Leptochloa chinensis identified as a new reservoir host of southern rice black-streaked dwarf virus

Southern rice black-streaked dwarf virus (SRBSDV) is a destructive pathogen of rice that is transmitted by the white-backed planthopper (WBPH, Sogatella furcifera). Identifying infectious reservoirs within the SRBSDV cycle is critical for developing effective disease management strategies. This research identifies Chinese sprangletop (Leptochloa chinensis), a noxious weed commonly found in rice ecosystems, as a previously unrecognized natural host of SRBSDV. SRBSDV infection was detected in L. chinensis samples collected from rice paddies exhibiting SRBSDV symptoms. Transcriptomic analyses, observation of SRBSDV virions, and typical profiles of SRBSDV-derived small interfering RNAs provided evidence of active, low-level, and asymptomatic viral infection. Genomic comparisons revealed minor genetic divergence in the viral RNA-dependent RNA polymerase (RdRP) gene, suggesting host-specific adaptation without compromising transmissibility. Further investigations using transmission experiments demonstrated that WBPHs microinjected with SRBSDV obtained from L. chinensis efficiently transmitted the virus to rice seedlings at a rate of 35.7%. This study emphasizes the necessity of integrating weed management into SRBSDV control strategies to disrupt viral reservoirs and mitigate outbreaks.