Molecular Characterization and Coat Protein Phylogeny of Broad Bean Wilt Virus-2 Infecting Leguminous Crops

Abstract

Broad bean wilt virus 2 (BBWV-2) infecting leguminous crops was investigated to determine its molecular characteristics, genetic diversity, and coat protein phylogeny across different host species. Field surveys in legume-growing regions revealed typical viral symptoms including mosaic patterns, leaf distortion, chlorotic mottling, stunted growth, and reduced pod formation in infected plants. Leaf samples collected from symptomatic and asymptomatic hosts were subjected to reverse transcription polymerase chain reaction (RT-PCR) using BBWV-2-specific primers targeting the coat protein gene. Amplification confirmed widespread occurrence of BBWV-2 across multiple leguminous hosts, indicating natural host range expansion under field conditions. Sequencing of representative isolates revealed nucleotide substitutions and amino acid variations within the coat protein region, suggesting ongoing evolutionary divergence among field populations. Phylogenetic analysis grouped all isolates within the BBWV-2 clade, showing close relationships with global reference isolates but forming distinct subclusters associated with host type and geographic origin. The observed genetic variability indicates moderate diversification likely driven by host adaptation and vector-mediated transmission dynamics. Despite variability, conserved genomic regions within the coat protein gene suggest functional constraints essential for viral stability and infectivity. Disease incidence was higher in mixed cropping systems and areas with high aphid vector activity, highlighting the epidemiological importance of vector dynamics in virus spread. The study emphasizes the need for continuous molecular surveillance of BBWV-2 in leguminous crops to monitor emerging variants and support effective disease management. These findings contribute to understanding the molecular epidemiology and evolution of BBWV-2 and provide a foundation for developing diagnostic tools and resistance breeding strategies in legume production systems.