EVOLUTION IN THE GENUSCUCURBITA

Origin and evolution of cultivated cucurbits

“…The cultivated species of Cucurbita can be divided into mesophytic annuals (C. maxima, C. argyrosperma, C. moschata, and C. pepo) or mesophytic perennial (C. ficifolia) (WHITAKER & BEMIS, 1964). Three species have defined ancestors.…”

“…The 22 wild and five cultivated species are extremely diverse in fruit color, size, and shape. The cultivated species are reproductively isolated from each other by genetic barriers and can be identified using morphological characteristics (WHITAKER & BEMIS, 1964;WHITAKER & BEMIS, 1975;NEE, 1990). The constant and relatively high chromosome number (2n = 40) as well as the complex isozyme pattern suggest an allopolyploid origin for the genus (SINGH, 1979;KIRKPATRICK et al, 1985).…”

SQUASH AND GOURD BEES (PEPONAPIS, XENOGLOSSA ) AND THE ORIGIN OF THE CULTIVATED CUCURBITA

“…None of the wild species are known to occur in Central America south of San Salvador (Whitaker and Davis, 1962), and until a recent investigation (Hurd and Linsley, 1967a) all of the Cucurbito in South America were believed to have been introduced by man. Except for C. andreana (Naudin, 1896) and C. ecuadorensis (Cutler and Whitaker, 1969) which are indigenous to South America, the known wild species are restricted to North America and are centered in the tropical or semi-tropical region south of Mexico City (Whitaker and Bemis, 1965). This does not apply to the xerophytic species which are found in the deserts of northwestern Mexico and southwestern United States.…”

“…This fact not only has important implications relative to the evolution of squash and gourd bees, but also suggests certain conclusions regarding the origin of the five cultivated speciesof Cucurbita (C. ficifolia, C. maxima, C. mixta, C. moschata and C. pepo) , a subject on which there has been much speculation (e.g., Bailey, 1929Bailey, , 1943Bailey, , 1948Baker, 1970;Cutler and Whitaker, 1961;Hurd and Linsley, 1964 et seq. ;Smith, 1969;Whitaker and Bemis, 1965;Whitaker and Bird, 1949;Whitaker and Bohn, 1950;Whitaker andCutler, 1965, 1966;Whitaker and Davis, 1962). Although it is not unusual to find that females of many groups of native bees are restricted in their pollen collecting to certain genera of plants, it is indeed unusual to find a species to species bee to pollen relationship within a single genus of plants.…”

Transgene escape: what potential for crop–wild hybridization?

“…Barriers may depend on genotype, as several combinations reported to be compatible by Esquinas-Alcazar & Gulick (1983) could not be produced by Íizko et al (2003), despite the use of embryo rescue. Furthermore, Whitaker & Bemis (1964) (Caradus & Williams 1995). F 1 hybrids are usually sterile (Somaroo & Grant 1972;Lautour et al 1978;Yang et al 1990 (Nenz et al 1996).…”