First Report of Tomato Brown Rugose Fruit Virus (ToBRFV) Infecting Commelina communis in China

Tomato brown rugose fruit virus (ToBRFV; genus Tobamovirus, family Virgaviridae) is an emerging plant pathogen noted for its high infectivity and epidemic potential. While initially confined to solanaceous crops, subsequent studies have shown that ToBRFV can cross family boundaries to infect plants in the Amaranthaceae, Apocynaceae, and Asteraceae (Salem et al., 2022), demonstrating strong cross-family transmission capacity. In May 2024, tomato (Solanum lycopersicum) plants showing chlorosis and rugosity symptoms were confirmed positive for ToBRFV in a greenhouse in Shandong Province, China, using reverse transcription-recombinase aided amplification with lateral flow strip (RT-RAA-LFS) assays (Cao et al., 2023). From the same location, five symptomatic Commelina communis (Commelinaceae) plants exhibiting interveinal chlorosis were also collected. All samples tested positive for ToBRFV using reverse transcription-recombinase aided amplification with lateral flow strip. Total RNA was extracted from symptomatic C. communis plants. Five overlapping fragments were amplified by reverse transcription polymerase chain reaction, and the 5’ and 3’ untranslated regions were obtained using the SUPERSWITCH RACE cDNA Synthesis Kit (Tiosbio, Beijing, China) (Wang et al. 2025). The complete genome (6,384 nt) was obtained by bidirectional Sanger sequencing of overlapping PCR fragments and assembled with DNAMAN v8.0. The sequence has been deposited in the China National GeneBank under accession number CNA0146566. Sequence comparison was performed using BLAST at the NCBI website, revealing 99.77% and 99.81% nucleotide identity with the Jordan isolate KT383474.1 and the Israel isolate KX619418.1, respectively. ToBRFV infection was further confirmed by reverse transcription quantitative PCR (RT-qPCR) using EPPO 2021 primers and probes, and western blot analysis on symptomatic leaves collected from field samples. To assess infectivity, crude sap prepared from symptomatic C. communis leaves (100 mg tissue per 1 mL 1× PBS) was mechanically inoculated onto healthy Nicotiana benthamiana (five plants), tomato cv. ‘Micro-Tom’ (five plants), and C. communis (five plants). Within 10 days, all mechanically inoculated plants developed typical ToBRFV symptoms, including chlorosis and leaf deformation. Infection in these symptomatic plants was confirmed by RT-qPCR and western blot analysis. In contrast, negative control plants inoculated with 1× PBS remained asymptomatic and tested negative for viral infection by RT-qPCR. This is the first report of natural ToBRFV infection in a monocotyledonous plant. The successful infection of C. communis indicates that this common weed can serve as a novel host, substantially expanding the known host range of ToBRFV from dicotyledonous to monocotyledonous species, with important implications for virus ecology and cross-species transmission risk.