Defense Responses of Salicylic Acid in Mango Fruit Against Postharvest Anthracnose, Caused by Colletotrichum gloeosporioides and its Possible Mechanism

The effects and mechanisms of salicylic acid (SA) on defense response to Colletotrichum gloeosporioides from mango fruits were investigated by in vitro and in vivo test. In vitro experiment results showed that SA significantly reduced mycelial growth of C. gloeosporioides in a concentration-dependent manner. SA effectively controlled anthracnose decay on inoculated mango fruit, as well as natural infection. Disease incidence and lesion diameter in SA-treated fruit were significantly lower than those of the control fruit. SA treatment increased the activities of chitinase, -1,3-glucanase, phenylalanine ammonia-lyase and polyphenoloxidase, and the content of total phenolic compounds and lignin in mango fruit. Moreover, SA treatment effectively maintained fruit firmness by suppressing conversion of insoluble protopectin into water soluble pectin. And correlation analysis showed there is a higher negative correlation between fruit firmness and disease incidence. These findings suggest that the effect of SA on postharvest diseases was attributed to its direct antimicrobial activity and the elicitation of resistant responses, as well maintaining the firmness in mango fruit. Therefore, SA treatment is a promising measure for controlling postharvest anthracnose rot in mango. Practical ApplicationsInduction of fruit resistance against pathogenic infection with biological or chemical elicitors has been thought to be a promising approach for controlling of postharvest diseases and reducing the use of synthetic fungicides. Anthracnose, caused by Colletotrichum gloeosporioides is the predominant postharvest disease in mango production that causes severe postharvest losses and fruit quality deterioration. SA is a natural plant substance involved in plant defense responses to biotic stresses. The present results from in vitro and in vivo experiment suggested that SA treatment could effectively inhibit mycelial growth of C. gloeosporioides, enhance resistance of mango fruit against the pathogen and reduce anthracnose rot, as well maintain fruit firmness. Hence, SA can be applied in mango storage and preservation.