ABSTRACT Tobacco streak virus (TSV), a thrips‐transmitted member of the genus Ilarvirus (Family Bromoviridae ), is an emerging pathogen responsible for substantial yield losses in cotton across South and Central India. During the 2018, 2019 and 2025 cotton‐growing seasons, roving field surveys conducted in North‐Western India recorded plants showing characteristic TSV‐like symptoms, including dark purple spreading necrotic lesions, diffuse ring spots with multiple necrotic patches on leaves, and necrosis of bracts and floral squares on tender plant tissues. Disease incidence in farmers' fields of Haryana, Punjab and Rajasthan ranged from 0.1% to 80%. Virus association was confirmed using a sequence‐based molecular approach: amplification of the coat protein (CP) gene by RT‐PCR, Sanger sequencing of amplicons, submission of sequences to the NCBI GenBank database, and phylogenetic placement with authenticated TSV isolates. Additional support was obtained by sap transmission assays and RT‐LAMP detection. Phylogenetic analysis demonstrated 99–100% nucleotide identity (Accession nos. MN542181, MN542180) with reference TSV isolates from other crop hosts. Earlier reports of TSV in cotton were mainly based on symptom observation or serological assays without sequence verification or phylogenetic characterisation of cotton isolates. The present study therefore provides the first molecular confirmation of natural TSV infection in Bt cotton BG‐II hybrids ( Gossypium hirsutum ) from North‐Western India, extending validated knowledge of the virus host range and regional distribution.
Gawande et al. (2026) studied this question.