Induction of defense-related proteins and growth promotion in tomato by mixture of Trichoderma harzianum OTPB3 and Bacillus subtilis OTPB1 and Pseudomonas putida OPf1 against Phytophthora infestans

Late blight incited by Phytophthora infestans is a destructive disease of tomato worldwide. The plant growth-promoting antagonists, which elicit induced systemic resistance (ISR) and enhance plant growth, are being used as safe alternatives to synthetic fungicides for the management of plant diseases. In this study, a combination of Trichoderma harzianum OTPB3 and Bacillus subtilis OTPB1 and Pseudomonas putida OPf1 alone were evaluated for induction of systemic resistance in tomato against P. infestans in comparison with fungicides and growth promotion. Seed treatment with fresh suspensions of a combination of T. harzianum OTPB3 and B. subtilis OTPB1 caused significant increase in growth parameters compared to P. putida OPf1, mancozeb and untreated control due to higher production of indole-3-acetic acid (IAA) and gibberellic acid (GA3). Reduction in the incidence of late blight was positively linked to increase of phenylalanine ammonia lyase, peroxidase, polyphenol oxidase and β-1,3-glucanase, the defense-related enzymes in tomato seedlings treated with microbial consortium of OTPB3 and OTPB1 followed by foliar spray of P. putida OPf1. The effects were on par with fenamidone and mancozeb treatments. The results reveal that seed treatment with microbial consortium containing T. harzianum OTPB3 and B. subtilis OTPB1 and foliar spray of P. putida OPf1 have practical significance in the management of late blight disease and also plant growth enhancement in tomato.