Ecological Characteristics and Vector-Driven Mechanisms of Rice Viral Diseases in a Tropical Island Agroecosystem

Rice viral diseases are emerging threats to tropical agroecosystems, yet their spatiotemporal dynamics and transmission ecology remain poorly understood. From 2021 to 2023, systematic field surveys were conducted across 13 rice-growing regions of Hainan Island, China, to assess virus incidence, diversity, and vector associations. Six known rice viruses were detected via RT-PCR, and virome profiling was performed using rRNA-depleted transcriptome sequencing. Brown planthopper (Nilaparvata lugens, BPH) abundance and virus-carrying rates were measured to evaluate their association with rice ragged stunt virus (RRSV) outbreaks. Virus incidence varied markedly across ecological zones and seasons: the semiarid to semihumid transitional zone showed the highest infection rates (approximately 45%), while humid and mountainous areas showed minimal detection. Incidence peaked in summer and autumn and was significantly higher in late-season rice. Virome analysis identified 18 RNA viruses, including nine novel species, spanning multiple viral families. Twelve viruses were detected in BPH and seven in rice, with RRSV being the most prevalent in both. Correlation analysis revealed a strong association between RRSV incidence and BPH virus-carrying rate (R² = 0.40, P < 0.001), but not with vector abundance. These results underscore the ecological and vector-related drivers of rice virus epidemics in tropical systems and support viruliferous vector monitoring as a tool for disease forecasting.