LAUSR

Abstract Auxin is a vital plant growth regulator and can also take a part in plant defense. The study focused on the efficacy of the major active form of auxin, indole-3-acetic acid (IAA), on inhibition of blue mold rot caused by Penicillium expansum in pear fruit wounds and the possible action mechanisms involved. Results indicated that IAA at 100–500 μg mL−1 significantly enhanced the resistance of pear fruit against blue mold rot when the treating interval was between 24 and 48 h, while it had no direct antifungal activities towards P. expansum in vitro. Moreover, IAA induced a significant increase on the activities of β-1,3-glucanase (GLU), chitinase (CHI) and phenylalanine ammonia-lyase (PAL) in pear fruit. Furthermore, the data revealed that the expressions of endoglu9, CHI4, PR1, PR4 and PAL were up-regulated substantially in pear fruit treated with IAA. The all findings highlight the efficiency of IAA on inducing the natural resistance of pear fruit against P. expansum and suggest that the mechanisms may be closely related to the elicitation of defense-related enzymes and genes.