Screening Selected Common Bean Genotypes for Resistance to Xanthomonas Axonopodis Pv. Phaseoli Constraining Bean Production in Kakamega County, Kenya
MetadataShow full item record
Beans play a significant role in food security owing to its nutritional value and generation of income. However, output of beans in Western Kenya is hindered by diseases, pests, soil infertility and unfavorable weather resulting to low productivity. Of the many diseases of beans, common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli (Xap) is a disease of economic importance in common beans (Phaseolus vulgaris L.). Due to the fact that chemicals have not been effective against CBB, the use of resistant genotypes is a central management strategy. The current study was carried out in the field and in the green house of KALRO-Kakamega in 2013 and 2014 to screen nine bean genotypes for resistance to common bacterial blight disease. Experiments were conducted in randomized complete block design with three replications in a 9×2×2 factorial factor during the greenhouse and field screening and 4×2×2×2 field experiment when assessing the role of soil amendments and method of cropping on disease incidence and severity. During growth, data on plant height, number of pods/plant, length of pods and size and number of CBB spots was taken. Yield parameters were also assessed. During the study, the isolates that were recovered from leaf samples were categorized as Xanthomonas like, with regard to their yellow pigment and convex mucoid morphology. Reaction to Xap was assessed as the number of spots on the leaves and diseased leaf area (DLA). The findings from the experiment revealed a significant variation (P<0.05) on the entire traits studied among the nine bean genotypes. The experiment revealed that the mean CBB disease severity was significantly lower in bean plants that were not inoculated compared to those that were inoculated. Disease incidence, distribution and severity differed significantly (P<0.05) among the different bean genotypes. The CBB was significant (P<0.05) in the bean genotypes and was influenced by the soil amendments applied and the method of cropping used either monocropping or intercropping. Data from the field and greenhouse experiments were in conformity. None of the evaluated genotype was immune to CBB. CAL77 and Cal 156A genotypes exhibited high level of resistance to CBB, thus a better variety to use. Seven genotypes namely Cal 285, Cal 256, CAL271A, Cal274, KK 8 and Cal 87 showed moderate resistance. In the green house, it was observed that disease symptoms were severe in beans planted in non-sterile soil and inoculated with Xap compared to those planted in sterile soil and non-inoculated respectively. In the field trials, it was noted that bean plants grown with DAP were significantly (P<0.05) taller, had more number of pods per plant and significantly (P<0.05) higher yield per plot than those grown on soils with chicken manure. Monocropped beans had significantly (P<0.05) higher growth and yield parameters that were studied. This study therefore recommends that further evaluation and screening be done, susceptible genotypes be tried in other locations; establish the factors that confer high levels of tolerance in Cal 77 and Cal 156A and advice farmers on the correct farming methods.
- MST-Botany