Symptomatology, transmission and molecular characterization of Rustica tobacco mosaic virus (RTMV) in nicotiana rustica

Abstract

Tobacco (Nicotiana spp.) is the most widely grown commercial non-food crop in the world. Among the numerous diseases, Rustica tobacco mosaic disease is the most concerning and destructive. In recent years, it has become one of the most severe disease, causing substantial yield loss and quality degradation in tobacco across many tobacco producing regions of the world. The virus was successfully isolated and maintained through mechanical transmission using sap inoculation under controlled glasshouse conditions. Symptomatology studies revealed characteristic mosaic patterns of light and dark green patches, leaf distortion, chlorosis, stunted growth, yellowing, puckering and a distinct erect growth habit with significant reduction in both the number and size of leaves. These symptoms were consistently observed in both naturally infected plants and those artificially inoculated, validating the pathogenic nature of Rustica tobacco mosaic virus. Molecular confirmation of the virus was achieved through PCR amplification using two pairs of coat protein (CP)-gene specific primers. A ~478 bp amplicon was consistently obtained from infected samples, corresponding to the CP gene of RTMV. The amplified CP-gene sequences were confirmed as Tobacco mosaic virus and submitted to NCBI GenBank under accession number PV368839, thus validating the virus identity at the molecular level.