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Three transgenic yellow crookneck squash (Cucurbita pepo var. melopepo) and five transgenic cantaloupe (Cucumis melo, Reticulatus group) lines were field-tested in 1993 and 1994, respectively, for resistance to Zucchini Yellow Mosaic Virus and Watermelon Mosaic Virus II. During both years, non-transgenic plants were inoculated with virus before transplanting to provide a high virus threat to the transgenic plants. Before and after transplanting, serological (ELISA) testing was used to obtain baseline information on transformed plants and to confirm field virus infection. In both years, plant disease development was rated weekly; yield was assessed during 1993. Disease progression, yield, and end-of-season ELISA indicated a significant reduction in frequency of disease incidence in the transgenic lines. Total squash yields did not differ between the transformed and unchanged lines, but the transgenic lines yielded more marketable fruit than the non-transgenic line.
Impact of natural infection of common corn smut (Ustilago maydis) on processing characteristics of three F1 hybrid sweet corn (Zea mays L.) cultivars was evaluated in a two-year study with early and late spring-planting dates. At harvest maturity, size and location of galls were recorded and quality characteristics measured. Galls on the lower stalk, upper stalk and tassel reduced fresh weight and diameter of husked ears while galls on the base of the plant reduced fresh weight only. Ear length was reduced by galls on the upper stalk. As gall size increased from 0 to >10.2 cm. diameter, ear fresh weight and diameter decreased. The presence of galls >10.2 cm diameter reduced ear length. Kernel depth was not affected by size or location of gall. Additional ears of the same three cultivars were sampled from commercial fields planted in mid-season near Walla Walla and Patterson, Wash. Galls located on the upper and lower stalk reduced fresh weight, length, diameter and kernel depth, while galls on the tassel or base had reduced or no effect on these parameters. As gall size increased, fresh weight, length, diameter, and kernel depth decreased.
The impact of natural infection of Ustilago maydis (causal agent of common smut) on processing characteristics of three F1 hybrid sweet corn (Zea mays L.) cultivars was evaluated in a 2-year study with early and late spring planting dates. At harvest maturity, size and location of galls were recorded and quality characteristics measured. Galls on the lower stalk, upper stalk, and tassel reduced fresh weight and diameter of husked ears, whereas galls on the base of the stalk reduced fresh weight only. Ear length was reduced by galls on the upper stalk. As gall size increased from 0 to greater than 10.2 cm in diameter, ear fresh weight and diameter decreased. The presence of galls greater than 10.2 cm in diameter reduced ear length. Kernel depth was unaffected by size or location of gall. Additional ears of the same three cultivars were sampled from commercial fields planted in midseason near Walla Walla and Patterson, WA. Galls located on the upper and lower stalk reduced fresh weight, length, and diameter, whereas galls on the base of the stalk reduced fresh weight only. As gall size increased, fresh weight, length, diameter, and kernel depth decreased.
In vitro dose responses of several calcium and potassium salts were determined on some commercially significant plant pathogens, including: Helminthosporium solani, Fusarium oxysporum f. sp. pisi race 2, Colletotricum coccodes, Phytophthora cactorum, Phytophthora cinnamomi, Phytophthora erythroseptica, Phytophthora infestans, Phytophthora megasperma, Pythium ultimum, and Venturia inaequalis. Mycelial growth inhibition was both salt-specific and dose-related. Pythium ultimum was completely inhibited by 75 mg·L−1 or greater calcium propionate, but needed 300 mg·L−1 or greater of calcium acetate and 40 mL·L−1 or greater of potassium silicate for complete inhibition. Phytophthora infestans was completely inhibited by 150 mg·L−1 or greater calcium acetate, 150 mg·L−1 or greater calcium propionate, or 5 mL·L−1 or greater potassium silicate. Phytophthora cactorum was completely inhibited by 300 mg·L−1 or greater calcium propionate, but required 600 mg·L−1 or greater calcium acetate and 10 mL·L−1 or greater potassium silicate for complete inhibition. Phytophthora cinnamomi was completely inhibited by calcium propionate at 600 mg·L−1 or greater or by 10 mL·L−1 or greater potassium silicate. Only potassium silicate inhibited Phytophthora megasperma, Phytophthora erthroseptica, V. inequalis, and H. solani at concentrations of 5 mL·L−1 or greater, 20 mL·L−1 or greater, 40 mL·L−1 or greater, or 80 mL·L−1 or greater, respectively. Potassium acetate did not completely inhibit any of the pathogens in this study when tested at concentrations 1200 mg·L−1 or less.