Seed priming with melatonin enhances chilling stress tolerance in tomato seedlings

Seed vigor is critical for uniform germination and emergence, directly influencing subsequent seedling development. This is especially important under both normal and stress conditions that may arise post-sowing. Chilling stress during emergence and early growth poses significant challenges for tomato seedlings, potentially leading to uneven emergence, abnormal growth, and higher seedling mortality. This study evaluated the effectiveness of combining drum-priming with melatonin to alleviate chilling stress during these two critical stages. Tomato seeds were primed with melatonin at various concentrations and compared to untreated controls under chilling stress conditions. Higher concentrations of melatonin significantly accelerated emergence and improved early growth under stress. These stress-mitigating effects were evidenced by reductions in oxidative stress markers, such as malondialdehyde and hydrogen peroxide, along with increased total polyphenol and flavonoid contents. Furthermore, melatonin priming preserved photosynthetic efficiency, typically reduced by chilling stress, and enhanced the activities of antioxidant enzymes, including catalase and peroxidase. These biochemical changes reduced oxidative damage and promoted stress resilience. Melatonin also accelerated the expression of genes within the C-repeat binding factor pathway, which is crucial for cold acclimation. This suggests that melatonin priming enabled quicker adaptation to chilling stress following sowing and bolstered seedling resilience during subsequent growth stages. Overall, our results demonstrate that melatonin priming not only enhances germination but also significantly supports seedling growth under adverse conditions. The findings highlight melatonin as a promising tool in crop management strategies to improve resilience against sudden chilling stress.