Fruit texture related changes and enhanced shelf-life through tomato root inoculation with Bacillus subtilis BEB-13BS

Bacillus subtilis BEB-13bs, a plant growth promoting rhizobacteria, has improved tomato firmness. Since firmer fruits are be expected to be more resistant to spoilage microorganisms and to have a longer shelf-life, root inoculation with this strain could be an alternative to extend tomato shelf-life. Thus, fruit texture-related changes were studied in tomato plants (Lycopersicon esculentum Mill.) inoculated with Bacillus subtilis BEB-13bs. Treatments were: 1) non-inoculated control treatment (CTL); 2) PGPR inoculated treatment (BS13). Evaluation was made at different ripening stages. Pericarp firmness and activity of poligalacturonase (PG), the major cell wall polyuronide degrading enzyme in tomato, were measured. The expression pattern of ripening-related genes was also examined. Pericarp firmness was significantly greater in light red (LR) fruits in the BS13 treatment compared to those in the CTL treatment. PG activity was reduced significantly by the BS13 treatment in LR and red (R) fruits compared to the CTL treatment. The expression pattern of Aco, gene coding for 1-aminocyclopropane-1-carboxylate oxidase (ACO), an enzyme that has a regulatory role in ethylene production during fruit ripening, showed a significant decrease in accumulation of the transcript at the R stage in the BS13 treatment compared to that in the CTL treatment. A shelf-life test was performed storing fruits at 25-27 °C for 10 d at the end of this trial, and fruits in the BS13 treatment were significantly firmer than those in the CTL treatment. Moreover, the percentage decay (non-acceptable fruits) was significantly lower in the BS13 treatment than in the CTL treatment. Additionally, the BS13 treatment promoted a significant increase in fruit fresh weight, size and yield per plant, compared to the CTL treatment. The present results support the development of an environment-friendly production tool based on PGPR for improving fruit quality through enhanced firmness and shelf-life.