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Rice tungro virus

Rice tungro disease is caused by the joint infection of two viruses: rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV). It is one of the most economically important viral diseases of rice in South and Southeast Asia.

Identification and symptoms

Infected plants show stunting, reduced tiller production and yellow to orange discoloration of leaves, beginning at the leaf tip. Affected hills bear short, partly emerged panicles with high spikelet sterility. Disease appears in patches reflecting vector flight patterns and field-edge effects.

Host crops and life cycle

The vector is the green leafhopper, Nephotettix virescens (and N. malayanus), which transmits both viruses semi-persistently. Acquisition takes a short feeding period and transmission likewise. Inoculum sources include infected ratoons, weed hosts and overlapping crops. Because the leafhopper transmits both viruses simultaneously, joint infection is the norm, and only joint infection produces the full disease syndrome.

Damage and economic impact

Tungro can cause severe losses, particularly under continuous-cropping systems with overlapping rice stages that maintain leafhopper populations year-round. Outbreaks have historically forced rotation of resistant varieties in countries including India, Bangladesh, Indonesia, Malaysia and the Philippines.

Management

  • Resistant varieties: IRRI and national programmes release tungro-resistant lines as the principal control. Rotation of resistance sources is recommended to slow virus or vector biotype evolution.
  • Vector control: monitoring of green leafhopper populations and judicious insecticide use targeting the vector before symptomatic plants appear. Insecticides effective against Brown Planthopper Paddy often also reduce leafhopper populations.
  • Cultural: synchronised planting across blocks reduces overlapping rice stages and breaks the vector's host continuity.

See also: Brown Planthopper Paddy, Brown Planthopper Paddy 2, Paddy Blast Disease, Bacterial Leaf Blight Paddy, Transplanting Paddy.

References

  1. Tungro. IRRI Rice Knowledge Bank.
  2. Green leafhopper. IRRI Rice Knowledge Bank.