M. RAMABHADRA RAJUVUNDAVALLI SWETHA BINDU2023-12-262023-12-262023-12-26D6448https://krishikosh.egranth.ac.in/handle/1/5810204450In the present study, on “Studies on diversity of Rhizoctonia solani Kuhn infecting rice in Godavari zone of Andhra Pradesh and its management” survey during kharif 2021 in ten villages from each district of West and East Godavari district. Survey revealed that the sheath blight disease severity was recorded highest in Maruteru (45%) and lowest in Seethanagaram (34%). Studies on cultural and morphological variability of twenty Rhizoctonia spp. isolates obtained from West and East Godavari districts of A.P. indicated that maximum radial growth was observed in WSB21-1 (9.00 cm) with high growth rate of (1.25 mm h-1). Colony colour varied from White (8/1 7.5YR), light brown (6/3 7.5YR), pale brown (6/3 10YR), brownish yellow (6/6 10YR), light yellowish brown (6/3 2.5Y). Six types of growth patterns were observed. Variation in sclerotia colour was observed viz., light brown, dark brown, brown and black brown. Different patterns of sclerotia were observed. Three different types of sclerotia distribution was observed i.e., aerial, surface and surface and aerial. Two types of sclerotia texture were observed i.e., rough and smooth. Time taken for sclerotial formation varied from three to seven days. Sclerotia number varied from 0 to 60. xiv Sclerotial width among isolates ranged from 1.56 to 2.63 mm (ESB21-3). Hyphal width varied from 3.82 (ESB21-4) to 14.68 μm (ESB21-3). Molecular variability was done for all twenty isolates by using ITS and Rhizoctonia specific primers. Among twenty isolates, twelve isolates amplified for Rs2.1 primer indicating that the isolates belong to AG2-1 and AG-8. One isolate was amplified using RoGr-1 primer indicating that isolate as R. oryzae. One isolate amplified by Rs8 primer indicating WSB21-2 belongs to AG-8. In vitro studies of fungicides revealed that Hexaconazole 5% SC, Thifluzamide 24% SC and Carbendazim 50%WP were found superior in inhibiting the R. solani at all concentrations i.e., upto R/5 (200 ppm). In vitro studies of organic extracts revealed that vitex leaf extract was effective against both mycelial growth and sclerotial production of R. solani, whereas, Dried ginger buttermilk extract was effective against only on sclerotial production of R. solani, however, Cow dung + Urine + Asafoetida was found effective against only on mycelial growth of R. solani. Jeevamrutham was found effective at lower concentrations viz., R/4 (2500 ppm) and R/5 (2000 ppm), whereas Bael leaf extract was found siginificantly superior upto R/2 (5000 ppm) in case of filter sterilized extracts on mycelial growth of R. solani. Pot culture studies of fungicides revealed that azoxystrobin 11%+ tebuconazole 18.3% found effective against sheath blight followed by thifluzamide 24% SC and hexaconazole 5% SC. Among the organic extracts, Sour buttermilk followed by Beejamruth, Cow dung + Urine + Asafoetida whereas, treated check carbendazim 75% WP also found effective with highest per cent inhibition.EnglishThesis