DOI link for Watermelon
Watermelon is an important vegetable crop accounting for 2% of the world area devoted to vegetable production (FAO 1995). It belongs to the xerophitic genus Citrullus Schrad. ex Eckl. et Zeyh. that thrives in the Old World tropics (Singh 1990). The center of diversity and possibly the center of origin of Citrullus is southern Africa (Rubatzky 2001; Dane and Lang 2004). There, diverse populations of the Citrullus spp. grow freely (Jarret et al. 1997; Mujaju et al. 2010; B. De Winter, pers. comm.). The genus Citrullus comprises four known diploid (n = 11) species. Among these species is the annual Citrullus lanatus (Thunb.) Matsum et Nakai, which is considered the most important Citrullus species, grows in tropical and subtropical climates throughout the world, and is a native of the dry sandy areas of southern Africa (Bates and Robinson 1995). The C. lanatus species includes the C. lanatus subsp. citroides [L.H. Bailey], the watermelon that is considered by some botanists as a group of ancient cultigens derived from the “tsamma” melon in southern Africa, and is also known as the Citron melon. The tsamma melon is adapted to semidry conditions and is an essential source of water and nutrients for animals, which results in the dissemination of the watermelon seeds throughout the African deserts. It is for this reason Citroides watermelon is also known as the cow melon.