NAGAMANI, P.KAVITHA, K2020-02-242020-02-242019http://krishikosh.egranth.ac.in/handle/1/5810143462D5869Rice (Oryza sativa L.) is an economically important cereal crop in different areas of world especially in Asia. It is severely affected by the bacterial leaf blight in regions of Asia with heavy rainfall during monsoon. BLB pathogen, Xanthomonas oryzae pv. oryzae was isolated from the diseased plants and the pathogenicity of the isolated culture was demonstrated by clip inoculation method on rice cultivar NLR 34449 and confirmed as Xanthomonas oryzae pv. oryzae. A total of 45 endophytic bacterial isolates were obtained from the healthy leaf samples of MTU-1010, BPT-5204 and NLR-34449 cultivars and out of which, 19 isolates were from nine villages spread across six mandals of the Nellore district. Similarly 26 isolates were from four villages spread across three mandals of the Chittoor district. Among the 45 endophytic bacterial isolates evaluated for the antagonistic efficacy by Agar Well Diffusion method, 12 isolates with inhibition zone diameter of more than 10.00 mm were considered for the Morphological, Molecular and Biochemical characterization. Among the 12 endophytic bacterial isolates, EMP-5 showed maximum inhibition zone of 16.8 mm followed by EBK-3 with 16.6 mm. Morphological characterization of the 12 isolates revealed the dominance of Gram negative bacteria with rod shaped cells over the Gram positive bacteria. With regard to Plant growth promoting (PGP) traits, EMP-5 showed positive for Phosphate solubilization, Siderophore production, HCN production, Ammonia Production, Amylase activity and Protease production. Molecular characterization of the selected endophytic isolates by 16S rRNA was carried for identification of bacterial endophytes. 16 S rRNA gene xv sequence of the EMP-5 isolate was compared with 16 S rRNA gene sequence available at NCBI database through BLASTN search. Isolate EMP-5 showed close similarity of 99.06 per cent with query cover of 98 per cent with Enterobacter asburiae. As per the results of the antagonistic efficacy studies and biochemical characterization, EMP-5 (Enterobacter asburiae) was selected for field studies. Among all the treatments, treatment T5 (i.e. seed bacterization with EMP-5 @ 109 cells /ml + foliar application of EMP-5 @109 cells / ml) recorded showed reduction in per cent disease index (4.92 %) increased plant growth promoting ability with plant height of 80.8 cm, increase in the no. of effective tillers (97.4 %), grain yield (5340 kg/ ha) and straw yield (6013 kg/ha) over the untreated control. Plant disease suppression and growth promotion are complex interactive processes that may be addressed by plant heightening using endophytic bacteria possessing plant growth promoting traits. The results strongly emphasize that endophytic bacteria (EMP-5) characterized in the study could be efficiently used for management of bacterial leaf blight and for plant growth promotion. The isolate has the potential to be developed into a bio-inoculant for sustainable rice production.en-USnullThesis