The Southern Rice Black-Streaked Dwarf Virus (SRBSDV), a plant virus disease first identified in China, has been detected in north Indian paddy fields. The virus is currently causing fears of reduced crop yields, especially at a time when extreme weather events have already hampered grain production.
Rice accounts for 40% of India’s total food grain basket.
Rice plants infected with the virus exhibit dwarfism, stiffness, and darkening of leaves. It is transmitted by the white-blacked planthopper that sucks on the sap of young plants, interfering with root development and plant growth.
The rice dwarf virus was first discovered in Guangdong Province, China, in 2001. It was confined to China for a couple of years before spreading to other countries such as Vietnam and Japan.
According to Rajbir Sing, director of the Agricultural Technology Application Research Institute, the incidence of the virus was mostly reported from crops planted in June. Crops planted in July did not show any signs of infection.
“Laboratory analysis showed the presence of virus in both the infected young plants and the body of the vector after the RNA was isolated,” he added.
The Indian government fears that the outbreak might add to losses caused by erratic southwest monsoon rainfalls. The area under paddy cultivation has been 6% lower in August this year compared to the same period last year.
An eight-member committee of experts formed by the Ministry of Agriculture and Farmers’ Welfare visited 24 fields located in the state of Punjab, Haryana, and Uttarakhand which were the areas most affected. From the collected samples, it was observed that between 2 to 10% of rice plants were affected, while some fields had an infection rate as high as 50%.
Singh said, “We observed that the disease mostly affected hybrid seed crops.”
Farmers had been advised to not flood their paddies with water and to monitor the plants for the presence of the vector on a weekly basis.
Investigations are currently underway to determine how the virus arrived in India and how it works against rice plants.
Gopala Krishana, the principal scientist at the Indian Agriculture Research Institute, stated, “Currently, we assume that the vector is ‘long-range migratory’ in nature, which would probably come through human routes. We are trying to decode the whole mechanism of the spread of the virus.”
While infected paddy plants die, scientists are not ready to estimate the extent of possible loss.
“Loss is certain, but we have no figures yet — it is still under monitoring and assessment,” a scientist in the investigating committee said.