S. C.; BRITO, A. dos S.; DINIZ, R. P.; OLIVEIRA, E. J. de; OLIVEIRA, S. A. S. de. Evaluation of resistance to bacterial blight in Brazilian cassava germoplasm and disease-yield relationships. Tropical Plant Pathology, 2021.

Abstracts:

Cassava, an important source of carbohydrates in many developing countries, is affected by several diseases including bacterial blight, caused by Xanthomonas phaseoli pv. manihotis (Xpm), responsible for considerable losses in production. A 3-year splitplot design experiment was conducted to evaluate the resistance of 83 Brazilian cassava genotypes to Xpm under field conditions, inoculated or not with bacterial suspension (108 CFU mL−1). The relationship between disease progress and yield traits was also studied. Disease severity was evaluated using an ordinal 0 (no symptoms) to 8 (maximum degree of the disease) scores. At 11 months after planting, the following traits were measured: plant height, above-ground yield (measured as the total weight of leaves and stem), fresh root yield, dry matter content in the roots, and dry root yield. Based on the calculated disease index (DI) and the area under the disease progress curve (AUDPC) values, the accessions were grouped into different classes of resistance/susceptibility. There were 16 accessions classified as moderately resistant (MR), 14 as moderately susceptible (MS), 41 as susceptible (S), and 12 as extremely susceptible (ES). Complete resistance to bacterial blight was not found. Despite the significant reduction in above-ground and root yield average for the inoculated plants, when compared to non-inoculated, there was no correlation between the severity (DI) or disease progress (AUDPC) and the agronomic performance of cassava genotypes. The selection of the best 10 accessions should be a priority, considering that the agronomic performance could increase the above-ground yield, fresh root yield, and dry root yield by 22.17%, 109.61%, and 114.64%, respectively.

Instituições parceiras:

Instituto Federal de Educação, Ciência e Tecnologia Baiano, IFBaiano; Embrapa Mandioca e Fruticultura, CNPMF.

Distribuição da resistência de genótipos de mandioca a doenças de raízes secas, moles e pretas e correlação com parâmetros de produtividade.

Distribution of resistance of cassava genotypes to dry, soft and black root diseases and correlation to yield parameters. 

Significado e impacto:

A resistência de genótipos de mandioca às doenças da podridão radicular seca, mole e preta causadas  respectivamente  por Fusarium spp.,  Phytophthora melonis) e espécie da família Botryosphaeriaceae, foi avaliada. Com base na análise de agrupamento de quatro grupos associados à resistência a doenças da podridão radicular, das raízes inoculadas e analisadas pela imagem digital, cerca de 10% dos genótipos foram classificados como resistentes à podridão seca e mole da raiz, e 2% foram classificados como resistentes à podridão negra da raiz, apenas 2% dos genótipos apresentaram resistência múltipla a esses grupos de doenças. Foram encontradas correlações entre as infecções da casca da raiz e da polpa pelo mesmo fungo. Estas informações são importantes em programas de melhoramento de mandioca para obter variedades superiores pois a podridão radicular é uma das doenças mais limitantes da produção de mandioca na Região Nordeste do Brasil.

TEIXEIRA, J. H. dos S.; GUIMARÃES, M. A. S.; CARDOSO, S. C.; BRITO, A. dos S.; PEIXOUTO, Y. S.; RIBEIRO, S. O.; OLIVEIRA, E. J. de; OLIVEIRA, S. A. S. de. Distribution of resistance of cassava genotypes to dry, soft and black root diseases and correlation to yield parameters. Journal of Phytopathology, n. 169 p. 350-359, 2021.

Abstract:

Root rot is one of the most limiting diseases of cassava production in the Northeast Region of Brazil, causing root-yield loss from 30% to 100%. This study aimed to evaluate the resistance of 76 cassava genotypes to dry (Fusarium spp.), soft (Phytophthora melonis) and black (species of the Botryosphaeriaceae family) root rot diseases. The roots were inoculated separately with isolates belonging to each of three disease group (dry, black and soft), by using the whole tuberous root inoculation method. The lesioned areas on the tuberous roots were measured by digital image analysis. Based on cluster analysis, four groups were found associated with the resistance to root rot diseases. About 10% of the genotypes were classified as resistant to dry and soft root rot, and 2% were classified as resistant to black root rot. Moreover, only 2% of the genotypes showed multiple resistance to these disease groups. Significant correlations were found between root peel and pulp infections by the same fungus, and between the root peel infections caused by P. melonis and Fusarium spp. These findings will be essential in the generation of plants with resistance to multiple root rot pathogens and will guide the cassava breeding programme to obtain superior varieties.

Instituições parceiras:

Instituto Federal de Educação Ciência e Tecnologia Baiano, IFbaiano, Guanambi; Embrapa Mandioca e Fruticultura, CNPMF.

Barreiras reprodutivas em mandioca: fatores e implicações para o melhoramento genético.

Reproductive barriers in cassava: factors and implications for genetic improvement.

Significado e impacto:

A mandioca é, na maioria das vezes, propagada de forma vegetativa, por meio de manivas. Também é possível a propagação por sementes, obtidas por reprodução sexuada, resultando em novas combinações genotípicas que podem melhorar o desempenho agronômico em comparação com os parentais. A obtenção de sementes, no entanto, é limitada pelas altas taxas de aborto floral. Descobertas sobre barreiras reprodutivas revelaram anormalidades morfológicas e efeitos da interação entre os parentais como determinantes da frequência de abortos florais. Também foram estudadas as condições ambientais mais favoráveis para a realização dos cruzamentos. Esses resultados contribuem para aumentar o êxito dos cruzamentos dentro do melhoramento da espécie, na busca de obter cultivares com características superiores do ponto de vista agronômico.

SOUSA, M. B. e; ANDRADE, L. R. B. de; SOUZA, E. H. de; ALVES, A. A. C.; OLIVEIRA, E. J. de. Reproductive barriers in cassava: factors and implications for genetic improvement. Plos One, November, 2021.

Abstract:

Cassava breeding is hampered by high flower abortion rates that prevent efficient recombination among promising clones. To better understand the factors causing flower abortion and propose strategies to overcome them, we 1) analyzed the reproductive barriers to intraspecific crossing, 2) evaluated pollen-pistil interactions to maximize hand pollination efficiency, and 3) identified the population structure of elite parental clones. From 2016 to 2018, the abortion and fertilization rates of 5,748 hand crossings involving 91 parents and 157 progenies were estimated. We used 16,300 single nucleotide polymorphism markers to study the parents’ population structure via discriminant analysis of principal components, and three clusters were identified. To test for male and female effects, we used a mixed model in which the environment (month and year) was fixed, while female and male (nested to female) were random effects. Regardless of the population structure, significant parental effects were identified for abortion and fertilization rates, suggesting the existence of reproductive barriers among certain cassava clones. Matching ability between cassava parents was significant for pollen grains that adhered to the stigma surface, germinated pollen grains, and the number of fertilized ovules. Non-additive genetic effects were important to the inheritance of these traits. Pollen viability and pollen-pistil interactions in cross- and selfpollination were also investigated to characterize pollen-stigma compatibility. Various events related to pollen tube growth dynamics indicated fertilization abnormalities. These abnormalities included the reticulated deposition of callose in the pollen tube, pollen tube growth cessation in a specific region of the stylet, and low pollen grain germination rate. Generally, pollen viability and stigma receptivity varied depending on the clone and flowering stage and were lost during flowering. This study provides novel insights into cassava reproduction that can assist in practical crossing and maximize the recombination of contrasting clones.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Estudo de associação genômica de tolerância à seca em mandioca.

Genome-wide association study of drought tolerance in cassava

Significado e impacto:

No primeiro estudo com o uso da  associação genômica ampla (GWAS= Genome-wide association)  para entender a tolerância à seca em mandioca, foram feitos avanços na identificação das variações em genes que podem influenciar os níveis de tolerância ao déficit hídrico, porem são  necessários estudos complementares sobre o  re-sequenciamento de genes no mapeamento do germoplasma, usando  maior número de genótipos e a posterior validação da expressão dos genes selecionados reguladores da resposta ao déficit hídrico que podem elucidar as bases fisiológicas da tolerância à seca, para auxiliar na seleção de genótipos com maior produtividade em condições de estresse hídrico.

SILVA, P. P. dos S.; SOUSA, M. B. e; OLIVEIRA, E. J. de; MORGANTE, C. V.; OLIVEIRA, C. R. S. de; VIEIRA, S. L.; BOREL, J. C. Genome-wide association study of drought tolerance in cassava. Euphytica, v. 217, n. 60, 2021.

Abstract:

Despite being considered a drought-tolerant species, cassava (Manihot esculenta Crantz) exhibits reduced growth and productivity under prolonged water stress. Therefore, the objective of this study was to identify the genomic regions associated with water deficit in cassava using a genome-wide association study (GWAS). A total of 49 cassava genotypes were evaluated under two water conditions: irrigated (control) and water deficit. An additional set of 252 clones grown for several years under water deficit conditions were used to validate the GWAS. The following traits were evaluated: yields of storage roots (RoY), shoots (ShY), and starch (StY); root dry matter content (DMC); drought tolerance index (DTI) and drought tolerance stability index (DTSI). The GWAS was performed using a multiple mixed linear model with a kinship matrix and population structure for each trait and water condition. Broad-sense heritability (h(2)) estimates were variable depending on the water conditions and characteristics under analysis. Overall, 62 single nucleotide polymorphisms (SNPs) were identified across all 18 cassava chromosomes. Additionally, it was possible to identify specific and stable markers across environments. The identified SNPs comprise approximately 160 transcripts, of which 119 were previously described and 41 have known functional annotations. Some of these transcripts are related to proteins involved in drought tolerance, such as APETALA 2 domain (AP2), photosystem II oxygen-evolving enhancer protein, PR5-like receptor kinase-related, beta-fructofuranosidase/saccharase, leucine zipper, and bZIP transcription factor. There is great potential for applying these SNPs in the marker-assisted selection of new cassava varieties that are tolerant of water deficit.

Instituições parceiras:

Universidade Federal do Recôncavo Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF; Embrapa Semiárido, CPATSA; Universidade Federal do Vale do São Francisco, UNIVASF.

