New Delhi: A research team from the premier Indian Agricultural Research Institute (IARI), Delhi, has found that the severe stunting that’s being reported in rice crops in India’s Green Revolution bowl was caused by a virus that was discovered in China over 20 years ago.
First reported in Guangdong, China, in 2001, the Southern Rice Black-streaked Dwarf virus has led to yield losses in Asian countries including China, Vietnam, and Japan.
Typical symptoms include pronounced stunting, darkening of leaves, and white waxy or black-streaked swellings along the veins on stems of rice plants, according to a research paper published in the journal Plant Pathology.
However, the IARI report has found a limited incidence of the disease in the areas surveyed during its field investigation in northwestern India.
“On an average, there was around 1 per cent incidence of stunt disease in rice across the surveyed locations… in the affected fields, the disease incidence varied from 2-10 percent,” a summary of the investigation report seen by ThePrint said.
The stunting is severe, with the affected plants reaching up to a quarter of the height of a normal plant.
“We have confirmed beyond doubt that the Southern Rice Black-streaked Dwarf virus is the cause of stunting. The vector (which transmits the virus) is the white-backed planthopper,” A.K. Singh, the director of IARI, told ThePrint.
Planthoppers are a group of small jumping insects that feed on a wide variety of plants.
“Farmers have been advised to use insecticides to effectively control planthoppers… Milky grains from infected plants were also subjected to tests which ruled out the possibility of seed transmission,” Singh added.
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How the virus was found
The IARI conducted a survey of the affected fields in Sonepat, Panipat, Karnal, Kurukshetra, Ambala, and Yamunanagar districts in Haryana.
Researchers found that the diseased plants have poorly-developed root systems, which affect nutrient delivery from soils.
The IARI has advised farmers and seed growers against using the infected crop to sow seeds for next season’s crops. State governments have also been advised not to allow infected plots for seed certification purposes.
According to the IARI report, a comprehensive investigation using three independent methods — transmission electron microscopy, RT-PCR, and real-time RT-PCR — was carried out to help detect the virus.
The infection was confirmed in 12 different varieties of both basmati and non-basmati rice. These include PB1962, PB1121, PB1509, PR114, PR136, PR130, PR131, Pioneer Hybrid, Swift Gold (manufactured by Bayer), and CSR 30.
“This is conclusive evidence of the association of Southern Rice Black-streaked Dwarf virus with rice stunt disease and its presence in white-backed planthopper vectors. Further, the absence of virus in seeds of infected plants revealed that it is not seed-transmitted,” IARI said in the summary report of the investigation.
According to the Punjab Agricultural University, Ludhiana, the stunting disease was first reported mid-July across several districts in Punjab — including Fatehgarh Sahib, Ludhiana, Hoshiarpur, and Mohali.
The university has advised farmers to inspect fields and spray insecticides to kill planthoppers that could transmit the virus to healthy plants.
(Edited by Uttara Ramaswamy)
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