Breeding squash and pumpkins.

Within the genus Cucurbita (Cucurbitaceae) there are fi ve domesticated species, three of which, C. pepo, C. maxima, and C. moschata, are important crop species grown world-wide. Although cultigens of all three species are found in temperate and sub-tropical climates, C. maxima and C. pepo are considered best adapted to temperate climates; whereas, many cultigens of C. moschata are restricted to tropical and subtropical climates. Cucurbita species have a vining habit of growth, and are monoecious with large showy fl owers that are bee pollinated. Horticulturally, domesticated members of this genus are conveniently classifi ed into three broad groupings: (1) summer squash cultigens, the fruit of which is consumed immature, about three to fi ve days after fruit set; (2) winter squash, the fruit of which is harvested when mature, about 50 to 60 days after fruit set, but which may require additional storage to reach optimum sugar levels for desirable eating quality; and (3) gourd and pumpkin cultigens that are used mainly for ornamental purposes. Although Cucurbita cultigens are considered highly outcrossed under natural conditions, they can be highly inbred without readily apparent inbreeding depression. They are often classifi ed in breeding books along with other self-pollinating crops. For this reason, the pedigree system of breeding has been widely and successfully adopted by most cucurbit breeders. For wide, interspecifi c crosses, the backcross system, together with selection, has also been utilized together with the pedigree system. Most breeding efforts have been for qualitative traits such as fruit appearance (size, color, shape), bush or vine habit of growth, and resistance to a few major diseases. Important quantitative traits are fruit size, seed size, and % dry matter of fl esh, the latter an important parameter of eating quality. Prior to 1980, most varieties of squash and pumpkins were open-pollinated. However, in North America there has been a plethora of new F1 hybrids introduced into the seed trade during the past 30 years, with the majority of cultivars having a bush or semi-bush habit of growth. Department of Biological Sciences, University of New Hampshire, Durham, NH 03824; e-mail: jbloy@unh.edu © 2012 by Taylor & Francis Group, LLC 94 Genetics, Genomics and Breeding of Cucurbits