Fiji maize rough dwarf disease

Fijivirus zeae, widely known in its pathogenic manifestation as the Maize Rough Dwarf Virus (MRDV), is a complex viral agent belonging to the Reoviridae family. It causes severe developmental disruptions in susceptible host plants, primarily impacting the plant's vascular anatomy and disrupting systemic transport of nutrients and growth hormones.

The primary host for this virus is maize (Zea mays), though the pathogen has a host range that includes various wild grasses. These alternative hosts serve as critical overwintering sites for the virus, ensuring that the inoculum is available in the field environment to initiate new infection cycles every spring when temperature conditions become favorable for insect vector activity.

Symptoms of the infection typically include extreme dwarfing, shortened internodes, and the development of small galls or enations on the undersides of leaves and stems. These enations give the affected parts of the plant a rough, textured appearance. Infected plants often exhibit excessive tillering, dark green discoloration, and poor grain fill, which can result in near-total crop failure in highly susceptible hybrid varieties.

The transmission mechanism is highly specific and relies exclusively on planthopper vectors, most notably Laodelphax striatellus. The virus is acquired by the insect during feeding on infected plant phloem. Once acquired, the virus multiplies within the vector and is transmitted to healthy corn plants during subsequent feeding sessions, turning the planthopper into a long-term carrier of the disease.

Management of Fijivirus zeae requires a multifaceted approach focused on preventing the initial infection. Growers should prioritize the planting of resistant maize hybrids that show lower susceptibility to viral replication. Furthermore, controlling weed populations in and around fields is essential to remove potential virus reservoirs, while timely insecticidal applications during the early vegetative stages can effectively suppress vector populations and reduce secondary spread.