Amino acid variations mediate the predisposition of drought stress of Carya cathayensis to Botryosphaeria canker disease.

Abiotic stresses alter the outcome of plant-pathogen interactions, mostly predisposing the host plant to pathogen infection. However, the crosstalk between plants and pathogens under abiotic stress in the predisposition remains unclear. Here, we investigated drought predisposition to the fungal pathogen Botryosphaeria dothidea (Bd) infection in Carya cathayensis. High levels of drought stress result in a significant increase in plant susceptibility to Bd. Variations in free amino acids (AAs), H2O2, and non-structural carbohydrates (NSC) in stem tissues were investigated. Drought significantly induced the accumulation of Pro, Leu, Ile, and H2O2 in the stems and decreased the NSC content. In the in vitro assays, B. dothidea was sensitive to H2O2; however, Pro played a protective role against exogenous H2O2. Leu, Ile, and Pro induced asexual reproduction of Bd. A novel model integrating the interactions of plant and pathogen responses that AA changes mediate the predisposition of B. canker disease to drought stress in C. cathayensis was proposed. Our results provide the first analysis of the drought predisposition of C. cathayensis to Botrysphaeria canker via AA accumulation.