Molecular Characterization of a Chilli Veinal Mottle Virus Isolate and Determination of Key Factors Influencing Its Transmission to Tobacco by Myzus persicae

Abstract

Chilli veinal mottle virus (ChiVMV, Potyvirus capsivenamaculae) is an emerging potyvirus threatening tobacco production in China, but its transmission biology remains poorly understood. Here, we molecularly characterized a ChiVMV isolate based on the coat protein (CP) gene from tobacco collected in Huaping, Yunnan Province, China. The CP gene consisted of 861 nucleotides encoding 286 amino acids and shared 95.25% identity with global isolates. Phylogenetic analysis placed the isolate within the Yunnan clade. We systematically investigated the effects of acquisition access period (AAP), inoculation access period (IAP), vector density, and temperature on transmission efficiency by Myzus persicae. qPCR assays revealed that a 5 min AAP was sufficient to achieve a viral load comparable to the maximum, whereas extending the AAP to 20 min resulted in reduced acquisition. Viral load in aphids declined progressively after acquisition, with residual amounts at 0.5 h, 1 h, 12 h, and 24 h post-acquisition representing 37.5%, 21.3%, 5.6%, and 2.9% of the initial copy number per aphid, respectively. Transmission assays showed that the highest efficiency was achieved under the tested conditions with an AAP of 5 min, an IAP of 24 h, a density of 5 aphids per plant, and a temperature of 25 °C. A significant interference between AAP and IAP was also observed. These findings provide insights into ChiVMV epidemiology and establish standardized conditions for resistance screening and transmission studies.