Source-sink-redox coordination associated with anthocyanin accumulation and enhanced grain productivity in gamma-irradiated rice lines.

Rice lines enriched with anthocyanins were developed from the Thai rice cultivar Pathum Thani 1 (PTT1) through gamma irradiation to investigate coordinated physiological, biochemical, and transcriptional responses associated with grain pigmentation and antioxidant metabolism. Three stable M6 lines were evaluated for agronomic, photosynthetic, carbohydrate, anthocyanin, antioxidant, redox, and transcriptional traits. The irradiation-derived lines showed significant increases in flag leaf area and shoot biomass compared with the parental cultivar, while PTTM-A2 and PTTM-A3 also exhibited significantly higher tiller number and grain yield than PTT1. Grain dry weight increment was enhanced in the irradiation-derived lines. PTTM-A3 exhibited the highest chlorophyll content, net photosynthetic rate, chlorophyll fluorescence performance, sucrose accumulation, total anthocyanin content, cyanidin-3-glucoside concentration, and antioxidant activity. Higher anthocyanin accumulation coincided with reduced H2O2 and malondialdehyde accumulation together with increased superoxide dismutase, catalase, and ascorbate peroxidase activities. RT-qPCR analysis showed higher transcript abundance of anthocyanin-related genes, particularly Kala4, OsC1, OsDFR, OsANS, and OsUFGT, together with higher transcript abundance of the OsTPS1 and OsHXK6 in the irradiation-derived lines. Pearson correlation and principal component analyses demonstrated relationships among photosynthetic performance, sucrose metabolism, anthocyanin accumulation, antioxidant capacity, oxidative stress markers, and grain productivity. These findings indicate that anthocyanin accumulation was associated with coordinated source-sink and redox-related traits in the selected M6 lines. However, because the underlying genetic alteration(s) associated with these phenotypes remain unidentified, these relationships should be interpreted as associative rather than causal. This study highlights the potential of gamma irradiation for developing functional rice lines with enhanced nutritional quality and agronomic performance.