Effects of nano-zinc oxide treatment on black spot and blue mold of postharvest apple

The effect of nano-zinc oxide at different concentrations against A.alternata and P.expansum of pathogenic bacteria in postharvest apple was demonstrated. Results indicated that nano-zinc oxide inhibited significantly the mycelium growth of A.alternata and P.expansum, and the inhibition efficacy was greatly enhanced when the concentration of nano-zinc oxide was increased. The inhibited ratio of 20% of nano-zinc oxide was respectively up to 86.85% and 49.60%, the former inhibitory effect was significantly better than the latter. The spore germination of A.alternata were 87.37% lower than the control after treatment with 20% zinc oxide. While the concentration of 15% zinc oxide treatment on P.expansum spore germination, the germination rate had dropped by 94.56% compared with the control. Lesion diameter of apple inoculated with A.alternata and P.expansum were decreased by nano-zinc oxide treatment when concentration at 5% showed the most effective, the lesion diameter reduced by 76.24% and 65.32% compared with the control. The higher concentration treatment did not increase the effect. It was suggested that nano-zinc oxide treatment could directly inhibit pathogens to decrease black spot and blue mold of postharvest apple. Key words:apple;nano-zinc oxide;alternaria alternata;penicillium expansum