Genetic diversity and structure analysis of Vigna unguiculata L. (Walp.) landraces from southeastern Mexico using ISSR markers

Cowpea ( Vigna unguiculata L. Walp.) is an important grain legume in tropical and subtropical regions. It requires low resource inputs and has a high nutritional value. Therefore, cowpea can play an important role in the development of agriculture. In southern Mexico, Mayan farmers have conserved and developed cowpea landraces for centuries. Nevertheless, information on their genetic diversity, conservation status and potential use is minimal. To generate information toward sustainable use, management and conservation of this species, we evaluated the genetic diversity and structure of 20 cowpea landraces from southeast Mexico using 10 inter-simple sequence repeat (ISSR) molecular markers. These ISSR markers generated 68 loci with a 67.7% polymorphism rate and average polymorphic information content of 0.36. The results of Bayesian assignation and the UPGMA analysis suggest the formation of two main groups defined by their genetic origin in southeast Mexico. High levels of genetic structure were found with a moderate level of genetic diversity distributed mainly between landraces. Low levels of intra-landrace variability were observed. Two landraces (P5 and P12) from Calakmul resulted in the high levels of genetic diversity. The selected markers were efficient at assessing genetic variability among Mexican cowpea landraces, providing valuable information that can be used in local conservation and participatory breeding programmes.