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The Nature of Bean Yield Reduction by Bean Yellow and Bean Common Mosaic Viruses. R. O. Hampton, Research Plant Pathologist, Agricultural Research Service, U. S. Department of Agriculture, and Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; Phytopathology 65:1342-1346. Accepted for publication 17 June 1975. DOI: 10.1094/Phyto-65-1342.

Naturally infected field bean (Phaseolus vulgaris 'Red Mexican U.I. 34') (RM34) plants were selected for typical symptoms of either bean yellow mosaic virus (BYMV) or bean common mosaic virus (BCMV), hand-harvested, and analyzed for disease-induced effects on the components of seed yield. Bean yellow mosaic caused a 33% reduction in the number of pods per plant and a 41% reduction in seed yield, relative to healthy control plants. Moderate and severe bean common mosaic caused 50% and 64% reductions in the number of pods per plant, respectively, and 53% and 68% reductions in seed yield. Path analysis of yield component relationships revealed that certain indirect effects on yield of BCMV-infected plants were greater than the direct effects of individual yield components. BCMV-infected plants with fewer pods per plant than normal also tended to produce fewer than normal seeds per pod, although plants selected for uniformity of BCM symptoms varied significantly with regard to this yield-component relationship. The qualitative effects of BYM and BCM on RM34 bean plants were similar.

Additional keywords: yield components, disease-induced yield loss, virus-induced yield loss, path coefficient analysis.