Qualidade culinária e perfil sensorial de variedades de mandioca de mesa colhidas em diferentes idades.

Culinary quality and sensory profile of cassava varieties harvested at different ages

Significado e impacto:

A mandioca doce ou de mesa, também conhecida como aipim, precisa ter as características  sabor, teores de sólidos solúveis, açúcar e ácido cianogênico que influenciam no  tempo de cozimento e quantidade de fibras, para atender às exigências sensoriais e tecnológicas dos consumidores.  Foram avaliadas estas qualidades das raízes de três variedades de mandioca relacionadas às pesquisas da Embrapa (BRS Aipim Brasil, BRS Dourada e Saracura) e de uma variedade comercial, Eucalipto, colhidas em três idades diferentes, quanto aos aspectos físicos, químicos e sensoriais pelo método CATA (Check-All-That-Apply = verifique tudo que se aplica) e foi possível definir a melhor idade de colheita das variedades avaliadas para atender os requisitos.

REIS, R. C.; OLIVEIRA, L. A. de; ALMEIDA, J. M.; JESUS NETA, PALMIRA de; SANTOS, F. D.; SANTOS, V. da S.; CRUZ, R. S. Culinary quality and sensory profile of cassava varieties harvested at different ages. Semina: Ciências Agrárias, Londrina, v. 42, n. 2, p. 657-678, mar./abr. 2021. 1679-0359.

Abstract:

Sweet cassava must be rapidly cooked and meet the sensory and technological requirements of consumers. The objectives of this study were to evaluate the culinary quality of sweet cassava varieties harvested at three ages and obtain the sensory profile of these varieties using the check-all-that-apply method (CATA). Roots of three cassava varieties released or recommended by Embrapa (BRS Aipim Brasil, BRS Dourada and Saracura) and the commercial variety Eucalipto, harvested at nine, 12 and 15 months of age, were evaluated for physical, chemical and sensory aspects. At nine months of age, the Saracura, BRS Aipim Brasil and BRS Dourada varieties did not differ in cooking time, averaging 41.62 min. The Eucalipto variety had similar cooking times at the three harvest ages, averaging 21.83 min. There was a difference between the four varieties at nine months, with Saracura exhibiting the lowest acceptance score (5.0) and differing from the Eucalipto variety, which showed an average score of 6.3. At 12 months of age, there was a significant increase in the acceptance of the Saracura and BRS Aipim Brasil varieties, which did not differ from Eucalipto and had an average score of 6.4. Consumers perceived differences between the sensory characteristics of the cassava varieties using CATA. The sensory terms "creamy", "soft" and "sticky" can be associated with greater acceptance of cooked cassava roots, whereas terms such as "floury", "slightly bitter", "no taste", "hard" and "fibrous" can be associated with less acceptance and are therefore undesirable from the consumer's point of view. Principal component analysis showed that the age at which the roots were harvested had a great effect on the culinary quality of cassava, regardless of the evaluated variety. The commercial variety Eucalipto was well-accepted by the consumers irrespective of root age and can be harvested at any of the evaluated ages. For the Saracura, BRS Aipim Brasil and BRS Dourada varieties, harvesting is recommended at 12 or 15 months so that better quality roots are obtained.

Instituições parceiras:

Embrapa Mandioca e Fruticultura, CNPMF; Universidade  Federal do  Reconcavo da Bahia, UFRB; Faculdade Maria Milza,  FAMAM; Universidade Estadual de Feira de Santana, UEFS.

Parâmetros genéticos e análise de trajetória do rendimento de raízes de mandioca sob condições de seca e colheita precoce.

Genetic parameters and path analysis for root yield of cassava under drought and early Harvest.

Significado e impacto:

Apesar de serem tolerante a condições de seca, poucas variedades de mandioca apresentam alto rendimento durante períodos de escassez de chuvas. O melhoramento genético visa gerar cultivares com alto rendimento de raízes em condições de cultivo desafiadoras. Para isso, é necessário identificar e selecionar materiais capazes de garantir alto rendimento em condições de seca. Por meio de estudos com 138 diferentes materiais de mandioca, foi possível concluir que a avaliação precoce do número de raízes é um indicador aplicável no melhoramento, de forma a predizer o rendimento de raízes frescas, favorecendo a obtenção de materiais superiores para cultivo em condições de seca em um período de tempo menor.

OLIVEIRA, C. R. S. de; BOREL, J. C.; PEREIRA, D. A.; CARVALHO, B. P. de; MEDRADO, E. da S.; ISHIKAWA, F. H.; OLIVEIRA, E. J. de. Genetic parameters and path analysis for root yield of cassava under drought and early harvest. Crop Breeding and Applied Biotechnology, v. 21, n. 3,  e36162137, 2021.

Abstract:

The objectives of this study were to estimate genetic parameters and identify traits that contribute to early yield in Manihot esculenta Crantz. Ten traits were evaluated in two experiments, one with 138 genotypes and the other with 133, using a completely randomized block design with four replications. All genotype effects were significant. The accuracy was high for the traits, except leaf retention (0.57), and reliability ranged from 0.33 to 0.75. Root weight (RW) and number of roots (NR) showed the highest selection effectiveness (CVr), although the estimate was less than 1. Moreover, RW and NR obtained high genetic correlation (0.70). Path analysis showed that only number of roots had a significant direct effect on root weight (0.49), and no indirect effect was found. Therefore, accessions exhibited sufficient genetic variability, and indirect selection based on early evaluation of number of roots can be applied in cassava breeding for fresh root yield, increasing gain over time.

Instituições parceiras:

Universidade Federal do Vale do São Francisco, UNIVASF; Embrapa Mandioca e Fruticultura CNPMF.

Estudo de associação genômica em larga escala, usando dados históricos, identifica a arquitetura genética conservada do conteúdo de glicosídeos cianogênicos em raiz de mandioca (Manihot esculenta Crantz).

Large-scale genome-wide association study, using historical data, identifies conserved genetic architecture of cyanogenic glucoside content in cassava (Manihot esculenta Crantz) root.

Significado e impacto:

A mandioca é uma das principais fontes de carboidratos em países tropicais, tanto para consumo humano quanto animal. No entanto, um dos obstáculos a seu consumo é a produção de ácido cianídrico, uma substância muito tóxica cuja exposição é potencialmente fatal. Os compostos capazes de liberar essa toxina na mandioca são os glicosídeos cianogênicos. Foi registrada de forma inédita a descoberta de dois genes que são responsáveis por até 30% do conteúdo de ácido cianídrico nas raízes de mandioca. A partir desta descoberta, foram desenhados marcadores moleculares capazes de rastrear esses genes. Esses resultados contribuem para uma seleção mais eficiente durante o melhoramento genético e representam avanços no sentido da obtenção de cultivares de mandioca com menor conteúdo de ácido cianídrico.

OGBONNA, A. C.; ANDRADE, L. R. B. de; RABBI, I. Y.; MUELLER, L. A.; OLIVEIRA, E. J. de; BAUCHET, G. J. Large-scale genome-wide association study, using historical data, identifies conserved genetic architecture of cyanogenic glucoside content in cassava (Manihot esculenta Crantz) root. The Plant Journal, v.105, p.754-770, 2021.

Abstract:

Manihot esculenta (cassava) is a root crop originating from South America that is a major staple in the tropics, including in marginal environments. This study focused on South American and African germplasm and investigated the genetic architecture of hydrogen cyanide (HCN), a major component of root quality. HCN, representing total cyanogenic glucosides, is a plant defense component against herbivory but is also toxic for human consumption. We genotyped 3354 landraces and modern breeding lines originating from 26 Brazilian states and 1389 individuals were phenotypically characterized across multi-year trials for HCN. All plant material was subjected to high-density genotyping using genotyping by sequencing. We performed genome-wide association mapping to characterize the genetic architecture and gene mapping of HCN. Field experiments revealed strong broad- and narrow-sense trait heritability (0.82 and 0.41, respectively). Two major loci were identified, encoding for an ATPase and a MATE protein, and contributing up to 7 and 30% of the HCN concentration in roots, respectively. We developed diagnostic markers for breeding applications, validated trait architecture consistency in African germplasm and investigated further evidence for the domestication of sweet and bitter cassava. Fine genomic characterization revealed: (i) the major role played by vacuolar transporters in regulating HCN content; (ii) the co-domestication of sweet and bitter cassava major alleles are dependent upon geographical zone; and (iii) the major loci allele for high HCN in M. esculenta Crantz seems to originate from its ancestor, M. esculenta subsp. flabellifolia. Taken together, these findings expand our insights into cyanogenic glucosides in cassava roots and its glycosylated derivatives in plants.

Instituições parceiras:

Boyce Thompson Institute; Cornell University; International Institute of Tropical Agriculture, IITA/Nigeria; Embrapa Mandioca e Fruticultura, CNPMF.

Genotipagem abrangente de um banco de germoplasma de mandioca brasileira (Manihot esculenta Crantz): insights sobre diversificação e domesticação.

Comprehensive genotyping of a Brazilian cassava (Manihot esculenta Crantz) germplasm bank: insights into diversification and domestication

Significado e impacto:

A diversidade da mandioca brasileira foi caracterizada em um estudo da genética de variedades crioulas de linhagens modernas do Banco de Germoplasma de Mandioca da Embrapa Mandioca e Fruticultura e os resultados encontrados esclarecem as características de origem da mandioca brasileira. Esses achados apoiam e facilitam o uso de recursos genéticos em programas de melhoramento incluindo a implementação de mapeamento de associação e estratégias de seleção genômica e a identificação precisa de cultivares, crucial para avaliação do impacto dos resultados destes  programas sobre a sobrevivência, reprodução e a taxa na qual uma população se encaminha para a extinção podendo  minimizar a perda de variação genética.

OGBONNA, A. C.; ANDRADE, L. R. B. de; MUELLER, L. A.; OLIVEIRA, E. J. de; BAUCHET, G. J. Comprehensive genotyping of a Brazilian cassava (Manihot esculenta Crantz) germplasm bank: insights into diversification and domestication. Theoretical and Applied Genetics, v. 134, p. 1343-1362, 2021.

