Southern Rice Black-streaked Dwarf Virus behind stunted paddy across Punjab: PAU
This is the first incident of the Southern Rice Black-streaked Dwarf Virus, a double stranded RNA virus that was initially reported in 2001 from Southern China, in Punjab
Amid reports of dwarfing of paddy plants across the state, Punjab Agricultural University (PAU) has revealed Southern Rice Black-streaked Dwarf Virus (SRBSDV) to be the cause behind same.
This is the first incident of the viral disease, a double stranded RNA virus that was initially reported in 2001 from Southern China, in Punjab,
After conducting a conference with the experts on Friday, PAU vice-chancellor (V-C), Dr Satbir Singh Gosal shared that SRBSDV is the real cause behind stunting of rice. Director, department of agriculture and farmers’ welfare, Punjab, Dr Gurvinder Singh, director of research, PAU, Dr A S Dhatt, additional directors of research Dr PPS Pannu, Dr GS Mangat and rice scientists were among those present in the conference.
Dr Dhatt elaborated that rice crop in Punjab was known to be affected by many bacterial and fungal diseases lately, but it was in mid July of this year that PAU started receiving complaints of stunted rice plants in farmers’ fields. Within a month, the complaints were received from almost all parts of Punjab and its adjoining states.
The experts stated that the infected plants were stunted with narrow erect leaves, with both roots and shoots of the plants severely affected. In severely infected rice fields, the infected plants showed withering. The height of the stunted plants showed reduction from 1/2 to 1/3rd than the normal plants. These plants had shallow roots and could be easily uprooted. These plants were observed in almost all the cultivated varieties in the farmer’s fields.
The team of PAU scientists visited different districts of the state to systematically decipher the cause behind these stunted rice crops. The laboratory analysis revealed the presence of Southern Rice Black-streaked Dwarf Virus (SRBSDV) in the analyzed samples. To further confirm the presence of virus, the molecular marker amplified DNA fragments from the samples were sequenced. The sequence data analyzed using online genomic databases showed more than 99 percent similarity to already reported/published SRBSDV sequences. The sequence data has also been submitted in the National Centre for Biotechnology Information (NCBI), an international genomic database.
In the trials conducted by the university, the stunting incidence has been observed to be associated with the date of transplanting as it was more in the crop transplanted between June 15 to 25 as compared to the crop transplanted after June 25 June. The team observed that the incidence was more pronounced in early sown paddy crops irrespective of the variety. The analysis of soil and plant samples collected from the affected fields showed no relationship of stunting with nutrition deficiency.
As per the earlier published scientific reports from elsewhere, SRBSDV is transmitted by white backed planthopper (WBPH) in persistent circulative and propagative manner. Nymphs of WBPH can transmit SRBSDV more efficiently as compared to their adults. Long distance transmission of this virus may occur through WBPH migrating with the typhoons and strong convection winds. The viruliferous WBPH nymphs and adults may transmit SRBSDV to rice plants at different growth stages.
Dr Gosal congratulated the team of rice scientists especially,Principal Plant Pathologist Dr Mandeep Singh Hunjan for deciphering the mystery of stunting in rice in the shortest possible time.
PAU issues advisory for farmers
The experts stated that as there is no corrective measure for the viral diseases, the only way out is to adopt preventive measures for managing the vector of this viral disease. Issuing an advisory for the farmers, the experts stated that farmers should regularly monitor the rice crop for presence of WBPH. A few plants in the field should be slightly tilted and tapped 2-3 times at the base at weekly intervals. WBPH nymphs/adults, if present, will be seen floating on water.
Further the farmers are advised to spray any of the insecticide on observing the WBPH viz. Pexalon 10 SC (triflumezopyrim) @ 94 ml/acre or Osheen/Token 20 SG (dinotefuran) @ 80 g/acre or Chess 50 WG (pymetrozine) @ 120 g/acre. For better results direct the spray towards the base of the plants.
The experts further advised to follow the transplanting dates recommended by PAU since stunting was observed to be more in early transplanted crops. It will not only help in managing the viral disease, but also save the water.