DIALLEL ANALYSIS OF HIGH CAROTENOID CONTENT IN CUCUMBER FRUIT

Authors: NAVAZIO, JOHN - DEPT HORT UW MADISON WI; Simon, Philipp

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: On a worldwide basis orange, red, yellow, and dark green vegetables and fruits account for most of the vitamin A consumed, in the form of provitamin A carotenoids. In contrast to other cucumber relatives the overwhelming majority of cucumber germplasm has little or no orange or yellow pigmentation. Because cucumber is the fourth most economically important vegetable and grown on over 1.5 million hectares for pickling or fresh consumption in nearly all countries, the development of cucumbers as a provitamin A carotenoid source could have nutritional significance in vitamin A deficient regions of the world. We have recently developed derivatives of orange oriental cucumbers that are adapted for U.S. production. In this study we intercrossed orange cucumbers with typical white-fleshed cucumbers and found that most progeny were white-fleshed. This means that cucumber breeders will not be able to use these hybrids to develop new orange varieties. This information will be useful to cucumber breeders in providing them with a set of predictions for the success in incorporating orange fruit color into new breeding materials.

Technical Abstract: Three orange-mesocarp derivatives of the xishuangbannan cucumber (Cucumis sativus L. var. xishuangbannanesis Qi et Yuan), P100, P101, and P104; and NPI (P105), an unrelated cucumber (Cucumis sativus L.) reported to have orange flesh, were selected as parents for a diallel experiment to evaluate inheritance of orange cucumber mesocarp pigment over 3 years. Visual color intensity and carotenoid content were closely related. A preponderance of additive genetic effects for cucumber mesocarp pigmentation was observed in grade size 2 fruit (immature fruit used for pickling). Both additive and nonadditive genetic effects were important in grade size 4 fruit (mature). Years and year x genotype interactions were highly significant for pigmentation of size 2 fruit, indicating the importance of environment on the expression of pigmentation in this size class. In contrast, color development was stable among years for size 4 fruit. P104 exhibited high general combining ability (GCA) estimates for size 4 fruit pigmentation across years, while P101 had high GCA estimates for size 2 fruit. The diallel analysis illustrated high fruit carotene content of parents per se. Most hybrid combinations of the diallel reduced carotenoid content relative to parents, indicating both dominance for low carotenoid content for both fruit sizes and lack of genetic complementation among parents to enhance fruit color. Genetic control of pigmentation in size 2 fruit appeared to be independent of that for size 4 fruit.