Effects of the antiauxin PCIB on microspore embryogenesis and plant regeneration in Brassica rapa

An efficient protocol to improve microspore embryogenesis and plant regeneration in Brassica rapa was established. The antiauxin p-chlorophenoxyisobutyric acid (PCIB) was used to enhance microspore embryogenesis and plant regeneration without an intervening callus phase. All the 4 tested genotypes responded positively to PCIB. The optimum concentration of PCIB application was found to be 40 μM in NLN-13 medium, which resulted in a 3.4- to 6.2-fold increase in the number of embryos (8.27–19.2 embryos per bud) and a 9.6-fold increase (21.33%) in the plant regeneration frequency in comparison with the controls. Heat-shock treatment by incubation at 35 °C for 1 day was more efficient in inducing embryogenesis in the 2 tested genotypes. The embryos, produced in NLN medium supplemented with 40 μM PCIB and transferred at the 21-day-old followed by a treatment at 4 °C for 5 days, reached the highest direct plant regeneration rate of 58.00%.