Abstract:

Cassava ( Manihot esculenta Crantz) is a major staple root crop of the tropics, originating from the Amazonian region. In this study, 3354 cassava landraces and modern breeding lines from the Embrapa Cassava Germplasm Bank (CGB) were characterized. All individuals were subjected to genotyping-by-sequencing (GBS), identifying 27,045 single-nucleotide polymorphisms (SNPs). Identity-by-state and population structure analyses revealed a unique set of 1536 individuals and 10 distinct genetic groups with heterogeneous linkage disequilibrium (LD). On this basis, a density of 1300-4700 SNP markers were selected for large-effect quantitative trait loci (QTL) detection. Identified genetic groups were further characterized for population genetics parameters including minor allele frequency (MAF), observed heterozygosity (H-o), effective population size estimate ((N) over cap (e)) and polymorphism information content (PIC). Selection footprints and introgressions of M. glaziovii were detected. Spatial population structure analysis revealed five ancestral populations related to distinct Brazilian ecoregions. Estimation of historical relationships among identified populations suggests an early population split from Amazonian to Atlantic forest and Caatinga ecoregions and active gene flows. This study provides a thorough genetic characterization of ex situ germplasm resources from cassava's center of origin, South America, with results shedding light on Brazilian cassava characteristics and its biogeographical landscape. These findings support and facilitate the use of genetic resources in modern breeding programs including implementation of association mapping and genomic selection strategies.

Instituições parceiras:

Universidade Cornell, Ithaca, NY USA;  Embrapa Mandioca e Fruticultura; Boyce Thompson Institute for Plant Research, Incorporation.

Estratégias de manejo da mosca-branca em mandioca.

Significado e impacto:

Descreve a evolução das moscas-brancas, importante praga que pode ser transmissora de patógenos causadores de doenças nas plantas. Na cultura da mandioca é a espécie Aleurothrixus aepim que domina a incidência no Nordeste do Brasil. A resistência de plantas é uma das estratégias para enfrentar este inseto sugador da seiva do floema. Apesar do pequeno tamanho, as colônias desse inseto podem ser vistas porque formam massas esbranquiçadas de aspecto cotonoso. Quanto a sua sobrevivência foram avaliados sua desenvolvimento em diferentes genótipos de mandioca que apresentaram  diferentes graus de resistência e  ou suscetibilidade  quando atacados pelo inseto e encontrados  quatro destes genótipos são resistentes podendo ser usados em programas de melhoramento genético da mandioca.

LIMA, W. H.; RINGENBERG, R.; FANCELLI, M.; LEDO, C. A. da S. Mosca-branca. Cultivar HF, ago./set., 2021.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB;  Embrapa Mandioca e Fruticultura, CNPMF.

Diversidade fenológica do florescimento e frutificação em germoplasma de mandioca.

Phenological diversity of flowering and fruiting in cassava germplasm.

SOUZA, S.; ALVES, A. A. C.; OLIVEIRA, E. J. de. Phenological diversity of flowering and fruiting in cassava germplasm. Scientia Horticulturae, v. 265,  e109253, 2020.

Significado e impacto:

A mandioca é amplamente cultivada em todo o mundo e uma das principais fontes de calorias para cerca de 750 milhões de seres humanos. O melhoramento genético contribui para melhorar a produtividade e a qualidade nutricional da mandioca e combater pragas que possam afetar a produção. Os programas de melhoramento genético dependem da capacidade de obtenção de progênies superiores após cruzamentos entre as plantas. Foram investigados 1.032 acessos de mandioca da Embrapa quanto ao florescimento e formação de frutos. A análise estatística avançada permitiu identificar um grupo com 6 acessos que são mais adequados para a realização de cruzamentos, permitindo maior êxito na formação de progênies.

Abstract:

Genetic and environmental factors can influence the flowering and fruit setting performance of cassava varieties. The objective of this work was to assess the genetic variability of cassava germplasm for flowering and fruiting traits, as well as to cluster the genotypes based on based on its flowering performance. A total of 1032 accessions were evaluated monthly from 3 to 12 months after planting – MAP for flower and fruit production using a grade scale ranging from 0 absence or poor flowering to 3 full flowering, and the accumulated degree-days ADD was recorded for each period. The following traits were analyzed: a the mean flowering score MFS from 3 to 12 MAP and b a weighted average of the flowering scores that emphasizes early flowering WAS. The cassava accessions were clustered based on principal component analysis PCA. Seven clusters were identified via PCA, with very contrasting traits including a early flowering 8.5 % of the accessions, Group 4); b) consistent flowering after 2036 ADD (0.6 % of the accessions, Group 2); and c) accessions that do not flower (54 % of the accessions, Group 7). For most of the cassava germplasm, flowering occurred during the longest photoperiod (5–6 MAP). This study demonstrated that accessions belonging to Group 2 are very interesting for breeding programs and genomic studies due to their high flowering throughout the year. This is the first report of phenological diversity of flowering and fruiting performance in cassava germplasm.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca.

Análise genética e fisiológica da resposta precoce à seca em Manihot esculenta e seu parente selvagem.

Genetic and physiological analysis of early drought response in Manihot esculenta and its wild relative.

MORGANTE, C. V.; NUNES, S. L. P.; CHAVES, A. R. de M.; FERREIRA, C. F.; AIDAR, S. de T.; VITOR, A. B.; OLIVEIRA, E. J. de. Genetic and physiological analysis of early drought response in Manihot esculenta and its wild relative.   Acta Physiologiae Plantarum, v.42, p.22, 2020.

Significado e impacto:

O sucesso do cultivo da mandioca em condições de déficit hídrico se deve a sua capacidade intrínseca de resistência às condições ambientais adversas. Com o propósito de fornecer novos conhecimentos sobre a tolerância à seca em Manihot spp. foram realizamos análises fisiológicas e moleculares da resposta precoce à seca em três variedades de mandioca e na espécie selvagem, Manihot glaziovii (maniçoba)visando o  desenvolvimento de marcadores moleculares funcionais para serem usados no  melhoramento que reforcem a tolerância natural da mandioca à seca, evidenciando o desempenho superior da maniçoba em condições de déficit hídrico e forneçam informações sobre a fenotipagem da seca na mandioca que possam  contribuir para futuros usos de marcadores moleculares para serem usados no cultivo assistido da mandioca.

Abstract:

Cassava (Manihot esculenta) is a staple food crop mostly grown in the tropics. Successful cultivation in marginal areas derives from its ability to withstand difficult environmental conditions. Aiming at providing new insights into drought tolerance in Manihot spp., we performed physiological and molecular analyses of early drought response in three cassava varieties and in the wild species, Manihot glaziovii (maniçoba). Plants grown in pots were subjected to three water regimes for 5 days, based on soil field capacity (FC): 75% (well-watered plants); 45% (moderately stressed plants), and 20% (severely stressed plants), under greenhouse condition. Analysis of leaf gas exchange showed a downward trend in photosynthesis, stomatal conductance, and transpiration, with intensification of the stress, in all genotypes, being significantly reduced only at 20% FC. Maniçoba stood out for maintaining a positive carbon balance in severe stress condition via stomatal aperture control. Photoinhibition of the photosystem II by drought was also evident only at 20% FC. There was no clear association between proline accumulation and drought stress tolerance. Expression analysis of nine genes encoding heat-shock proteins, transcription factors, a cell redox homeostasis protein, and a no-hit protein confirmed the activation of classical stress-responsive pathways, especially those involved in oxidative damage avoidance. These results reinforce the intrinsic drought tolerance of cassava, highlight the superior performance of maniçoba under water deficit conditions, and give insights into drought phenotyping in cassava and contribute to further development of functional molecular markers to be used in assisted breeding.

Instituições parceiras:

Embrapa Semiárido, Petrolina, CPATSA; Universidade Federal do Vale do São Francisco, UNIVASF; Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Diagnose precoce de couro de sapo da mandioca em tecidos pulverizados usando espectroscopia de infravermelho próximo.

Early diagnosis of cassava frog skin disease in powdered tissue samples using near-infrared spectroscopy.

FREITAS, E. L.; BRITO, A. C.; OLIVEIRA, S. A. S. de; OLIVEIRA, E. J. de. Early diagnosis of cassava frog skin disease in powdered tissue samples using near-infrared spectroscopy. European Journal of Plant Pathology, v.156, p.547–558, 2020.

Significado e impacto:

A mandioca é um alimento básico e fonte de amido para milhões de pessoas em todo o mundo. A praga “couro de sapo” provoca perdas significativas de rendimento da cultura. Um método de diagnose de couro de sapo em mandioca, muito mais rápido e barato, com precisão superior a 80%, é descrito nesse trabalho. A economia trazida por esse método pode torná-lo o principal método de detecção da doença num futuro próximo.

 

Abstract:

Cassava frog skin disease (CFSD) causes significant yield losses in cassava (Manihot esculenta Crantz). One issue with control is late diagnosis. The objective of this work was to test near-infrared spectrometry (NIRS) and compare calibration and classification models for early detection of CFSD. NIRS analysis was performed on 238 cassava accessions (120 healthy and 118 with CFSD). Six classification models were used: a support vector machine with a linear kernel (SVM), a Bayesian generalized linear model (BGLM), a parallel random forest (PRANDF), an extreme learning machine (ELM), a high dimensional discriminant analysis (HDDA), and a partial least squares (PLS) model. Their predictive abilities were evaluated based on their accuracy and agreement (based on Cohen’s Kappa coefficient). The models demonstrated high efficiency at distinguishing diseased and healthy accessions, with an overall accuracy >80%. The Cohen’s Kappa coeficiente values (0.83–0.98) for four of the models (the SVM, BGLM, PRANDF and PLS) indicated that there was almost perfect agreement between their classification results. The SVM and BGLM models exhibited high accuracy (99.07 and 98.92%, respectively) and reproducibility (both 0.98) in classifying the accessions according to their CFSD status. NIRS is a viable alternative for the detection of CFSD with the advantages of early and accurate detection, high speed and low cost compared to traditional diagnostic methods.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Estudos de associação em todo o genoma para amido ceroso na mandioca.

