Isolation and screening of nitrogen fixing endophytic bacterium

Abstract

The present study is on the isolation, characterization and screening of endophytic bacterium i.e., Gluconacetobacter diazotrophicus which was isolated from the tissues of surface sterilized roots of four different crops viz., sugarcane, maize, pineapple and carrot. The morphological and biochemical tests permitted characterization of Gluconacetobacter diazotrophicus isolates. Further the plant growth promoting traits such as nitrogen fixing ability, production of phytohormones (Indole acetic acid and Gibberellic acid), phosphorus and zinc solubilization and antagonistic activity by dual culture method were assessed. Out of 113 isolated screened only 10 efficient isolates from various crops were selected based on nitrogen fixing capacity. An isolate from sugarcane GdS25 fixed maximum nitrogen i.e., 147µg of N/mg of Carbon used and produced maximum concentration of Indole acetic acid (4.94µg/ml) and Gibberellic acid (7.1µg/25ml) respectively. GdS25 showed phosphorus solubilization zone of hydrolosis 2.1cm where as zone of zinc solubilisation of 3.5cm. An isolate from sugarcane GdS25 exhibited 83% inhibition against Rhizoctonia bataticola and 88% against Exerohilium maydis. The GdS25 is more potent as compared to the reference strain G. diazotrophicus MTCC1224.Five efficient isolates viz., GdS25, GdS26, GdM5, GdM6 and GdP7 will be taken up for further studies.