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Resistance

Inheritance of Resistance to Erwinia Root Rot in Sugarbeet. R. T. Lewellen, Research Geneticist, Science and Education Administration, U.S. Department of Agriculture, U.S. Agricultural Research Station, Salinas, CA 93915, (now Plant Breeder, Hellenic Sugar Industry, Thessaloniki, Greece); E. D. Whitney(2), and C. K. Goulas(3). (2)(3)Plant Pathologist, and Foreign Research Associate, respectively, Science and Education Administration, U.S. Department of Agriculture, U.S. Agricultural Research Station, Salinas, CA 93915. Phytopathology 68:947-950. Accepted for publication 16 December 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-947.

Increased susceptibility to Erwinia soft rot of sugarbeet (Beta vulgaris L.) was introduced inadvertently into commercial hybrid sugarbeet cultivars grown in California and Arizona. Two noninbred sugarbeet lines with different gene frequencies for resistance and susceptibility to infection by a variety of Erwinia carotovora were used as parents to study the inheritance of resistance. Individual roots from the parental lines and their F1, F2, B1P1, and B1P2 generations were grown and inoculated in 2 yr of field testing at two locations. The difficulty of establishing maximum rates of infection in susceptible genotypes caused some problems in the interpretation of the data. On the basis of frequency distributions for resistant and susceptible roots in the segregating generations and in the progeny from resistant and susceptible selections, we concluded that resistance is simply inherited and controlled by dominant gene action. A single dominant allele may be responsible for a high level of resistance in the root. The presence of a second, quantitative genetic mechanism that partially controls the rate of rot development within susceptible roots also was suggested.

Additional keywords: disease resistance, genetic vulnerability, Erwinia carotovora, bacterial vascular necrosis and rot.