Integrative genomics reveals shared and stress-specific adaptive pathways underlying acidic soil-associated metal toxicity in rice

Soil acidity-associated toxicities of aluminum (Al), cadmium (Cd), and manganese (Mn) severely constrain rice productivity in upland ecosystems. To investigate the genomic basis of adaptation to acidic soil-related metal stress, we conducted an integrated meta-QTL (M-QTL) and functional genomics analysis in rice. Meta-analysis of 681 QTLs and MTAs from 53 QTL mapping and GWAS studies identified 79 robust M-QTLs, including ten overlapping regions associated with Al-, Cd-, and Mn-responsive traits. A multi-criteria prioritization framework identified 98 candidate genes supported by positional overlap, transcriptomic recurrence, and functional annotation, enriched for ion transport, detoxification, and redox regulation pathways. M-QTL10.9 emerged as a major hotspot enriched for glutathione-S-transferase genes, whereas M-QTL9.5 contained the highest density of prioritized candidates linked to Al and Cd responses. Comparative physiological & biochemical analyses of the contrasting rice genotypes Sahasarang and IR64 revealed genotype-dependent differences in antioxidant responses, metal partitioning, metabolic regulation, and cell wall remodeling under individual and combined metal stresses. Expression profiling of prioritized candidate genes, including OsACO family genes, OsZIP10, and OsGSTU10, further revealed genotype-dependent transcriptional divergence under combined stress. The identification of overlapping M-QTLs across Al, Cd, and Mn datasets suggests both shared and stress-specific adaptive responses to acidic soil-associated metal stress in rice.