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Nature of Resistance in Soybean to Cowpea Chlorotic Mottle Virus. Mandhana Bijaisoradat, Department of Plant Pathology, University of Georgia, Athens 30602; C. W. Kuhn, department of Plant Pathology, University of Georgia, Athens 30602. Phytopathology 75:351-355. Accepted for publication 5 October, 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-351.

Soybean lines screened to determine their reaction to cowpea chlorotic mottle virus were classified into six disease categories. Lines in three of these categories reacted with local chlorosis and systemic mosaic; they differed on the basis of virus accumulation, symptom severity, and symptom incubation period. Cultivar Davis was susceptible, Jackson was moderately resistant, and plant introduction (PI) 346304 was resistant. Restricted virus replication was responsible for resistance in the latter two soybean lines. Lines in two resistant categories reacted locally with necrotic lesions. Lesions on cultivar Bragg were 3.3 times as large as those on Williams. Small quantities of virus were produced in uninoculated leaves of both hosts. A sixth category was characterized by a complex reaction which included both chlorosis and necrosis in PI 96983; virus accumulation was high in inoculated leaves and very low in uninoculated ones which sometimes recovered from symptoms. Inoculum concentration and time of year strongly influenced virus accumulation; however, neither factor altered the relative rankings of the lines in different disease categories.