Somatic embryogenesis and artificial seed production in Zonal (Pelargonium × hortorum) and Regal (Pelargonium × domesticum) geranium

Abstract

MARSOLAIS, A. A , , WILSON, D. P. M., TSUJITA, M. J . , and SENAKATNA, T. 1991. Somatic clnbryogenesis and artificial seed production in Zonal (Pelnrgoniutt~ X I~ortor~rrn) and Regal (Pelor-goniutn X dotne.sticurn) geranium. Can. J . Bot. 69: 1188-1193. Somatic embryos have been produced from petioles and hypocotyls of Zonal geranium and from petioles of Regal geranium. Somatic embryos of both species have been desiccated and subsequently germinated. Some important factors that influence the rate of somatic embryo production in geranium arc discussed. They include culture medium factors such as auxin and auxin dosage, carbohydrates, amino acids, pH, and basal medium composition. The donor plant genotype also appeared to have an effect on somatic embryogenesis and survival after desiccation.

Influence of 2,4-D and BAP on callus growth and the subsequent regeneration of somatic embryos in long-term cultures of Pelargonium x domesticum cv. Madame Layal

“…Petioles from young partially expanded leaves were surface-sterilized according to the method of Marsolais et al (1991) by agitating them for 20 min in a 1.4% solution of sodium hypochlorite containing one drop of Tween 20 per 400 ml followed by five separate rinses with sterile distilled water. The petioles were cut into 5 mm long segments and plated side-down, regardless of the orientation in vivo, on the surface of the culture medium.…”

“…The test tubes were sealed with plastic film and incubated in a growth chamber at 24ºC under a 16/8 hrs (light/dark) photoperiod with light supplied by white fluorescent lighting at an intensity of 46 µmol m -2 s -1 . MS medium (Murashige and Skoog, 1962) with 50 mg l -1 ascorbic acid, 50 mg l -1 citric acid (Marsolais et al 1991), 30 g l -1 sucrose, and 6.5 g l -1 agar at pH 5.6 was used as the basal medium. Iron was provided as the ethylenediaminetetraacetic acid iron salt, and its content was lowered to 86.9 µmol l -1 .…”

“…Histological examinations of the regeneration response after the application of this method to the cultivar Madame Layal (Pelargonium x domesticum) confirmed that somatic embryos were formed, i.e., bipolar structures (Wilson et al 1994). Although this protocol in combination with this cultivar was very suitable for the production of somatic embryos (Marsolais et al 1991;Haensch, 1999), the regeneration had already occurred within four weeks after culture initiation, even on the medium with 2,4-D and BAP. For this reason, petioles are always needed for this protocol as the responding material for each regeneration process.…”

“…In other regeneration experiments with petioles of Pelargonium x hortorum and Pelargonium x domesticum, the most effective treatment for the induction of somatic embryogenesis was a medium supplemented with a combination of 2,4-dichlorophenoxyacetic acid (2,4-D) and BAP (Marsolais et al 1991). Histological examinations of the regeneration response after the application of this method to the cultivar Madame Layal (Pelargonium x domesticum) confirmed that somatic embryos were formed, i.e., bipolar structures (Wilson et al 1994).…”

“…Most published studies on somatic embryogenesis in ornamental pelargoniums are based on explants, in particular hypocotyls, of very young seedlings of Pelargonium x hortorum (Marsolais et al 1991;Hutchinson and Saxena, 1996a;Hutchinson and Saxena, 1996b;Hutchinson et al 1996a;Hutchinson et al 1996b;Murthy et al 1996;Wilson et al 1996;Croke and Cassells, 1997;Hutchinson et al 1997a;Hutchinson et al 1997b;Murthy et al 1999;Senaratna et al 1999;Hutchinson et al 2000;Murch and Saxena, 2001;Senaratna et al 2002). After a critical evaluation of these published results, and a consideration of morpho-histological studies of somatic embryo-like structures from their cultures, it was concluded that there has not yet been any proof of somatic embryogenesis from hypocotyls of this species (Haensch, 2004a).…”