Influence of N fertilisation on the isolation of Acetobacter diazotrophicus and Herbaspirillum spp. from Indian sugarcane varieties

 Observations of newer diazotrophs like Acetobacter diazotrophicus and Herbaspirillum spp. in Indian sugarcane varieties is reported here for the first time. A. diazotrophicus was isolated from sugarcane plants where N fertilisation was nil, and numbers in the Indian cultivars were estimated to be up to 10⁶–10⁷ colony forming units g¹ fresh weight. N fertilisation was the limiting factor for the isolation of A. diazotrophicus, as evidenced by selective growth patterns in different concentrations of N sources, but Herbaspirillum spp. were found to occur both in N fertilised and unfertilised samples. The fact that N is not the limiting factor for Herbaspirillum spp. was evidenced in a similar study of its growth pattern in different N sources. Received: 14 May 1998