Pathogenicity Groups of Bean Common Mosaic Virus Isolates in Kenya. Michael E. Omunyin, Kenya Agricultural Research Institute (KARI), National Horticultural Research Center, P.O. Box 220, Thika, Kenya. E. M. Gathuru, Department of Biological Sciences, Egerton University, P.O. Box 536, Njoro, Kenya; and D. M. Mukunya, Crop Science Department, University of Nairobi, P.O. Box 30197, Nairobi, Kenya. Plant Dis. 79:985-989. Accepted for publication 27 June 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0985.

Studies were conducted to determine the geographic distribution of bean common mosaic virus (BCMV) in areas of Kenya with high intensity of bean (Phaseolus vulgaris L.) cultivation and to identify virus strains by using differential P. vulgaris cultivars. The incidence of BCMV in farmers' fields in Central, Rift Valley, Eastern, Western, and the lake basin areas of Kenya varied from 0 to 60%. Disease prevalence was associated with the distribution pattern of the aphid vector, Aphis fabae, and seed selection practices by farmers. Fourteen virus isolates from infected beans were differentiated into four BCMV pathogenicity groups (PGs). These included the KN1 (PG VI) and KN3 (PG V) groups as well as two potentially new groups. The majority of isolates were the necrosis-inducing type. Implications are discussed for bean improvement research in Kenya.

Keyword(s): black root, cropping pattern, potyvirus, seed management