Common Beans

Common bean is the most important pulse crop in Kenya, though small scale farmers have limited access to pest resistant seeds. This has therefore made common bean yields remain below 1000kgha-1 , while the potential is 2000kgha-1. However phenolics are secondary metabolites present in plants and this could be an attribute contributing to common beans resistance to bean fly infestation. The objective of this study was to devise effective ways of managing bean fly by use of phenolic content present in commercial varieties of common beans. This was achieved by determining the total phenol content of the beans. The bean varieties were; KK 8, Tasha, KK 15 (Resistant check), Chelalang, Wairimu dwarf, Ciankui, GLP 585, Miezi mbili, GLP 2 (Susceptible check), GLP 1004, GLP 24, and GLP 1127. Experimental design was RCBD with three replications. Data collected were subjected to ANOVA, mean values were separated using LSD at 5% level of significance. Chelalang, Tasha, GLP 1004, KK 8, GLP 585 a nd KK 15 showed resistance and high yields. Phenol content was significant (P< 0.05) in resistant common bean varieties (KK8, Tasha, Chelalang, GLP 585, KK15, and GLP 1004). The common beans which showed significant resistance to bean fly had significant (P< 0.05) high yields of above 1000Kgha-1. Therefore from the study it was evident that presence of phenol content in common beans deters bean fly infestation.

The common bean (Phaseolus vulgaris), is a high protein crop and the main legume in the cropping system of
western Kenya. Despite its importance, common bean yields are low (<1.0 t/ha) and declining. Bean Common mosaic virus (BCMV) and Bean common mosaic necrosis virus (BCMNV) are the most common and most destructive and can cause a yield loss as high as 100%. In Kenya, limited cultivars and exotic genotypes with resistance to BCMV and BCMNV strains have been reported. Reports indicate BCMNV being a widespread virus compared to BCMV in western Kenya. This study therefore, sought to screen popular cultivars for resistance to the virus. Sixteen popularly grown bean cultivars together with cowpea (Vigna unguiculata), soybean (Glycine max) and groundnut (Arachis hypogaea) were planted in a green house in a
completely randomized block design with three replicates. The plants were inoculated with BCMNV Enzyme Linked
Immunosorbent Assay (ELISA) positive isolate at 3-leaf stage. Data was taken weekly for 3 weeks on type of symptoms expressed and number of plants infected. Ten bean cultivars were susceptible, 4 tolerant and 2 resistant. For improved yields of common bean, farmers should be advised to plant certified seeds for all legumes in the cropping system.