Hrp proteins as bioinducers for the biocontrol of bacterial diseases in tomato and pepper plants in greenhouse

Background/Objective. Diseases such as bacterial spot in tomato (Solanum lycopersicum) and bacterial spot in chili pepper (Capsicum annuum) cause significant global economic losses. A sustainable alternative for their control is the use of protein inducers (Harpin proteins = Hrp) that activate plant defense responses by being recognized by the plant immune system, inducing defense mechanisms against pathogens. The objective of this research was to evaluate the biological effectiveness and optimal application dose of the biological inducer BioFensa (based on Hrp proteins), produced in a pilot plant, to control these diseases. Materials and Methods. Three greenhouse experiments were conducted to evaluate the biological effectiveness of BioFensa (1 μg mL⁻¹). The protein inducer was tested for controlling bacterial spot (X. euvesicatoria strain BV865 [1] and BV801 [2]), as well as bacterial speck (P. syringae pv. tomato, strain DC3000 [3]). Each experiment included 5 treatments and 11 replicates. Additionally, an experiment was conducted to determine the optimal dose of BioFensa (0.01, 0.1, and 1.0 μg mL⁻¹) against X. euvesicatoria strain BV801, with 7 treatments and 8 replicates [4]. In the four experiments in total, plants were sprayed with BioFensa (3 mL per plant) 24 hours before infection, and symptoms were evaluated after 30 days by counting spots on the foliar tissue. Results. BioFensa was effective in significantly reducing damage in chili and tomato plants (LSD, p≤0.05). At a high concentration (1 μg mL⁻¹), it prevented the appearance of spots on tomato plants by 53%, while for chili plants against strain BV865, it prevented spots by 60%. On the other hand, for chili plants against strain BV801, at low concentrations (0.01 and 0.1 μg mL⁻¹), symptoms were significantly reduced by 38-41%, whereas at a higher concentration (1 μg mL⁻¹), this effect was not maintained, suggesting a limit in the perception of inducers by the plants. Conclusion. The results suggest that BioFensa has the potential to be an effective alternative to control diseases in horticultural crops such as tomatoes and chili peppers.