Effects of powdery mildew infection on chloroplast and mitochondrial functions in rubber tree

Powdery mildew (Oidium heveae Steinm.) is one of the most important leaf diseases in rubber tree (Hevea brasiliensis). However, physiological and molecular processes associated with the Hevea-powdery mildew interaction are still unclear. In this study, effects of powdery mildew infection on the mitochondrial and chloroplast functions in rubber tree were comprehensively investigated. Powdery mildew damaged the structure and function of mitochondria prior to chloroplasts, causing inner and outer membranes disruption. The intact rate of mitochondria membrane was reduced from 70% in control leaves to 23.1% in the leaves at 5 days after inoculation (dai). Significant decreases in the activities of cytochrome c oxidase, NADH oxidation and malate dehydrogenase (MDH) were observed in the powdery mildew-infected leaves. Tricarboxylic acid cycle (TCA) and electron transfer capacity were seriously impaired after powdery mildew invasion. Chlorophyll (Chl) contents, maximal photochemical efficiency (Fv/Fm), actual photochemical efficiency of photosystem II (FPSII), and electron transport rate (ETR) were dramatically decreased in the infected leaves from 10 dai. Our results provided new insights into understanding the mechanism of Hevea-powdery mildew interaction in rubber tree.