Resistance of Watermelon Seedlings and Fruit to the Fruit Blotch Bacterium

Seedlings of 22 watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] cultivars and two plant introductions were screened in the greenhouse for resistance to the fruit blotch bacterium. There were significant differences in disease severity among cultivars, but no cultivar was immune to the bacterium. In field tests, fruit of 18 commercial cultivars were inoculated individually or became infected naturally from diseased foliage. Cultivars with relatively resistant fruit included `Sugar Baby', `Jubilation', `Mirage', `Calsweet', `Crimson Sweet', `Royal Sweet', and `Sangria'. The more susceptible cultivars generally had a light-colored rind. Cultivar level of resistance to bacterial fruit blotch may not be sufficient under conditions conducive to severe disease development.