Mapping and Validation of QTLs for the Amino Acid and Total Protein Content in Brown Rice

Highly nutritious rice production will be benefited with the improvement of amino acid content and protein content. The identification of quantitative trait loci (QTL) associated with the protein content (PC) and amino acid content (AAC) of rice grains could provide a basis for improving the nutritional value of rice grains. Here, we conducted QTL analyses using recombinant inbred lines from the cross between indica (Milyang 23 or M23) and japonica (Tong 88-7 or T887) rice varieties, afterwards employing genotyping-by-sequencing (GBS) to obtain a high-density genetic map. A total of three and 17 QTLs were detected for AAC and PC. Among them, two QTLs associated with more than 10 AACs, qAAC6.1 and qAAC7.1, were identified for the first time in this study. Each favorable allele that increased the AAC of the two QTLs was derived from M23 and T887, respectively. Allelic combination of qAAC6.1M23 and qAAC7.1T887 showed significantly higher content of associated amino acids than other allelic combinations. Near-isogenic line (NIL) possessing qAAC7.1T887 with M23 genetic background had significantly higher AACs than both parents. These results indicate that the pyramiding of QTLs would be useful in developing brown rice with a high amino acid and protein content.