Alternaria blossom-end rot and seedling blight of cucurbits in Al-Qassim

Poor stand and blossom-end rot of watermelon (Citrulus lanatus), Charleston Gray cultivar were the most serious diseases in several fields at Al Qassim region, central Saudi Arabia, in 1986. Alter-naria sp. wasassociatedwith the infected seedlingsand blossom-endrotted fruit. The funguswasinter-nally seedborne in 100 % of the seeds extracted from infected watermelon fruit and in 26 % the seeds in symptomless fruits. Inoculation of cucurbit certified seeds with the Alternaria sp. caused seedling blight on two watermelon cultivars, Charleston Gray and Black Diamond; muskmelon (Cucumis melo) cvs.Green Flesh Honeydew and Crenshaw; Cantaloupe (c. melo var. canatalupensis) cvs. Amco Sweet, lanexbr Conari and Casaba Golden Beauty. Cucumber (c. sativus) cv. Amco Sweet MT and Squash (c. maxima)<br>cvs. U.E. G. Arrow Lebanese and Caserta. The cucurbit cultivars varied in suscebtibility of their leaves<br>and hypocotyls to infection with the Alternaria sp. Bright field microscopic examination of stained sections of infected seeds and seedlings of watermelon revealed the presence of the fungus in seeds and hypocotyls.An analyses of nutrient elements in healthy and infected watermelon fruit showed comparable levels of Cu, Fe, K, Mg and Zn in the blossom and pedicel ends of the fruit regardless of infection. The concentra-tion of Ca in blossom-end of the fruit was significantly (P=0.05) less than in pedicel-end regardless of infection