COAT PROTEIN TRANSGENIC RESISTANCE TO WATERMELON MOSAIC AND ZUCCHINI YELLOWS MOSAIC-VIRUS IN SQUASH AND CANTALOUPE

Three yellow crookneck squash (Cucurbita pepo var. melopepo) and five cantaloupe (Cucumis melo, Reticulatus group) lines, genetically altered for resistance to zucchini yellow mosaic virus and watermelon mosaic virus, were field tested in 1993 and 1994, respectively. During both years, nontransgenic plants were inoculated with virus before transplanting to provide a high virus threat to the transgenic plants. Before and after transplanting, serological testing (enzyme-linked immunosorbent assay [ELISA]) 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 in 1993. Disease progression, yield, and end-of-season ELISA indicated a significant reduction in disease incidence in the transgenic lines. Total squash yield did not differ between the transformed and unchanged lines, but the transgenic lines yielded more marketable fruit than did the nontransgenic line.