The objectives of the present study were to assess the population structure and genetic diversity in traditional sweet cassava cultivars collected in Bbackyard^cultivations in the municipalities of Maringá, Cianorte, and Toledo, State of Paraná, Southern Brazil, using 13 SSR molecular markers. All the loci analyzed were considered polymorphic with a mean of 3.15 alleles per locus; the mean polymorphism information content (PIC) value found was 0.4598, indicating that the primers were reasonably informative and the heterozygosity amplitude observed ranged from 0.0270 (GA134) to 0.8718 (SSRY45), with a mean of 0.4762, while the mean genetic diversity obtained was 0.5407, ranging from 0.3138 (GA21) to 0.6502 (GA140). The most divergent combinations were BGM434T-BGM20M, BGM35C-BGM20M, BGM430T-BGM232M, BGM430T-BGM164M, BGM430T-BGM322M, and BGM35C-BGM164M. The analysis of population structure distributed the traditional cultivars assessed in four different groups. The analysis of molecular variance (AMOVA) estimated that 11, 15, and 74 % of the variance were between groups, between individuals within groups, and between individuals within the population as a whole, respectively. The F is (0.170) and F it (0.259) values indicated a number of heterozygotes present in the population under study lower than that necessary to reach the Hardy-Weinberg equilibrium. The genetic variability found among the traditional sweet cassava cultivars assessed was considered wide, and the groups that were most distant were mostly cultivars from Toledo and Maringá.

No abstract

HIGHLIGHTS• The 303 traditional sweet cassava cultivars from Brazil, were divided based on their genetic diversity into four groups, separating them according to the region of origin. The first group contained cultivars from Paraná (South region), the second from Paraná and Santa Catarina (South), the third from Mato Grosso do Sul (Midwest) and fourth one from Minas Gerais (Southeast).• Highly divergent combinations were found, between cultivars from different regions, which can be used as parents in breeding programs. Abstract:The objective of this work was to screen sweet cassava accessions collected in smallholding areas in the Midwestern, Southeastern and Southern regions of Brazil, using 15 SSR molecular markers, to determine population structure and genetic diversity. Polymorphism was detected in every loci analyzed, with mean of 6.33 alleles per locus, and mean polymorphism information content (PIC) of 0.6057, pointing out that the primers were highly informative. The observed heterozygosity ranged from 0.0709 (SSRY 101) to 0.9398 (GA 12), with a mean of 0.6511, and mean genetic diversity of 0.6578, ranging from 0.3592 (GA 136) to 0.8116 (SSRY 21). The most dissimilar combinations observed were BGM526PR-BGM596MS, BGM526PR-BGM622MS and BGM526PR-BGM629MS. The traditional cassava cultivars assessed were divided into four distinct groups: two with cultivars from the South, one from the Southeast and one from the Midwestern region of Brazil. The variances among and within groups determined by the analysis of molecular variance were 44 and 56%, respectively. The PhiPT parameter (analogue to Fst) of 0.44 indicates high differentiation among groups. Broad genetic diversity was found among the traditional sweet cassava cultivars assessed, and the most divergent groups were formed by cultivars from the South and the Midwestern regions of Brazil.

Sweet cassava is a food culture of great importance because it is a source of nutrition and energy for millions of people in tropical and sub-tropical regions. For that reason, genetic diversity and population structure studies are necessary in order to obtain more information regarding the evaluated genotypes, reassuring their use in future breeding programs. The objective of this study was to evaluate the genetic diversity and population structure of 51 traditional sweet cassava accessions collected in the Southern of Minas Gerais State, Brazil, using 20 microsatellite markers. All markers used to genotype the 51 sweet cassava accessions were polymorphic (PIC = 0.4080). Four sub-populations were identified using different methods (Bayesian analysis and multivariate analysis). The PhiPT (analogous Wright Fst) index of 0.073 indicated a moderated genetic variability among the studied traditional sweet cassava accessions. The dissimilarity index ranged from 0.097 to 0.560. Among the most divergent accessions stands out BGM 690, BGM 655 and BGM 660, which are the most recommended for obtaining a heterosis in order to increase yield production.