Partial Characterization of a Carla-Like Virus Infecting Yam (Dioscorea spp.) from China

Area of Science:

• Plant Virology
• Molecular Diagnostics
• Agricultural Entomology

Background:

• Dioscorea opposita (yam) is an important crop globally.
• Virus infections can significantly impact yam yield and quality.
• Accurate identification of plant viruses is crucial for disease management.

Purpose of the Study:

• To identify viruses affecting Dioscorea opposita imported into New Zealand.
• To characterize the identified virus using molecular and microscopic techniques.
• To determine if this represents a new host-virus association.

Main Methods:

• Post-entry quarantine testing of yam.
• Mechanical inoculation of herbaceous indicator plants.
• Electron microscopy for virus particle visualization.
• Reverse transcription-polymerase chain reaction (RT-PCR) for virus detection.
• Cloning and sequencing of viral replicase gene.

Main Results:

• No symptoms or viruses were detected directly from yam plants.
• Systemic infection, chlorosis, and stunting were observed in Nicotiana occidentalis.
• Filamentous virus particles (approx. 600 nm) were observed in symptomatic N. occidentalis.
• RT-PCR confirmed the presence of a carlavirus, distinct from other tested genera.
• Sequencing revealed high amino acid similarity to Hop latent virus, Aconitum latent virus, and Potato virus M.

Conclusions:

• A carlavirus is associated with symptomatic Nicotiana occidentalis inoculated from Chinese yam.
• This finding suggests a new host-virus association, as carlaviruses have not been previously reported in yams.
• Further research is needed to fully characterize this novel yam-infecting carlavirus.