PROTEIN SOLUTIONS FROM Xanthomonas AS RESISTANCE INDUCTORS FOR THE CONTROL OF BACTERIAL SPOT IN TOMATO

Abstract

Bacterial spot, caused by Xanthomonas vesicatoria, is a tomato (Solanum lycopersicum) disease and its control is usually with chemical products. However, there are alternatives to mitigate diseases, such as activation of resistance state in plants through pathogen-associated molecular patterns (PAMP) inductors. In this study the effect of protein solutions from X. vesicatoria were evaluated as PAMP inductors and activation of resistance state in tomato against bacterial spot under in vitro conditions. Protein solutions from X. vesicatoria strain BV801 (BV801) were obtained, and its protein profile was determined by SDS-PAGE. The BV801 protein solutions with antibacterial activity against X. vesicatoria was evaluated in culture medium with the double-layer plaque assays. The in vitro resistance induction trial in tomato was carried out by means of a completely randomized experimental design with 8 treatments: seven protein concentrations (0.0, 0.001, 0.01, 0.1, 1.0, 10 and 100 μg mL^-1) inoculated with BV801 and a control of healthy plants (without proteins and without BV801). The results showed that 19 major protein bands formed the protein profile of BV801, which did not show antibacterial activity in vitro against X. vesicatoria. A 50 % reduction in the disease caused by the bacterial spot was found in tomato plants treated with protein solutions from BV801, at concentrations 0.1, 1.0 and 10 μg mL^-1 (Kruskal-Wallis, P ≤ 0.05); furthermore, plant growth maintained statistical similarity with healthy control plants (Tukey, Bonferroni, P ≤ 0.05). The protein solutions from BV801 are PAMP inductors and increased the tomato plants resistance to bacterial spot disease.