Serratia nematodiphila CT-78 was previously shown to be antagonistic against Xanthomonas oryzae pv. oryzae, thus reducing rice bacterial leaf blight. This study examined the changes in activities of the two defense-related enzymes polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) to clarify whether induced resistance contributes to the disease-reducing effect of S. nematodiphila CT-78. Applications of 10⁷ CFU/mL CT-78 suspensions by seed soaking, foliar spraying and their combination significantly induced both PPO and PAL activities at early stages which peaked up at 2 days after pathogen inoculation. The combined application of seed soaking and foliar spraying of CT-78 showed stronger and continuous inductions of the enzyme activities 0-7 days after pathogen inoculation. Detection of hydrogen peroxide (H₂O₂) accumulation in rice leaf tissues supported the involvement of induced resistance in the observed disease reduction. H₂O₂ accumulated in a higher level in leaf tissues of rice plants treated with CT-78 suspensions and inoculated with the pathogen compared to those either treated with CT-78 suspensions or inoculated with the pathogen alone. This indicates enhanced oxidative responses in rice plants against pathogen infection. The results show that the application of S. nematodiphila CT-78 induces resistance at early stages to protect rice plants against bacterial leaf...