Effect of Pollination Techniques on Fruit Set and Seed Yield of Egusi Melon (Citrullus colocynthis)

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Cucurbit Genetics Cooperative Report 15:80-81 (article 31) 1992

J.O. Kuti and C. Rovelo
Horticulture Research Laboratory, College of Agriculture, Texas A&I University, Kingsville, TX 78363

Citrullus colocynthis (L.) Schrad, known as egusi melon in Nigeria, belongs to the Cucurbitaceae family (3). It is a prostrate herbaceous perennial, probably an ancestral type of watermelon, and is cultivated extensively for its fruits and seeds (4). The seeds are edible and rich in oil and protein. Unlike the typical watermelon, flowers of egusi melon are smaller, less showy than those of most other species of cultivated Cucurbitaceae (6) and are pollinated by honey bees (5). Egusi is monoecious, and pistillate flowers open early into e morning and are receptive for one day only. Thus, continuous regular fruit set depends on daily activity of honey bees (1). Little information exists on the effect of controlled pollination and seed production of egusi melo. The objective of this study was to compare effects of controlled or hand-pollination and bee-pollination of egusi melon flowers on fruit set and seed yield.

In May 1992, 150 randomly selected seedlings of egusi melon were transplanted from the greenhouse to a field plot on a Willacy sandy loam soil at the Texas A&I University Research Farm. The plot design was 10 rows of 5 plants with 2.5 m intrarow spacings with three replications. Prior to anthesis, 50 pistillate flowers were pollinated by hand daily at about midday. Another 50 flowers were tagged from each block and allowed to be pollinated by honey bees. Fruits were harvested 110 days after anthesis and the seeds were extracted from each fruit. Dada obtained for hand-pollinated and bee-pollinated plants were: number of flowers/plant, number of fruits/plant, fruit size, number of seeds/fruit and seed weights of random 100-seed samples. Seeds were tested for their viability using the tetrazolium method of Moore (2). Analysis of variance was used to partition the variation in fruit set and seed yield into pollination techniques.

Fruit set and seed yield of egusi melon pollinated by hand and bees are presented in Table 1. While no significant differences were found between pollination techniques for number of flowers/plant and number of seeds/fruit, highly significant (P<0.01) differences were found between pollination techniques for number of fruits/plant, seed weight and seed viability. Mean fru8it weight and fruit size were significantly (P<0.05) affected by pollination technique. Based on our results, honey bees appear to be far more efficient pollinators of egusi melon than controlled or hand-pollination method. The percentage of flowers that set fruit under controlled pollination was generally between 20%, while under natural or be-pollination more than 85% of flowers set fruits. Factors responsible for the inhibition of fruit set in hand-pollinations of egusi melon are not known and are under investigation in our laboratory.

Table 1. Effect of pollination methods on fruit set and seed yield of egusi melon (Citrullus colocynthis).

Pollination Method

Yield parameter
Hand
Bee

Significancez
No. flowers/plant 8 7 ns
No. fruits/plant 1 6 **
Mean fruit wt (kg) 5.2 3.2 *
Fruit diam (cm) 12.4 9.4 *
No. seed/fruit 367 347 ns
Seed wt (g/100) 5.7 19.9 **
Seed viability (%) 10 90 **

z ns, * and ** indicate not significant, and significant at the 5% and 1% level, respectively.

Literature Cited

  1. Mohr, H.C. 1986. Watermelon breeding. In: M.J. Bassett, ed. Breeding Vegetable Crops. AVI Publishing Co., NY p. 37-66.
  2. Moore, R.P. 1973. Tetrazolium straining for assessing seed quality. In: W. Heydecker, ed. Seed Ecology. Butterworth, London. p. 347-366.
  3. Okoli, B.E. 1984. Wild and cultivated cucurbits in Nigeria. Econ. Bot. 38:350-357.
  4. Oyolu, C. 1977. A quantitative and qualitative study of seed types of egusi (Colocynthis citrullus L.) Tropical Sci. 19:55-62.
  5. Porter, D.R. 1933. Watermelon breeding. Hilgardia 7:533-552.
  6. Rosa, J.T. 1928. Inheritance of flower types in Cucumis and Citrullus. Hilgardia 3:233-250.
  7. Sawaya, W.N., N.J. Daghir and P. Khan. 1983. Chemical characterization and edibility of oil extracted from Citrullus colocynthis seeds. J. Food Sci. 48:104-107.