Variability and management of rhizoctonia solani kuhn, the incitant of sheath blight of rice
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Date
2018
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CCSHAU
Abstract
Present investigation entitled ―Variability and management of Rhizoctonia solani Kuhn, the incitant of sheath blight of rice‖ revealed that Rhizoctonia solani isolates showed a considerably variation in cultural and morphological characters and pathogenic behaviour. There was no correlation of geographic location and source of isolation of the pathogen of the fungal isolates with the cultural, morphological and pathogenic clustering. ITS species specific primers indicated the intraspecific variation within R. solani isolates. R. solani was most dominant species associated with sheath blight complex in Haryana. However, R. oryzae was also found associated to the extent of 1.5%. Out of 307 rice genotypes evaluated, only one rice genotype i.e. RMS-BL-6 showed consistent resistant reaction against sheath blight during both years, indicating that resistance against sheath blight is rarely found. Among botanicals aqueous extracts of garlic cloves and turmeric powder proved effective in reducing disease severity while among fungicides azoxystrobin 18.2% + difenoconazole 11.4% SC and thifluzamide 23.9% SC proved to be the best treatments. None of the fungicide persisted till the harvest of crop i.e. 44 days after their last spray application in rice grains, cropped soil, paddy straw and husk indicating that these fungicides are safe for human, animal and environmental point of view. Among the combination of botanicals and fungicides, application of azoxystrobin 18.2% + difenoconazole 11.4% SC (1 ml/l) followed by extract of garlic cloves or turmeric powder at 50 g/l proved most effective but found out inferior to azoxystrobin 18.2% + difenoconazole 11.4% SC and thifluzamide 23.9% SC. All the herbicides inhibited the mycelial growth, sclerotial formation and sclerotial germination in vitro. Under field conditions pretilachlor 50 EC and pendimethalin 30 EC reduced the sheath blight severity alongwith significant increase in grain yield of paddy.
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