VIEW ARTICLE

Resistance

Bacterial Vascular Necrosis and Rot of Sugar Beet: Effect on Cultivars and Quality. E. D. Whitney, Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, U.S. Agricultural Research Station, Salinas, CA 93901; R. T. Lewellen, Geneticist, Agricultural Research Service, U.S. Department of Agriculture, U.S. Agricultural Research Station, Salinas, CA 93901. Phytopathology 67:912-916. Accepted for publication 10 January 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-912.

An epiphytotic caused by an Erwinia sp. on sugar beet in the San Joaquin Valley of California in part was caused by a greater susceptibility of newly introduced hybrid cultivars. The greater susceptibility of the hybrid cultivars resulted predominantly from the use of highly susceptible pollen parents, but also was influenced by the F₁ moderately susceptible seed parent. The Erwinia-susceptible pollen parents were selected for virus yellows resistance from a moderately Erwinia-resistant parent. This suggested that an association might exist between yellows resistance and bacterial rot susceptibility. Our results did not support this hypothesis. All cultivars tested were susceptible to some degree to bacterial rot, but there was variability among selections, suggesting that the pathogen probably has been present for many years in soil and became obvious after the introduction of more susceptible cultivars. A disease index (mean percentage of rot per beet) was found to be a reliable means of estimating cultivar susceptibility.