Genome-wide association studies for waxy starch in cassava.

CARMO, C. D. do; SOUSA, M. B. e; BRITO, A. C.; OLIVEIRA, E. J. de. Genome-wide association studies for waxy starch in cassava. Euphytica, v. 216, n. 82, 2020.

Significado e impacto:

A capacidade dos estudos de associação do genoma completo (GWAS em inglês, Genome-wide association study) para detectar variantes relacionadas ao amido ceroso e identificar genes alternativos ou regiões genômicas  em mandioca, foi avaliada  pois, embora a herança genética do fenótipo de amido ceroso seja considerada monogênica e recessiva, é possível que outras regiões genômicas contribuam para o fenótipo ceroso. Foi analisando   um conjunto de 382 amostras (cerosas e não cerosas) usando  SNPs (single nucleotide polymorphisms) na avaliação de todos os genótipos em relação à presença de amido ceroso. As regiões e genes identificados neste trabalho podem direcionar novos estudos e revelar processos biológicos relacionados ao fenótipo ceroso como parte dos esforços que recentemente são feitos para melhorar suas propriedades pois o  amido de mandioca ceroso tem algumas vantagens sobre o amido de outras fontes devido ao seu sabor neutro e propriedades de colagem.

Abstract:

Cassava (Manihot esculenta Crantz) is an important crop for starch production, and recently much effort has been directed towards improving its starch properties. Waxy cassava starch has some advantages over starch from other sources due to its neutral flavor and pasting properties. The genetic inheritance of the waxy starch phenotype is considered to be monogenic and recessive; however, it is possible that other genomic regions contribute to the waxy phenotype. The aim of this study was to evaluate the power of genome-wide association studies (GWAS) to detect variants related to waxy starch and to identify alternative genes or genomic regions. For this purpose, a set of 382 samples (waxy and non-waxy) was analyzed using a panel of 20,956 single nucleotide polymorphisms (SNPs). All genotypes were evaluated in relation to the presence of waxy starch, determined using the 2% iodine test. The GWAS was performed using the retrospective CAse–control Retrospective Association Testing (CARAT) model. Kinship and population structure were also investigated and added to the model. Ten SNPs were found to be significant and located on chromosome 2 and co-located in genomic regions. The significant SNPs are in a region near the Granule-bound starch synthase I (GBSSI) and Beta-amylase genes. Additive and epistatic effects were also found among the significant SNPs, and these need to be better investigated in segregant populations of waxy sources. The regions and genes identified in this work may drive further studies and reveal biological processes related to the waxy phenotype.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF; Universidade de São Paulo, USP.

Identificação de genótipos de mandioca cerosa usando espectroscopia de infravermelho.

Identification of waxy cassava genotypes using fourier‐transform near‐infrared spectroscopy.

CARMO, C. D. do; SOUSA, M. B. e; PEREIRA, J. dos S.; CEBALLOS, H.; OLIVEIRA, E. J. de. Identification of waxy cassava genotypes using fourier-transform near-infrared spectroscopy. Crop Science,v. 60, n. 2, Jan. 2020.

Significado e impacto:

Foi realizado estudo para identificar clones de mandioca (Manihot esculenta Crantz) com amido ceroso (isto é, livre de amilose) por rastreio de folhas em vez de raízes, e para validar modelos de previsão para classificar esses fenótipos  com o uso de ferramentas de fenotipagem que permitem a avaliação precoce das características da raiz através  da seleção indireta de variáveis extraídas dos espectros foliares, que se mostrou uma boa estratégia para um melhoramento mais eficiente.
 
Abstract:

High‐throughput phenotyping tools that allow the early and accurate evaluation of important agronomic traits have gained space in current breeding programs. The aim of this study was to evaluate the potential of Fourier‐transform near‐infrared spectroscopy (FT‐NIRS) to identify cassava (Manihot esculenta Crantz) clones with waxy starch (i.e., amylose‐free) by screening leaves rather than roots, and to validate prediction models for classifying these phenotypes. We analyzed the spectra of 162 waxy and 180 nonwaxy genotypes from five different growing environments. The mean FT‐NIRS spectra and principal component analysis (PCA) were used to investigate the potential for grouping the data. For classification, five supervised pattern recognition techniques were tested: Bayesian generalized linear model (BGLM), high‐dimensional discriminant analysis (HDDA), partial least squares‐discriminant analysis (PLS‐DA), parallel random forest (PRANDF), and support vector machines with linear kernel (SVM). The mean spectra and the PCA did not allow discrimination of the genotypes based on starch classification. The SVM and BGLM showed the highest classification accuracy in cross‐validation (.86–.87), with higher concordance rates (.88–.83), sensitivity (.87–.85) and specificity (.88). The BGLM and SVM models also obtained better indices in the external validation, with high accuracy (.85) and correct classification of 93% of the waxy genotypes.

Instituições parceiras:

Fundação de Amparo à Pesquisa do Estado da Bahia, FAPESB; Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq; Embrapa Mandioca e Fruticultura, CNPMF.

Identificação e validação de pontos de mutação associados ao fenótipo ceroso em mandioca.

Identification and validation of mutation points associated with waxy phenotype in cassava.

CARMO, C. D. do; SOUSA, M. B. e; SILVA, P. P. dos S.; OLIVEIRA, G. A. F.; CEBALLOS, H.; OLIVEIRA, E. J. de. Identification and validation of mutation points associated with waxy phenotype in cassava. BMC Plant Biology, v. 20, p.164, 2020.

Significado e impacto:

 A identificação e  validação  de alelos mutantes alternativos que evidenciem a ausência da enzima amido sintase I (GBSSI, Granule-Bound Starch Synthase I) relacionada a grânulos e que é responsável pela síntese de amilose, podem permitir o desenvolvimento de seleção assistida por moléculas para promover a mutação do amido ceroso em mandioca.

Abstract:

Background: The granule-bound starch synthase I (GBSSI) enzyme is responsible for the synthesis of amylose, and therefore, its absence results in individuals with a waxy starch phenotype in various amylaceous crops. The validation of mutation points previously associated with the waxy starch phenotype in cassava, as well as the identification of alternative mutant alleles in the GBSSI gene, can allow the development of molecular-assisted selection to introgress the waxy starch mutation into cassava breeding populations.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; International Center for Tropical Agriculture, CIAT; Embrapa Mandioca e Fruticultura, CNPMF.

Espécies de Colletotrichum causadoras da antracnose da mandioca (Manihot esculenta Crantz) em diferentes eco-zonas na Região do Recôncavo da Bahia, Brasil.

Colletotrichum species causing cassava (Manihot esculenta Crantz) anthracnose in different eco-zones within the Recôncavo Region of Bahia, Brazil.

OLIVEIRA, S. A. S. de; SILVA, L. L. da; NASCIMENTO, D. de S.; DIAMANTINO, M. S. A. S.; FERREIRA, C. F.; OLIVEIRA, T. A. S. de. Colletotrichum species causing cassava (Manihot esculenta Crantz) anthracnose in diferente eco-zones within the Recôncavo Region of Bahia.

Significado e impacto:

A mandioca é produzida e usada na alimentação em todo o mundo, mas pode ter sua produção limitada por doenças como a antracnose, causada por microrganismos do gênero Colletotrichum. Para conter o impacto da doença, é importante desenvolver cultivares resistentes por meio do melhoramento genético. O melhoramento genético, por sua vez, depende do conhecimento dos agentes causadores e das características da doença. Por meio de ferramentas de biologia molecular, foram identificadas 7 diferentes espécies do gênero Colletotrichum causadoras da antracnose na região do Recôncavo da Bahia. Foi encontrado o principal agente causador da doença, Colletotrichum fructicola. As descobertas serão úteis para guiar a seleção ao longo do melhoramento visando obter variedades resistentes.
 

Abstract:

A survey to investigate the occurrence of cassava anthracnose disease (CAD) and distribution of Colletotrichum spp. in cassava plantations in different eco-zones of the Reconcavo Region in Bahia, Brazil, investigated during the rainy season of 2014. A total of 50 cassava fields distributed among 18 municipalities were visited and intensity of anthracnose evaluated. The highest disease incidence (DI) (83.3%) was in samples collected in São Félix, and the lowest (34.4%), in Varzedo. Municipalities that presented the highest values for DI were located within the ‘Af’ Köppen–Geiger eco-zone, also presenting the highest values for the estimated McKinney disease index. Based on previous studies of multilocus phylogeny, seven different species of Colletotrichum were identified (Colletotrichum fructicola, Colletotrichum tropicale, Colletotrichum gloeosporioides s.s, Colletotrichum theobromicola, Colletotrichum siamense, Colletotrichum brevisporum and Colletotrichum plurivorum) and a new approach based on ERIC-PCR was used aiming to group the 82 isolates according to these findings. The highest percentage of genetic variance (> 78%) was among isolates within fields. Based on the survey and genetic analysis, C. fructicola is probably the main causal agent of cassava anthracnose in the Recôncavo Region, since this species was present with highest incidence in all eco-zones, 47.61, 42.86 and 57.14% for Af (tropical rainforest climate), As (tropical dry savanna climate) and Aw (tropical wet savanna climate), respectively. This study is the first report of C. fructicola lineages as the most likely pathogen causing anthracnose disease of cassava in Brazil, and these findings may be used to guide the selection of resistant varieties.

Instituições parceiras:

Universidade Estadual de Feira de Santana, UEFS; Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Uma nova estratégia de multiplicação baseada no tratamento de manivas para material propagativo de mandioca.

A novel seed treatment-based multiplication approach for cassava planting material.

OLIVEIRA, E. J. de; OLIVEIRA, S. A. S. de; OTTO, C.; ALICAI, T.; FREITAS, J. P. X. de; CORTES, D. F. M.; PARIYO, A.; LIRI, C.; ADIGA, G.; BALMER, A.; ROBINSON, M. A novel seed treatment-based multiplication approach for cassava planting material. Plos One, v.15, n.3, e0229943, March, 2020.

