Effects of preharvest melatonin and boric acid applications on the pomological and biochemical characteristics of highbush blueberry (Vaccinium corymbosum cv. ‘Camellia’)

The application of boric acid and melatonin in blueberry cultivation has recently gained attention for their potential to enhance fruit quality and biochemical stability. Boric acid and melatonin contribute to cell wall integrity, pollen tube development, and nutrient transport, whereas melatonin, a bioactive compound with strong antioxidant properties, improves stress tolerance and supports fruit quality. In this study, the synergistic effects of foliar applications of boric acid (0, 5, 10, 15 ppm), melatonin (0, 5, 10, 15 ppm), and some combinations (0, 2.5+2.5, 5+5, 7.5+7.5 ppm) at early bloom, full bloom, and post-bloom stages were investigated on the pomological and biochemical traits of highbush blueberry (Vaccinium corymbosum cv. ‘Camellia’). The combined treatment of 5+5 ppm melatonin + boric acid produced the highest ascorbic acid content, while the 7.5+7.5 ppm combination significantly enhanced antioxidant activity. Boric acid alone at 5 and 10 ppm also improved antioxidant capacity. Although no significant differences were observed in fruit size or firmness, the treatments notably influenced titratable acidity, anthocyanin accumulation, and ascorbic acid content. These findings indicate that preharvest melatonin and boric acid applications can modulate key biochemical attributes, such as ascorbic acid, anthocyanins, and antioxidant activity, thereby improving the nutritional and functional quality of highbush blueberry fruits.