Efficient induction of microspore embryogenesis using abscisic acid, jasmonic acid and salicylic acid in Brassica napus L

The stress hormones abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA) play an important role in the regulation of physiological processes and are often used in tissue culture to promote somatic embryogenesis and to enhance the quality of somatic embryos. Despite many studies on Brassica napus microspore culture, the effects of stress hormones (ABA, JA and SA) on microspore embryogenesis are not well explored. In this study, the effects of three incubation periods (6, 12 and 24 h) at different levels of ABA, JA and SA (0, 0.2, 0.5, 1.0, 2.0 and 5.0 mg l(-1)) on microspore embryogenesis of rapeseed (B. napus L.) cv. 'Regent' were investigated. ABA (0.5 mg l(-1) for 12 h) enhanced microspore embryogenesis by about threefold compared with untreated cultures and increased normal plantlet regeneration by 68 %. ABA treatment also effectively reduced secondary embryo formation at all concentrations tested but enhanced callusing at high levels, for example 67 % at 1.0 mg l(-1) for 24 h. Highest embryo yield (286.0 embryos Petri dish(-1)) was achieved using 1.0 mg l(-1) JA for 24 h and highest normal plantlet regeneration (54 %) was observed in cultures exposed to 0.5 mg l(-1) JA for 12 h. JA (5.0 mg l(-1) for 24 h) also reduced the germination of microspore-derived embryos on regeneration medium by 21 %. SA at 0.2 and 0.5 mg l(-1) for 6 h increased microspore embryogenesis (184.0 and 193.4 embryos Petri dish(-1)) relative to the control (136.2 embryos Petri dish(-1)). However, SA did not improve normal regeneration, secondary embryo formation or callusing. Microspore embryogenesis and plant regeneration could be improved by ABA, JA as well as SA when the appropriate level and duration of incubation were selected.