First Report of Ludwigia Yellow Vein Vietnam Virus Infecting <i>Ludwigia prostrata</i> in China

Begomoviruses are economically important plant pathogens widely distributed across tropical and subtropical regions, infecting diverse dicotyledonous crops and weeds and frequently causing severe yield losses. In April 2023, plants of Ludwigia prostrata Roxb. exhibiting conspicuous viral symptoms characteristic of Begomovirus infection—including mosaic, leaf rolling, and yellow vein clearing—were observed at Nanbin Farm in Sanya, Hainan Province, China (Figure 1). To determine the causal agent, symptomatic leaf samples were collected, and total nucleic acid (TNA) was extracted using the FastPure Plant Total RNA Isolation Kit (Vazyme, RC401) following the manufacturer’s instructions, with the DNase treatment omitted. Viral metagenomics was performed on an Illumina sequencing platform (OE Biotech, Shanghai, China), yielding approximately 49.4 million high-quality reads (Q &gt; 30). After filtering out reads that mapped to the host plant genome, the remaining reads were assembled and analyzed via BLASTn against the GenBank Virus Reference Database (ftp://ftp.ncbi.nlm.nih.gov/refseq/release/viral/). Among these, 50 clean reads (150 bp, paired‑end) were found to map to the genome of Ludwigia yellow vein Vietnam virus (LuYVVNV; genus Begomovirus, family Geminiviridae), covering 58.6% of its full-length sequence. To confirm the presence of LuYVVNV, two pairs of primers (F1: 5′-GTTGTATGCTCGCTATCAAATAC-3′ / R1: 5′-TTCTGTACATTCTGTACAGTCTG-3′ and F2: 5′-GCATTCAACATGTACGACAATG-3′ / R2: 5′-CTGGGCGTTTCTTAAGAGTAT-3′) were designed for PCR amplification. Both primer pairs yielded amplicons of the expected sizes—295 bp for primer pair F1/R1 and 475 bp for primer pair F2/R2. The PCR products were purified, cloned using the TA/Blunt-Zero Cloning Kit (Vazyme), transformed into E. coli DH5α cells, and subjected to Sanger sequencing. Sequence analysis of the amplified fragments revealed 99.6% and 99.7% nucleotide identity with a LuYVVNV isolate previously reported from Hainan (GenBank: OP948731.1), confirming the infection of Ludwigia prostrata by LuYVVNV. Furthermore, based on the Sanger sequencing results, the complete genome of the LuYVVNV isolate (GenBank: PX859765.2) was amplified from the diseased leaf samples using primer pairs (F:5′-TACGACAATGAGCCCAGTACAG-3′ / R:5′-CATGTTGAATGCCTCACCGAAC-3′). An amplicon of 2,763 bp was obtained. BLASTn analysis revealed that this complete genome sequence shared the highest nucleotide identity (99.1%) with LuYVVNV-HN isolate (GenBank: OP948731.1), suggesting that the new discovered isolate is closely related to the LuYVVNV-HN isolate. LuYVVNV was first reported in 2008 from weeds in Vietnam (Ha et al., 2008) and is known to infect Ludwigia octovalvis, Impatiens balsamina, and tobacco (Wang et al., 2023). To our knowledge, this is the first report of Ludwigia prostrata serving as a natural host for LuYVVNV. This discovery not only expands the known host range of LuYVVNV but also highlights the critical epidemiological role of Ludwigia prostrata. Whiteflies serve as critical vectors for transmitting begomoviruses (Czosnek et al., 2017), while Ludwigia prostrata, with its short life cycle and strong dispersal capacity, acts as an efficient natural reservoir. Therefore, integrated weed and pest management strategies should be implemented, along with targeted viral disease prediction and weed control in crop cultivation areas, to prevent the spread of this virus to economically important crops.