First report of southern rice black streaked dwarf virus associated with rice dwarf symptoms in Indian Punjab

摘要

In the North Indian rice-growing regions of Punjab and Haryana, specifically, reports of a mystery dwarfing phenomenon began to flood in during the kharifl 2022 season. The typical symptoms included stunted/dwarfed plants that failed to grow even after application of recommended dosages of nutrients. In other instances, severe stunting was seen, leaving rice plants only half or a third of their typical size (Fig. 1). The dwarf plants showed shorter, dark green and stiff leaves and had shallow roots which could be easily uprooted. Eventually, the infected plants began to wither. These plants were observed in almost all the cultivated varieties in the farmers’ fields. Regardless of the variety, the stunting was more obvious in the early-sown paddy crop than the late-sown. The stunting symptoms were observed in 5-7 per cent of the fields in Fatehgarh Sahib, Patiala, SAS Nagar, Ropar and Ludhiana districts of Punjab. In the affected fields, the incidence of stunted plants ranged from 1 to 6 per cent.However in some isolated fields, the disease incidence was reported to be as high as 20 per cent. There were two rounds of sampling. In the first round, a total of 22 plant samples (Table 1) were collected from the farmers ’ fields during the surveys conducted. Seven of these appeared to be apparently healthy plants, whereas 15 were dwarfed plants. These samples included whole tillers from the infected as well as healthy plants. After detaching from the plant, these were sealed in polybag and immediately kept on dry ice in ice-box and brought to laboratory for analysis. The samples were kept at -30 deg C before processing.