Exogenous Calcium Improved Resistance to Botryosphaeria dothidea by Increasing Autophagy Activity and Salicylic Acid Level in Pear

Pear ring rot, caused by Botryosphaeria dothidea, is one of the most serious diseases in pear. Calcium (Ca 2+ ) was reported to play a key role in the plant defense response. Here, we found that exogenous calcium could enhance resistance to B. dothidea in pear leaves. Less H 2 O 2 and O 2 − but more activated reactive oxygen species scavenge enzymes accumulated in calcium-treated leaves than in H 2 O-treated leaves. Moreover, the increased level of more ascorbic acid-glutathione was maintained by Ca 2+ treatment under pathogen infection. The expression of core autophagy-related genes and autophagosome formations were enhanced in Ca 2+ -treated leaves. Silencing of PbrATG5 in Pyrus betulaefolia conferred sensitivity to inoculation, which was only slightly recovered by Ca 2+ treatment. Moreover, the salicylic acid (SA) level and SA-related gene expression were induced more strongly by B. dothidea in Ca 2+ -treated leaves than in H 2 O-treated leaves. Taken together, these results demonstrated that exogenous Ca 2+ enhanced resistance to B. dothidea by increasing autophagic activity and SA accumulation. Our findings reveal a new mechanism of Ca 2+ in increasing the tolerance of pear to B. dothidea infection.