Screening of Bacteria as Antagonist against Xanthomonas oryzae pv. oryzae, the Causal Agent of Bacterial Leaf Blight of Paddy and as Plant Growth Promoter

The aim of this study is to screen and characterize bacteria isolated from different sources that has potential as antagonistic bacteria against Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial leaf blight of paddy and as a plant growth promoter. Ninety three bacteria were successfully isolated from different sources including compost, rhizosphere, water, roots and leaves from paddy field. By using chloroform vapours method, only 16 bacterial isolates showed positive antagonistic activity indicated by inhibition zone around bacterial colony against Xoo on nutrient agar plate. Twelve antagonistic bacteria were able to produce protease indicated by clear halo zone around bacterial colony on skim milk agar. Fourteen antagonistic bacteria were able to produce cellulase indicated by clear zone against red colour of congo red. Fifthteen antagonistic bacteria were able to produce lipase indicated by crystallize zone around bacterial colony. All antagonistic bacteria were able to produce siderephore which exhibited by orange halo zone around bacteria colony on CAS agar. All 16 antagonistic bacteria were able to produce IAA indicated by red colour development of antagonistic bacterial culture supernatant mixed with Salkowski reagent. Only 13 antagonistic bacteria were able to solubilize phosphate shown by clear halo zone around the bacteria growth on NBRIP agar. All antagonistic bacteria were able to fix nitrogen indicated by colour change of Nitrogen free agar from green to blue. Molecular identification by 16s rRNA amplification successfully identified the antagonistic bacteria as Bacillus sp. (5), Acinetobacter sp. (2), Bacillus licheniformis (1), Pseudomonas putida (1), Burkholderia cepacia (1), Bacillus amyloliquefaciens (1), Staphylococcus warneri (1), Pantoea vagans (1), Pantoea sp. (1), Oceanobacillus oncorhynchi (1) and Paenibacillus cineris (1)