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Resistance

Inheritance of Nonnecrotic Resistance to Southern Bean Mosaic Virus in Cowpea. H. A. Hobbs, Department of Plant Pathology, University of Georgia, Athens 30602, Present address: USDA-ARS Crop Science Research Laboratory, Forage Research Unit, P.O. Box 5367, Mississippi State, MS 39762; C. W. Kuhn(2), K. E. Papa (deceased)(3), and B. B. Brantley(4). (2)(3)Department of Plant Pathology, University of Georgia, Athens 30602; (4)Department of Horticulture, Georgia Station, University of Georgia, Experiment 30212. Phytopathology 77:1624-1629. Accepted for publication 26 May 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1624.

Inheritance of nonnecrotic resistance to the cowpea strain of southern bean mosaic virus (SBMV) was determined in cowpea. Crosses between a cowpea line (California Blackeye) susceptible to SBMV and three resistant lines (Early Pinkeye, Iron, and P1 186465) and crosses among the three resistant lines were evaluated for virus concentration and symptoms of individual plants of F₁ and F₂ generations. F₃ plants of the crosses were evaluated for symptoms. Virus concentration was determined by absorbance readings at 260 nm of purified virions or by enzyme-linked immunosorbent assay. The moderate resistance of Early Pinkeye was conferred by a single gene with partial dominance for resistance. Resistance in Iron appears to be controlled by multiple genes with incomplete dominance. The extreme resistance of PI 186465 was largely controlled by one gene with partial dominance for resistance; however, minor genes appeared to be operating and affecting virus concentration and symptoms in plants not homozygous for the major gene. Determination of virus concentration, rather than symptomatology alone, was indispensable for genetic interpretation of some crosses. Correlation of symptom severity with virus concentration in F₂ populations varied among crosses.