VIJAYA GOPAL DEPARTMENT, ABIYYANI SUMAN2016-09-092016-09-092015http://krishikosh.egranth.ac.in/handle/1/76258Sheath blight is a devastating disease caused by Rhizoctonia solani Kuhn in rice crop. Biocontrol agents have great demand now-a-days as they are replacing chemical pesticides to a large extent as they are cost effective, ecofriendly and easily available. Pseudomonas fluorescens is one among them which not only enhances the plant growth but also controls the fungal pathogens by production of anti fungal metabolites. Present investigation is focussed towards isolation of fluorescent Pseudomonas from rice rhizosphere and in vitro, in vivo evaluation of antagonistic activity of these isolated fluorescent Pseudomonas against Rhizoctonia solani causing sheath blight in rice crop. Thirty Pseudomonas fluorescens isolates were isolated from rice rhizospheric soils of twenty two villages of Parigi and Doma mandals of Rangareddy district, Telangana as the district has severe sheath blight incidence. Latitude, longitude, elevation, GPS numbers of the place of collection of soil samples are recorded and point map has been generated by using Arc GIS software and rectification of the toposheets was done by Erdas image 9.3 software. The isolates are purified by observing under UV light and they were culturally, morphologically and biochemically identified as Pseudomonas fluorescens according to Bergey’s manual of Determinative Bacteriology. Biochemical characterization revealed that all the isolates were positive for catalase, oxidase, citrate utilization, gelatine liquefaction, denitrification and negative for indole tests. These isolates were screened in vitro for Plant growth promoting attributes like phosphate solubilizatin, siderophore, IAA, ammonia and HCN production. Results revealed that 76.67% isolates solubilized phosphorous and produced siderophores. 93.33% isolates produced IAA and all the thirty isolates i.e., 100% produced ammonia and HCN. All the isolates were further screened in vitro for antagonistic activity against the fungal pathogen Rhizoctonia solani causing sheath blight and found that all isolates inhibited the fungal pathogen and highest inhibition was found with the organism DMP1 (53.43%). Pot culture experiment was conducted for in vivo evaluation of Pseudomonas fluorescens against the challenge inoculated rice crop by using various methods of inoculation. Results revealed that seed treatment method of application of Pseudomonas fluorescens with the isolate DMP1 effectively controlled and reduced the disease severity of 42.56% at 60 DAT, 41.12% at 70 DAT and 40.81% at 80 DAT caused by the Rhizoctonia solani compared with the other methods of inoculation. Seed treated plants especially with the organism DMP1 not only controlled the disease but improved the growth parameters like plant height (56 cm, 74 cm and 82.6 cm at 30,60 and 90 DAT respectively), Leaf area index (4.71 at 60 DAT), chlorophyll content (39.60 and 48.17 at 30 and 60 DAT ) and yield parameters like number of tillers (13.7, 17.3 and 17.3 at 30,60 and 90 DAT), panicles (13.7 at 90 DAT) and grain yield per plant (32.69 gms) followed by root dipping and foliar method of application of biocontrol agents. When the methods of inoculation are compared seed treatment method improved the growth and yield parameters in the challenge inoculated rice crop. When the challenge inoculated plants are scored for the disease, it was observed that the seed treated method of inoculation to the rice showed resistance towards the disease with a score of 1.2.enISOLATION, CHARACTERIZATION, RICE FIELDS, BIOLOGICAL, CONTROL, CAUSING SHEATH, BLIGHT , RICEThesis