Significado e impacto:

A mandioca, fonte de amido e um dos mais importantes alimentos básicos do mundo, é propagada pelo plantio de secções do caule conhecidas como manivas. Essa propagação é pouco eficiente, limitando o impacto dos investimentos no melhoramento genético. Para melhorar a propagação da mandioca, foi proposta uma formulação química para aplicação nas manivas. Esse tratamento das manivas leva a um aumento no fator de propagação de até 3 vezes, com ganhos de eficiência calculados em 1 a 1,9 anos no ciclo tradicional de 5 anos.

Abstract:

Cassava (Manihot esculenta Crantz) is an important food security crop in many parts of the developing world. The crop’s high yield potential and multitude of uses–both for nutrition and processing–render cassava a promising driver for the development of rural value chains. It is traditionally propagated from stem cuttings of up to 30 cm in length, giving a multiplication rate as low as 1:10. Propagating cassava traditionally is very inefficient, which leads to challenges in the production and distribution of quality planting material and improved cultivars, greatly limiting the impact of investments in crop breeding. The work described in the present study aimed to develop a seed treatment approach to facilitate the use of shorter seed pieces, increasing the multiplication rate of cassava and thus making the crop’s seed systems more efficient. After several tests, formulation was identified, consisting of thiamethoxam 21 g ha-1, mefenoxam 1.0 g ha-1, fludioxonil 1.3 g ha-1, thiabendazole 7.5 g ha-1 and Latex 2% as a binder. Plant growing from seed pieces treated with this formulation displayed increased crop establishment and early crop vigor, leading to an improved productivity throughout a full growing cycle. This allowed to reduce the cassava seed piece size to 8 cm with no negative effects on germination and crop establishment, leading to yields comparable to those from untreated 16 cm pieces. This, in turn, will allow to increase the multiplication ratio of cassava by a factor of up to 3. Notably, this was possible under regular field conditions and independently of any specialised treatment facilities. Compared with existing seed production protocols, the increased multiplication rates allowed for efficiency gains of between 1 to 1.9 years compared to conventional five-year cycles. We believe that the technology described here holds considerable promise for developing more reliable and remunerative delivery channels for quality cassava planting material and improved genetics.

Instituições parceiras:

Syngenta Foundation for Sustainable Agriculture; National Crops Resources Research Institute,NaCRRI; Embrapa Mandioca e Fruticultura, CNPMF.

BRS Novo Horizonte - nova variedade de mandioca para uso industrial.

BRS Novo Horizonte - a new cassava variety for industrial use.

OLIVEIRA, E. J. de; FUKUDA, W. M. G.; OLIVEIRA, S. A. S. de; RINGENBERG, R.; SILVA, M. R.; SOUZA, A. da S.; SILVA, A. L. L.; OLIVEIRA FILHO, M. dos S.; FARIA, M. L.; SILVA, R. de J. S. BRS Novo Horizonte - a new cassava variety for industrial use. Crop Breeding and Applied Biotechnology, v.20, n.2. e28882028, 2020. 
 

Significado e impacto:

Foi obtida pela Embrapa Mandioca e Fruticultura por meio de seleção fenotípica a nova variedade de mandioca BRS Novo Horizonte. Cruzamentos artificiais foram realizados entre os acessos BGM0116 (parental feminino) e BGM1727 (parental masculino) para uso industrial, principalmente para produção de amido, devido ao rendimento das raízes que permitem a extração de amido em proporção entre 39% e 44% maiores do que as variedades locais, e por ser adaptada para sistemas de cultivo mecanizado. Foi registrada no Ministério da Agricultura, Pecuária e Abastecimento, (MAPA) em agosto de 2017 (N. 37275) sendo a Empresa Brasileira de Pesquisa Agropecuária, EMBRAPA, responsável pela produção de muda de semente básica.

Abstract:

The new cassava variety ‘BRS Novo Horizonte’ was developed and released in Bahia, Brazil for industrial use, particularly for starch production. The fresh and dry root yields were 39% and 44% higher, respectively, than those of local varieties. The root quality traits allowed the extraction of high-quality starch.The variety is also adapted for mechanized cropping systems.

Instituições parceiras:

Embrapa Mandioca e Fruticultura, CNPMF; Universidade Federal do Recôncavo da Bahia, UFRB; Bahiamido S.A.

Mudas de variedades de mandioca são responsivas à adubação orgânica.

Seedlings of cassava varieties are responsive to organic fertilization.

JALA, I. M.; SILVA, C. C. da; SAMPAIO FILHO, J. S.; OLIVEIRA, E. J. de; NÓBREGA, R. S. A. Seedlings of cassava varieties are responsive to organic fertilization. Semina: Ciências Agrárias, Londrina, v. 40, n. 5, suplemento 1, p. 2151-2164, 2019. 

Significado e impacto:

Foi avaliado o efeito do adubo orgânico composto de estercos (bovinos e caprino) e resíduos de podas de árvores  para suprir a necessidade de substratos de cultivo de fácil aquisição  que estimulem o crescimento das mudas derivadas de plantas sadias, para evitar a disseminação de doenças em  três genótipos de mandioca (BRS Formosa, BRS Tapioqueira e BRS Kiriris) visando a redução do tempo em viveiro e dos  custos de produção das mudas. O adubo na proporção de 50% de adubo orgânico e 50% de Latossolo estimulou o crescimento inicial e os genótipos responderam eficientemente a esta adubação orgânica podendo  serem propagados nesses substratos de cultivo.

Abstract:

In Brazil, there is already a recommendation for the production of cassava seed-cuttings for the production of seedlings originated from micropropagation, which may be extended for the production of seedlings obtained from cuttings from healthy plant stems, in order to avoid the spread of diseases. Therefore, it is essential to establish adequate cultivation substrates of easy acquisition which may stimulate the growth of seedlings, both to reduce the nursery period, as well as the seedling’s production costs. The objective of this work was to evaluate the effect of organic fertilizers made from bovine and goat manures, and tree pruning residues, to produce seedlings of three cassava varieties. The plots were set in a completely randomized design, with six replicates. The treatments consisted of three cassava genotypes (BRS Formosa, BRS Tapioqueira and BRS Kiriris) and five proportions of organic fertilizer: soil (0: 100, 20:80, 40:60, 60:40 and 80:20). The evaluations were performed 30 and 45 days after planting (DAP). There were isolated effects for shoot dry mass, total dry mass, leaf area and number of leaves. Interactions were verified for root length, chlorophyll a and total chlorophyll index, root dry mass and shoot dry mas/root dry mass ratio 45 DAP. The organic fertilizer stimulated the initial growth of cassava seedlings in the three varieties studied in the proportion of 50% of organic fertilizer and 50% of Latosol. Varieties BRS Formosa and BRS Kiriris showed the highest Dickson Quality Scores. Genotypes reacted efficiently to organic fertilization and can be propagated on these easily acquisition cultivation substrates. 

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura; CNPMF.

Uma nova espécie e híbridos putativos de Manihot (Euphorbiaceae) do Brasil.

A new species and putative hybrids of Manihot (Euphorbiaceae) from Brazil.

SANTOS, A.; MARTINS, M. L. L.; MARTINS, F. M.; CARVALHO, P. C. L. DE; LEDO, C. A. da S.; AMORIM, A. M. A new species and putative hybrids of Manihot (Euphorbiaceae) from Brazil. Plant Systematics and Evolution, 2019. 

Significado e impacto:

Uma nova espécie de mandioca silvestre, batizada de Manihot reflexifolia, foi descoberta na Chapada Diamantina, região central do Estado da Bahia, Brasil. Uma descrição completa da espécie, de outros híbridos frequentes na região e métodos de diferenciação entre esta e outras espécies e variedades de mandioca são fornecidos. As descobertas representam avanços no estudo da mandioca e permitem ampliação do conhecimento da variabilidade genética disponível para ciência descritiva e melhoramento genético.

Abstract:

This work describes and illustrates the new species Manihot reflexifolia, sp. nov. and compares its leaf anatomy to Manihot reniformis and probable hybrids between the two species. Manihot reflexifolia is also compared to Manihot jacobinensis from which it can be distinguished by its cylindrical petioles, elliptical to short lanceolate, reflexed leaf lobes and staminate flowers restricted to the terminal portion of the inflorescence (upper half), while M. jacobinensis has dorsiventrally flattened petioles, suborbicular to obovate leaf lobes, and staminate flowers along the entire inflorescence axis. The new species is restricted to rocky outcrops of the Chapada Diamantina in central Bahia State, Brazil. An identification key to Manihot species from rocky outcrops of Chapada Diamantina is provided. The leaf anatomy of M. reflexifolia, M. reniformis and the putative hybrids was analyzed using optical and scanning electron microscopy. Leaf anatomy was sufficient to characterize M. reflexifolia, M. reniformis and the putative hybrids, as well as to identify the first two wild taxa as potential progenitors of the hybrids (M. reflexifolia × M. reniformis). The most useful anatomical characteristics were the morphology of the petiole and midrib, bundle sheath extension, organization and quantity of vascular bundles, organization and composition of the mesophyll, and the presence of epidermal papillae.

Instituições parceiras:

Herbário Centro de Pesquisas do Cacau, CEPEC; Universidade Estadual de Santa Cruz, UESC; Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Diferenciação de linhagens de Colletotrichum gloeosporioides s.l.” associadas com a antracnose de mandioca por BOX e ERIC-PCR.

Differentiation of lineages within "Colletotrichum gloeosporioides s.l." associated with cassava anthracnose disease by BOX" and ERIC"PCRs.

SILVA, L. L. da; BRAGANÇA, C. A. D.; FERREIRA, C. F.; DIAMANTINO, M. S. A. S.; OLIVEIRA, S. A. S. de. Differentiation of lineages within "Colletotrichum gloeosporioides s.l." associated with cassava anthracnose disease by BOX" and ERIC"PCRs. Journal of Phytopathology, v.167, p.218-229, 2019. 

