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The drawings of Antoine Nicolas Duchesne for his Natural History of the Gourds

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Harry S. Paris

The Genus Cucurbita

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1As mentioned previously, Linné (1753, 1767) recognized six species of Cucurbita. Two of them, the bottle gourd and the watermelon, were removed to separate genera in the first half of the 19th century.

Description

2The genus Cucurbita, as recognized today, has plants that are robust, herbaceous, frost-sensitive, usually trailing, rather large (2 or more meters from end to end), viney, with leaves consisting of a long petiole and a palmate, 5-lobed lamina; at the juncture of nearly each petiole and stem, primordia of a branch, a forked tendril, and a unisexual flower occur. The flowers are quite large (10-20 cm diameter), showy and yellow-orange, nectar-producing, and are functional for one day, in the early-morning hours. The calyx has five, usually awl-shaped sepals that are fused into a cup at the base and the five petals of the corolla are free at their ends but fused at the base. The stamens have the anthers fused into a single column bearing hundreds of heavy, clumped pollen grains. The pistillate flowers bear inferior ovaries containing hundreds of ovules. Ordinarily, pollination is by bees. The fruits of wild plants are spherical, oblate, globular, oval, oviform, or pyriform, and always small, 3-10 cm in length (up to 15 cm in C. ecuadorensis, Andres & Robinson 2002), usually with broad dark green stripes alternating with narrow orange, yellow, light green or white stripes. Fruits of cultivated forms, though, show tremendous variation in shape, size, and color (Paris 2000e). The fruits usually contain hundreds of plump, more-or-less oval seeds, 5-25 mm long, often beige but with variation for color among and within species, that have a distinct margin all around the edge, the dimensions of the seeds fairly proportional in size to the size of the fruits and of shape (relative dimensions) inversely proportional to the shape (length-to-width ratio) of the fruits (Paris & Nerson 2003).

Taxonomy

3Several decades ago, as many as 27 species of Cucurbita were listed, but crossing experiments revealed that half of these were merely variants that were cross-fertile with others. Present-day taxonomy of Cucurbita is based on crossability, in the same fashion as Duchesne based his species limitations, and 12 or 13 species are recognized (Nee 1990, Table 2). Five of the species, C. pepo L., C. maxima Duchesne, C. moschata Duchesne, C. ficifolia Bouché, and C. argyrosperma Huber, are domesticated, and a sixth, C. ecuadorensis Cutler & Whitaker, may have been domesticated and later abandoned (Andres & Robinson 2002). Of these species, only the first three were known to Duchesne, and only these three are widely distributed in cultivation.

Origin of the Three Major Species

4The genus Cucurbita is native to the Americas (Whitaker 1947). Archeological remains indicate that the cultivated species originated and were domesticated by Native Americans allopatrically and at different times in different localities (Whitaker & Cutler 1965). Cucurbita pepo has been found growing wild in its native North America and was widely distributed on that continent in pre-Columbian times. This species was domesticated in at least two localities, one of them being in Mexico about 10,000 years ago (Smith 1997). Cucurbita maxima has been found growing wild in its native South America but there is no record of it having expanded beyond that continent prior to the arrival of Europeans (Whitaker & Bohn 1950, Nee 1990). Cucurbita moschata appears to have originated in tropical areas of northern South America (Nee 1990, Wessel-Beaver 2000) and seems to have reached the Caribbean Islands prior to Columbus.

Terminology

5The words “pumpkin” and “squash” are used to designate an edible Cucurbita fruit or edible-fruited form of Cucurbita. Although these two words are often used interchangeably, their root meanings are different. The word “pumpkin” is derived from the Latin pepo which in turn is derived from the Greek pepon for a rounded or enlarged fruit. Hence, the word “pumpkins” is appropriately applied to edible, round-fruited Cucurbita. The word “squash” is derived from the Native North American root word, asq, meaning an uncooked or unripe fruit; asq in plural form is asquash (Trumbull 1876). Therefore, “squashes”, is redundant, and I prefer to use the word “squash” as both singular and plural for non-round, edible-fruited Cucurbita.

