APPROACHES FOR REDUCING EXPLANT BROWNING OF "CANGXILI" PEAR ( PYRUS PYRIFOLIA NAKAI) IN TISSURE CULTURE

The explants of Cangxili, a pear ( Pyrus pyrifolia Nakai) genotype, were found to grow well on the medium MS+1.0 mg/L BA+ 0.02 mg/L NAA. The explants were soaked in a solution containing 8-hydroxyquinoline (8-HQS) for different time duration, the treatment for 20 min gave the most satisfactory results: it prevented the browning of the explants and had no inhibiting effect of their growth, with a browning rate of 10% and a survival rate of 90%. In contrast, 8-HQS treatment for 2 hr resulted in a 100% browning and 0% survival. Survival rate varied with the season of explant collection. Highest browning rate occurred in explants collected in April. From May on, the browning rate decreased, and it was reduced to 0 in October. In antioxidant treatments, lower temperature plus 20 min 8-HQS (0.002 mg/L) or sodium benzoate (0.2 mg/L) before inoculation appeared to be optimum for reducing browning rate and improving survival of the explants.