Rice Grassy Stunt Virus (RSGV)

Disease name | Symptoms | Confirmation | Problems with similar symptoms | Why and where it occurs | Causal agent | Host range | Life cycle | Mechanism of damage | When damage is important | Economic importance | Management principles | Selected references | Contributors

Plant damage (IRRI)

Diagnostic summary

Damage to plants	symptoms of virus infection no panicle production
Signs and symptoms	stunting excessive tillering very upright growth habit grassy and rosette appearance leaves short, narrow, and yellowish green with numerous small rusty spots or patches, which form blotches infected plants usually survive until maturity, but produce no panicles the symptom develops 10-20 days after infection
Factors favoring disease development	availability of the vector all growth stages especially the tillering stage of the rice crop

Full fact sheet

Disease name	Rice grassy stunt virus (RGSV)
Symptoms	Diseased hills are severely stunted with excessive tillering and a very upright growth habit Diseased hills has a grassy and rosette appearance Leaves short, narrow, and yellowish green with numerous small rusty spots or patches, which form blotches Retention of green coloration of the leaves after application of sufficient nitrogenous fertilizers Infected plants usually survive until maturity, but produce no panicles The symptom develops 10-20 days after infection Infected plants (IRRI) Infected plant (IRRI)
Confirmation	The grassy or rosette appearance of the infected plant easily distinguishes the diseased plant from the normal plants. Severe stunting with yellow and rusty spots on leaves is prominent.
Problems with similar symptoms	Stunting and increased tillering symptoms can be confused with the rice yellow dwarf and rice dwarf disease.
Why and where it occurs	The virus exists in the vector and in the rice crop. Brown planthopper nymphs and adults transmit it where rice is grown year-round. RGSV is generally endemic. The macropterous forms or the long winged adults of the insect are important in spreading the disease than the short winged forms. They feed on the diseased plant for at least 30 minutes to pick-up the virus. Higher infection is attained after prolonged inoculation feeding periods of up to 24 hours. The availability of the vector encourages the damage.
Causal agent or factor	The grassy stunt virus is transmitted by the brown planthopper Nilaparvata lugens Stal. The disease can also be transmitted by Nilaparvata bakeri Muir and N. muiri China. The interaction between the virus and its vector is persistent without transovarial passage. The insect acquires the virus during at least 30 minutes of feeding period. The plants can be infected in as little as 9 minutes of feeding. Incubation in the insect takes around 5-28 days with an average of 11 days, whereas in plants, incubation ranges from 10 to 19 days. Viruliferous insects remain infective for life. Rice grassy stunt virus (RGSV) is a member of the Tenuiviruses. It has fine filamentous particles, which are 6-8 nm in diameter. It has a nodal contour length of 950-1,350 nm. The particles have one capsid protein and the genome is made up of four single-stranded RNA.
Host range	The disease is only found in the rice crop.
Life cycle
Mechanism of damage	Both nymphs and adults of brown planthopper transmit grassy stunt virus. The insects can get the virus by feeding on diseased plants in a 6 hr-acquisition access period (minimum of 30 minutes). Longer feeding periods of up to 24 hours caused higher percentage of infected insects. After a latent period of 5-28 days (average of 10-11 days), the brown planthoppers can transmit the virus in an inoculation access period of several minutes to 24 hr (minimum of 5-15 minutes). The infected insects can transmit the virus until they die.
When damage is important	The disease affects all growth stages of the rice crop. Infected plants live until maturity, however, the most vulnerable plant growth stage is tillering, and at which infected hills produced no panicles.
Economic importance	The grassy stunt virus is not a widespread problem. It became a serious problem during brown planthopper outbreaks in 1975 to 1977 in Indonesia. During sporadic outbreaks, it can cause serious damage in limited areas. For example, yield loss is higher when infection occurs early in the season.
Management principles	A single dominant gene governs resistance. A strain of wild rice, Oryza nivara Sharma & Shastry, was found to be resistant to the pathogen. The control of brown planthopper, either with chemical, resistant varieties, or other control measures, result in the control of RGSV.
Selected references	Cabauatan PQ, Hibino H. 1991. Monoclonal antibodies for detection of rice viruses: grassy stunt, dwarf, gall dwarf, and ragged stunt. In: Maramorosch K, editor. Biotechnology for biological control of pests and vectors. Boca Raton, Florida (USA): CRC Press, Inc. p 119-131. Hibino H, Usugi T, Omura T, Tsuchizaki T, Shohara K, Iwasaki M. 1985. Rice grassy stunt virus: a planthopper-borne circular filament. Phytopathology 75:849-899. International Rice Research Institute (IRRI). 1983. Field problems of tropical rice. Manila (Philippines): IRRI. 172 p. Ling KC. 1972. Rice virus diseases. Manila (Philippines): International Rice Research Institute. 134 p.
Contributors	Suparyono, JLA Catindig, and PQ Cabauatan