Identification of putative metabolic biomarker underlying cooked rice elongation

Rice (Oryza sativa L.) is a staple food for over half of the world’s population. However, rice grain quality is one of the major problems facing rice breeders across the world. Cooked rice elongation, cooked rice expansion, and water absorption have been identified as some of the parameters used in gauging rice grain quality. Biomarkers such as proteins or metabolites can be used to differentiate among a pattern of variations among various samples (e.g., various locations within a plant, various germplasm accessions); consequently, they present a type of internal validation for a given biological state. In the present study, we investigated the putative metabolite biomarkers associated with the variation of cooked rice elongation for Hua Jing Xian 74 (receptor), Basmati 370 (donor), and five hybrid lines resulting from a cross of these parent lines. We also investigated their cooked rice expansion and water absorption properties. After carrying out cooked rice elongation studies, metabolomics studies, correlation analyses, V-plot analyses, and thorough searches in public metabolite databases (Metlin, Massbank and KEGG), and in-house secondary metabolite database, we identified a metabolite with molecular weight of 280.25 and retention time of 6.4 min as a putative biomarker associated with cooked rice elongation in the varieties investigated. We also discovered that changes in cooked rice elongation and changes in cooked rice expansion follow a similar pattern; however, it appears that cooked rice elongation and cooked rice expansion do not affect water absorption in these rice lines. Our findings may facilitate the improvement of the cooked rice elongation of hybrids resulting from the crosses of Basmati 370 and Hua Jing Xian 74. Our results also offer interesting insight into cooked rice elongation, cooked rice expansion, and water absorption.