Genetic Variability of Tomato Yellow Leaf Curl Virus (TYLCV) Isolates Based on Coat Protein Gene Sequencing

Abstract

Tomato yellow leaf curl virus (TYLCV) is a major constraint in tomato production worldwide, causing severe yield losses through leaf curling, chlorosis, and plant stunting. High genetic variability among virus isolates contributes to rapid adaptation, vector transmission efficiency, and breakdown of host resistance. The present study investigated the genetic variability of TYLCV isolates based on coat protein (CP) gene sequencing. Symptomatic tomato plants exhibiting characteristic viral symptoms were collected from major cultivation areas, and viral infection was confirmed using PCR amplification with TYLCV-specific primers targeting the CP gene. Amplified products were sequenced, and the obtained nucleotide sequences were analyzed to assess genetic diversity, mutation patterns, and phylogenetic relationships among isolates. The results revealed significant nucleotide variation within the coat protein gene, indicating the presence of genetically diverse TYLCV populations across different geographical regions. Phylogenetic analysis grouped isolates into distinct clusters, reflecting both regional differentiation and possible multiple introduction events. Certain isolates showed close genetic similarity despite geographical separation, suggesting long-distance dispersal facilitated by vector populations and plant material movement. Amino acid substitutions in the coat protein region indicated potential implications for virus infectivity, host interaction, and adaptation. The observed genetic variability underscores the evolutionary potential of TYLCV and its ability to overcome resistance in tomato cultivars. The findings provide important insights into the molecular epidemiology of TYLCV and support the development of effective disease management strategies, including the deployment of resistant cultivars and integrated vector control approaches for sustainable tomato production.