6Inedible Cucurbita fruits or inedible-fruited forms of Cucurbita are referred to as “gourds”. The word “gourds”, however, is also used to refer to other genera of the Cucurbitaceae.

Domestication and Use

7Wild and primitive Cucurbita gourds almost always have thin, extremely bitter, very fibrous fruit flesh. For this reason, initial use of Cucurbita by man was probably the consumption of the edible, non-bitter seeds (Cutler & Whitaker 1961). Only later did people begin to consume the entire immature fruits, selecting for less bitter or non-bitter variants. Consumption of the mature fruit flesh is probably the most recent usage, as in addition to lack of bitterness, several fruit-flesh characteristics needed to be selected. These included decreased fibrousness and increased thickness, moisture-retention, carotenoids, starch, and sugar content of the flesh, as well as non-lignification of the fruit rind to allow for easy slicing of the fruit (Paris 1989, 2000e).

8Cucurbita are most often grown for human consumption of their entire young fruits or mature fruit flesh. Cultigens with fruits deviating greatly from a 1:1 length-to-width ratio usually are grown for the former purpose whilst those with fruits deviating little from this ratio usually are grown for the latter purpose (Paris 1989). The reason for the divergence from this 1:1 ratio in cultigens used for the consumption of their immature fruits apparently stems from the desire for relatively less volume of the soft placenta-containing endocarp and relatively more of the colored exocarp and firm, fleshy mesocarp tissue. These cultigens, however, have maintained the primitive lignified-rind characteristic, as the onset of lignification occurs only as the fruits approach maturity (Schaffer et al. 1986). The near 1:1 length-to-width ratio is the ancestral characteristic, perhaps offering some physical advantage or may simply represent a balance between the genes for lengthening as opposed to those for broadening the fruit axis (Sinnott 1936). Obviously, with a relatively larger placenta, there would be less restriction on the number and/or size of seeds produced therein. The Cucurbita grown for consumption of the mature fruit flesh usually have the derived characteristic of non-lignified rinds. Others, almost always round-fruited, are grown for consumption of the seeds or for extraction and consumption of the oil in the seeds. The different characteristics needed for the optimal use of the mature versus the immature fruits during domestication may have been the igniter, together with separate domestication events at different localities, of the explosion of phenotypic variability in each of these species, and resulted in their extreme polymorphy. One only needs compare the Cucurbita with the other Cucurbitaceae of major economic importance. Melon, Cucumis melo L., is another highly polymorphic species; most melons are used when mature but some, usually long-fruited, are consumed immature. Cucumber, Cucumis sativus L., is not highly polymorphic; relatively long-fruited, it is consumed only when immature. Watermelon, Citrullus lanatus (Thunb.) Matsumura & Nakai, is not highly polymorphic either; its spherical to oblong fruits are almost always consumed when mature.

9Other Cucurbita, often inedible, bitter, and small-fruited, are grown as ornamentals and still others, usually large-fruited of poor eating quality, are grown for consumption by animals or for holiday decorations or shows. Cucurbita is grown by some for consumption of its flowers or young shoots.

Climatic Adaptation and Distribution

10C. pepo, C. maxima, and C. moschata are all highly polymorphic and widely grown in regions of suitable climate (Lira Saade & Montes Hernandez 1994, Merrick 1995, Robinson & Decker-Walters 1997). Of these three, C. pepo is the most widely distributed, the most economically important, and has been considered the most polymorphic.

11C. pepo is the most temperature tolerant, succeeding in cool-temperate regions through to subtropical climates, failing in tropical climates only because of its susceptibility to diseases. Most of the cultivars of this species are grown for their immature fruits, generally known as summer squash. These begin to bear fruits very quickly, some 50 days after seeding. The most popular cultivar-group, known as Zucchini or Courgette, is a relatively recent development and probably has greater monetary value today than the fruits of the rest of the genus combined. Fruits of C. pepo pumpkins attain full maturity at 85 to 100 days after sowing.

