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Resistance

A Cowpea Line Has Distinct Genes for Resistance to Tobacco Ringspot Virus and Cowpea Mosaic Virus. Fernando Ponz, Department of Plant Pathology, College of Agricultural and Environmental Sciences, University of California, Davis 95616, Current address: Instituto Nacional de Investigaciones Agrarias, Departamento de Proteccion Vegetal, Carretera De La Coruna, Km. 7, Apartado 8111, 28040 Madrid, Spain; Mary L. Russell(2), Adib Rowhani(3), and George Bruening(4). (2)(3)(4)Department of Plant Pathology, College of Agricultural and Environmental Sciences, University of California, Davis 95616, (3)Current address: Foundation Seed and Plant Materials Services, Department of Plant Pathology and Agricultural Experiment Station, University of California, Davis 95616. Phytopathology 78:1124-1128. Accepted for publication 21 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1124.

A previous survey of cowpea (Vigna unguiculata) lines identified one, Arlington (USDA plant introduction number 293453), that was both resistant to the comovirus cowpea mosaic virus strain SB (CPMV) and a source of protoplasts that restrict CPMV replication. We report that the budblight strain of tobacco ringspot virus (TobRV), which infects several cowpea lines including Blackeye 5, failed to induce symptoms in Arlington cowpea seedlings or to be detected at 10–12 days after inoculation by enzyme-linked immunosorbent assay. F1 progeny of Blackeye 5 × Arlington all resisted infection by TobRV. Among F2 progeny, resistance to TobRV and to CPMV were inherited as single dominant characters, but they segregated distinctly. TobRV, as well as CPMV, interfered with the increase of the comovirus cowpea severe mosaic virus in Arlington cowpeas. Previous results showed that Arlington cowpeas possess an inhibitor of CPMV-SB proteinase. No similar activity was detected against a TobRV proteinase. Thus, the resistances of Arlington cowpeas to TobRV and to CPMV, although similar in several respects, are controlled by separate genetic loci and probably operate under distinct mechanisms.