Seed priming with melatonin improves drought tolerance in maize

Maize is the most important agricultural species in sub-Saharan Africa, supplying approximately 50% of the calories and proteins ingested. Due to increasing drought conditions from climate change, maize crop yields are projected to decline by 24% in the next decade. New strategies to aid farmers in coping with drought circumstances are urgently needed. Seed priming or presoaking, soaking seeds in a solution before planting, has been proposed to improve drought tolerance. Melatonin, a plant growth regulator, improves drought tolerance through multiple mechanisms. We investigated if priming maize seeds with melatonin could improve germination and drought tolerance. We hypothesized that priming maize seeds in a melatonin solution would significantly improve plant drought tolerance. We created three groups of 60 maize seeds: control (no priming), priming with water, and priming with a melatonin solution. We primed seeds for 6 hours and allowed them to germinate. We planted seeds and exposed them to drought conditions for 14 days. Cumulative percent germination was higher in the water and melatonin-primed groups and lowest in the control group. Cotyledon (first leaf) emergence was earliest for the melatonin-primed group and latest for the control group. The melatonin-primed group was superior to the control and water-primed groups in plant height, weight, and viability after drought exposure. The results of this study demonstrate that seed priming with melatonin improved plant height, weight, and viability under drought conditions when compared to priming with water or no priming. Priming seeds with melatonin may offer a simple and inexpensive method of improving drought tolerance in maize plants.