Rakesh Kumar and Todd C. Wehner
Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609
Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus] belongs to the family Cucurbitaceae and subtribe Benincasinae (24). Other members of the Cucurbitaceae are cucumber, melon, pumpkin, and gourd. The genus Citrullus has been divided taxonomically into four species: C. lanatus (Syn. C. vulgaris), C. ecirrhosus, C. colocynthis, and C. rehmii. Diploid watermelon has 22 chromosomes (2n=22, x=11) with a genome size of 420 million base pairs (9, 18).It is native to southern Africa, mainly the Kalahari Desert area (2). The secondary center of origin is China. Watermelon can be found growing wild in various parts of western hemisphere, particularly in India (13) and in the Mediterranean region, including Iran and Egypt.