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Resistance

Effect of Soil Temperature on Resistance of Tomato Cultivars to Bacterial Wilt. T. W. Mew, Former Research Associate, Asian Vegetable Research and Development Center (AVRDC), P. O. Box 42, Shanhua, Tainan 741, Taiwan, Present address: International Rice Research Institute, P. O. Box 933, Manila, The Philippines; W. C. Ho, Former Research Assistant, Asian Vegetable Research and Development Center (AVRDC), P. O. Box 42, Shanhua, Tainan 741, Taiwan, Present address: East-West Center, University of Hawaii, Honolulu, HI 96822. Phytopathology 67:909-911. Accepted for publication 5 January 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-909.

Resistance to bacterial wilt (caused by Pseudomonas solanacearum) in some tomato cultivars was influenced by changes in soil temperature. The cultivar VC 48 was not affected by the different temperature treatments and maintained a moderate resistance (20-40% wilted plants) to P. solanacearum at 26, 30, and 32 C. Cultivars VC 8 and VC 11 were resistant (1-20%) at 26 C, but became moderately susceptible (40-60%) and susceptible (more than 60%), respectively, at 32 C. The rate at which the plants wilted also differed among the cultivars at different soil temperatures. At 26 C there were no significant differences among the four resistant cultivars, whereas at 32 C more than 50% of the VC 9 and VC 11 plants wilted in 5 or 6 days, a rate similar to that of the susceptible checks. Cultivar VC 48 still was moderately resistant at the end of 19 days at all temperatures. Cultivars Kewalo and KL 1 also differed in reactions to wilt at different soil temperatures. At 26 C initial wilt symptoms were observed 11 days after inoculation in Kewalo and after 7 days in KL 1. At soil temperatures of 30 and 32 C both cultivars succumbed rapidly.