Improvement of somatic embryogenesis in zonal geranium

Abstract

A number of media constituents including sucrose, ammonium nitrate and plant growth regulators were evaluated in an attempt to improve somatic embryo production in zonal geranium (Pelargonium x hortorum) cv. Scarlet Orbit Improved. Somatic embryo production was characterized by the quantity and type of somatic embryo induced by the treatments. Sucrose at 4% supported the highest number of total somatic embryos while improving the proportion of the morphologically normal cotyledon-stage somatic embryos. Addition of ammonium nitrate also improved embryo production. With 1.89 mM ammonium nitrate, normal cotyledon-stage embryo development was increased by 53%; the proportion of normal cotyledon-stage embryos decreased and abnormal embryos with leaves or serrated margins in cotyledons (fringed-shoot type) increased with higher ammonium nitrate concentrations. The effect of plant growth regulators on somatic embryogenesis indicated that exogenous supply of indole-3-acetic acid (IAA) at a range of 0.25 to 4/zM failed to promote somatic embryogenesis. In contrast, benzyladenine (BA) up to 2.0 #M increased the total embryo number and the proportion of desirable cotyledon-stage embryos. There was no interaction between IAA and BA. Our research has demonstrated that improvement in both quantity and quality of somatic embryos can be achieved in zonal geranium.

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

“…Although there is a report about the regeneration of somatic embryos from suspension cultures in P. peltatum hybrids (Robichon et al 1997), the classification of regenerating structures as somatic embryos is unconvincing because it was not shown that the one presented structure was clearly separated from the parental tissue and that the other more developed structures were real bipolar structures. The only histological report clearly confirming the formation of bipolar structures in pelargoniums is the one involving somatic embryogenesis in the cultivar Madame Layal (Pelargonium x domesticum) (Wilson et al 1994). The results of this report are confirmed by the present study.…”

“…Such embryogenesis can lead directly to globular embryos through which the stock of embryogenic cells would be exhausted after a certain time. In the histological analysis of Wilson et al (1994), no pre-embryogenic determined cells were reported. The analysis shows that normal sub epidermal parenchyma cells are the origin of embryogenesis.…”

“…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.…”

“…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).…”

Morpho-histological study of somatic embryo-like structures in hypocotyl cultures of Pelargonium � hortorum Bailey

“…Average regeneration rates of up to 0.1 to 0.5 somatic embryos per explant have been achieved using petioles (Marsolais et al 1991;Haensch 1999). Therefore, most of the published work on somatic embryogenesis in Pelargonium hortorum is based on explants of very young seedlings, especially hypocotyls (Marsolais et al 1991;Slimmon et al 1991;Visser et al 1992;Qureshi and Saxena 1992;Gill et al 1993Gill et al , 1994Saxena 1996a, 1996b;Hutchinson et al , 1997aHutchinson et al , 1997bHutchinson et al , 2000Murthy et al 1996Murthy et al , 1999Wilson et al 1996;Croke and Cassels 1997;Senaratna et al 1999Senaratna et al , 2002Murch and Saxena 2001). Somatic embryos are defined, with general acceptance (Brown et al 1995), as new individuals that develop both a shoot apex and a discrete radicular end (Haccius 1978).…”