Effects of applying Bacillus subtilis before harvest on tomato fruit physicochemical properties

Plant growth-promoting bacteria (PGPB) naturally occur in the environment and offer various plant benefits. The Bacillus genus, part of the PGPB group, is effective in post-harvest disease control and may influence fruit quality mechanisms. The objective was to evaluate the pre-harvest application of different doses of a commercial B. subtilis formulation on the physicochemical and qualitative characteristics of tomato fruits. Conducted in a randomized block design with five treatments and four blocks, increasing doses of the biofungicide Serenade® (B. subtilis) were applied via foliar spray: 0.0 (Control), 2.0, 4.0, 6.0, and 8.0 L ha−1. The study measured soluble solids (SS), pH, titratable acidity (TA), ratio (SS/TA), ascorbic acid (AA), citric acid (CA), firmness, total phenolic compounds (TPC), antioxidant capacity (DPPH), lipid peroxidation (LP), hydrogen peroxide (H2O2), antioxidant enzyme activity (superoxide dismutase - SOD, catalase - CAT, and peroxidase - POD), total soluble sugars (TSS), reducing sugars (RS), starch, respiration, and ethylene content. Doses of 4 and 6 L ha−1 of B. subtilis increased SS (13%), TA (58%), AA (30%), CA (17%), TPC, DPPH (50%), H202 (30%), CAT activity (11%), POD, starch (46%), and respiration, while the ratio (SS/TA) was reduced by 27%, as well as LP (20%), SOD activity (6%), and RS content (28%) compared to the control. Pre-harvest application of the B. subtilis-based biofungicide at doses of 4 and 6 L ha−1 improved tomato fruits’ physicochemical and qualitative characteristics, enhancing the antioxidant system and reducing membrane damage to maintain tissue integrity.