Inhibitive effects of some treatments on the browning rate during the in vitro culture of Acacia karroo Hayne

Acacia karroo Hayne is an arbor species widely distributed in South Africa with the characteristics of fast growth and drought resistance. The species was introduced to China recently. In vitro culture is an effective method to rapidly produce plants and a strategy to minimize somaclonal variation among regenerated plants. Browning, however, is a problem in establishing the in vitro culture system. The present study diminished the problem by selecting explants, using different browning inhibitors and chilling treatment. Results showed that the use of embryos as explants reduced the browning ratio to 46.7%, whilst stem segment explants were browned up to 56.7%. The adventitious buds were successfully induced in the modified tissue culture medium supplemented with 5.0 mg·L^-1 6-BA and 0.1 mg·L^-1 NAA. The proliferation coefficient of adventitious buds is 2.8.