Induction of embryogenic callus in Cucurbita pepo hypocotyl explants by indole‐3‐ethanol and its sugar conjugates

Abstract

Hypocotyl explants of pumpkin (Cucurbita pepo L.) were inoculated aseptically on solid media containing Murashige and Skoog (MS) macro‐ and micronutrients, organic supplements, glucose as a carbon source, and indoleacetic acid (IAA) or one of its possible metabolic precursors, i.e. indole‐3‐ethanol [3‐(2‐hydroxyethyl)‐indole, tryptophol], 2‐(indol‐3‐yl)‐ethyl α‐L‐arabinopyranoside (tryptophol arabinoside), and 2‐(indol‐3‐yl)‐ethyl β‐D‐glucopyranoside (tryptophol glucoside). Embryogenic callus and adventitious roots developed on the explants, the response depending on the source of auxin, its concentration, and endogenous, possibly genetic, factors. Hypocotyl sections did not form embryogenic tissues and did not survive on media which did not contain an auxin or auxin precursors. Fewer explants responded to IAA than to indole‐3‐ethanol. Its arabinopyranoside was even more effective, while only a few hypocotyl sections proliferated in the presence of the corresponding glucopyranoside. Embryogenic callus induced by any of the four above compounds could be subcultured on media containing the same source of auxin. Selected callus lines have been maintained for more than three years and have continued to form embryoids. Indole‐3‐ethanol and IAA were suitable for clonal propagation of regenerated plantlets by axillary and apical bud culture.

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

“…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). However, Jelaska (1980) and Jelaska et al (1985) reported that the presence of 2,4-D in the culture medium inhibited embryo development of squash beyond the globular stage. In contrast, Jelaska (1986) found that for squash a constant exposure to auxin was necessary for both the induction and development of somatic embryos.…”

Somatic embryogenesis in Cucurbitaceae

“…Moreover, the mode of regeneration seemed dependent upon 2,4-D concentration such that a high concentration led to somatic embryogenesis while a lower concentration induced caulogenesis, as was observed for cucumber (Rajasekaran et al 1983) and melon (Tabei et al 1991). Jelaska (1980, andJelaska et al (1985) observed different morphogenetic responses in squash tissue, depending on the growth regulators added. Media with NAA or IBA produced embryos that were able to undergo complete development whereas most embryos were restricted to the globular stage on media with 2,4-D. No61 et al (1992) observed that squash embryo abnormalities were related to 2,4-D concentration in induction medium.…”

Plant regeneration via somatic embryogenesis in Styrian pumpkin: cytological and biochemical investigations

“…Auxins are absolutely required for the induction of somatic embryogenesis from different Cucurbitaceae species (Debeaujon and Branchard, 1993). In many studies somatic embryogenesis was obtained with a high concentration of an auxin source often in combination with other auxins or cytokinins (Jelaska et al, 1985;Juretic´and Jelaska, 1991;Tabei et al, 1991;Kintzios et al, 2002). While the maturation of squash somatic embryos was commonly conducted on medium without growth regulators, embryo maturation was described as being most successful on the medium supplemented with 11.4 lM IAA (Jureticá nd Jelaska, 1991).…”

“…Several types and combinations of plant growth regulators and explant sources have been tested for induction of somatic embryogenesis from various Cucurbitaceae species (Jelaska et al, 1985;Juretic´and Jelaska, 1991;Chee, 1991Chee, , 1992Metwally et al, 1998;Kintzios et al, 2002). Somatic embryogenesis is a complex pathway leading to the formation of embryos from sporophytic tissue.…”