Cucumber green mottle mosaic virus: A persistent seed‐borne threat to cucurbits

Abstract

Cucumber green mottle mosaic virus (CGMMV; Tobamovirus viridimaculae , Virgaviridae ) is a mechanically transmitted plant virus that poses a major threat to cucurbit (cucumber, watermelon, melon and squash, among others) production worldwide. Its virions are rigid, non‐enveloped, rod‐shaped particles (~300 nm × 18 nm) composed of helically arranged monomers of the coat protein (CP) which encapsidate a positive‐sense (+) single‐stranded RNA genome (~6.4 kb). The CGMMV (+) RNA encodes two replication‐associated proteins, a movement protein, and the CP. CGMMV virions are extremely stable and can persist for extended periods in plant debris and on contaminated surfaces. The virus is primarily associated with Cucurbitaceae , but it can infect plants from other families. Two major genetic types are recognized: Clade I and Clade II, often assimilated to European (EU) and Asian (AS) types, respectively, with Clade II isolates typically causing more severe symptoms and spreading globally. Transmission occurs mainly via mechanical contact, including through contaminated soil and tools, irrigation water, and infected seed, with seed‐to‐seedling transmission ranging widely from <0.1% to ~70%. Infected plants display stunting, foliar mosaic and deformation, and fruit discoloration and malformation, leading to severe economic losses. Resistances are available in commercial cultivars but do not abolish virus multiplication. Effective control requires integrated management combining prevention, rapid detection, and containment. CGMMV also serves as a valuable model for studying molecular interactions between cucurbits and viruses, and for gene functional studies in this plant family.