Effects of gibberellin, abscisic acid and embryo desiccation on normal plantlet regeneration, secondary embryogenesis and callogenesis in microspore culture of Brassica napus L. cv. PF704

Most of the microspore-derived embryos can not regenerate normally in rapeseed. The effects of gibberellins (GA3), abscisic acid (ABA), and embryo desiccation on normal plantlet regeneration were studied. The donor plants were grown in a growth chamber at day/night temperatures of 15/10 °C with a 16/8h photoperiod, respectively. Microspores were isolated from whole buds of 2.5-3.5mm in length, containing late-uninucleate and early-binucleate microspores, and cultured in modified NLN-13 liquid medium. After 30 days, cotyledonary embryos were transferred to B5 medium. The study of GA3 concentrations (0, 0.05, 0.1, 0.15, 0.2 mg/l) showed that the use of 0.1 and 0.15 mg/l of filter sterilized GA3 were the optimum treatment for normal plantlet production (50% and 44%, respectively). Among the various time periods of embryos desiccation (0, 3, 5, 10, 15, 20 min.), air drying of embryos for 10 min. produced the highest normal plantlets (60%). In the third experiment, 9 desiccation-ABA treatments (TrT9) were tested. T6 (no desiccation) or T7 (5 min-desiccation) treatments with 40 ^M ABA in B5 medium exhibited the highest number of normal plantlets (68% and 63%, respectively).