Standardization of optimum melatonin concentration for drought tolerance at germination and early development stage in rice (CO-54)

Drought stress poses a serious threat to production and nutritional security. In recent years, foliar application of plant growth regulators (PGRs) and nutrients are increasingly employed to overcome physiological constraints resulting in enhanced crop production. Melatonin is a new biomolecule recently found to ameliorate the effect of biotic and abiotic stresses in crop plants. Hence, the present experiment was conducted to assess the optimum concentration of melatonin to mitigate the adverse effect of drought stress on germination and growth components in rice variety CO-54. In this experiment, PEG-mediated drought stress (-0.5 MPa) was imposed with different concentrations of melatonin (at doses of 50, 100, 150, 200, and 250 µM) seed treatments. Together, these results indicated that 200 µM melatonin-treated seeds showed a greater germination percentage (60%), root length (12.23cm), shoot length (8.23cm), fresh and dry weight (0.126g and 0.095g), high vigor index (1910.22), promptness index (64.83), and germination stress index (100) respectively. The result of this experiment provides a shred of strong evidence suggesting that seed treatment of 200 µM melatonin could be considered an effective technique for mitigating the detrimental effects of drought by promoting seed germination and thereby increasing the growth components of seedlings in rice. The study demonstrates that melatonin can shield rice seedlings from the effects of drought stress.