Benzoic acid inhibits peach root development via disrupted auxin distribution

Allelopathic effects are commonly observed in plant communities, with benzoic acid (BA) identified as a primary autotoxin contributing to peach replanting disease. However, the effects of BA on peach root growth remain unclear. In this study, we evaluated the morphological changes in peach roots and the auxin signaling responses to BA stress. Our results showed that BA treatment significantly reduced root length and inhibited lateral root emergence. Gene expression analysis revealed that several auxin-related genes, such as PpARF19 , PpAUX1 , PpYUCCA10 , were significantly reduced after BA treatment. Using transgenic peach roots with the DR5::GUS auxin reporter, generated through our optimized non-sterile root transformation protocol, we observed that BA treatment disrupted the DR5::GUS expression pattern in root tips and lateral root primordia. Hormone measurements indicated a slight reduction in auxin accumulation and a significant increase in the auxin antagonistic hormone salicylic acid. These findings suggest that BA induces autotoxicity in peach plants by impairing root growth through alterations in auxin signaling and biosynthesis pathways. This study enhances our understanding of allelopathic effects in plant interactions and provides valuable insights for mitigating challenges in peach orchards.