Genetic diversity among air yam (dioscorea bulbifera) varieties based on single sequence repeat markers

Dioscorea is the largest genus in the Dioscoreaceae family, and includes a number of economically important species including the air yam, D. bulbifera L. This study aimed to develop new single sequence repeat primers and characterize the genetic diversity of local varieties that originated in several municipalities of Brazil. We developed an enriched genomic library for D. bulbifera resulting in seven primers, six of which were polymorphic, and added four polymorphic loci developed for other Dioscorea species. This resulted in 10 polymorphic primers to evaluate 42 air yam accessions. Thirty-three alleles (bands) were found, with an average of 3.3 alleles per locus. The discrimination power ranged from 0.113 to 0.834, with an average of 0.595. Both principal coordinate and cluster analyses (using the Jaccard Index) failed to clearly separate the accessions according to their origins. However, the 13 accessions from Conceição dos Ouros, Minas Gerais State were clustered above zero on the principal coordinate 2 axis, and were also clustered into one subgroup in the cluster analysis. Accessions from Ubatuba, São Paulo State were clustered below zero on the same principal coordinate 2 axis, except for one accession, although they were scattered in several subgroups in the cluster analysis. Therefore, we found little spatial structure in the accessions, although those from Conceição dos Ouros and Ubatuba exhibited some spatial structure, and that there is a considerable level of genetic diversity in D. bulbifera maintained by traditional farmers in Brazil152CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão tem2007/04805-

A comparative genetic diversity assessment of industrial and household Brazilian cassava varieties using SSR markers

This study was carried out in order to assess the genetic diversity of 20 cassava (Manihot esculenta Crantz) genotypes with high phenotypic performance using microsatellite markers. Two groups were considered for this study: eleven varieties for industrial uses and nine for household consumption. By using nine microsatellite primers, high polymorphism was identified in all the loci analyzed, with values reaching 100%. On average, 3.4 alleles per locus were found, with 0.371 the value estimated for the observed heterozygosity and 0.555 for gene diversity for the entire set of varieties. The genetic variability found in both varieties, cultivated on a large-scale in the South Center region of Brazil, is wide enough to allow the choice of divergent parental genotypes to be used in crosses to obtain new recombinant genotypes. Furthermore, the analyses indicated a high genetic variability within the two groups (I: varieties for industrial uses; II: varieties for household consumption). However, varieties for household consumption attain higher genetic variability, probably due to high priority placed on selection of different sensorial traits. In the cluster analysis, a tendency for separation of varieties for industrial use and household consumption was verified. Our results represent an important source of information to the cassava breeding program in Brazil