Salicylic acid impact on Penicillium digitatum and Alternaria alternata in vitro and post-harvest lemon diseases

Lemons are susceptible to the post-harvest decay caused by Penicillium digitatum and Alternaria alternata, causing the green mold and black rot disease, respectively. The current study aimed to investigate the potential impact of salicylic acid (SA) as a natural defense inducer on radical growth, spore germination, and disease development afflicted by P. digitatum and A. alternata. Antifungal activities of SA were determined in vitro by plating fungal cultures on medium supplemented to various SA concentrations (0, 1, 2, 4, 6, 8, and 16 mM). Our in vitro experiments demonstrated that SA significantly reduced conidial germination and the radial growth of both pathogens in a dose-dependent manner. Moreover, in vivo assays confirmed that SA remarkably reduced lesion diameter on the lemon fruits treated by 8- and 16-mM SA before inoculation by both tested pathogens. To sum up, we suggested a potential implication of SA as a post-harvest treatment to control P. digitatum and A. alternata on a lemon at commercial scales.