MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF SELECTED COMMON BEAN (Phaseolus vulgaris L.) GENOTYPES FOR RESISTANCE TO ANTHRACNOSE (Colletotrichum lindemuthianum)

Abstract

Common bean (Phaseolus vulgaris L.), is one of the most important legume crop for provision of proteins in peoples’ diet globally and including Kenya. Anthracnose (Colletotrichum lindemuthianum) is a common disease of legumes that causes yield loss of up to 90-100%. The aim of the study was to investigate selected common bean genotypes for anthracnose resistance in Kenya. The study was carried out in three varied agro-ecological zones; University of Eldoret, Bungoma and Busia. Forty four common bean genotypes were selected for this study. Fifteen genotypes among the forty four were evaluated on field experiment to ascertain anthracnose incidence, severity and morphological traits associated with anthracnose resistance. Four bean genotypes were used as experimental controls. Glasshouse experiment was done to assess the reaction of common bean anthracnose differential set on anthracnose pathogen infection. Field experiment was carried out on RCBD and was replicated three times while the glasshouse experiment was laid down using CRD with three replications. Laboratory experiment was done in KALRO Njoro, where molecular characterization was done on the forty four genotypes using SSR markers of bean resistance to anthracnose. Data was collected on incidences, severities, and morphological traits and subsequently subjected to ANOVA in SAS version 9.1. Means were separated using Tukeys’ and Pearson correlation analysis was carried out to estimate interrelationship between the morphological traits association with anthracnose resistance on the genotypes. Molecular analysis was carried out on the forty four genotypes in the laboratory using SSR markers specific to beans and anthracnose resistance. All the molecular data were analyzed using Genstat Version 12. The results on incidence and severities revealed six genotypes to be resistant to anthracnose. Site variation was significant at (p≤0.05) with Eldoret recording the lowest average incidences of 53%, followed by Bungoma 76% and Busia 82% which recorded highest. KK15, Tasha and Chelalang were resistant in all sites, and this could be attributed to their genetic resistance. Morphological characterization showed significant difference on genotypes with positive correlation. C. lindemuthianum infection on the differential set revealed resistant genotypes. Eight SSR markers used during the study were significant (p≤0.05) and excellent in identifying anthracnose resistant genotypes. It is therefore concluded that, morphological and molecular characterization led to identification of tolerant and resistant common bean genotypes which are of potential use to the farmers and plant breeders and hence it is recommended that management of anthracnose by use of resistant common bean genotypes is essential to provide increased bean yields globally and in Kenya.