Effect of combined salt and microplastic stress on the microbiota structure of the rice–oriental armyworm system

Salt and microplastic (MP) stress likely co-occur in coastal plains, yet their combined influence on multi-trophic members remains poorly understood. We investigated whether combined salt (120 mM) and polyethylene (PE-MP) (10 mg/L) stress affected biomass and microbial diversity and structure in rice and oriental armyworm. The results showed that rice biomass remained unchanged, armyworm weight decreased under individual stressors (0.17-0.19 g) but recovered under combined stress (0.21 g). Microbiota structure shifted in rice and armyworms under combined stress, except for fungal microbiota in armyworms, which were unaffected. Furthermore, significant correlations were observed among armyworm weight, fungal communities in rice, and bacterial communities in armyworms. For instance, armyworm weight was positively correlated with the Ascomycota abundance in the rice, which in turn was positively correlated with Proteobacteria abundance in armyworm, and Proteobacteria abundance was positively correlated with functional pathways. These results provide evidence of microbiota alterations in the rice-armyworm system under combined NaCl and PE exposure, highlighting the adaptation of insect to stressed plants (NaCl + PE). The observed adaptation could potentially be mediated through dynamic plant-insect microbiota interactions.