PJB-2021-542
STATUS, MOLECULAR DIAGNOSTICS OF PATHOGEN AND MANAGEMENT OF NEWLY EMERGING FALSE SMUT DISEASE OF RICE IN NORTH KARNATAKA
Gururaj Sunkad
Abstract
Rice false smut is an important emerging biotic stress caused by the fungus Ustilaginoidea virens, long been considered as minor disease, but recently it occurred frequently and emerged as a major disease in rice production in command areas of north Karnataka. A comprehensive and systematic survey was carried out to know the disease status, determine the cultural and morpho-molecular characterization of the pathogen and in vitro and in vivo evaluation of fungicides against the rice false smut during kharif 2015 and Summer, 2016 followed by large-scale and farm trails in farmers fields to identify the best fungicide during 2017-18. The results indicated that there is a variation in false smut disease severity with respect to location and season. Potato sucrose agar medium was found to be superior by recording the higher radial growth for culturing the pathogen. The mycelium of the fungus was white, acute angle branching, smooth and good growth with dark brown coloured and globular shaped chlamydospores. Mycelial width was 6.35µm and size of chlamydospore was 55.05 µm. The DNA of U. virens was successfully amplified with general ITS1 and ITS4 primers and specific UVR1 and UVR4 primers. The size of amplified DNA ranged 620 bp in general primers and 320 bp in specific primers. BLAST results revealed that the pathogen isolate belonged to the U. virens with 99 per cent homology. The new combi fungicide molecule Trifloxystrobin (25%) + Tebuconazole (50%) 75% WG was found highly effective for mycelial inhibition and management of disease under in vitro and in vivo. The fungicide was also very effective in farm and large-scale demonstration trials in controlling the false smut and also resulted higher percent increase in yield over recommended un treated check treatment. Hence, the foliar spray with Trifloxystrobin (25%) + Tebuconazole (50%) 75% WG has been recommended and included in the university package of practices of University of Agricultural Sciences, Raichur, Karnataka for the farmers of region to manage the disease.
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