BLOSSOM-END ROT CONTROL IN TOMATO (Solanum lycopersicum L.) FRUIT USING PLANT GROWTH REGULATORS

The tomato (Solanum lycopersicum L.) is the second most produced vegetable worldwide. Mexico ranks eighth as a producer and is the main exporter. This crop adapts to diverse climates and soil types, although it is susceptible to diseases and physiological disorders. Blossom-end rot (BER) is the most relevant, with damage that can reach up to 50 % of greenhouse production. This study aimed to evaluate the effect of foliar application of abscisic acid (ABA) combined with 24-epibrassinolide (EBL) to assess BER of tomato fruit in plants fed with low calcium (Ca) concentration (45 mg L-1) in the supplied nutrient solution. Likewise, the physiological and metabolic changes that these growth regulators generate in planta were determined. A 4 × 4 factorial experiment was established in a completely randomized design. Four concentrations of ABA (0, 60, 100, and 140 mg L⁻¹) and four of EBL (0, 0.0024, 0.0048, and 0.0096 mg L⁻¹) were evaluated as factors, with four replications. The percentage of BER and fruit set, photosynthesis, stomatal conductance, intercellular CO₂, transpiration, Ca concentration in leaves and fruits, and the concentration of amino acids and proteins were determined. In the first evaluation (20 d of treatment), treatments ABA3EBL2 and ABA3EBL0 showed a lower incidence of BER (80 and 66 %). In the second evaluation, EBL decreased transpiration by 50.6 %. ABA1EBL1 (35.7 %) and ABA3EBL0 (30.5 %) increased fruit Ca, while ABA2EBL1 increased leaf Ca by 62.2 %. ABA0EBL1, ABA1EBL1, ABA3EBL0, and ABA1EBL3 increased total amino acids more than twofold, and ABA2EBL2 increased protein by up to 13.6 %. These results indicate that the early application of ABA and EBL reduces BER and improves physiological and metabolic parameters in tomato plants.