Rice Yellow Mottle Virus

GS3 – Agriculture

Context

• The Rice Yellow Mottle Virus (RYMV) is severely impacting rice cultivation across Africa, posing a significant threat to food security.

Origin & Spread

• Historical Origin: Likely emerged in the 19th century in the Eastern Arc Mountains of East Africa, transferring from wild grasses to cultivated rice.
• First Identification: Detected in 1966 near Kisumu, Kenya, during efforts to intensify rice production.

Virology

• Virus Type: Belongs to the genus Sobemovirus.
• Genetic Traits: Known for high genetic variability, which complicates resistance and control efforts.

Transmission Routes

• Insect Vectors:
  • Beetles (family Chrysomelidae)
  • Grasshoppers
• Animal Vectors:
  • Cows, rats, donkeys (through movement and contact)
• Mechanical & Contact Transmission:
  • Contaminated tools
  • Direct leaf-to-leaf or root contact
  • Infected plant stubble left in the soil

Symptoms in Rice Plants

• Early Symptoms:
  • Yellow-green streaks and mottling on young leaves
• Progressive Damage:
  • Stunted growth
  • Poor tillering
  • Incomplete panicle formation
  • Sterility
  • Plant death in severe infections

Impact on Crop Yield

• Yield Losses:
  • Ranges from 25% to 100%
  • Particularly devastating in young plants and fields without protection/control measures