The family Cucurbitaceae comprises ca. 130 genera and 900 species (Jeffrey 1980). Citrullus, Cucumis, Cucurbita, and Lagenaria, which are four major cucurbitaceous genera, include many economically important vegetable crops grown on arable land throughout the world: cucumber {Cucumis sativus; In = 14), melon (Cucumis melo; 2n = 24), watermelon (Citrullus lanatus; In = 22), and pumpkins and squash (Cucurbita pepo, Cucurbita maxima, Cucurbita moschata; 2n = 40). Cucurbit plants are trailing or vining,tendril-bearing, and frost-sensitive annuals (Wehner and Maynard 2003). They are mostly monoecious and require various insects, especially bees, for pollination. Within fruits of each species, there is a wide assortment of sizes, shapes, color variants,flesh textures, flavors, etc. (Sitterly 1972). Breeders are continually developing improved varieties that are better adapted to a wider range of growing conditions, have multiple-disease resistance, offer labor-saving and high-yielding abilities, and meet the fluctuating demands of economics and consumers.
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