Identification of Quantitative Trait Loci for [delta]^sup 13^C and Productivity in Irrigated Lowland Rice

Stable carbon isotope ratio (δ^sup 13^C) in plants has been suggested as a useful indicator for cumulative Ci/Ca signature in a leaf, water use efficiency, and crop productivity, and is known to have genotypic variation in rice (Oryza sativa L.). We conducted a field study to identify quantitative trait loci (QTLs) for δ^sup 13^C and other related leaf traits, such as leaf N, specific leaf area, and SPAD value, using recombinant inbred lines derived from an indica × japonica cross grown under flooded conditions. We also examined the genetic associations of δ^sup 13^C with yield, yield components, and biomass productivity. Putative QTLs for δ^sup 13^C were identified on chromosomes 2, 4, 8, 9, 11, and 12 across plant parts, stages, and years. Differential expression of QTL for δ^sup 13^C among stages suggests that each QTL had different functions by stages. The QTLs for δ^sup 13^C were associated with a few colocated QTLs for leaf traits indicating that their physiological and genetic associations with leaf traits may be complex. Values of δ^sup 13^C at maturity were negatively correlated with harvest index and gram yield. However, genetic association of these traits could not be clarified due to the absence of co-located QTLs. Further examination would be useful to elucidate the physiological and morphological functions of QTLs for δ^sup 13^C found in this study. [PUBLICATION ABSTRACT]