The effect of Melatonin on Improvement of Growth and Biochemical Traits of Alfalfa (Medicago sativa L.)

Alfalfa (Medicago sativa L.), a pivotal forage crop, plays a crucial role in sustainable agriculture. However, its productivity is often hampered by biotic and abiotic stresses. This research investigated the effect of melatonin, as a growth regulator and a potential substitute for auxin, on callus production and biochemical characteristics in this plant. Experiments were performed in three different culture media: M1 (basal), M2 (MS supplemented with melatonin, kinetin, and 2,4-D), and M5 (MS supplemented with melatonin, kinetin, and NAA). Results showed that melatonin at 35 and 65 days led to a significant increase in fresh and dry weights of calluses derived from both leaf and stem explants, with a more pronounced effect on stem-derived calluses. Melatonin significantly increased the total phenolic content, while no significant changes in total protein content were observed. The auxin content in melatonin-treated calluses was higher than in the basal medium, with stem-derived calluses exhibiting higher auxin levels than leaf-derived calluses. Analysis of protein patterns by SDS-PAGE revealed a decrease in the expression of protein bands with molecular weights of 14.4 and 18.4 kDa in melatonin-treated samples compared to the basal medium. Our findings suggest that melatonin can be used as an effective growth regulator and a potential alternative to auxin in alfalfa callus induction.