Molecular Epidemiology and Coat Protein Diversity of Cucumber Green Mottle Mosaic Virus in Cucurbit Greenhouses

Abstract

Molecular epidemiology and coat protein diversity of Cucumber green mottle mosaic virus (CGMMV) was investigated in cucurbit greenhouse production systems to assess virus incidence, genetic variability, and transmission dynamics. Leaf and fruit samples exhibiting mottling, chlorosis, deformation, and reduced vigor were collected from cucumber, melon, and watermelon crops and screened using reverse transcription polymerase chain reaction (RT-PCR) with CGMMV-specific primers. High virus incidence was detected across multiple greenhouse units, indicating widespread dissemination under protected cultivation conditions. Sequencing of the coat protein gene from representative isolates revealed nucleotide substitutions and amino acid changes among populations from different host species and greenhouse locations. Phylogenetic analysis grouped all isolates within the CGMMV clade, with distinct subclusters reflecting geographic and host-associated variation. Despite observed variability, conserved genomic regions within the coat protein gene suggest functional constraints essential for viral assembly and stability. Molecular epidemiological analysis indicated potential mechanical transmission through contaminated tools, irrigation systems, and handling practices commonly associated with greenhouse management. No strong host-specific segregation was observed, although minor clustering suggested localized adaptation. Disease severity was strongly associated with intensive cultivation practices, high plant density, and inadequate sanitation measures, which facilitated rapid virus spread. The study highlights the importance of molecular surveillance for early detection and monitoring of CGMMV in protected cucurbit systems.