Identification of a Broad Bean Wilt Virus 2 (BBWV2) Isolate (BBWV2-SP) from Spinacia oleracea L

Spinach (Spinacia oleracea L.) is an important leafy vegetable but is vulnerable to viral infections that significantly affect its quality and yield. In this study, we identified virus-infected spinach exhibiting typical symptoms with yellowing, wrinkling, and mottling in Beijing. But conventional RT-PCR screening for twelve common plant viruses yielded negative results. Then, using transcriptome sequencing along with a de novo assembly approach, we obtained the complete viral genome, which consists of RNA1 (5916 nucleotides) and RNA2 (3576 nucleotides). BLASTN analysis against the NCBI viral genome database revealed high homology with broad bean wilt virus 2 (BBWV2), leading us to designate this isolate as BBWV2-SP (GenBank accession numbers PV102464 and PV102465). Phylogenetic analysis indicated that BBWV2-SP shares 96.69% nucleotide sequence identity with a Liaoning isolate from Chenopodium album MN786955 and clusters within the Chinese evolutionary lineage. We developed primers targeting the conserved region of the RNA2 coat protein, amplifying a 478-base-pair product. All symptomatic spinach samples tested positive, while asymptomatic controls remained negative, confirming the causal relationship between BBWV2-SP and the observed disease symptoms. This study provides the complete genome assembly of the spinach isolate BBWV2-SP and establishes a molecular detection protocol for BBWV2 in spinach. These findings offer essential technical support for field monitoring, epidemiological surveillance, and disease control strategies, while also enhancing our understanding of BBWV2's genetic diversity and mechanisms of pathogenicity.