Isolation and Characterization of Sesbania Root Nodule Endophytes for PGP, Biocontrol and Biodegradation Properties

Abstract

This work deals with study of endophytes harbouring Sesbania rostrata which has till now been exploited only for root and shoot nodulation properties, their mechanism and organisms involved in the same.The plant is important in the context that it is a broad range host for most rhizobial species, with its special feature of forming root as well as stem nodulation, its wide usage as green manure to improve soil organic content and also as livestock feed. These important properties of the plant make it important to identify and characterize the endophytes that harbour this plant and provide it such multiple properties. In an attempt to identify Sesbania rostrata root nodule endophytes, plants from different location were collected, nodules were taken and 8 distinct organisms were isolated of which two belong to Rhizobium sp., two belong to Bacillus sp., two belong to Enterobacteriaceae and one is an uncultured clone close to Rhizobium sp. as established by biochemical properties, ARDRA pattern and partial 16S rRNA sequencing. Based on initial tests, isolates were analyzed for their capacity of phosphate solubilization (tricalcium phosphate and rock phosphate), phytase production, IAA production, glyphosate and monocrotophos degradation and production of lytic enzymes like cellulose, chitinase and xylanase. Of these 8 isolates, three isolates were positive for all the parameters tested. These three isolates namely R1, RM1 and R43 belonged to Sinorhizoiumsp., Bacillus sp. and Erwinia sp. respectively. To the best of my knowledge, phytase and chitinase production by rhizobia has not been reported yet. All three isolates were able to degrade approximately 40% of supplemented glyphosate (30mM) and 30% 0f supplemented monocrotophos (20mM) which is again not reported for rhizobia. Phytase production and organophosphate degradation is known for Bacillus sp., Pseudomonas sp. and Enterobacter sp.only. These multipurpose isolates can be employed for checking plant growth promotion and organophosphate degradation under field conditions.