Ensuring a sustainable source of nutritious food is critical for long-duration space missions. Thai landrace rice 466HM exhibits high nutritional value and stress resilience, making it a promising candidate for space cultivation, yet its response to low Earth orbit (LEO) conditions remains poorly understood. This study compared rice grains maintained under terrestrial conditions with grains stored aboard the Shijian-19 (SJ-19) reusable satellite, orbiting at ~336 km for 13.5 days under microgravity (2⁻⁷ × 10⁻⁷g) and an absorbed radiation dose of ~0.153 rad (Si). Volatile compound profiling, texture analysis of cooked grains, and simulated gastrointestinal digestion followed by peptide mass fingerprinting were performed. LEO-exposed rice grains exhibited a 1.67-fold increase in adhesiveness compared to Earth-based rice (p < 0.01), while hardness remained unchanged between the two groups (p > 0.05), alongside distinct alterations in flavor-related volatile compounds and peptide profiles. Principal component analysis revealed clear separation between Earth and LEO-exposed samples, indicating microgravity-associated shifts in digestible peptide composition. Cytotoxicity assessment using MTT assays in HT-29 and HepG2 cells confirmed the safety of both rice types. These findings demonstrate that orbital conditions influence the compositional, functional, and sensory attributes of rice, providing insights relevant to space agriculture and astronaut nutrition.

Radiation beyond Earth’s atmosphere poses a major challenge for space agriculture by affecting seed viability and plant establishment. As a controllable terrestrial analogue of cosmic radiation, gamma (γ) irradiation provides a practical model for evaluating crop resilience. Although rice ( Oryza sativa ) is a promising space crop candidate, germination alone does not ensure developmental or metabolic stability under irradiation stress. Here, eight Thai rice cultivars were screened for radiation tolerance based on early seedling performance following γ-irradiation at 150, 300, and 900 Gy. All cultivars retained high germination capacity (> 90%) across all doses, whereas shoot and root elongation exhibited clear dose-dependent inhibition, with root growth showing greater sensitivity. Based on relative growth maintenance, cultivar 248HT was identified as the most γ-radiation tolerant genotype and selected for in-depth analysis. Untargeted metabolomics of roots and shoots revealed pronounced, tissue-specific metabolic reprogramming in response to irradiation. Roots displayed strong upregulation of metabolites associated with redox homeostasis, including NAD⁺ salvage intermediates and glutathione-related compounds, alongside suppression of nitrogen- and nucleotide-intensive pathways. Targeted phytohormone profiling further demonstrated a consistent reduction in gibberellic acid (GA₃) and accumulation of abscisic acid (ABA), resulting in a lowered GA₃:ABA ratio that aligned with reduced elongation growth. Collectively, these results indicate that radiation tolerance in rice is underpinned by coordinated hormonal recalibration and metabolic shifts that prioritise oxidative stress mitigation, DNA repair, and controlled growth. The superior performance of 248HT highlights it as a promising candidate for further space related radiation stress studies and provides metabolomic markers for selecting or engineering radiation-resilient rice varieties.