Pseudomonas aeruginosa inducing rice resistance against Rhizoctonia solani: production of salicylic acid and peroxidases.

Three isolates ofPseudomonas aeruginosa were used for seed treatment of rice; all showed plant growth promoting activity and induced systemic resistance in rice againstRhizoctonia solani G5 and increased seed yield. Production of salicylic acid (Sal) byP. aeruginosa bothin vitro andin vivo was quantified with high performance liquid chromatography. All three isolates produced more Sal in King’s B broth than in induced roots. Using a split root system, more Sal accumulated in root tissues of bacterized site than in distant roots on the opposite site of the root system after 1 d, but this difference decreased after 3 d. Sal concentration 0–200 g/L showed no inhibition of mycelial growth ofR. solani in vitro, while at ≥300 g/L it inhibited it.P. aeruginosa-pretreated rice plants challenged inoculation withR. solani (as pathogen), an additional increase in the accumulation of peroxidase was observed. Three pathogenesis-related peroxidases in induced rice plants were detected; molar mass of these purified peroxidases was 28, 36 and 47 kDa. Purified peroxidase showed antifungal activity against phytopathogenic fungiR. solani, Pyricularia oryzae andHelminthosporium oryzae.