Somatic embryogenesis in Cucurbitaceae

Abstract

Strategies based on the application of biotechnologies to crop improvement programmes generally require regeneration of whole plants from cells or tissues cultivated in vitro. In Cucurbitaceae, regeneration can occur either through a caulogenic or an embryogenic developmental pathway. Reports of somatic embryogenesis have dealt with the main cultivated crops, i.e. cucumber, melon, squash and watermelon. Somatic embryogenesis and plant recovery are obtained from numerous sources including protoplasts, but the best results are observed with explants coming from seedlings, especially cotyledons and hypocotyls. The genetic constitution of mother plants also seems to play a key role in the success of embryogenesis, but few systematic studies on genotype effect have been published. Somatic embryos can exhibit developmental abnormalities, particularly when they arise from protoplast-derived cultures. Generally, data concerning embryo yield, rate of germination and plant development and characteristics of regenerated plants and their progeny, has not been provided in previous reports. The potential use of somatic embryogenesis in cucurbit breeding programmes is stressed in this review.

Growth regulator pretreatment improves somatic embryogenesis from leaves of squash (C ucurbita pepo l.) and melon ( Cucumis melo l.)

“…Auxin is usually required for the induction of somatic embryogenesis, with 2,4-D being used alone or in combination with other auxins (Debeaujon and Branchard 1993;NadolskaOrczyk and Malepszy 1987;Rajasekaran et al 1983;Tabei et al 1991). For example, somatic embryogenesis from cotyledons of squash was achieved on 22.6 µM 2,4-D in two different cases (Chee 1992;Noel et al 1992).…”

Observations on the combined effects of light, NAA and 2,4-D on somatic embryogenesis of cucumber (Cucumis sativus) hybrids

“…Cade et al (1988); Kuijpers et al (1996) kept cucumber explants in the dark before transfer to the light. The initiation phase required a strong auxin such as 2,4-dichlorophenoxyacetic acid (2,4-D), often in combination with other auxins (Debeaujon and Branchard 1993). During the next phase, induced callus became committed to form embryos.…”

Increase of embryogenic callus formation in cucumber by initial culture on high concentration of 2,4-dichlorophenoxyacetic acid

“…Initial culture on picloram or NAA, or on 2,4-D at a low concentration (1.4 #M) did not result in any embryogenic callus formation. Embryogenic callus formation increased to 40% if during the initial phase of the culture (10 days), the 2,4-D concentration was raised to 14 #M. Prolonged culture on 14 #M 2,4-D resulted in less embryogenic callus formation.Abbreviations: BA -benzylaminopurine; 2,4-D-2,4-dichlorophenoxyacetic acid; NAA -naphthaleneacetic acid Embryogenic callus formation from leaf explants of cucumber has been reported by various authors (Malepszy and Nadolska-Orczyk 1983;Chee and Tricoli, 1988;Bergervoet et al 1989;Debeaujon and Branchard, 1993;Lou and Kako, 1994). In our hands, the published procedures resulted in low frequencies of embryogenic callus formation.…”

“…Abbreviations: BA -benzylaminopurine; 2,4-D-2,4-dichlorophenoxyacetic acid; NAA -naphthaleneacetic acid Embryogenic callus formation from leaf explants of cucumber has been reported by various authors (Malepszy and Nadolska-Orczyk 1983;Chee and Tricoli, 1988;Bergervoet et al 1989;Debeaujon and Branchard, 1993;Lou and Kako, 1994). In our hands, the published procedures resulted in low frequencies of embryogenic callus formation.…”