). Inoculation of rice plants with N2 fixing endophytic bacteria has resulted in increased growth and yield. Nitrogen fixing endophytic bacteria inoculation of rice seedlings has been shown to significantly increase biomass and grain yield of rice included Gluconacetobacter diazotrophicus, Serratia marcescens, Burkholderia sp. and Azoarcus sp. (Bhattacharjee et al., 2008; Choudhury & Kennedy, 2004). There is a possibility that endophytic N2-fixing bacteria might play an important role in maintaining the yield of wetland rice in the mountains of northern Thailand without fertilizer input.