Effect of Diseased Plant Elimination on Genetic Diversity and Bean Common Mosaic Virus Incidence in Phaseolus vulgaris Germ Plasm Collections. R. E. Klein, Postdoctoral Research Associate, Department of Plant Pathology, Washington State University, Pullman 99164-6430. S. D. Wyatt, and W. J. Kaiser. Associate Professor, Department of Plant Pathology, Washington State University, Pullman 99164-6430, and Research Plant Pathologist, USDA-ARS, Western Regional Plant Introduction Station, Washington State University, Pullman 99164-6402. Plant Dis. 74:911-913. Accepted for publication 2 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0911.

Genetic diversity and incidence of seedborne bean common mosaic virus (BCMV) in Centro Internacional de Agricultura Tropical (CIAT) Phaseolus vulgaris germ plasm seed samples was compared to seed samples of the USDA accessions from which the CIAT samples were originally derived. Following approximately three seed-increase cycles at CIAT during which individual plants obviously infected with BCMV were eliminated, overall and within-sample diversity in 120 seed samples had declined by 45 and 66%, respectively. BCMV incidence also declined by 30%, from an average of 6% in 26 USDA samples to 4.2% in the CIAT samples, but tolerant and visually symptomless infections became more common in the CIAT samples. The distribution of BCMV incidences among samples was also altered.