Integrated transcriptomics and metabolomics revealed the role of the flavonoid pathway in the resistance of Zanthoxylum bungeanum against leaf rust

Leaf rust caused by Coleosporium zanthoxyli is a destructive disease that threatens Zanthoxylum bungeanum plantations. To address this, screening for resistant cultivars and exploring their resistance mechanisms are crucial for effective disease management. However, the mechanisms underlying Z. bungeanum's resistance remain unclear. In this study, we conducted in vivo and in vitro experiments to screen for the resistant cultivar Qiujiao (QJ) and the susceptible cultivar Fengxian Dahongpao (FD). Subsequently, the resistance mechanisms of Z. bungeanum were analyzed by integrating transcriptome and metabolome, the result showed the flavonoid pathway served as the primary metabolic pathway for QJ to confer resistance against C. zanthoxyli. Upon infection with C. zanthoxyli, the key genes (PAL, CHI, and HCT) and enzymes (PAL, C4H, and 4CL) involved in the flavonoid pathway were upregulated in QJ, and the total flavonoid content was increased in QJ. Additionally, eight flavonoids from this pathway demonstrated inhibitory effects on C. zanthoxyli spore germination, with naringenin and phloretin exhibiting the stronger activity. Collectively, the flavonoid pathway plays a dominant role in the resistance of Z. bungeanum leaves against C. zanthoxyli.