Analysis of flavor and molecular diversity of Kenyan Lablab Bean (Lablab Purpureus (L.) Sweet) accessions

Abstract

The legume species Lablab purpureus L. Sweet grows in most tropical environments. It is used as a cover crop and green manure and provides a high–protein food for humans and livestock feed. The study was carried out to analyse flavour components and molecular diversity of Kenyan lablab accessions. Twenty four accessions from the National genebank and farmers were evaluated for odour and bitter taste intensities using sensory tests. Analysis of cyanogenic glycosides was carried out using the picrate method and volatile compounds were isolated and separated using gas chromatography. The genetic diversity of 50 accessions was studied using Amplified fragment length polymorphism (AFLP) markers. The sensory evaluations showed significant (p<0.05) differences for the bitter taste but none for odour. Accession 10706 and 13096 exhibited the highest and lowest means respectively for both bitter and odour taste. The levels of cyanogenic glycosides were not different for the 24 accessions, but significant (p<0.05) differences were observed in the volatile compounds isolated from the accessions with upto 89% similarity of the accessions. Two hundred and sixty two volatile compounds were identified using literature databases. The molecular study revealed a total of 180 polymorphic bands. The overall mean expected heterozygosity (He) for all the populations was 0.189. The Eastern population had the highest He of 0.297. The plot of the first and second principal coordinates for cluster analysis revealed an overlap of the accessions forming a tight cluster, with the exception of four; namely Mwingi-3 and 12000 from Eastern population, 12187R3 and 10706R1 from Coast and Rift Valley populations. The Unweighted pair group using mathematical arithmetic averages (UPGMA) cluster analysis generated from the distance matrix revealed three major groups. Group 1 had accessions 10706R1 and Mwingi-3, group 2 had accessions 12187R3 and 12000, while group 3 had the rest of the accessions. The low diversity revealed from these results may be due to the narrow genetic base for breeding stocks, and exchange of germplasm across the country. Results obtained from this study will be of great help in lablab accession management by ensuring maximization of exploitation of this vital resource as well as in developing breeding strategies for Lablab purpureus.