Long-term effects of seed priming with polyethylene glycol on sweet sorghum: from enhanced drought tolerance and photosynthesis to improved field yield

Background Seed priming is a cost-effective strategy to enhance crop stress tolerance, yet the persistence of its effects throughout the life cycle and the underlying molecular mechanisms remain largely unexplored, particularly in sweet sorghum, a valuable bioenergy crop vulnerable to drought. This study aims to investigate whether polyethylene glycol (PEG) priming enhances drought tolerance in sweet sorghum and its associated molecular responses, and whether these effects persist to improve yield under field conditions. Materials and Methods Sweet sorghum seeds were primed with PEG6000 (150 g L −1 ) or left unprimed. Priming effects were evaluated through physiological and transcriptomic analyses under controlled drought conditions, followed by field validation across multiple cultivars over two consecutive growing seasons. Results PEG priming significantly improved seedling growth and photosynthetic capacity under drought stress, with biomass increased by 67.3% compared to unprimed controls. Transcriptomic analysis revealed that priming upregulated key genes in the target of rapamycin (TOR) pathway (TOR1 and LST8) and genes involved in photosystem II repair and carbon metabolism. Notably, the beneficial effects persisted to maturity, increasing biomass by 31.4–46.6% and panicle weight by 45.4–72.5% across three cultivars under field conditions. Conclusion PEG priming enhances drought tolerance in sweet sorghum through TOR-mediated regulation of photosynthesis and carbon metabolism, with sustained benefits that translate to improved yield in the field. This study provides a mechanistic basis for seed priming as an effective and practical strategy to enhance crop productivity in water-limited environments.