Multitarget antifungal mechanism of 5-aminolevulinic acid hydrochloride on black spot rot of sweet cherry fruit against Alternaria alternata

Black spot rot in sweet cherries, caused by Alternaria alternata infection, severely restricts the marketing of sweet cherries. This study aimed to evaluate the inhibitory effects of 5-aminolevulinic acid hydrochloride (5-ALA hydrochloride) on A. alternata and its possible mechanism. The development of A. alternata in vitro was completely suppressed by 60 g L −1 of 5-ALA hydrochloride treatment. 5-ALA hydrochloride induced morphological alterations and cytoplasmic leakage, suggesting the disruption of the cell membrane, as verified through propidium iodide staining. Laser scanning confocal microscopy observations revealed that 5-ALA hydrochloride led to the formation of reactive oxygen species, indicating the occurrence of intracellular oxidative stress. While black spot symptoms were significantly reduced under 5-ALA hydrochloride treatment. Further research revealed that 5-ALA hydrochloride altered the transcript levels of A. alternata . The expression of cell wall disintegration-related genes was activated by 5-ALA hydrochloride treatment. Based on these results, we concluded that 5-ALA hydrochloride control of black spot rot can be carried out through multiple targets and that 5-ALA hydrochloride can be applied as an ideal fungicide. • 5-aminolevulinic acid hydrochloride inhibited A. alternata growth in vitro and vivo. • 5-ALA hydrochloride disrupted the membrane integrity of A. alternata. • 5-ALA hydrochloride inhibited MDA accumulation and ROS production of A. alternata. • 5-ALA hydrochloride changed the morphology and ultrastructure of A. alternata. • Transcriptional mechanism of 5-ALA hydrochloride against A. alternata was analyzed.