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2-Thiouracil-Induced Changes in Alfalfa Mosaic Virus Infectivity and Nucleoprotein Components in Hypersensitive Bean. C. W. Kuhn, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602; Phytopathology 63:1235-1238. Accepted for publication 22 March 1973. DOI: 10.1094/Phyto-63-1235.

2-Thiouracil caused the number and size of local lesions produced by alfalfa mosaic virus (AMV) on hypersensitive bean to increase 2.0 and 2.4 times, respectively. When sap extracts were made from infected leaves, thiouracil-treated leaves caused 100-1,000 times more local lesions than control leaves. As bean plants matured from 8 to 13 days after planting, the number of lesions decreased for both thiouracil and water-treated leaves. Reducing light intensity caused lesion size to increase on both treated and untreated leaves, and thiouracil caused approximately a similar increase at all light intensities. Thiouracil increased AMV nucleoprotein in bean by 1.8 times and specific infectivity by 17 times. Density-gradient profiles revealed that the middle and bottom AMV nucleoprotein components could not be observed in virus preparations from nontreated bean but small quantities of each component were present in virus preparations from thiouracil-treated bean. The increased infectivity appeared to be related to the presence of the bottom and middle nucleoprotein components.