Study of the effect of azelaic acid on phenyl alanine ammonia lyase enzyme activity in response to cucumber downy mildew

Downy mildew caused by Pseudoperonospora cubensis is one of the most damaging diseases of cucurbits, including cucumber. Treatment of plant products with inducers to complement or replace the effect of chemical fungicides for disease control is of particular interest. Azelaic acid is a natural compound that induces plant defense responses through a priming mechanism. The objective of this study was to investigate the effect of azelaic acid on Phenylalanine ammonia lyase enzyme activity in cucumber tissues before and after inoculation with downy mildew causal agent. In this study, cucumber plantlets were inoculated with pathogen two days after treated with azelaic acid. PAL enzyme was measured at ۶, ۱۲, ۲۴, and ۷۲ hours post-inoculation using a spectrophotometer. The results showed that PAL enzyme activity increased in Aza-treated plants at ۶ and ۷۲ hours compared to the control. Also, the enzyme content increased at ۱۲ hours post-inoculation with the pathogen and then gradually decreased to the lowest amount in ۷۲ hours. In Aza-treated plants, the enzyme content increased significantly after inoculation with the pathogen, indicating that Aza treatment can play a positive role in disease resistance. The findings of this study show that Azelaic acid can be used as a natural, simple, and inexpensive compound in plant disease control programs.