Molecular Characterization and Epidemiology of Onion Yellow Dwarf Virus (OYDV) in Allium Crop Production Areas

Abstract

Onion and other Allium crops are of high economic importance worldwide, but their production is severely constrained by viral diseases that reduce bulb yield, quality, and storage life. Among these, Onion Yellow Dwarf Virus (OYDV), a member of the genus Potyvirus, is recognized as a major pathogen causing yellow streaking, dwarfing, leaf deformation, and overall plant decline. The present study was undertaken to investigate the molecular characterization and epidemiology of OYDV in major Allium crop production areas. Field surveys were conducted across different cultivation regions, and symptomatic and asymptomatic plant samples were collected for analysis. Total RNA was extracted from samples and subjected to reverse transcription polymerase chain reaction (RT-PCR) using OYDV-specific primers targeting conserved genomic regions. Amplified products were sequenced and analyzed for molecular identity and phylogenetic relationships using BLAST and comparative sequence analysis tools. Epidemiological data including disease incidence, spatial distribution, and association with environmental and agronomic factors were recorded to understand virus spread dynamics. The results confirmed the widespread occurrence of OYDV in symptomatic Allium plants, while asymptomatic samples showed no amplification. Sequence analysis revealed high nucleotide similarity with previously reported OYDV isolates from different geographical regions, indicating genetic conservation with some degree of variability among isolates. Phylogenetic analysis demonstrated clustering of isolates into distinct groups, suggesting possible regional differentiation and multiple introduction events. The epidemiological assessment indicated higher disease incidence in fields with dense planting, high aphid activity, and overlapping cropping cycles. The study provides important insights into the molecular diversity and epidemiology of OYDV in Allium production systems and highlights the need for effective virus management strategies. Early detection, vector control, and use of virus-free planting material are essential for minimizing losses and ensuring sustainable Allium cultivation.