Genetic diversity and structure of pigeonpea germplasm assessed by microsatellite markers
The pigeonpea is an important grain legume in various regions of the world. It is a pulse that is cultivated mainly by small farmers in semi-arid tropical regions for various purposes, including food security, livestock feed, and agroforestry systems. We examined the genetic diversity and structure of 73 pigeonpea accessions from 10 origins, including regions of Brazil, Central America, and India. Allelic diversity and polymorphism, molecular analysis of variance (AMOVA), Bayesian analysis (Structure) and a dendrogram were estimated based on data concerning 11 microsatellite loci. AMOVA revealed wide genetic differentiation among the pigeonpea populations, with FST ranging from 0.22 to 0.25. Expected heterozygosity in the accessions was greater than the observed heterozygosity in eight of the 11 loci, with the observed heterozygosity ranging from 0.06 to 0.55. Polymorphic information content ranged from 0.13 to 0.67 among the 11 loci. Genetic similarity among pigeonpea accessions ranged from 0.26 to 0.93, indicating considerable variability among them, with the formation of three groups, one of which included all Brazilian accessions. Two groups were formed in the Structure analysis, indicating reduced allele sharing between the populations of Northeast Brazil and other populations. This information highlights the importance of incorporating germplasm from the Brazilian Northeast into pigeonpea breeding programs in Brazil, to increase the variability in germplasm collections.