Diversity of Ricebean (Vigna umbellata L.) Germplasm in the Northern Philippine Highlands Based on Agro-morphological Characteristics and Simple Sequence Repeat Markers

Abstract

Rice bean (Vigna umbellata L.) is one of the underutilized food legumes in the Philippines but is integral in the cropping system of highland local farmers. To get more understanding on the germplasm diversity of this legume in the area for conservation and breeding purposes, morpho-agronomic and genetic characterization using simple sequence repeats (SSR) markers were carried out on 28 ricebean germplasm. Morpho-agronomic characters exhibited mid to high diversity (0.42 to 0.71). Characters such as climbing habit, primary leaflet width, seed width, terminal leaf width, and pod width had the highest diversity indices. Ward’s cluster analysis grouped the ricebean germplasm into five clusters. In SSR analysis using a set of 10 SSR primer pairs, the genetic similarities among selected ricebean germplasm ranged from 0.39 to 0.86 showing mid to high similarities. A total of 89 alleles were detected with an average of 8.9 alleles for each locus, and the polymorphism information content value for SSR loci varied from 0.45 for CEDG021 to 0.94 for primer CEDG003 with an average of 0.78. Cluster diagram based on the similarity matrix generated six clusters at 0.86 similarity index. Fruit setting ability, pod width, seed width, and 100-seed weight are important characters for seed yield improvement in ricebean germplasm. Further, the grouping of ricebean germplasm with high seed weight and yield, many pods per cluster, and many seeds per pod suggest a potential gene pool of ricebean in the northern Philippine highlands, which can be utilized for future breeding improvement programs.