Biological Control of Green Mould Decay in Postharvest Chinese Bayberries by Pichia membranaefaciens

The effect of the yeast antagonist Pichia membranaefaciens for control of green mould decay caused by Penicillium citrinum or Verticicladiella abietina and natural decay in postharvest Chinese bayberries (Myrica rubra Seib & Zucc.), and the possible mechanisms were investigated. The results showed that 1 × 10⁹ colony‐forming units (CFU)/ml of washed cell suspensions of the yeast provided better control of green mould decay than yeast in culture broth at the same concentration. Treatment with cell‐free culture filtrates or autoclaved cell cultures had little effect on disease incidence. The concentration of a washed cell suspension of P. membranaefaciens had a significant effect on efficacy in controlling disease incidence. At a concentration range from 1 × 10⁶ to 1 × 10⁹ CFU/ml, the higher the concentration of the antagonist, the lower was the incidence of the disease. In the inoculated wounds of Chinese bayberries, populations of P. membranaefaciens increased by approximately 145‐ and 41‐fold, respectively, after incubation at 20°C for 2 day or at 1°C for 8 day. P. membranaefaciens significantly induced activities of two defence‐related enzymes chitinase and β‐1, 3‐glucanase in Chinese bayberries. The in vitro experiment showed that spore germination and germ tube elongation of the two pathogens were markedly inhibited by washed cell suspensions of P. membranaefaciens. In addition, P. membranaefaciens significantly reduced natural decay in Chinese bayberries. These results indicate that P. membranaefaciens can effectively reduce fruit decay possibly by directly inhibiting pathogen growth and indirectly by inducing disease resistance. Thus, we suggest that P. membranaefaciens has potential as a biocontrol agent to control fruit decay in Chinese bayberries during postharvest storage.