98 – II.2. SQUASHES, PUMPKINS, ZUCCHINIS, GOURDS (CURCURBITA SPECIES)
South American populations in the survey may uncover wider genetic diversity
(e.g. collections with differential resistance to viral diseases have been identified).
Field observations have shown that some average-sized fruits contain more than
500 seeds, and that each plant can produce numerous fruits (Lira, Andres and Nee, 1995).
Cucurbita maxima
Cucurbita maxima is one of the most diversified cultivated species of the genus.
Its variation includes numerous races and local varieties, and many commercial cultivars,
some edible and some ornamental, with trailing and subshrub habits, and with fruits and
seeds that are sometimes unique in dimension, shape and colour. Some varieties have also
proven to have various degrees of resistance to several viral diseases (Tapley, Enzie and
Van Eseltine, 1937; Millán, 1947; Martínez-Crovetto, 1974, 1965; Rochelle, 1974; Maluf
and Souza, 1984). A total of 52 cultivars of this species were described by Tapley, Enzie
and Van Eseltine in 1937. These cultivars differ not only in morphological characteristics,
but in aspects of agronomic interest, such as duration of the life cycle, productivity and,
in some cases, in their ability to adapt to limiting ecological conditions.
Castetter (1925) and others (Whitaker and Davis, 1962; Robinson and
Decker-Walters, 1997; Decker-Walters and Walters, 2000) have addressed the diversity
displayed by C. maxima forms, and several types have been identified. The “Banana”
type includes long fruits which are pointed at both ends, with a soft rind and brown seeds.
The fruits of the “Delicious” type are turbinate-shaped and have shallow ribs, a hard rind
and white seeds and a high-quality flesh. The “Hubbard” type includes oval fruits, with
pointed or curved ends, a very hard rind and white seeds. Fruits of the “Show” type are
wide and orange coloured with a smooth rind and white seeds. A wide variability in this
type is seen in India. The “Turban” type contains turban shaped fruits. Most C. maxima
fruits are eaten at maturity as the fruit is of high quality. However, fruits of the “Marrow”
type are picked a few days post-anthesis for consumption, have a soft skin, are oval or
pear shaped, bulbous and have white seeds (see Annex 2.A2 for additional information on
horticultural types).
Of particular interest among C. maxima are varieties of the Mammoth group in the
“Show” type (“Mammoth Chilli” or “Mammoth Whale”) whose fruits reach gigantic
dimensions. Some C. maxima fruits exceeding 450 kg in weight have been documented.
Also impressive are the turbinate fruits like “French Turban” and “Turks Cap”.
Cucurbita moschata
Cucurbita moschata also displays striking morphological variation: the variation of
its fruits (colours, shapes and widths, and the durability of the fruits, shell, etc.) and seeds,
the number of variants with life cycles of different length, the existence of numerous
cultivars developed in various parts of the world, and the existence of races and local
varieties with outstanding agronomic characteristics, suggest the extensive genetic
variation of this species. Some examples of interesting regional variants are found in the
Yucatan Peninsula (and possibly in other regions of Latin America), with two life cycles
of different length (Lira, 1988; 1985), as well as the variants grown in some Mexican
states (e.g. Chiapas, Guanajuato), which have been found to be resistant to certain viral
diseases, and which have been used in improvement programmes (Garzón-Tiznado,
Montes-Hernández and Becerra, 1993; Gallegos, 1990). The most variation of fruit and
seeds of C. moschata occur in Columbia (Wessel-Beaver, 2000b). During the 500 years
of cultivation in China, C. moschata has adapted to different agro-ecological conditions,
