Mimics of the Growth Regulator Zaxinone Increase Saffron Yield and Improve its Nutritional Value

Biostimulants enhance plant growth and performance by effectively improving nutrient utilization for sustainable agriculture. Herein, we aimed to investigate the impact of two biostimulants, MiZax3 and MiZax5, on agronomic performance, yield traits, and nutritional quality of saffron (Crocus sativus L.) in two consecutive seasons. We observed a significant increase of 17% and 30% on plant height with foliar application of MiZax3 and MiZax5 at 10 µM, respectively. Application of MiZax3 and MiZax5 at a lower concentration of 5 µM enhanced the number of leaves by approximately 55% and 45%, respectively. Importantly, stigma fresh weight was increased by 59% with MiZax3 at 5 µM in 2023, while the number of flowers plant−1 increased by 117% and 71% with MiZax5 at 5 µM in 2022 and 2023, respectively. In addition, MiZax3 and MiZax5 showed a pronounced positive effect on bioactive compounds in saffron stigmas. We observed a significant increase of 40–98% in crocin with MiZax3 at 5 µM, 48–81% in crocetin, 68–115% in picrocrocin, and 110–151% in safranal contents with MiZax5 at 5 µM over the control. Nutritional analysis further revealed higher contents of carbohydrate, fat, protein, and carotenoid, as well as of calcium, magnesium, iron, and zinc in saffron leaves upon treatment with both biostimulants at 5 µM concentration, demonstrating their biofortification potential. In conclusion, our findings indicate that low concentrations (5 and 10 µM) of MiZax3 and MiZax5 can significantly improve the yield, quality, and nutritional value of saffron, revealing these biostimulants as effective tools for sustainable saffron cultivation.