Growth stimulation and induction of systemic resistance in tomato against early and late blight by Bacillus subtilis OTPB1 or Trichoderma harzianum OTPB3

Abstract

The plant growth -promoting rhizobacteria and fungi are known to enhance growth and induce systemic defense responses in plants. The efficacy of Bacillus subtilis OTPB1 and Trichoderma harzianum OTPB3 were evaluated for in vitro antibiosis to Alternaria solani and Phytophthora infestans, growth stimulation, and induction of systemic resistance in tomato seedlings against early and late blight. Cell suspensions of OTPB1 or spore suspensions of OTPB3 were incorporated into plastic pots containing tomato seed var. Arka vikas and data were recorded 30days after inoculation. Both isolates inhibited mycelium growth of A. solani and P. infestans under in vitro conditions and significantly increased root and shoot growth, leaf area and seedling vigour index in tomato. The levels of indole-3-acetic acid (IAA) and gibberellic acid (GA3) were increased significantly in roots of seedlings treated by OTPB1 or OTPB3 by 29.12% and 45.82% or 54.34% and 67.59%, respectively, as compared to uninoculated controls. Treatment with OTPB1 or OTPB3 enhanced the levels of defense–related enzymes including peroxidase, polyphenol oxidase and superoxide dismutase in tomato plants. This study also showed that in addition to plant growth and antibiosis, OTPB1 and OTPB3 enhanced systemic resistance in tomato seedlings through induction of growth hormones and defense enzymes. The use of OTPB1 or OTPB3 in raising disease-free and quality tomato seedlings in pot trays is discussed.