Plant disease control and PGPR effects by entomopathogenic Bacillus thuringiensis

Abstract: Bacillus thuringiensis (Bt) is a bacterium used as a microbial insecticide (BT agent). However, some strains with plant disease control effect and plant growth promoting effect has been reported. In addition, it has been reported that B. thuringiensis forms a biofilm on the root of tomato and induced systemic resistance to plants. Therefore, in this research, we focused on such function of B. thuringiensis and aimed to develop usage as biofertilizer and biostimulant in commercialized Bt strains and Bt agents. We investigated the growth promoting effect using BT treated seed. In addition, we investigated the disease control effect and PGPR effect by applying BT to the root of tomato in the greenhouse. Two Bt strains (BT-17, BT-20) and Jackpot® which are effective in suppressing plant diseases and plant parasitic nematodes in the pot test were used as the test strain. (Experiment 1) Tomato seeds were immersed in a Bt suspension for 24 hours and the roots were elongated using a roll towel method and measured. (Experiment 2) The Bt suspension was periodically applied at the root of the tomato in the greenhouse. Then, Phytophthora infestans incidence rate, plant height, weight per bunch, weight per fruit, and number of fruits per bunch were investigated. In Experiment 1, the roots of Bt treated seeds significantly increased compared to the control plot. In Experiment 2, the disease control effect, plant height, second bunch weight and weight per fruit in the second bunch were significantly higher in the jackpot treated plot than in the control plot.