Cucurbit Genetics Cooperative Report 23:96-98 (article32) 2000
Thomas C. Andres
The cucurbit Network, 5440 Netherland Ave., D24, Bronx, NY 10471
Earle and Jones (1962) rank the Cucurbitaceae as one of the highest plant families in terms of mean protein content as well as mean oil content of its seeds, and assert that it “appear(s) to offer outstanding promise as potential sources of new oilseeds.” Over a dozen genera contain species, both domesticated and wild, that have been exploited for their oil (Table 1). Some are grown exclusively for their oilseeds, or at least contain cultivars that are grown for such purposes. But most have multiple uses, such as the fluted pumpkin, Telfairia occidentalis, which is cultivated in southern Nigeria primarily as a vegetable for its nutritious shoots and only secondarily for its oil-rich seeds. Even where the seed oil is the primary product, byproducts are often used as animal feed. Most cucurbit oilseeds are cultivated on a small scale for subsistence use and therefore are poorly known outside of local areas; thus the reason for this survey. None have attained the commercial importance of the hull-less oil pumpkin (Cucurbita pepo) in spite of their food potential. while oil pumpkin is unique in not having a hard seedcoat, which imparts certain advantages discussed in this volume’s reports from the Oil Pumpkin Conference, other species contain different desirable traits that have not been fully exploited.
Worldwide the most popular edible seed in the family come from the genus Cucurbita.All the species in the genus contain edible seeds with both a high protein and oil content. In comparing the other species in the genus to the oil pumpkin, some have larger seeds while others bear fruit with a higher ratio of seeds to flesh. cucurbita argyrosperma, for example, was domesticated in pre-Colombian Mexico and Central America chiefly for its seeds. The silver-seeded form of C. argyrosperma has large seeds with pronounced seed margins that facilitate hand-dehulling. Some cultivars and landraces of cucurbita maxima have seeds containing the largest kernels in the genus, but these seeds lack a distinct margin. this later species, along with C. pepo , is used in southern Russia for seed oil. Cucurbita ficifolia tolerates cool temperatures and is cultivated at higher altitudes than any other Cucurbita . Its large, flat seeds are laboriously hand-dehulled by descendants of the Incas and sold at appropriately high prices in regional Andean markets. Cucurbita moschata , which grows best in hot humid lowlands, is also sometimes grown for its edible seeds. There is one report of a paid of recessive naked seed genes found in C. moschata in China (Zhou, 1987). It remains to be seen whether this is under the same genetic control as the oil pumpkin and whether this trait can be crossbred into other Cucurbita species.
Attempts have been made starting in the 1940s to cultivate some of the wild species of Cucurbita for use of their seeds, particularly the xerophytic species that thrive on marginal lands. The wild species contain much smaller seeds than the domesticates , but what they lack in size is made up for in quantity of seeds produced in the numerous, thinly fleshed gourd-like fruits borne on each vine. Therefore the net yield in kernels is high. The greatest effort at producing such a new crop has been invested in the buffalo gourd (Cucurbita foetidissima). This wild perennial species from the southwestern U.S. and northern Mexico grows particularly well in traditionally non-arable, semi-arid regions. Preliminary studies have shown great potential for this and other xerophytic species, including Cucurbita palmata, C. digitata, and Apodanthera undulata. But attempts at commercial production in the southwestern U.S. and adjacent northwestern Mexico, as well as Chile, Lebanon, Pakistan, and Australia, have not yet succeeded. Cost-effective cultural practices and commercial acceptance have not been realized. This demonstrates the difficulty of domesticating a wild plant.
Tropical Africa and India represent the richest regions for the use of Cucurbitaceae oilseeds. Different tribes often have various uses and names for the same species of cucurbit. Vernacular names such as “egusi” are confusingly applied in Nigeria to the oilseeds of both Cucumeropsis mannii and at least two species of Citrullus, all of which are used to make egusi soup. Manu local uses have not been adequately studied even among species that constitute important dietary sources of protein and oil. In regions where there is a shortage of animal protein in the human diet, cucurbit oilseeds are used as meat extenders or as an alternative source of protein.
The most widely grown species in Africa is watermelon (Citrullus lanatus). Its black, brown, red, tan or green colored seeds have some of the most diverse uses in the family and are very popular in local areas, particularly in Nigeria, where the subspecies colocynthoides is cultivated. Since the flesh is bitter in this subspecies, the plants are grown solely for the seeds, which are larger than typical watermelon seeds. The bitter flesh helps protect the fruit from animal predation. Citrullus seeds may be ground into a substance like peanut butter, used as a condiment and thickener in soup and gravies, or used as flour to make bread. In West African cooking, a flavoring called ogiri is made from fermented Citrullus seeds, or sometimes from other cucurbit and leguminous seeds. The pale yellow oil extracted from Citrullus seed is sold commercially and used as a cooing and frying oil, and the residual protein-rich meal is sometimes friend in this oil. The oil is also used for making soap and as an illuminant. The snackseeds are popular in China where they are sometimes pickled in soya sauce or sugared. In the Central African Republic, the dry dehulled seeds are popped like puffed rice. A related wild species, Citrullus colocynthis, naturally produces an abundance of seeds in desert regions. While it has been exploited primarily for the laxative drug derived from its fruit pulp, it has also been known since Biblical times as a source of seed oil.
