Population Structure and Genetic Diversity of Sweet Cassava Accessions from the Midwestern, Southeastern and Southern Regions of Brazil

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.

Population structure and genetic diversity in sweet cassava accessions from South of Brazil

“…The heterozygosity (Ho) per locus varied between 0.0000 (GA 013), 0.2179 (GA134), and 0.2436 (GA140) to 0.0833 (SSRY019), 0.8333 (GA 057), and 0.8718 (SSRY 050), with a mean of 0.6185, while the observed genetic divergence ranged from 0.5688 (GA 134), 0.5887 (SSRY 101), and 0.6145 (SSRY065) to 0.7417 (SSRY019) and 0.7424 (GA 131), with a mean of 0.6751 (Table 2). Similar results were found in other studies on genetic divergence of cassava plants using microsatellite loci, where the majority of alleles had frequencies below 0.95 [17,11,15,8,32,12,33,18,34,31].…”

“…Studies conducted by Gonçalves et al [33] evaluated 51 traditional cassava accessions collected in southern Minas Gerais state, Brazil, using 20 microsatellites and found an average of 3.4 alleles per marker. Three hundred traditional cultivars of cassava and 3 commercial cultivars from Brazil were evaluated using 15 markers, and a mean of 6.33 alleles per locus were obtained [18]. More recently, 144 cassava accessions collected in seven places in Southern Brazil were evaluated using 25 SSR markers [34].…”

“…Among these molecular markers, microsatellites, or simple sequence repeats (SSRs), stand out as an excellent tool for the evaluation of genetic diversity among accessions [15,16,12]. This is due to their high reproducibility, simplicity, speed, small amount of DNA required, low cost of use, great resolution power, wide distribution by the genome, and reproducibility [8,17,18]. In this context, the objective of this study was to characterize and to evaluate the genetic diversity of sweet cassava accessions collected in Western of Paraná and in the Midwestern of Santa Catarina and to determine the population structure of these accessions based on microsatellite markers.…”

High-density DArT-based SilicoDArT and SNP markers for genetic diversity and population structure studies in cassava (Manihot esculenta Crantz)

“…In contrast to subpop1, the average diversity between individuals within subpop2 was 0.391 which shows the significant divergence within the subgroup (Table 3). This level of differentiation of individuals inside the group indicates that even among individuals clustered by genetic proximity, there is still high variability [78]. The high level of admixture found in subpop2 again reflects the genetic variation within the group [62].…”

Diversidade Genética Entre Acessos de Mandioca Por Meio de Caracteres Agronômicos

“…Pode-se verificar por meio da Figura 4 que os descritores são correlacionados, positivamente e negativamente, entre si (o que corrobora com o resultado apresentado na Figura 3). Esse fato significa que a seleção em relação a um descritor pode culminar em uma seleção positiva ou negativa quando praticada, e a importância de caracterizar coleções que mantêm a diversidade da cultura (ORTIZ et al, 2019).…”