FLOWERING TIME GENE EXPRESSION OF GmTF2a AND SOME POD AND SEED CHARACTERISTICS OF SOYBEAN AFFECTED BY SPRAYING WITH MELATONIN AND SEEDING DATE

This study was conducted at the research station of the College of Agriculture - University of Anbar during the season 2022 to investigate the effect of melatonin and seeding date on the gene expression of flowering gene in soybean (GmTF2a) and some   characteristics of soybean pods and seeds. Environmental differences appear from year to year due to global warming which makes studying seeding dates important, as well as using growth regulators that help adapt to surrounding conditions. Five seeding dates were applied starting from 10th April with an interval of 15 days in between and four concentrations of melatonin 0, 100, 200, 300 µM applied at the V3 growth stage (three fully developed trifoliate leaf nodes) of soybean. Flowering gene expression differed as seeding dates and melatonin treatment differed. Early seeding dates and high levels of melatonin showed an increased gene expression of GmTF2a, which reached 6.96 folds for plants sown 10th of May, while it went down to 1.53 folds for those sown very late on 9th Jun. Melatonin concentration of 300 µM was superior by showing 14.42 folds of gene expression compared to control (0 µM) which showed 5.17 folds only. Plants sown on Jun 9th reached 50% flowering earlier (62 days) while 10th April gave plants flowered 86 days after seeding. On the other hand, melatonin application reduced days required to reach 50% flowering. The date May 10th was superior giving 161.05 pods per plant, 4.50 cm pod length, 2.65 seeds per pod, 395.7 seeds per plant, and 6.8% wrinkled seeds. While the date May 25th excelled in weight of one seed which reached 0.133 mg. On the other hand, the date 10th April gave the lowest averages for the mentioned traits. Melatonin treatment of 300 µM was superior in all studied traits by giving 161.05 pod plant-1, 4.58 cm pod length, 2.87 seeds per pod, 0.131 mg weight of one seed, 398.5 seeds per plant, and 6.8% wrinkled seeds. Treatment of 0 µM gave the lowest averages of all traits and the highest wrinkled seeds percentage 11.84%.