Effects of Latent Infection of Preharvest Pathogens and Inhibition of Post-harvest Gray Mold of Red Globe Grapes Treated with Salicylic Acid

To clarify the influence of salicylic acid(SA)sprayed at pre-harvest on latent infection and post-harvest gray mold of grapes,isolated and identified the main latent pathogens during the growth of Red Globe grapes,and studied the inhibition effect of salicylic acid to pathogens,and the influence on expression of related resistance genes. Red Globe grape was used as the experimental material and was sprayed with different concentration of SA solution(0,0.5,1.0,2.0 mmol/L)respectively in the same period,including the period of swelling,color change and 2 days before harvest(pre-harvest period). Tissue separation method was used to isolate latent infection pathogenic fungi that invaded grapes in different periods. Through the morphological characteristics observation and molecular phylogeny identification,the main species of latent infecting fungi were identified,the diameter changes and incidence of spots were counted after inoculated with Botrytis cinerea in grapes,and the expression change of resistance genes were detected. The results showed that SA treatment could reduce the latent infection rate of pathogenic fungi significantly during grape growth and development before harvesting,and had control effects on latent infection at different parts of grape obviously. The effect of SA treatment group was better than other groups,and the control effects of SA on latent infection to the bottom and pedicle were better than the top and stem of the grape under 1.0 mmol/L SA. The total of four main latent pathogenic fungi species were isolated and identified during the growing period,including Botrytis cinerea,Alternaria alternate,Penicillium discolor and Aspergillus niger. The treatment of 1.0 mmol/L SA could increase the resistance of grape to Botrytis cinerea significantly when inoculated with Botrytis cinerea after grape post-harvest,which could induce the up-regulation of VvPAL1,VvChi4D and VvGlu1 expression genes in grapes,and could induce the up-regulation of VvPAL2,VvPAL7 and VvPAL15 genes expression in the mid-and late stage. SA could increase the resistance to pathogen latent infection of Red Globe grape pre-harvest,and had a significant inhibitory effect on gray mold at grape post-harvest.