Rice stripe virus

Rice stripe virus (RSV)
Virus classification
Group: Group V ((-)ssRNA)
Order: Unassigned
Family: Unassigned
Genus: Tenuivirus
Species: Rice stripe virus

Rice stripe virus (RSV) is an RNA plant pathogen of the genus Tenuivirus.[1] RSV is prevalent in Japan, China, and Korea and can infect plants of the family Poaceae, which include wheat and corn (see maize stripe virus).[2] Damage from this disease causes major reductions in rice crop yield every year.[2]

It is spread primarily by Laodelphax striatellus, a small planthopper that feeds and damages rice plants by sap-sucking.[3] Three other planthopper insects that transmit RSV include Unkanodes sapporona, Unkanodoes albifascia, and Terthron albovittatum. The virus propagates in the planthopper and is passed down to 90% of a female's eggs.[4] However, mechanically transmitting the virus by injecting sap from an affected plant to a healthy plant has not been widely successful.[4]

Symptoms

Rice plants are susceptible to infection starting at the seedling age. The only known means of virus transmission is via planthoppers. Typical symptoms of RSV include pale and discontinuous yellow stripes, blotches, and dead tissue streaks on the leaves.[5] Severe infections cause grey necrotic streaks and result in the death of the plant.[6]

Young plants

Infection causes the most damage during seedling stage to maximum tillering stage[7] because during this time interval, the plants are at a higher risk of death.[5] Affected seedlings are stunted in growth with leaves that elongate without unfolding. Their color pales to white with drooped, curled, dead leaves. In Japan, this disease was called "Yurei Byo" (ghost disease) because of these symptoms.[7] If the plants grow, they produce few, if any, tillers and panicles with empty spikelets.

Mature plants

Infected mature plants do not have severe chlorosis or blotches, but ripening may be hindered. They can still produce rice, but with less vigor.[5]

Structure

The virus is made up of four ssRNA segments, seven open reading frames,[2] a nucleocapsid protein, and an RNA polymerase protein. It is 8 nm in diameter[1] and 500-2000 nm long.[6]

Epidemics

This table from KnowledgeBank.irri.org summarizes reported epidemics of RSV.[5]

Year Country Area Affected (ha) Reference
1960s Japan 500,000 Maeda et al. (2006)
1960s Eastern and Southern China 2,660,000 Wang et al. (2008)
1963-67 Japan 500,000 to 620,000 annually Nemoto et al. (1994)
1973 Japan 620,000 Ou (1985)
1973 Taiwan 1,045 Lee (1975)
1986 Japan 170,000 Nemoto et al. (1994)
Not indicated Yunnan Province, China 67,000 Wang et al. (2008)
2002 Jiangsu Province, China 780,000 Wei et al. (2009)
2003 Jiangsu Province, China 957,000 Wei et al. (2009)
2004 Jiangsu Province, China 1,571,000 Wei et al. (2009)
2005-06 Zhejiang Province, China 100,000 Wang et al. (2008)
2007 Zhejiang Province, China 17,600 Zhu et al. (2009)
2007-08 Korea 84% of rice fields Jonson et al. (2009)

Prevention

The lowland rice plants in Japan (japonica-type) are easily afflicted by RSV, however, upland japonica-type,indica-type, and Javanese varieties are resistant genetically. Hybrid varieties Chugoku 31 and St No1 were bred in Japan by crossing japonica-type cv. Norin No 8 with indica-type Modan. The offpring of this cross was then crossed with cv. Norin 8. Chugoku 31 and St No1 have been used to breed different varieties of RSV resistant rice plants in Japan.

Since the 1950s, Japanese rice farmers have adopted the practice of planting rice early in the season. This allows the plants to grow passed the tillering stage by the time planthoppers immigrate from wheat and barley plants.[5]

References

  1. ↑ 1.0 1.1 Xiong (2008)
  2. ↑ 2.0 2.1 2.2 2.3 Wei (2009)
  3. ↑ Zhang (2010)
  4. ↑ 4.0 4.1 4.2 Gingery (1983)
  5. ↑ 5.0 5.1 5.2 5.3 5.4 Castilla 2009
  6. ↑ 6.0 6.1 "Rice Stripe Virus" (2000)
  7. ↑ 7.0 7.1 Rice Stripe Tenuvirus (2013)

Bibliography