Constitutive metabolomic profile of a transgressive segregant of rice with superior salinity tolerance potentials due to unique morphological features and well-modulated growth

Understanding the nature of non-parental phenotypes created by transgressive segregation is important in creating novel genetic recombinants that can withstand different environmental conditions for crop production. FL510, a transgressive salinity-tolerant rice genotype from a cross between IR29 (salt-sensitive) and Pokkali (salt-tolerant), has tolerance mechanisms active under control conditions and improves survival upon the onset of salinity. This study compares normal-state metabolomes and lipidomes of FL510 with its parents. Principal component analysis (PCA) of the identified analytes showed clear and expected similarity between FL510 and Pokkali, while partial least squares discriminant analysis (PLS-DA) emphasized overlaps between the metabolic profiles of IR29 and FL510. The analysis identified metabolites with inherited patterns of abundance from either parent in FL510 and those with unique, non-parental abundances, and these were supported by differential expression of key pathway-related genes identified through transcriptome analysis. Strigolactone precursor production was identified as a key feature in FL510, which may help explain its unique architecture that is beneficial for osmotic stress. We also identified a divergence between productivity under ideal environments leading to free radical production versus tempered production that offers better survival under marginal growing conditions. FL510 showed an inheritance of hormone and amino acid abundances from Pokkali, which further explains some of its architectural and previously studied stress-response features. Meanwhile, the similarity of FL510 with IR29 in terms of flavonoid indicates an inheritance of productivity and is consistent with previous reports of induction for these molecules under stress, rather than being active under control conditions. MAIN CONCLUSION: Through repeated genetic recombination of genetically distant alleles, the transgressive segregant FL510 gained unique, non-parental signaling pathways and complementary metabolome features from both parents leading to positive net genetic gains.