Paddy dwarfing: PAU decodes mystery, blames virus first reported in China

University Vice-Chancellor Dr Satbir Singh Gosal, said that a team of scientists, including Dr Gurvinder Singh, director, Department of Agriculture and Farmers’ Welfare, Punjab; Dr P P S Pannu, ADR (NR&PHM), Dr A S Dhatt, director of research, PAU, Dr G S Mangat, ADR (Crop Improvement), and Dr Mandeep Singh Hunjan, principal plant pathologist, managed to decipher the mystery behind stunting in rice in the shortest possible time.

Dr Dhatt said it was in mid-July that PAU started receiving complaints of stunted paddy plants. “The samples were collected from different districts and analysed for the detection of different rice pathogens, including nine viruses and one phytoplasma. The laboratory analysis was carried out using PCR-based molecular markers on all diseases of rice. These markers indicated the presence of  SRBSDV in the analysed samples,” said Dr Dhatt.

To further confirm it, PAU scientists said the molecular marker amplified DNA fragments from the samples sequenced. Resulting data showed more than 99 per cent similarity to already reported or published SRBSDV sequences. The sequenced data has also been submitted to National Centre for Biotechnology Information (NCBI), an international genomic database.

Scientists said that in addition to rice, SRBSDV also infects different weed species as nymphs of WBPH can transmit the virus more efficiently as compared to adults. They said long-distance transmission of this virus may occur through WBPH migrating with the typhoons and strong convection winds.

They said that since there was no corrective measure for the viral disease, farmers should regularly monitor the crop for the presence of WBPH and a few plants should be slightly tilted and tapped 2-3 times at the base at weekly intervals. Secondly, if WBPH nymphs/adults are seen floating on water, then insecticides, including Pexalon 10 SC (triflumezopyrim) @ 94 ml/acre or Osheen/Token 20 SG (dinotefuran) @ 80 g/acre or Chess 50 WG (pymetrozine) @ 120 g/acre, can be sprayed towards the base of the plants.

Last but not the least, scientists said that in future, the farmers are advised to follow the transplanting dates advised by PAU since stunting was observed to be more in the early transplanted crops. It will not only help in managing the viral disease but also save water.

Many farmers in Punjab and Haryana have been complaining about stunted rice plants for the past 20-25 days. The height of the stunted plants showed a reduction from 1/2 to 1/3rd of the normal plants. These plants had shallow roots and could be easily uprooted. Such plants were observed in almost all the cultivated varieties in the farmers’ fields. Dwarfing of plants was reported at 10% to 25% in general and in some cases, it exceeded 40%. In the beginning, it was related to mineral deficiency, weather conditions and/or may be caused by typical rice viruses. The stunting had also been observed in different varieties planted in trials at PAU, Ludhiana. In these trials, the stunting incidence had been observed to be associated with the date of transplanting as it was more in the period of June 15 to June 25 transplanting as compared to the crop transplanted after June 25.