12C. maxima is also fairly cool-tolerant. Cultigens used for consumption of the immature fruits are grown in South America, but this practice has had little application elsewhere. C. maxima is almost always grown for consumption of the mature fruit flesh, which is generally of the highest quality found among the species of Cucurbita. Full maturity is attained usually at 95 to 115 days after sowing. However, C. maxima is generally not as widely distributed as C. pepo because it requires a somewhat longer season to mature.

13C. moschata, on the other hand, is well-adapted to the tropics. C. moschata is almost always grown for consumption of its mature fruits, which often have intensely colored fruit flesh. Some cultigens, typically long-fruited, are grown in Central America for use of their immature fruits. Except for a few cultigens that can be found in temperate zones, the distribution of this species is otherwise found to be tropical, sub-tropical, and semi-arid, warm-temperate. The time from sowing to fruit maturity often is four months or more. The fruits produce a cuticular wax which seems to be the basis of preventing sunscalding in the intense insolation of lower latitudes. Restricting the range of this species is the daylength-sensitivity of many of its cultigens, expressed as lack of development of flowers during the long summer days of higher latitudes.

Recorded History of the Cucurbita

14The written history of the Cucurbita begins with the arrival of Europeans in the Americas. A manuscript reported that Columbus entered a small river in Cuba on 3 December 1492 and saw a village field in which were grown “calabazas, a glorious sight” (Gray & Trumbull 1883). Possibly, these were large bottle gourds, Lagenaria siceraria (Molina) Standley, but the enthusiasm would be all-the-more-likely if these were pumpkins, and if so, quite likely C. moschata. This vague account was followed by others like it of subsequent explorers who sighted cucurbits growing in the Americas.

15The first unquestionable testimonials to the existence of Cucurbita in Europe, to my knowledge, are a miniature illustration completed by 1508 in Touraine, in the Loire Valley of France, for the Livre d’Heures d’Anne de Bretagne (Bilimoff 2001, Paris et al. 2006) and the festoons, completed by 1518, at the Villa Farnesina in Rome, Italy. The former is a color image depicting a branch of a plant bearing a pyriform, striped gourd of C. pepo. The festoons contain images of three fruit forms, two of pumpkins one of oviform-pyriform gourds, of C. pepo as well as three different fruit forms of pumpkins of C. maxima (Caneva 1992, Ravelli 2004, Janick & Paris 2006). The next depictions of Cucurbita are of two C. pepo pumpkins drawn for the herbal of Leonhart Fuchs (1542), from which inferior copies were made in subsequent herbals (Paris 2000e). Fuchs also had, in his unpublished Vienna Codex that was finished by 1562, pictures of a number of other forms of C. pepo, including pumpkins, scallop squash, acorn squash and gourds. The next unquestionable image of C. maxima was to appear only much later, in the herbal of L’Obel (1576). C. moschata does not appear in the festoons. The collection of drawings in the estate of Conrad Gesner contains one, drawn in 1562, that appears to be a cheese-type pumpkin of C. moschata (Zoller et al. 1979). However, the first generally recognized depiction of C. moschata, also apparently a cheese-type pumpkin, was not published until over a century later (Rheede tot Draakenstein 1688).

Infraspecific Classification to Subspecies and Cultivar-Groups

16C. pepo encompasses wild as well as cultivated plants. In the past, its wild plants were given species designations but as they have been found to be completely fertile with cultigens, these designations have been demoted to the rank of subspecies. Wild plants of two subspecies have been found, C. pepo subsp. fraterna (Bailey) Lira Saade, Andres & Nee in Mexico and C. pepo subsp. texana (Scheele) Filov (syn. subsp. ovifera (L.) Decker) in the U.S.A. No wild progenitor has yet been found for the default subspecies grouping, C. pepo subsp. pepo. This classification into subspecies has been based on results obtained using techniques of molecular genetics, most notably promoted by Decker (1988). Teppner (2004) has suggested that primitive pumpkins from Mexico and Guatemala having fruits which are relatively small, oblate, thick-rinded, with strong main ribs and interstitial ribs, be referred to separately as C. pepo subsp. gumala, and that these may represent an antecedent of C. pepo subsp. pepo.

