Identification and Characterization of Three Novel Solemo-like Viruses in the White-Backed Planthopper, Sogatella furcifera

White-backed planthoppers (WBPH; Sogatella furcifera, Hemiptera: Delphacidae) serve as significant vectors for rice viruses and harbor various insect-specific viruses (ISVs). In this study, we identified three previously unknown viruses that infect WBPH, which are classified under the plant-associated viral family Solemoviridae. Interestingly, these viruses were assigned to an unclassified clade, indicating the presence of novel viral taxa within the Solemoviridae family. To further explore the characteristics of these viruses, we analyzed vsiRNA (virus-derived small interfering RNA) patterns. The analysis revealed that Sogatella furcifera solemo-like virus 1 (SFSolV1) and Sogatella furcifera solemo-like virus 2 (SFSolV2) exhibit typical dicer-mediated patterns of vsiRNA, similar to those found in leafhoppers, grasshoppers, thrips, and whiteflies. Furthermore, we successfully obtained the full genome of SFSolV1 and observed a 100% infection rate in our laboratory WBPH populations. Moreover, our investigation into the infection and distribution characteristics of SFSolV1 demonstrated that this virus is more abundant in male adults compared to female adults. These findings highlight the need for further research to better understand the interactions between this virus and insects. Agricultural insects play a crucial role in transmitting plant viruses and host a considerable number of insect-specific viruses (ISVs). Among these insects, the white-backed planthoppers (WBPH; Sogatella furcifera, Hemiptera: Delphacidae) are noteworthy rice pests and are responsible for disseminating the southern rice black-streaked dwarf virus (SRBSDV), a significant rice virus. In this study, we analyzed WBPH transcriptome data from public sources and identified three novel viruses. These newly discovered viruses belong to the plant-associated viral family Solemoviridae and were tentatively named Sogatella furcifera solemo-like virus 1-3 (SFSolV1-3). Among them, SFSolV1 exhibited a prevalent existence in different laboratory populations, and its complete genome sequence was obtained using rapid amplification of cDNA ends (RACE) approaches. To investigate the antiviral RNA interference (RNAi) response in WBPH, we conducted an analysis of virus-derived small interfering RNAs (vsiRNAs). The vsiRNAs of SFSolV1 and -2 exhibited typical patterns associated with the host's siRNA-mediated antiviral immunity, with a preference for 21- and 22-nt vsiRNAs derived equally from both the sense and antisense genomic strands. Furthermore, we examined SFSolV1 infection and distribution in WBPH, revealing a significantly higher viral load of SFSolV1 in nymphs' hemolymph compared to other tissues. Additionally, in adult insects, SFSolV1 exhibited higher abundance in male adults than in female adults.