Paenibacillus lentimorbus B-30488r controls early blight disease in tomato by inducing host resistance associated gene expression and inhibiting Alternaria solani

The ability of Paenibacillus lentimorbus B-30488(r) (B-30488(r)) in reducing the early blight (EB) disease caused by Alternaria solani in tomato was assessed. Foliar application of the bacteria reduced the disease incidence by 45.3% as compared to control. In vitro studies indicated that B-30488(r) effectively reduces the radial growth of A. solani in dual culture, and SEM studies demonstrated complete degradation of fungal hyphae on co-culture with B-30488(r). Both B-30488(r) and A. solani exhibited high similarity in the nutrient utilization of carbon sources present in tomato tissues. Changes in gene expression studied using RT-PCR analyses indicate significant up-regulation of defense and growth-related genes in tomato plants treated with B-30488(r) foliar spray and A. solani challenged plants pre-treated with B-30488(r) foliar spray. Principal component analysis results indicated that tomato plants treated with A. solani affected microbial community structure and population of the rhizosphere as compared to B-30488(r). Results suggest that P. lentimorbus B-30488(r) has a multiple mode of action for its biological control activity by inducing resistance in tomato plants, by degrading the pathogen cell wall, and by competing for similar sources of nutrients on the phyllosphere. Additionally, B-30488(r) would not affect microbial populations on the rhizosphere of the tomato plants. (C) 2012 Elsevier Inc. All rights reserved.