Unveiling the Synergistic Effects of Melatonin, Arginine, and Nano-Chelated Zn-Fe on Enhancing Fruit Quality in Apricot ().

Apricot () is a delicious and highly nutritious fruit, rich in organic acids, various vitamins, sugars, proteins, and minerals, and possesses multiple medicinal properties. To enhance fruit yield and quality while reducing the use of chemical fertilizers, an experiment was conducted on the basis of a randomized complete block design with three replications in the north of Dohuk, Iraq during 2023. Apricot trees were foliar-sprayed with 28 different combination levels of arginine, melatonin, and nano-chelated zinc-iron. The results showed that most treatments led to improvements in both quantitative and qualitative traits of apricot fruits compared to control. Among them, the application of arginine 150 ppm + melatonin 400 μmol/L + Zn-Fe nano-chelate 2 and 3 g/L resulted in the most significant increases in fruit firmness (21.14% and 21.93%), fruit weight (35.60% and 35.35%), fruit length (25.77% and 20.26%), fruit yield (27.11% and 26.95%), the contents of vitamin C (20.73% and 20.39%), soluble sugars (33.51% and 33.58%), and total soluble solids (17.60% and 17.72%) compared to control. These treatments also improved the concentrations of calcium (49.26% and 47.84%), magnesium (20.97% and 26.36%), potassium (58.40% and 67.43%), zinc (11.19% and 19.26%) and iron (9.46% and 11.07%) in the fruit, while reducing total acidity. In addition, they enhanced leaf area and chlorophyll content (SPAD index). Ultimately, these two treatment combinations are recommended for improving both the quantity and quality of apricot production.