Ethylene: A Natural Regulator of Sex Expression of Cucumis melo L

Abstract

Sex expression in cucumber (Cucumis sativus L.) and muskmelon (C. melo L.) was correlated with endogenous ethylene production. Plants of gynoecious (all female) sex types of the two species produced more ethylene than monoecius (male-female) plants. Sex expression in cucurbits is influenced by genetic, environmental, and hormonal factors. Monoecious strains of cucumber (Cucumis sativus L.) and muskmelon (C. melo L.) bear staminate (male) and pistillate (female) flowers. Gynoecious strains normally produce only pistillate flowers. Other cucumber and muskmelon strains produce staminate or pistillate and, in addition, perfect (hermaphroditic) flowers in various combinations. For example, andromonoecious strains are those that begin with staminate flowers and, eventually, also produce hermaphroditic flowers. Exogenous application of auxin (1, 2) and inhibitors of gibberellin biosynthesis (3) promote monoecious strains to form pistillate flowers, that is, increase femaleness. Application of gibberellin promotes formation of male flowers in monoecious and gynoecious phenotypes of cucumber (4, 5). Sex expression can be modified by daylength and temperature. Generally, short days and cool temperatures favor femaleness, while long days and high temperatures favor maleness, although there are exceptions (6). Determinations of endogenous growth substances indicate that strains with genetically strong female sex expression contain more auxin (7) and less gibberellin-like substances (8) than strains with strong male sex expression. There are certain differences between species; for example, gibberellin application does not cause male flower formation in gynoecious muskmelon (9). However, the results obtained with hormone applications and hormone determinations suggest the hypothesis that sex expression in cucurbits is controlled by an endogenous auxin-gibberellin balance (3, 7, 8, 10).Ethylene and 2-chloroethylphosphonic acid (ethephon), an ethylene-releasing compound, have recently been shown to promote femaleness in cucurbits (11, 12); thus, the effect of ethylene is similar to that of auxin. Exogenous application of auxin increases ethylene production by cucumber plants (13

The effect of growth regulators on sex expression in melon (Cucumis melo L.)

“…Byers et al (1972) found that treating monoecious cucurbits with ethylene or compounds that promote ethylene synthesis causes earlier production of pistillate flowers, that is, promote feminization. They found that application of GA 3 promotes masculinization in cucumber gynoecious plants, but not in melon gynoecious plants.…”

Application of Silver Nitrate Induces Functional Bisexual Flowers in Gynoecious Cucumber Plants (Cucumis sativus L.)

“…Plants are gynoecious if the genotype is A-gg, monoecious if the genotype is A-G-, hermaphrodite if the genotype is aagg, and andromonoecious if the genotype is aaG- (Kenigsbuch and Cohen, 1990). It is known that ethylene inhibitors induce the formation of bisexual flowers in gynoecious melon plants (Byers et al, 1972), which is why ethylene is considered to inhibit stamen development in melon plants. Recently, it was reported that the A gene encodes ACC synthase and was designated CmACS-7.…”

A Preliminary Study for Cucurbita moschata Duchesne (Loche) Crop Production under the Hydroponic Dutch Bucket System

“…However, flowering and its ratio can me modulates by phytohormones in cucurbits [32] which could be tested as a cheaper alternative. Future attempts in hydroponic "Loche" production should consider external application of ethylene or ethylene-releasing compounds in well-stablished transplants as for melon [33] and cucumber [34] and/or direct modulation of any of the genes involved in sex determination for cucurbits already identified [35,36]. The former only probable if the parthenocarpic origin of the fruit is validated [6] since no male flowers might be obtained.…”