Cowpea mild mottle virus (Carlavirus vignae) identified as one of the agents associated with veinal necrosis and bud blight disease in soybean (Glycine max L.) in India.

Soybean plants showing the symptoms of veinal necrosis and bud blight were examined to identify the associated viral agent. Transmission electron microscopy revealed the flexuous and filamentous virus particles. DAC-ELISA of symptomatic samples confirmed the presence of cowpea mild mottle virus (CPMMV) while other tested viruses GBNV, SMV, SVNV, TSV and TRSV were found to be absent. RT-PCR using CPMMV coat protein (CP) gene primers consistently produced an 867-bp amplicon, whereas amplification was not observed for other viruses confirming its association with the disease. Sequence analysis of the CPMMV CP gene showed 99% similarity with Indian urdbean isolate (MH345698) followed by other CPMMV isolates (89-98%) and clustered phylogenetically distinct from Brazil, China and Ghana isolates. Mechanical sap inoculation resulted in 30-60% transmission efficiency across host species. Nicotiana benthamiana exhibited severe systemic infection and seedling wilting, indicating high susceptibility. Cowpea and French bean developed systemic chlorosis and necrosis, while soybean genotypes showed restricted symptoms. DAC-ELISA, RT-PCR and RT-qPCR confirmed CPMMV infection, with viral copy numbers ranging from 8.54 × 10⁵ to 5.7 × 10⁸ in field-collected soybean and 4.7 × 10⁸ in N. benthamiana. Cowpea and French bean accumulated moderate viral loads, whereas soybean genotypes Pusa-12 and PS-1670 supported limited replication. No other viruses were detected. These results conclusively establish CPMMV as the causal agent of veinal necrosis and bud blight disease in soybean and demonstrate its differential infectivity and accumulation across host species. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-025-04640-8.