Phenotypic and Genetic Characterization of Selected Kenyan Vigna Radiata (l.) Wilckzek (Mung Bean) Genotypes

Abstract

Mung bean (Vigna radiata (L.) Wilckzeck) is a leguminous crop grown for its nutritious seeds and as a fodder crop. Characterization of mung bean germplasm is, therefore, a prerequisite for the use of its genetic resources. The objective of this study was to evaluate the phenotypic and genetic variations among seven genotypes from eastern Kenya where they are mainly grown. Phenotypic diversity was determined using 13 morphological traits done in triplicate and the data was analysed using Minitab software version 19.2. The Principal Components were also computed and Eucledian distance tool used to construct the dendogram. Two main clusters I and II were obtained with cluster I having four genotypes while cluster II comprised three genoypes. The first and the second principal component accounted for 35.6% and 29.1% phenotypic variation respectively while cumulatively they accounted for 64.7% of the total variation. Simple sequence repeat markers were used to assess the genetic diversity of the seven mung bean genotypes. A set of 10 standardized Simple Sequence Repeats markers were used and eight of them had distinct and consistent amplification profiles while two were monomorphic. Twenty three alleles were detected in all the 7 genotypes on all chromosomes after analysis. The average number of alleles per locus shown by each marker ranged from 2-5 alleles and the average was 2.875 across loci. Genetic diversity, allele number and polymorphic information content (PIC) was determined using powermarker (version 3.25) and phylogenetic tree constructed using DARWIN version 6.0.12. Analysis of Molecular Variance was calculated using GenALEx version 6.5. The PIC values ranged from 0.1224(CEDG056) to 0.5918 (CEDG092) with a mean of 0.3724. Among the markers, CEDG092 was highly informative while the rest were reasonably informative except CEDG056 which was less informative. Gene diversity ranged from 0.1836(CEDG050) to 0.5102(CDED088) with an average of 0.3534. The Jaccards dissimilarity matrix indicated that genotypes VC614850 and N26 had the highest level of dissimilarity while VC637245 and N26 had lowest dissimilarity index. The phylogenetic tree grouped the genotypes into three clusters with cluster III having one unique genotype (VC6137B) only. Cluster I and II were further discriminated into sub clusters. Analysis of Molecular Variance indicated that the highest genetic variation (99%) was between individuals. Principal Coordinate Analysis depicted that two coordinates were able to explain 66.05% of the overall genetic variation. These findings indicate that use of agronomic traits and polymorphic SSR markers will be of great use in germplasm characterization and determination of genetic diversity. The highly informative marker can therefore be used in selection of parents during mung beans plant breeding programs.