Genetic structure and diversity in the Dioscorea cayenensis/D. rotundata complex revealed by morphological and isozyme markers

Abstract

ABSTRACT.Of the 600 known yam species, only 10 are utilized as food, and the Dioscorea cayenensis/D. rotundata species complex is among the most cultivated. In Brazil, these species are commercially cultivated in the northeast region and are cultivated in the south and southeast regions as subsistence crops by traditional agriculturists. This study aimed to evaluate the genetic diversity of 21 local varieties of D. cayenensis and 2 D. rotundata accessions using 7 isozymic loci and 24 morphological markers, and to investigate the diversity distribution in different levels of organization, such as swidden fields and communities of Vale do Ribeira. Cluster analyses for both the isozymic and morphological data separated the 2 D. rotundata accessions from the D. cayenensis accessions from Vale do Ribeira. The analysis with morphological characteristics showed the presence of 2 subgroups (Iguape and Cananéia) within group I, which included all of the local varieties from Vale do Ribeira; this result may indicate the influence of the cultural units on the morphological variation. Molecular analysis of variance indicated that most of the isozymic variability was concentrated among swiddens within communities (42.5%) and within communities (40.3%). Most of the morphological variability was also concentrated among swidden fields within communities (44.8%). The correlation between geographic and genetic distances indicated that neither morphological (r = 0.17) nor isozymic diversity (r = -0.15) is structured in space. Thus, the traditional agriculturists of Vale do Ribeira maintain and manage a great diversity of D. cayenensis varieties in their communities.

Genetic diversity assessment of yams (Dioscorea spp.) from Ethiopia using inter simple sequence repeat (ISSR) markers

“…rotundatacomplex ( Table 2). Bressan et al (2014) also evaluated 21 local varieties of D. cayenensis and two D. rotundata accessions using 7 isozyme loci and 24 morphological markers, and reported the existence of high genetic variability with 100% polymorphism using isozyme marker. Dansi et al (2000) and Mignougna et al (2002) also studied genetic diversity of D. cayenensis/D.…”

Genetic diversity Study of <i>Dioscoreas</i> Using Morphological Traits and Isozyme Markers Analyses

“…However, AAT showed a higher level of genetic polymorphism than other markers in this study and previous studies. AAT is the most effective discriminant for some tuber crops with a higher level of polymorphisms than other isozymes markers (Efisue, 2013 andBressan et al, 2014). The isozyme marker analysis indicated that D. alata species were distantly related to D. rotundata and D. cayenesis.…”

“…Isozymes, being biochemical expressions of the genetic make-up of the plant, can be used to greatly improve the accuracy of cultivar identification. Bressan et al (2014) used isozymes analysis in delineating yam cultivars into different species. The results revealed clear genetic diversity of the yam species between and within communities under study.…”

Genetic variability of yam based on quantitative descriptors

“…Among the many available clustering methods, unweighted pair group method with arithmetic mean (UPGMA) has been the most used, due to the present higher values of cophenetic correlation coefficients, which measure the association between dissimilarty matrix and the cluster matrix (Mohammadi and Prasanna, 2003). For this reason, this method has been used in several studies that aim to characterize and assess the genetic variability of yams, such as those by Bressan et al (2014) and Efisue (2015).…”

“…However, in other studies of genetic variability characterization of yams, UPGMA method has been used simultaneously with principal components and both are complemented by graphic dispersion analysis (Mwirigi et al, 2009;Norman et al, 2011;Michael, 2013;Mulualem and Michael, 2013;Siadjeu et al, 2015). These techniques are used in many studies of genetic variability characterization of yams (Mwirigi et al, 2009;Norman et al, 2011;Mulualem and Michael, 2013;Bressan et al, 2014;Efisue, 2015;Siadjeu et al, 2015). Thus, this study aimed to assess the genetic variability among genotypes of yam (D. rotundata), collected in four municipalities from the Recôncavo Baiano region, based on quantitative descriptors through multivariate methods.…”