Significado e impacto:

A mandioca é importante em diversos países dos trópicos, usada principalmente na alimentação humana e animal. A antracnose, causada por Colletotrichum gloeosporioides, é uma das pragas que mais afetam sua produção mundial. Diferentes técnicas moleculares têm sido utilizadas para estudar a diversidade e auxiliar na identificação de espécies do gênero Colletotrichum. Essa identificação tem sido difícil, tendo em vista que a praga é provocada por fitopatógenos encontradas em patossistemas. Na busca de métodos mais precisos para diferenciar isolados do fungo causador da antracnose, a técnica de ERIC-PCR foi a mais adequada, permitindo a identificação de duas novas espécies associadas com a praga. Os achados representam avanços para o desenvolvimento de estratégias de combate à antracnose de mandioca.

Abstract:

Several molecular techniques have been used to differentiate species or genetic lineages of microorganisms prior to sequencing. Among them, BOX- and ERIC-PCRs may provide specific banding patterns for different species, allowing its differentiation. Therefore, the objective of this study was to evaluate these techniques as a tool for differentiation of phylogenetic lineages belonging to the Colletotrichum gloeosporioides species complex associated with cassava anthracnose disease. Sets of BOX- and ERIC-PCR primers were used to assess the differentiation of lineages belonging to the complex with 81 C. gloeosporioides sensu lato (s.l.) isolates from different cassava producing regions. Some were identified by sequencing, such as Colletotrichum fructicola, Colletotrichum tropicale, C. gloeosporioides s.s, Colletotrichum theobromicola, Colletotrichum siamense, Colletotrichum brevisporum and Colletotrichum sichuanensis. The primers were able to amplify DNA fragments from all isolates. The ERIC-PCR presented a wider range of banding patterns in comparison to BOX-PCR, providing better differentiation of the individuals, as well as a higher correlation with the phylogenetic data was obtained by ERIC-PCR and the combined data set for “BOX-/ ERIC-PCRs,” inferred by Mantel test. However, the use of concatenated data (BOX-/ ERIC-PCRs) reduced the discriminatory capacity presented by ERIC-PCR alone, probably due to the lowest resolution of BOX-PCR. Therefore, ERIC-PCR technique enabled efficient differentiation of isolates belonging to the C. gloeosporioides complex and can be used to analyse multiple isolates in a collection and also being an important tool as a guide in the decision-making process prior to sequencing. Based on this methodology, it was possible to identify two new species associated with cassava anthracnose disease, C. brevisporum and C. sichuanensis, being the first report of these two species associated with cassava anthracnose disease in Brazil.

Instituições parceiras: 

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Seleção genômica para características produtivas em populações reprodutoras de mandioca biparental.

Genomic selection for productive traits in biparental cassava breeding populations

TORRES, L. G.; RESENDE, M. D. V. de; AZEVEDO, K C. F.; SILVA, F. F. e; OLIVEIRA, E. J. de. Genomic selection for productive traits in biparental cassava breeding populations. PLoS ONE, v. 14, n. 7, e0220245, July 2019. 20 p.

Significado e impacto:

A mandioca é uma colheita rústica, que parece ter um mecanismo de aclimatação, pois não possui grandes requisitos ambientais e cresce em varios climas e regiões, porem, o rendimento médio das raízes está muito abaixo do seu potencial devido ao manejo inadequado e ao uso de variedades não melhoradas porque seu cultivo é baseado na seleção natural com propagação vegetativa que inclui vários estágios de seleção e tem uma taxa de melhoria muito lenta devido à biologia das espécies, como floração deficiente, longo ciclo reprodutivo, diversidade genética limitada e baixa. O uso de variedades melhoradas é uma opção para aumentar a produção da cultura sem aumentar a área de plantio. Os 290 clones de mandioca do Programa de Melhoramento da Mandioca (CBP) da Embrapa Mandioca e Fruticultura (Cruz das Almas, Brasil) foram genotipados e fenotipados para algumas características agronômicas importantes. As informações obtidas no nível molecular foram utilizadas nas análises genéticas para acelerar a seleção efetiva de clones.

Abstract:

Cassava improvement using traditional breeding strategies is slow due to the species’ long breeding cycle. However, the use of genomic selection can lead to a shorter breeding cycle. This study aimed to estimate genetic parameters for productive traits based on pedigree (pedigree and phenotypic information) and genomic (markers and phenotypic information) analyses using biparental crosses at different stages of selection. A total of 290 clones were genotyped and phenotyped for fresh root yield (FRY), dry matter content (DMC), dry yield (DY), fresh shoot yield (FSY) and harvest index (HI). The clones were evaluated in clonal evaluation trials (CET), preliminary yield trials (PYT), advanced yield trials (AYT) and uniform yield trials (UYT), from 2013 to 2018 in ten locations. The breeding stages were analyzed as follows: one stage (CET), two stages (CET and PYT), three stages (CET, PYT and AYT) and four stages (CET, PYT, AYT and UYT). The genomic predictions were analyzed via k-fold cross-validation based on the genomic best linear unbiased prediction (GBLUP) considering a model with genetic additive effects and genotype × location interactions. Genomic and pedigree accuracies were moderate to high (0.56–0.72 and 0.62–0.78, respectively) for important starch-related traits such as DY and FRY; when considering one breeding stage (CET) with the aim of early selection, the genomic accuracies ranged from 0.60 (DMC) to 0.71 (HI). Moreover, the correlations between the genomic estimation breeding values of one-stage genomic analysis and the estimated breeding values of the four-stage (full data set) pedigree analysis were high for all traits as well as for a election index including all traits. The results indicate great possibilities for genomic selection in cassava, especially for selection early in the breeding cycle (saving time and effort).

Instituições parceiras:

Universidade Federal de Viçosa, UFV; Embrapa Mandioca e Fruticultura, CNPMF; 

Embrapa Florestas, CNPF.

Modelos de predição antecipada do rendimento de raízes de mandioca em diferentes regimes hídricos.

Early prediction models for cassava root yield in different water regimes.

VITOR, A. B.; DINIZ, R. P.; MORGANTE, C. V.; ANTONIO, R. P.; OLIVEIRA, E. J. de. Early prediction models for cassava root yield in iferente water regimes. Field Crops Research, v. 239, p. 149-158, 2019. 

Significado e impacto:

A mandioca é uma das principais culturas alimentares do mundo, sendo cultivada com frequência em regiões secas, onde seu rendimento pode ser impactado pela escassez de água, especialmente no contexto das mudanças climáticas. Foi desenvolvido com sucesso um método matemático capaz de prever com até 91% de precisão, 4 meses após o plantio, o rendimento agronômico final de plantas de mandioca, tanto sob irrigação quanto em condições de seca. Para isso, o modelo utiliza os parâmetros área foliar, número de raízes, rendimento de raízes e condutância estomática, todos medidos aos 4 meses após o plantio, muito antes do momento da colheita. Os resultados contribuem tanto para a produção mundial de mandioca quanto para o melhoramento genético visando adaptação ao déficit hídrico.

Abstract:

The development of cassava (Manihot esculenta Crantz) varieties with greater tolerance of water deficit depends on optimized phenotyping tools. The objective of this work was to develop early prediction models of final root yield (12 months after planting - MAP) using physiological and agronomic data obtained at 4 MAP under two water regimes. Nine genotypes of cassava were evaluated under two treatments (irrigated and with water deficit), using a complete randomized block design, in a factorial scheme of 2 harvest periods (at 4 and 12 MAP) × 9 genotypes, with four replications. Both treatment groups were irrigated until 3 MAP. After this period, irrigation was interrupted for the water deficit treatment group. Fourteen physiological and agronomic traits were evaluated in all harvest periods. Four prediction models were evaluated: linear regression with stepwise selection (LRSS), linear regression with backward selection (LRBS), Bayesian ridge regression (BRR), and partial least squares (PLS). Most ofthe models presented a high predictive ability for final root yield (R2 ranging from 0.83 to 0.91). However, in all prediction scenarios, the PLS model presented a high R2 (0.84 to 0.91) associated with the lowest root-mean-square error (RMSE) (0.82 to 1.60). Differences in the predictive ability of the models may have occurred due to the relative importance of the early traits. In the case of PLS, the most important traits for the model were stomatal conductance, root yield at 4 MAP, leaf area index and number of roots. Regardless of the water condition, the physiological and agronomic data collected at an early stage could successfully be used to predict the final root yield with great efficiency. This strategy can reduce the cost of phenotyping, increasing the capacity for analysis and optimization of genetic gains for tolerance to drought in cassava.

Instituições parceiras:

Modelos preditivos e seleção de caracteres agronômicos e fisiológicos para tolerância ao déficit hídrico em mandioca.

Prediction models and selection of agronomic and physiological traits for tolerance to water deficit in cassava.

SILVA, P. P. dos S.; SOUSA, M. B. e; OLIVEIRA, E. J. de. Prediction models and selection of agronomic and physiological traits for tolerance to water deficit in cassava. Euphytica, v.215, n.73, 2019. 

Significado e impacto:

A mandioca é fonte de amido para cerca de 800 milhões de pessoas em todo o mundo. A cultura, que é frequentemente produzida em regiões secas, é a terceira fonte de carboidratos mais importante da América Latina, África e Ásia. Os programas de melhoramento genético buscam identificar genótipos tolerantes ao déficit hídrico. Considerando os altos custos e tempo gasto para a fenotipagem de características fisiológicas e agronômicas, a seleção dos parâmetros certos que são capazes de prever o rendimento da mandioca sob condições de déficit hídrico é uma ferramenta importante para apoiar e acelerar os programas de melhoramento. Foram desenvolvidos modelos matemáticos capazes de prever o rendimento de raízes em mandioca com até 75% de correspondência, baseando-se no número de raízes por planta, índice de área foliar, número de folhas no oitavo mês e rendimento da parte aérea.

