Characterization of Grain Quality and Starch Properties of Rice under the Combined Salt-Drought Stress

The effects of combined salt-drought stress on rice grain quality and starch properties remain poorly understood. A pot experiment was conducted with control, salt, drought, and combined salt-drought stress. Compared with the control, rice grain yield decreased by 24.8% to 65.9% under salt, 12.4% under drought, and 25.1% to 69.5% under combined salt-drought stress. Milling, appearance, and eating quality deteriorated under stress, especially under combined stress, with a 33.0% decrease in taste value and 51.1% increase in amylose content. The amylopectin content declined, while the protein content increased, further impairing palatability. Microscopic and structural analyses revealed cracks, pores, fractured granules, and a smaller average granule size under stress, resulting in lower crystallinity and disrupted molecular order, especially under combined stress. By reducing rapidly digestible starch and increasing resistant starch, stress may help moderate postprandial glucose responses. Overall, combined salt-drought stress synergistically compromises rice yield and quality, providing insights for breeding stress-resilient, high-quality rice.