Abstract: In order to clarify the regulatory effect of melatonin on the drought resistance of dryland wheat (Triticum aestivum L.) during seed germination stage, the dryland wheat variety Shangmai 5226 was used as the experimental material to determine the effects of different concentrations (0, 75, 150 and 300 μmol/L) of melatonin priming on seed germination and seedling physiological indexes under different drought intensities [0, 10%, 15%, 20% and 25% of polyethylene glycol (PEG-6000)]. The results indicated that with the intensification of drought stress, germination potential, germination rate, seedling water content, coleoptile length, radicle length, radicle number, and chlorophyll content showed a decreasing trend, while soluble sugar and proline contents increased. Compared with the drought-stressed treatments that did not receive priming, melatonin priming at 75 and 150 μmol/L increased germination potential and germination rate to varying degrees under 10%, 15%, and 20% PEG-6000 treatments (except for germination rate under 20% PEG-6000), and melatonin priming at 75, 150, and 300 μmol/L significantly enhanced soluble sugar content under 10% and 15% PEG-6000 treatments. The comprehensive evaluation using the membership function method showed that under melatonin priming at 75 and 150 μmol/L, the comprehensive evaluation values for the 10% and 15% PEG-6000 treatments were higher than those of the corresponding drought-stressed treatments without priming; similarly, under 300 μmol/L melatonin priming, the values for the 15% and 25% PEG-6000 treatments were higher than those of their respective controls without priming. In conclusion, 75 and 150 μmol/L melatonin priming could effectively alleviate the drought stress of 10% and 15% PEG-6000 intensities.

Key words: dryland wheat (Triticum aestivum L.), melatonin, seed priming, seed germination stage, drought resistance