Endophytic Bacterial Population in Philippine Sugarcane Cultivars and Isolation of Nitrogen-fixing Strains

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The number of endophytic bacteria in the stem of sugarcane cultivars collected from different sites in the Philippines ranged from 10⁴ to 10⁹ cells ml^-1 juice. Bacterial population was correlated with the sugar content (% Brix) of the juice and varied depending on the cultivar and sampling site. Twenty-eight isolates had a positive reaction in the acetylene reduction assay (ARA). Presumptive tests indicated that 15 isolates were putative strains of Acetobacter diazotrophicus, 5 isolates showed similar characteristics to those of Herbaspirillum seropedicae, and 8 isolates consisted of Herbaspirillum rubribalbicans-like strains. This study confirmed the existence of N₂-fixing endophytic bacteria in sugarcane cultivars in the Philippines.