Distribution of BCMD and Response of Common Bean Varieties to Bean Common Mosaic Virus in Western Kenya

Abstract:Common bean (Phaseolus vulgaris L) is the main legume crop grown by small farm holders in Kenya. Its grains are very vital in human nutrition and source of income for peasant farmers. The yield is approximately 530 kg ha-1 and the country’s production is estimated at 613,902 tons per year. However, bean production in Kenya has kept on declining due to biotic and abiotic factors. In biotic, viral diseases are major yield reduction factor in bean production among them Bean Common Mosaic Disease (BCMD), caused by Bean common mosaic virus (BCMV) and Bean common mosaic necrosis virus (BCMNV) are most wide spread viruses with disease incidence of up to 100%. The general objective of the study was to determine the distribution of BCMD in three agro ecological zones of western Kenya and the response of common bean varieties to BCMV isolate. A diagnostic survey was done in 6 clusters (Bujumba, Alupe, Madola, Kimaeti, Ndareti and Chebich) of Busia and Bungoma counties in the long and short rain seasons of 2017. Farms for study in each cluster were randomly selected. Bean common mosaic disease (BCMD), incidence and severity were calculated and recorded. Leaf samples from each cluster, were collected for serological analysis. Sixteen bean varieties were planted in a greenhouse and some from each variety inoculated with BCMV isolate. BCMD incidence and severity were calculated, recorded and Leaf samples taken for serological tests. The results showed the occurrence of BCMD in all the clusters with varied incidence; 36.58%, 29.40%, 34.33%, 37.95%, 42.78% and 39.45 respectively as shown above clusters. Sixteen bean cultivars screened for re to BCMD showed that Chinese black kidney and Libya bean cultivars were tolerant to BCMV, but serologically tested positive to BCMV, while Red haricot, KATB1 and Mwitemania were more susceptible to disease with incidence. BCMD occurrence in all agro ecological zones in western Kenya is due infected seeds, availability of aphids or BCMV inoculum in other host plant. Resistant genes should be introgressed in local varieties