17Earlier, I classified the edible-fruited cultigens of C. pepo into eight groups, based on the polygenically inherited fruit-shape characteristic (Paris 1986b). To these I later added three groups of gourds (Paris 2000e) and integrated the botanical and horticultural classifications. The integrated classification is summarized very briefly in Table 3. This infraspecific classification for C. pepo was supported by the results of subsequent studies that used DNA polymorphisms to determine genetic differences among dozens of C. pepo accessions (Ferriol et al. 2003, Paris et al. 2003). I should point out here that these results suggested that a cultivated gourd having smaller fruits than any other, ‘Miniature Ball’, represents the ancestral form of C. pepo. Unfortunately, this gourd was not among the very many that were illustrated by Duchesne, but the five races secondaires designated by Duchesne can easily be assigned to the modern subspecific classification (Table 3).

18Most of the C. pepo cultivar-groups have a recorded history that is centuries long and it can be conjectured that the Pumpkin Group, at least, goes back for thousands of years. What appear to be images of plants or individual fruits of the Pumpkin, Scallop, Acorn, Vegetable Marrow, Cocozelle, and Crookneck Groups as well as the three groups of gourds date to the 16th century (Paris 2000e, Paris & Janick 2005). The Straightneck and Zucchini Groups appear to have originated and developed much more recently, in spite of the fact that Duchesne did illustrate straightneck fruit in 1770 (Paris 2000c, e).

19Infraspecific genetic relationships have not been worked out for C. maxima and C. moschata. Tentative groupings have been suggested for these two South American natives by Jeffrey (2001) and Goldman (2004). More permanent assignment of groupings awaits a great deal more study and documentation concerning their wealth of phenotypic variation and DNA polymorphism as exhibited within their native continent as well as in the various parts of the world where they are grown today (Andres 2004a, b). Fruits of over 100 cultivars of Cucurbita, beautifully photographed and escorted by delightful prose, have been presented in a recent book by Goldman (2004).

Table 3. Infraspecific classification of Cucurbita pepo to subspecies and cultivar-group (after Paris 2000e).

Subspecies classification

Cultivar-group

Brief Fruit Description

Duchesne’s

pepo

Cocozelle

Long, bulbous cylindrical

Les Giraumons & les Citrouilles

pepo

Pumpkin

Round, or nearly round

Les Giraumons & les Citrouilles

pepo

Round, Smooth-rinded

Small, round gourd

L’Orangin & les Coloquinelles

pepo

Vegetable marrow

Short, tapered cylindrical

Les Giraumons & les Citrouilles

pepo

Warted

Medium-small, round, warted

Les Barbarines

pepo

Zucchini

Uniformly cylindrical

Les Giraumons & les Citrouilles*

texana

Acorn

Turbinate, ridged and furrowed

Les Pastissons

texana

Crookneck

Long, narrow neck

Les Pastissons**

texana

Oviform, Smooth-rinded

Small, egg or pear gourd

Les Cougourdettes

texana

Scallop

Flat, scallopped

Les Pastissons

texana

Straightneck

Short, thick neck

Les Pastissons

*Had Duchesne encountered representatives of the Zucchini Group, he might have classified them with Les Giraumons & les Citrouilles (The Long-fruited Squash and the Pumpkins). However, as discussed later, the bush growth habit of the zucchini cultivars probably would have suggested to him a relationship with Les Pastissons
(The Pattypans). Hence, he might have considered them to be Pastissons giraumonés (Long-fruited Pattypans).
**Duchesne would undoubtedly have classified representatives of the Crookneck Group as Pastissons (Pattypans), had he encountered them.

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