Improvement of somatic embryogenesis in zonal geranium

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 ×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 µM failed to promote somatic embryogenesis. In contrast, benzyladenine (BA) up to 2.0 µM 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.