Citrullus lanatus (Thunb.) Matsum. & Nakai - Cucurbit Breeding ...

e found in wild relatives of the cultivated watermelon, such as C. colocynthis, and are typically used in Africa
as forages.
Historically, watermelon cultivars bearing giant fruit of 100 kg or more have been bred specifically for
fruit competitions at State and local agricultural fairs. 'Cobbs Gem', 'Carolina Cross #183', 'Florida Giant', and
'Weeks NC Giant' are some of the popular cultivars. Their fruit have very thick rind (Gusmini and Wehner,
2004), low sugar content, fibrous flesh, and susceptibility to hollowheart and shape defects. The Guinness book
of records (Matthews, 1993) reports the largest watermelon grown to be one of ten giant fruit weighing 119 kg
harvested in 1990 in Arrington, Tennessee, by B. Carson.
In recent years, consumers in the United States have been increasingly interested in seedless fruit
weighing 7 to 10 kg. In 2003, a new fruit type was introduced under the name of mini watermelon. Cultivars
produce fruit that are round, have a thin rind, and weigh between 1.5 and 4.0 kg. Leading cultivars among those
currently available are 'Petite Perfection', 'Precious Petite' (Syngenta Seeds - Rogers Brand), and cultivars of the
Bambino trademark (Seminis Vegetable Seeds), as well as other cultivars being tested for release (Molinar and
Mueller, 2004; Schultheis et al., 2005) in the next few years. Even though mini watermelons occupy a small
portion of the market, their introduction and appreciation by consumers has increased the interest of watermelon
breeders in cultivars having reduced fruit size.
Fruit weight in watermelon production is an important descriptor of fruit type, although it can also be
considered a yield component. Yield is defined as the total weight per production unit: in the United States,
growers expect to harvest at least "one load of fruit" per acre of land, corresponding to 50.52 Mg/ha of
marketable fruit (Maynard, 2001). Marketable fruit must be free of defects, and fall into the weight classes
most desired by the consumers. Currently, smaller sizes are preferred over the traditional large watermelon as a
dessert for parties and picnics. In addition, the average American family, composed of three to four persons,
eats watermelon only occasionally and may prefer watermelons that can be eaten in a single meal.
The genetics of watermelon have been studied widely, and several genes have been characterized
(Cucurbit Gene List Committee, 1979; Cucurbit Gene List Committee, 1982; Henderson, 1991; Henderson,
1992; Rhodes and Dane, 1999). However, single genes or quantitative trait loci have not been identified for
watermelon fruit weight. In two preliminary studies on the inheritance of fruit weight, significant additive,
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