Genetic connection between cell-wall composition and grain yield via parallel QTL analysis in indica and japonica subspecies

Grain yield is a complicated trait, which is highly associated with biomass productivity. The cell wall is a central element of biomass, and its biogenesis contributes to plant architecture and development. However, the genetic link between cell-wall property and grain yield is largely unclear. Here, we report on identification of quantitative trait loci (QTLs) for grain yield-related traits and cell-wall composition with a set of chromosomal segment substitution lines (CSSLs) that were generated by using 9311, an indica cultivar as donor, and Nipponbare, a japonica cultivar as recipient. Nipponbare and 9311 showed significant differences in grain yield-related traits and cell-wall composition. Genotyping with molecular markers, 125 lines covering 95.6% of the whole genome of 9311 were employed for phenotypic and chemical examinations. Thirty-seven QTLs for grain yield-related traits and nineteen QTLs for cell-wall composition have been identified. In addition to correlation analysis, we found overlapped and closely linked QTLs for two sets of traits. Fine-mapping further narrowed a QTL for cellulose content together with HD17, a known QTL for heading date and grain yield, suggesting that plants may regulate cell wall biogenesis and grain yield via related means. Our study provided genetic clues for cloning QTLs for both complicated traits.