Source: Times of India [summ. Mod.DHA, edited]
Scientists from Haryana Agricultural University have found that the dwarfing disease in paddy crops in the country is not only caused by _Southern rice black streaked dwarf virus_ (SRBSDV), but also by _Rice gall dwarf virus_ (RGDV). Information has also been obtained on the host range of these viruses.
SRBSDV infection has been found to be more prevalent in the disease, and this virus also affects some weeds in local wheat crops, which is a concern. There has been no instance of the virus infecting wheat in the area. Therefore, farmers should destroy weeds in wheat fields to reduce the risk of dwarfing disease in paddy crops.
The scientists continually record the distribution and spread of the viruses. They recommend regular sanitary measures for fields and irrigation drains to prevent further spread of the disease.
[Symptoms of black streaked dwarf disease (BSDD) of rice include darkening and distortion of leaves, black streaked tumours along leaf veins, as well as severe stunting of plants. BSDD due to _Rice black streaked dwarf virus_ (RBSDV; genus _Fijivirus_) has been known to cause serious crop losses in South East Asia. RBSDV also affects some other gramineous hosts including maize, wheat, oat, and barley. It is spread by planthoppers including _Laodelphax striatellus_ and _Unkanodes_ species.
_Southern rice black streaked dwarf virus_ (SRBSDV; genus _Fijivirus_) has been identified more recently and is now considered an emerging BSDD pathogen in Asia. It is transmitted by the white-backed planthopper (WBPH; _Sogatella furcifera_), which is not a vector of RBSDV, while the RBSDV vector _L. striatellus_ cannot spread SRBSDV. SRBSDV can also affect maize, sorghum, and several grasses as additional crop or reservoir hosts.
_Rice gall dwarf virus_ (RGDV; genus _Phytoreovirus_) is spread by the leafhopper _Recilia dorsalis_. It is known to occur in coinfections, for example with _Rice stripe mosaic virus_ (genus _Cytorhabdovirus_), which shares the same vector. RGDV also affects a range of cereal crops and grasses, causing severe stunting, leaf galls, and severe reduction of grain yield.
Disease management for rice viruses may include cultural practices, vector control, and use of cultivars with resistance to the virus, the vector, or both. High vector numbers are often associated with outbreaks of the viruses they transmit. This is a major concern in the region where rice crops are frequently affected by viruses and their insect vectors (see previous ProMED posts in the archives).
India (with states):
SRBSDV particles, electron micrographs:
https://www.dpvweb.net/dpvfigs/d296f02.jpg (galls) and
https://www.frontiersin.org/files/Articles/834712/fmicb-13-834712-HTML/image_m/fmicb-13-834712-g001.jpg (& rice stripe mosaic)
SRBSDV, characterisation & information:
Information on phytoreoviruses:
Review of rice viruses:
List of major rice viruses via:
Virus taxonomy via:
Information on rice planthoppers via:
http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/insects/item/planthopper (with pictures)