EVALUATION OF CITRULLUS SP GERM PLASM FOR RESISTANCE TO WATERMELON MOSAIC VIRUS-2

A total of 670 Citrullus species accessions were evaluated for resistance to watermelon mosaic virus 2. In greenhouse tests seedlings to be evaluated were mechanically inoculated, and in field tests plants in spreader rows were mechanically inoculated. Plants were considered virus free by the absence of disease symptoms and by negative results in enzyme-linked immunosorbent assay. Our working definition of resistance was the ability of a plant to withstand, oppose, lessen, or overcome the attack of a pathogen. Plants were considered resistant if virus free 10-14 days after final inoculation in the greenhouse, or virus free 4-6 wk after inoculation of the spreader-row plants in the field, even though many were subsequently infected. Selections from 10 C. lanatus accessions (PI 189316, PI 189317, and PI 189318 from Zaire; PI 244018, PI 244019, and PI 255137 from South Africa; PI 164708 from India; and PI 494529 and Egun, which are Egusi-types, and PI 306782 from Nigeria) were resistant in both field and greenhouse tests. Five C colocynthis accessions (PI 386016, PI 386024, PI 386025, and PI 386026 from Iran and PI 388770 from Morocco) possessed some resistance in both field and greenhouse tests.