Abstract:

The development of efficient and accurate strategies for evaluating and predicting the root yield of cassava (Manihot esculenta Crantz) can reduce the effort and time spent on phenotyping complex traits associated with productivity and abiotic stress. The objective of this study was to select phenotypic traits that are highly associated with fresh root yield (FRY) as well as to establish a prediction model of the performance of genotypes under water deficit conditions. A total of 49 cassava genotypes were evaluated in a complete randomized block design, with three replications and two water conditions: well-watered (control-WW) and water deficit. The physiological and agronomic traits were divided into three groups: Phys (all physiological traits); Phys + ShY (all physiological traits, with addition of shoot yield) and Phys + Agro (all physiological and agronomic traits). They were evaluated using six different predictive models: classification and regression trees, artificial neural network, support vector machines, extreme learning machine (ELM), generalized linear model with stepwise feature selection (GLMSS) and partial least squares (PLS). These same groups, but reduced to only the most important predictive traits, were also analyzed. The most important traits for predicting FRY were number of roots per plant, leaf area index, number of leaves measured in the eighth month, and shoot yield. The selection of the most important traits resulted in the best adjustment of the models, with GLMSS, ELM, and PLS being the models that presented the highest reliability of prediction according to the values of r2 > 0.75 with RMSE ranging from 0.49 to 0.51.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Seletividade de inseticidas contra Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) em mandioca.

Selectivity of inseticides against adult Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) on cassava.

FELTRIN-CAMPOS, E.; RINGENBERG, R.; CARVALHO, G. A.; GLAESER, D. F.; OLIVEIRA, H. N. de. Selectivity of Insecticides against adult trichogramma pretiosum riley (Hymenoptera: Trichogrammatidae) on cassava. Journal of Agricultural Science, v. 11, n. 1, p. 546-552, 2019. 

Significado e impacto:

A microvespa Trichogramma pretiosum se alimenta de ovos de insetos e larvas que parasitam a mandioca, sendo uma alternativa biológica e ecologicamente viável ao controle das pragas provocadas por eles. O manejo integrado de pragas consiste na aplicação de métodos químicos e biológicos juntos, como por exemplo, aplicação de inseticida e insetos predadores, com o objetivo de alcançar maior eficácia no combate. Com essa finalidade, o inseticida precisa ser seletivo, ou seja, afetar o inseto que provoca a praga, mas não o agente biológico que a combate. Os inseticidas químicos mais comuns aplicados na cultura da mandioca foram apenas moderadamente nocivos à microvespa T. pretiosum em laboratório, aumentando as chances de sua aplicação como agente biológico no combate a pragas da mandioca.

Abstract:

In this study, the effects of various chemical and biological insecticides on adults of the parasitoid species Trichogramma pretiosum (Riley) were examined in cassava. The chemical insecticides zeta-cypermethrin, lufenuron + profenofós, imidacloprid, thiamethoxam, and teflubenzuron and the biological agents Bacillus thuringiensis and Baculovirus erinnyis were evaluated. For each treatment group, the effects were evaluated using T. pretiosum mortality rates, longevity of females, the number of eggs parasitized by the F0 generation, and number of emergent F1 parasitoids. The insecticides were classified using the International Organization for Biological Control categories. The tested insecticides had little effect on longevity and survival of adults, but all affected parasitism (F0) and were moderately harmful to the parasitoid. In relation to the emergent (F1) generation, the pesticides were either harmless or slightly harmful, except for zeta-cypermethrin which was classified as harmful with a 100% reduction in parasitoid emergence. The results indicate that the tested insecticides were moderately harmful to T. pretiosum in the laboratory; future studies will examine the effects of the insecticides under semi-field and field conditions to confirm their toxicity.

Instituições parceiras:

Universidade Federal da Grande Dourados, UFGD; Universidade Federal de Lavras, UFLA; Embrapa Agropecuária Oeste, CPAO; Embrapa Mandioca e Fruticultura, CNPMF.

Primeiro relato de Cassava Torrado-Like Virus, Cassava Polero-Like Virus e Cassava New Alphaflexivirus associados com a praga couro-de-sapo de mandioca no Brasil

First report of cassava torrado-like virus, cassava polero-like virus and cassava new alphaflexivirus associated with cassava frogskin disease in Brazil

OLIVEIRA, S. A. S. de; FERREIRA, C. F.; DIAMANTINO, M. S. A. S.; SANTOS, T. A.; PEREIRA, J. dos S.; OLIVEIRA, E. J. de. First report of cassava torrado-like virus, cassava polero-like virus and cassava new alphaflexivirus associated with cassava frogskin disease in Brazil. Journal of Plant Pathology, August, 2019. 

Significado e impacto:

A mandioca (Manihot esculenta Crantz) é uma das culturas de maior importância socioeconômica no Brasil e no mundo, com ocorrência em todo território nacional. Contudo, alguns fatores limitam a produção dessa cultura, a exemplo de pragas como a couro-de-sapo que pode reduzir a produção de raízes em até 100%. Por meio de técnicas de biologia molecular, foram identificados três vírus relacionados com couro-de-sapo em um plantio de mandioca. É o primeiro relato da associação da praga aos três vírus. A descoberta representa uma primeira etapa no desenvolvimento de estratégias de combate a esse fator limitante da produção de mandioca no Brasil.

Abstract:

Cassava (Manihot esculenta Crantz) plants with typical symptoms of frogskin disease (CFSD) have been observed since 2012 in Cruz das Almas, Bahia, Brazil. The above ground parts of the plants were asymptomatic, however, the roots showed typical symptoms of woody-like appearance, thickened cork-like peel, opaque aspect, and coalescent lip-like slits in a honeycomb pattern. Plants did not test positive for phytoplasma based on a nested-PCR reaction for the 16S region (Alvarez et al. 2009). Therefore, we hypothesized a viral infection. To verify our hypothesis, total RNAwas extracted from 0.5 g of plant tissue using CTAB followed by reverse transcription and polymerase chain reaction with specific primers for: (i) cassava frogskin-associated virus – CsFSaV; (ii) ‘cassava torrado-like virus’–CsTLV; (iii) ‘cassava polero like virus’–CsPLV and (iv) ‘cassava new alphaflexivirus’– CsNAV, as described by Carvajal-Yepes et al. (2014). Amplicons were obtained for CsTLV (RNA1: 834 bp, RNA2: 719 bp), CsNAV (1227 bp) and CsPLV (1001 bp). No amplicons were obtained for CsFSaV. PCR products were sequenced in both directions, manually edited and deposited in the NCBI database: CsTLV (MN194209, MN194210 and MN194211) and RNA 2 (MN194212, MN194213 and MN194214), CsPLV (MN172358, MN207078 and MN207079) CsNAV (MN207080, MN207081 and MN207082). A BLASTn analysis of the viral sequences showed 96–100% identity with CsTLV (RNA1 polyprotein: KC505250), CsTLV (RNA2 polyprotein: KC505251); CsPLV (RNA-dependent RNA polymerase and coat protein: KF885738) and CsNAV (replicase, TGB1, TGB2, and coat protein: KC505252 and KY288516), respectively (E-value <0.001). The three putative virus species (CsTLV, CsNAV and CsPLV) were described for the first time by Carvajal Yepes et al. (2014) on association with CFSD together with CsFSaVin Colombia.To our knowledge this is the first report of these three viruses associated with CFSD in Brazil.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura, CNPMF.

Estrutura genética de lesões de mandioca (Manihot esculenta Crantz) de Angola avaliadas através de marcadores (ISSR)

Genetic structure of cassava populations (Manihot esculenta Crantz) from Angola assessed through (ISSR) markers

AFONSO, S. D. J.; MOREIRA, R. F. C.; LEDO, C. A. da S.; FERREIRA, C. F.; SANTOS, V. da S.; MUONDO, P. A. Genetic structure of cassava populations (Manihot esculenta Crantz) from Angola assessed through (ISSR) markers. African Journal of Biotechnology, v. 18, n.7, p. 144-154,  February, 2019. 

Significado e impacto:

A estrutura genética de plantas de mandioca foi analisada  em três províncias angolanas (Cuanza Norte, Uige e Malanje) utilizando marcadores moleculares (ISSR markers ) visando identificar a variabilidade genética e o seu potencial para ser utilizado na diversificação das culturas de mandioca na Angola e para entender melhor sua história evolutiva. Essa análise permitiu conhecer a estrutura das populações e a ascendência dos indivíduos podendo contribuir para o desenvolvimento de novas variedades.

Abstract:

Eighteen ISSR primers (between Simple Repeated Sequences) were used to estimate the genetic diversity of Angolan cassava populations in order to identify genetic variabilities and their potential to be used in the diversification of cassava crops in Angola. In order to do so, three populations from three Angolan provinces were analyzed (Cuanza Norte, Uige and Malanje), which totaled 40 genotypes. In total, 116 bands were amplified with 93.24% polymorphism and 6.4 markers per ISSR primer, on average. Nei’s gene diversity (H) and Shannon indices (I) applied to the analyzed accessions presented values ranging from H = 0.20 to 0.24 and I = 0.29 to 0.50 which are intermediate values. The total gene diversity (HT) was 0.3113, and it showed high heterozygosity in Manihot populations; this outcome indicated that these populations presented gene variability. ANOVA showed 10.41% total variance between populations and 89.59% within them. Molecular featuring revealed gene diversity in each of the assessed populations; there was gene structuring between populations.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia (UFRB), Instituto Politécnico de Ensino Superior do Kwanza Sul, Angola; Embrapa Mandioca e Fruticultura (CNPMF; Instituto de Investigação Agronômica (IIA), Malanje, Angola.

Identificação de duplicatas em bancos de germoplasma de mandioca com base em polimorfismos de nucleotídeo único (SNPs).

Identification of duplicates in cassava germplasm banks based on single- nucleotide polymorphisms (SNPs).

ALBUQUERQUE, H. Y. G. de; OLIVEIRA, E. J. de; BRITO, A. C.; ANDRADE, L. R. B. de; CARMO, C. D. do; MORGANTE, C. V.; VIEIRA, E. A.; CUNHA, E. F. M.; FALEIRO, F. G. Identification of duplicates in cassava germplasm banks based on single- nucleotide polymorphisms (SNPs). Scientia Agricola, v. 76, n. 4, p. 328-336, July-Aug, 2019. 

Significado e impacto:

O custo da conservação, sob condições de campo e in vitro, dos recursos genéticos  do banco de  germoplasma de mandioca de várias unidades de pesquisa da Embrapa, é extremamente alto e impõe limitações à manutenção e expansão destes bancos, assim a incorporação de novas adesões para otimizar a conservação deve ser feita de maneira estratégica e que possa capturar a diversidade genética adicional podendo-se utilizar marcadores de polimorfismo de nucleotídeo único (SNP=single-nucleotide  polymorphism).

