Pathogenicity Groups of Bean Common Mosaic Virus in the USDAPhaseolusGerm Plasm Collection

The pathogenicity groups of seedborne bean common mosaic virus (BCMV) strains in the USDA Phaseolus germ plasm collection were identified by systemic infection of differential P. vulgaris cultivars. All BCMV pathogroups (PG)(sensu Drijfhout) except PG III were detected, and 10 BCMV cultures simulated a new pathogroup, PG VIII. Six of these cultures, however, were resolved into two different BCMV strains, and 14 of 19 PG VI-simulating cultures were similarly resolved. PG V cultures were rare, except in mixed infections with other pathogroups (.)