EVALUATION OF ADAPTABILITY POTENTIAL AND GENETIC DIVERSITY OF KENYAN DOLICHOS BEAN (Lablab purpureus (L.) SWEET) GERMPLASM

Abstract

Lablab purpureus L., synonym Dolichos lablab (L.) Sweet; 2n = 22 or 24 belongs to the family Leguminosae. It is widely grown in Kenya and popular among many Kenyan communities as a grain legume, animal fodder and green manure. The main growers of Lablab purpureus in Kenya are small scale farmers who either grow it as intercrop or pure stand. However, Lablab purpureus can be regarded as an under-exploited species. Limited research has been conducted on the species as a food crop in Kenya and consequently information on its adaptability and genetic diversity is scanty. Farmers‟ choice of type of Lablab purpureus to grow is based on seed availability and colour preference. Consequently genotypes are not grown in suitable specific agroecological environments hence low yields are obtained. Cultivars are distinguished by maturity period and morphological traits, and being an under-exploited crop, variety development is still in its infancy and so is the varietal classification. The objectives of the study were: to assess the status of Lablab purpureus in Kenya; to evaluate the adaptability potential of Lablab purpureus to various agro-ecological conditions in Kenya; to assess the phenotypic diversity of Lablab purpureus and to evaluate the genotypic diversity of Lablab purpureus using simple sequence repeats (SSRs) molecular marker. To achieve the above objectives, a baseline survey covering major Lablab purpureus growing areas of Kemya was conducted. Field experiments on agroecological adaptability were performed using randomized complete block design in three agro-ecological environments. Morphological characterization was conducted using a descriptor from Asian Vegetable Research Development Center (AVRDC). Molecular characterization was donducted by using sinple sequence repeat (SSR) molecular markers specific for Lablab purpureus and subjecting the DNA to polymerase chain reaction (PCR). Data obtained from the survey was subjected to descriptive statistics (percentages and means) using GenStat statistical software. Analysis of variance (ANOVA), correlation analysis, principal component analysis and cluster analysis were conducted for agroecological adaptability and morphological characterization data using GenStat statistical software. Data from molecular experiment was subjected to summary statistics, analysis of molecular variance (AMOVA), principal coordinate analysis and cluster analysis using GenAlex and Darwin softwares accordingly. Results of the baseline survey indicated the main challenges in Lablab purpureus production in Kenya as; pests and diseases, unavailability of good quality seed, low yielding cultivars, cultivars that take long periods to mature and lack of technical knowhow by farmers. Four accessions proved to have high yield potential and of relatively short maturity period in specific agroecological environments and could therefore be considered in future Lablab purpureus improvement programmes. Morphological characterization indicated that Lablab purpureus germplasm grown in Kenya exhibits a wide variability in quantitative traits and narrow variability in qualitative traits. Molecular characterization revealed that the Kenyan Lablab purpureus genotypes have a high degree of relatedness and of narrow genetic base.