Abstract: 

Genetic  redundancy  in  cassava  (Manihot  esculenta  Crantz)  presents  a  challenge  to efficient management of genetic resources. This study aimed to identify and define the ge-netic structure of duplicates in cassava germplasm from various Embrapa research units, using single-nucleotide  polymorphism  (SNP)  markers.  We  evaluated  2,371  accessions  with  20,712  SNPs.  The  identification  of  duplicates  was  performed  based  on  multilocus  genotypes  (MLG),  adopting a maximum genetic distance threshold of 0.05. The population structure was defined based  on  discriminant  analysis  of  principal  components  (DAPC).  A  total  of  1,757  unique  and  614 duplicate accessions were identified. The redundancy of the collections ranged from 17 % (Belém, PA – Brazil) to 39 % (Petrolina, PE – Brazil), with an average of 21 %. This redundancy between  different  research  units  is  probably  due  to  the  historical  sharing  of  accessions,  as  well as collections carried out in the same region, or even to the intense germplasm exchange between farmers with different genotype names. In terms of genetic structure, the 250 principal components explained 88 % of the genetic variation of the SNP markers and defined the hierar-chical structure of the duplicate cassava germplasm in 12 groups. Since heterotic groups have not yet been identified for cassava, crosses between accessions of the 12 DAPC groups may be  promising.  All  MLGs  were  allocated  within  the  same  DAPC  group,  corroborating  duplicate  analyses yet still revealing high variability between groups that were quite distinct based on the first two discriminant functions. Our results contribute to optimizing the conservation of genetic resources, together with understanding diversity and its use in crop improvement.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia (UFRB); Embrapa Mandioca e Fruticultura, CNPMF; Universidade Federal de Viçosa, UFV; Embrapa Semiárido, CPATSA; Embrapa Cerrados, CPAC; Embrapa Amazônia Oriental, CPATU.

Parâmetros genéticos, análise de trilhas e seleção indireta de características agronômicas do germoplasma de mandioca.

Genetic parameters, path analysis and indirect selection of agronomic traits of cassava germplasm.

DINIZ, R. P.; OLIVEIRA, E. J. de. Genetic parameters, path analysis and indirect selection of agronomic traits of cassava germplasm. Anais  da  Academia Brasileira de Ciências,  Rio de Janeiro ,  v. 91, n. 3,  e20180387,    2019. 

Significado e impacto:

Este estudo teve como objetivo estimar parâmetros genéticos de correlações fenotípicas e genotípicas entre características morfológicas, agronômicas e de qualidade radicular de plantas de mandioca, bem como estudar relações de causa e efeito e determinar a relação direta e indireta existente entre as características morfoagronômicas do germoplasma de mandioca.

Abstract:

This study aimed to estimate genetic parameters and correlations between morphological, agronomic and root quality traits of cassava plants, as well as to study cause and effect relationships through path analysis. A total of 814 genotypes were evaluated from 2011 to 2015. The joint analysis of the data was performed by the mixed models approach. The predicted genetic values of the genotypes were used to estimate the genetic correlations among as well the path analysis. The estimates of heritability of the genotype means ranged from 0.31 (commercial fresh root yield – CRY) to 0.62 (plant height - PLH). The highest genetic correlation coefficient estimates were observed for starch yield (STY) × total fresh root yield (FRY) (0.97). The results of the path analysis showed that FRY had the highest direct effect on STY, but the indirect selection based on FRY was not efficient to improve the gain of STY.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura CNPMF.

Melhoria da detecção específica de Xanthomonas phaseoli pv. manihotis baseada no gene pthB.

Improvement of the specific detection of Xanthomonas phaseoli pv. manihotis based on the pthB gene.

MELO, R. de C. C.; BRAGANÇA, C. A. D.; PESTANA, K. N.; SILVA, H. S. A.; FERREIRA, C. F.; OLIVEIRA, S. A. S. de. Improvement of the specific detection of Xanthomonas phaseoli pv. manihotis based on the pthB gene. Acta Scientiarum. Agronomy, v. 41, e42708, 2019. 

Significado e impacto:

Métodos diagnósticos envolvendo ferramentas de Biologia Molecular, como a reação em cadeia da polimerase (PCR), têm alta eficácia na detecção de microrganismos específicos. A detecção da bacteriose da mandioca, causada pelo microrganismo Xanthomonas phaseoli, é possível por meio de PCR. No presente estudo, pesquisadores descrevem uma melhoria no método que o tornou eficaz para detectar com êxito esse microrganismo usando a técnica de PCR. O procedimento é de custo relativamente baixo e pode ser reproduzido com facilidade em laboratório.

Abstract:

Modifications were made in the PCR conditions aiming to overcome the problem of nonamplification of the Xanthomonas phaseoli pv. manihotis (Xpm) fragment, using the primer pair XV / XK described in the literature. The objective of this study was to propose changes in the primers already described (XV / XK_MOD) and validate the use of these new primers in identifying Xpm. The validation procedure was carried out with the primer pair XV and XK_MOD, using different strains of Xpm, other plant pathogenic and endophytic bacteria genera and one isolate of X. phaseoli pv. passiflorae. As a control, additional reactions were conducted in multiplex with the universal primers for the 16S rRNA gene of the bacteria together with XV / XK and XV / XK_MOD. Using the forward primer (XV) described in the literature together with the modified reverse primer (XK_MOD), it was possible to achieve amplification from DNA extracted from in vitro cultures and from infected tissue, but no amplification was noticed for the primer pair described in the literature, confirming the effectiveness of the proposed modification.

Instituições parceiras:

Universidade Federal do Recôncavo da Bahia, UFRB; Embrapa Mandioca e Fruticultura,  CNPMF.

Características agronômicas de genótipos de mandioca tipo industrial em diferentes épocas de colheita.

Effect of harvesting times on agronomic characteristics of industrial cassava genotypes.

LESSA, L. S.; LEDO, C. A. da S.; SANTOS, V. da S. Effect of harvesting times on agronomic characteristics of industrial cassava genotypes. Revista Brasileira de Ciências Agrárias, v. 14, n. 2, e5647, 2019.

Significado e impacto:

A avaliação das características agronômicas dos genótipos de mandioca concluiu que as variedades BRS Tapioqueira, BRS Caipira e BRS Poti Branca podem ser incorporadas ao sistema de produção da região do Recôncavo da Bahia, o híbrido 9783-13 apresentou rendimento radicular superior aos demais e que todos apresentaram médias para produtividade superiores à média da região do Recôncavo e do estado da Bahia, e podem ser colhidos 12 meses após o plantio.

Abstract:

The use of cassava genotypes low-yield coupled with inappropriate harvest times lead to the country’s low average yield. This study aimed to evaluate the agronomic characteristics of cassava genotypes at different harvest times in the Recôncavo region of Bahia. The experiment was conducted during two crop cycles in Cruz das Almas, Bahia, with eight cassava genotypes (BRS Poti Branca, BRS Caipira, BRS Kiriris, BRS Verdinha, BRS Tapioqueira, 9624-09, 98150-06 and 9783-13) were evaluated at different harvest times. The characteristics yield of shoot, root, flour and starch, root dry matter and harvest index were evaluated, as well as their correlation with the harvest time. Data were submitted to analysis of variance and fitted to linear regression models. The means of all the characteristics increased with the permanence of the plants in the field. The correlations between the harvest time and yield characteristics were high and positive. All genotypes evaluated had yield means higher than the means of the Recôncavo and the state of Bahia, indicating the yield potential of the genotypes. 

Instituições parceiras:

Embrapa  Acre, CPAF-Acre;  Embrapa Mandioca e Fruticultura, CNPMF.

Regressão categórica tripla para seleção genômica: aplicação ao melhoramento da mandioca.

Triple categorical regression for genomic selection: application to cassava.

LIMA, L. P.; AZEVEDO, C. F.; RESENDE, M. D. V. de; SILVA, F. F. e; VIANA, J. M. S.; OLIVEIRA, E. J. de. Triple categorical regression for genomic selection: application to cassava breeding. Scientia Agricola, v. 76, n. 5, p. 368-375, Sept./Oct. 2019. 

Significado e impacto:

Os programas de melhoramento da mandioca ( Manihot esculenta ) aumentaram intensamente e recentemente utilizam informações genômicas, assim foi proposto um método denominado  regressão categórica tripla (TCR / G-BLUP), que estima a herdabilidade e  utiliza o método G-BLUP. A eficiência de todos os métodos também foi testada, usando dados reais de seis caracteres da mandioca neste estudo, para melhorar os métodos estatísticos de seleção genômica que teriam um   impacto positivo no melhoramento genético da mandioca.

Abstract:

Genome-wide selection (GWS) is currently a technique of great importance in plant breeding, since it improves efficiency of genetic evaluations by increasing genetic gains. The process is based on genomic estimated breeding values (GEBVs) obtained through phenotypic and dense marker genomic information. In this context, GEBVs of N individuals are calculated through appropriate models, which estimate the effect of each marker on phenotypes, allowing the early identification of genetically superior individuals. However, GWS leads to statistical challenges, due to high dimensionality and multicollinearity problems. These challenges require the use of statistical methods to approach the regularization of the estimation process. Therefore, we aimed to propose a method denominated as triple categorical regression (TCR) and compare it with the genomic best linear unbiased predictor (G-BLUP) and Bayesian least absolute shrinkage and selection operator (BLASSO) methods that have been widely applied to GWS. The methods were evaluated in simulated populations considering four different scenarios. Additionally, a modification of the G-BLUP method was proposed based on the TCR-estimated (TCR/G-BLUP) results. All methods were applied to real data of cassava (Manihot esculenta) with to increase efficiency of a current breeding program. The methods were compared through independent validation and efficiency measures, such as prediction accuracy, bias, and recovered genomic heritability. The TCR method was suitable to estimate variance components and heritability, and the TCR/G-BLUP method provided efficient GEBV predictions. Thus, the proposed methods provide new insights for GWS.

Instituições parceiras:

Universidade Federal de Viçosa, UFV; Embrapa Floresta, CNPF;  Embrapa Mandioca e Fruticultura, CNPMF