Vol.:(0123456789) 1 3 Genetica DOI 10.1007/s10709-017-9957-y ORIGINAL PAPER Genetic diversity and structure of the zombi pea (Vigna vexillata (L.) A. Rich) gene pool based on SSR marker analysis Sujinna Dachapak 1  · Prakit Somta 1  · Supalak Poonchaivilaisak 2  · Tarika Yimram 1  · Peerasak Srinives 1   Received: 9 May 2016 / Accepted: 6 February 2017 © Springer International Publishing Switzerland 2017 America, Africa and Asia, and Australia. NJ tree also sug- gested that American and Australian accessions are origi- nated from East African zombi peas, and that the cultivated accessions from Africa and Asia were genetically distinct, while those from America were clustered with some cul- tivated accessions from Africa. These results suggest that Africa is the center of origin and diversity of zombi pea, and that domestication of this pea took place more than once in diferent regions. Keywords Zombi pea · Diversity · Domestication · Microsatellite marker · Underutilized legume Introduction The genus Vigna is an agro-sociological important plant taxon. It comprises more than 100 leguminous plant species distributed in wide and diverse areas of Africa, America, Australia and Asia (Lewis et al. 2004). Nine Vigna species are considered as domesticated crops, including cowpea (V. unguiculata (L.) Walps.), zombi pea (V. vexillata (L.) A. Rich), Bambara groundnut (V. subterranean (L.) Verdc.), mungbean (V. radiata (L.) Wilczek), azuki bean (V. angu- laris (Ohwi) Ohwi and Ohashi), rice bean (V. umbellata (Thunb.) Ohwi and Ohashi), black gram (V. mungo (L.) Hepper), moth bean (V. aconitifolia (Jaqc.) Maréchal), and créole bean (V. refexo-pilosa Hayata) (Tomooka et al. 2002, 2011). These species are grown mainly for dry seeds by small farmers in several cropping systems of tropical and sub-tropical regions. In addition, some other Vigna species are cultivated and/or harvested for seeds and pods as food, and for leaves and stems as feedsby local people in Africa, Asia, Australia and America (Tomooka et al. 2011). Abstract Zombi pea (Vigna vexillata (L.) A. Rich) is an underutilized legume species and a useful gene source for resistance to biotic and abiotic stresses, although there is little understanding on its genetic diversity and structure. In this study, 422 (408 wild and 14 cultivated) accessions of zombi pea from diverse origins (201 from Africa, 126 from America, 85 from Australia, 5 from Asia and 5 from unknown origin) were analyzed with 20 simple sequence repeat (SSR) markers to determine its genetic diversity and genetic structure. The SSR markers detected 273 alleles in total with a mean of 13.6 alleles per locus. Polymorphism information content values of the markers varied from 0.58 to 0.90 with an average of 0.76. Overall gene diver- sity was 0.715. Gene diversity and average allelic richness was highest in Africa (0.749 and 8.08, respectively) and lowest in America (0.435 and 4.10, respectively). Nei’s genetic distance analysis revealed that the highest distance was between wild Australia and cultivated Africa (0.559), followed by wild West Africa and wild Australia (0.415). STRUCTURE, neighbor-joining (NJ), and principal coor- dinate analyses consistently showed that these zombi pea accessions were clustered into three major groups, viz. Electronic supplementary material The online version of this article (doi:10.1007/s10709-017-9957-y) contains supplementary material, which is available to authorized users. * Prakit Somta pksomta@gmail.com; agrpks@ku.ac.th 1 Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Nakhon Pathom 73140, Thailand 2 Program in Plant Biotechnology, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Nakhon Pathom 73140, Thailand