Endophytic Nitrogen Fixing Bacteria from Sugarcane (Sacharum spp.) Genotypes Cultivated in India

Sugarcane is one of the significant crop plants in India serving as a source of sugar and ethanol. It is of interest for sustainable growth of sugarcane to study the diazotrophic endophytic bacteria associated with plant. The present investigation aimed to isolate, identify and characterize the diazotrophic endophytes from internal tissue of sugarcane shoots, leaves and roots of sugarcane genotypes cultivated in India. The plant samples (roots, shoots and leaves) were collected and after surface sterilization used for isolation of nitrogen fixing bacteria on nitrogen free media. The isolates were identified on the basis of morphological, physiological and biochemical characters followed by 16S rRNA gene sequencing.The nitrogen fixing ability of the putative endophytes were estimated by microkjeldhal method.  A total of 83 putative diazotrophic endophytic bacteria were isolated from 5 genotypes of sugarcane, the isolates belonged to Genera of Azospirillum, Gluconobacter, Burkholderia, Herbaspirillum, Azoarcus and Agrobacterium. Maximum isolates were obtained from shoots followed by leaves and roots. The physiological characterization revealed that species of Gluconoacetobacter had optimum pH 4-4.5 for growth whereas other isolates grew optimally at pH 6.0-7.0. The other parameters   remained the same for most of the isolates with respect to optimum temperature (28-30°C,) NaCl concentration (0.5 to 1% (w/v) and sucrose concentration (5 to 15% (w/v). It was observed that molecular nitrogen fixed by Glucanoacetobacter sp. strain B1 isolated from shoot of sugarcane genotype Co 86032 showed maximum Nitrogen fixed (38.73 mg per gm of sucrose consumed) in vitronitrogen fixation.  Different properties viz. Nitrogen fixation ability, antimicrobial activity and PGPR production etc.  of isolates of endophytes were  studied with an objective of development and  commercial exploitation of consortium of endophytic nitrogen fixing microbial bioinoculant  in future  for increase in the yield and quality of crop with decreasing nitrogen chemical fertilizers.

Keywords: Sugarcane, diazotrophs, endophytes, Glucanoacetobacter