As in the genus Citrullus, there are some cultivars of Cucumis that are used solely for seed production. For example, Cucumis melo ‘chate’ is grown in Ethiopia in sorghum fields as an oil crop. Seeds of both Cucumis sativus and C. melo are used for food and medicine in parts of Africa and India. There are sketchy reports not listed in Table 1 of other species of Cucumis used for seed oil. For example, C. metuliferus in Niger, as well as C. pustulatus (syn. C. figarei ) in Uganda may be used for seed oil.
Several genera, including Fevillea, Hodgsonia , and Telfairia, contain large oil-rich seeds. For example, Fevillea cordifolia has seeds 5-6 cm across with 10-15 seeds in a 10-12 cm round fruit. “Thus, on a weight per fruit basis, the seed-oil content…is apparently higher than in any other dicotyledon and among the highest ever reported for any plant” (Gentry and Wettach, 1986). With the exception of Telefairia occidentalis , these seeds also have thick, difficult to remove hulls.
There are significant discrepancies in the literature on the oil and protein composition and percentage oil content of many of these poorly known oilseeds. This is presumably due to cultivar and environmental differences or to actual misidentifications. But some species among the genera Luffa and Fevillea, are reported to contain either edible or poisonous seed oil. This confusion in the ethnobotanical literature may be due to different extraction methods and contaminants from the seed coat. The nutritional value and possible toxicity of cucurbit oilseeds need to be studied further, and the seeds need to be evaluated for suitability for edible oil versus drying oil for industrial purposes, such as paints and varnishes.
Table 1. Cucurbitaceae species that have been exploited for their seeds.
| Scientific name | Major seed production areas | Seed and oil uses | Notes (annual and monoecious unless otherwise stated) |
|---|---|---|---|
| Acanthosicyos horridus | southwest coast of Africa | snackseed, almond substitute in confectionary, ground into flour | semi-domesticate, dioecious, xerophytic, perennial |
| Apodanthera undulata | Southwest U.S. and northern Mexico | potential industrial oil | wild, xerophytic, perennial |
| Benincasa hispida | Southeast Asia | edible seeds, anthelmintic | domesticate |
| Citrullus colocynthis | Northern Africa, Middle East, India | baking flour, soup thickener, cooking & frying oil, soap, illuminant, medicinal | wild & semi-domesticate, perennial |
| Citrullus lanatus | West Africa, Middle East. southern Asia | snackseed, baking flour, soup thickener, cooking & frying oil, soap, illuminant, medicinal | domesticate & wild |
| Cucurbita spp. | Americas, Eastern Europe, Africa, Asia | snackseed, edible oil, anthelmintic, potential diesel fuel in the xerophytic species | domesticate & wild, some xerophytic and perennial |
| Cucumeropsis mannii | tropical West Africa | roasted, fermented, powdered or pasted for soup thickener, cooking oil | domesticate |
| Cucumis melo | East Africa, southern Asia | roasted snackseed, fermented seedcakes, cooking oil, illuminant, medicinal | domesticate |
| Cucumis sativus | India, France | roasted snackseed, confectionary, cooking oil, illuminant, anthelmintic | domesticate |
| Ecballium elaterium | Mediterranean, Middle East | industrial oil | wild, monoecious & dioecious subspecies, perennial |
| Fevillea spp. | Neotropics | illuminant, industrial oil, medicinal oil | wild, dioecious |
| Hodgsonia macrocarpa | northern India and southern China | raw or roasted seed, edible oil, illuminant | recent domesticate, dioecious, perennial |
| Lagenaria siceraria | tropical Africa | cooking oil, medicinal oil | domesticate |
| Luffa spp. | tropical Africa & Asia, Brazil | cooking oil (may be poisonous), medicinal oil | domesticate |
| Momordica spp. | Paleotropics | cooking oil, illuminant, industrial oil | domesticate |
| Praecitrullus fistulosus | northern India, Pakistan | roasted seed | domesticate |
| Telefairia occidentalis | humid West Africa | raw roasted snackseed, fermented, or powdered seed as a high protein flavor enhancer and thickener in cooking, soap or roasted seed, edible oil, cosmetics | domesticate, dioecious, perennial |
| Telefairia pedata | East Africa | raw or roasted seed, edible oil, cosmetics | domesticate, dioecious, perennial |
| Thladiantha nudiflora | Southeast Asia | medicinal | wild, dioecious, perennial |
| Trichosanthes cucumerina | India, tropical Asia | industrial oil, anthelmintic | domesticate, usually dioecious |
Literature Cited
- Earle, F.R. and Q. Jones. 1962. Analyses of seed samples from 113 plant families. Econ. Bot. 16(4):221-250.
- Gentry, A.H. and R.H. Wettach. 1986. Fevillea — a new oil from Amazonian Peru. Econ. Bot.40(2): 177-185.
- Zhou, X.L. 1987. A study on the breeding of named kernel pumpkin and its genetic behavior. Acta Hort. Sin. 14(2):115-118.