Accumulation of phytoalexins and alteration in plant hormone profiles in rice leaves following sap sucking by the brown planthopper and green rice leafhopper

This study investigated the accumulation of cultivar-specific phytoalexins in rice-abietoryzins and oryzalactone-as well as known phytoalexins-momilactone A, phytocassane A, and oryzalexins A and S-in response to sap sucking by the brown planthopper (BPH) and the green rice leafhopper (GRL). The analysis revealed that BPH feeding induced abietoryzin accumulation in a cultivar known to accumulate these phytoalexins following fungal infection. Additionally, oryzalactone and oryzalexin S accumulated after insect attack in specific cultivars, unlike oryzalexin A. Plant hormone profiling revealed distinct associations: momilactone A accumulation was strongly correlated with salicylic acid (SA); phytocassane A with jasmonic acid, jasmonic acid-isoleucine, isopentenyladenine, and abscisic acid (ABA); and oryzalactone/oryzalexin S with both SA and ABA. These findings suggest that distinct signaling pathways regulate the induction of specific phytoalexins. The analysis of phenolic metabolites showed only minor changes in response to insect feeding. The findings highlight the broad inducibility of phytoalexins in rice and reveal the complex hormonal regulation underlying their biosynthesis during herbivore attack.