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Cowpea Stunt: Inheritance Pattern of the Necrotic Synergistic Reaction. G. Pio -Ribeiro, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602, Present address of senior author: Departamento de Agronomia, Universidade Federal Rural de Pernambuco, Dois Irmãos, 50000 Recife PE., Brazil; C. W. Kuhn(2), and B. B. Brantley(3). (2)(3)Department of Horticulture, The Georgia Station, Experiment 30212. Phytopathology 70:250-252. Accepted for publication 4 September 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-250.

Cowpea cultivars California Blackeye, Clay, and Iron reacted to an inoculum mixture of cucumber mosaic virus and a Georgia isolate of blackeye cowpea mosaic virus (BlCMV) with severe stunt and necrosis (SSN), severe stunt (SS), and mild mottle, respectively. The F1 plants of the crosses California Blackeye × Clay, California Blackeye × Iron, and Iron × California Blackeye reacted with severe stunt and intermediate necrosis (SSIN), and F1 plants of Clay × Iron had an SS reaction. In F2 populations, the disease reactions segregated in a ratio of 1:2:1 (SSN:SSIN:SS). Thus, the necrotic reaction is controlled by an allele, at a single locus, which exhibits incomplete dominance. This assumption was confirmed by the data from backcrosses and F3 populations. The resistance of Iron to BlCMV and cowpea stunt was not detected in any plants in the F1, F2, F3, or backcross populations.