Exogenous Melatonin Improves Pear Resistance to Botryosphaeria dothidea by Increasing Autophagic Activity and Sugar/Organic Acid Levels.

ABSTRACT

Pear is an important fruit tree worldwide, but it is often infected by the pathogen Botryosphaeria dothidea, which causes pear ring rot disease. To explore the effect of exogenous melatonin on the disease resistance of pear, we treated inoculated pear fruits with different concentrations of melatonin. The results showed that 100 µΜ of melatonin had the most significant effect with resistance to B. dothidea. In addition, melatonin treatment significantly reduced the diameter of disease lesions and enhanced the endogenous melatonin content in pears inoculated with B. dothidea. Compared with the control treatment, melatonin treatment suppressed increases in reactive oxygen species (ROS) and activated ROS-scavenging enzymes. Treatment with exogenous melatonin maintained ascorbic acid-glutathione at more reductive status. The expression levels of core autophagic genes and autophagosome formation were elevated by melatonin treatment in pear fruits. Silencing of PbrATG5 in Pyrus pyrifolia conferred sensitivity to inoculation that was only slightly attenuated by melatonin treatment. After inoculation with B. dothidea, exogenous melatonin treatment led to higher levels of soluble sugars and organic acids in pear fruits than H2O treatment. Overall, our results demonstrate that melatonin enhances resistance to B. dothidea by increasing autophagic activity and soluble sugar/organic acid accumulation.