The QTL Analysis of RuBisCO in Flag Leaves and Non-Structural Carbohydrates in Leaf Sheaths of Rice Using Chromosome Segment Substitution Lines and Backcross Progeny F2 Populations

In rice (Oryza sativa L.), the maintenance of high photosynthetic rate of flag leaves and the carbon remobilization from leaf sheaths after heading is a critical physiological component affecting the yield. To clarify the genetic basis of RUBisCO content of the flag leaf, a major determinant of photosynthetic rate, and nonstructural carbohydrate (NSC) concentration in the third leaf sheath at heading, we carried out quantitative trait loci (QTL) analysis with 39 Koshihikari/Kasalath chromosome segment substitution lines (CSSLs) and backcross progeny F-2 population derived from target CSSL holding the QTL/Koshihikari in the field. QTLs for RuBisCO content and NSC concentration at heading were detected between R2447-0286 and R2447-8716 on chromosome 10, respectively, by comparing Koshihikari with four CSSLs for chromosome 10 (SL-229, -230, -231 and -232). The progeny QTL for RuBisCO content and for NSC concentration at heading qRCH-10 and qNSCLSH-10-1, respectively, were detected at similar marker intervals between RM8201 and RM5708. In addition, QTLs for RUBisCO content: at 14 et after heading, qRCAH-10-1 and qRCAH-10-2, were detected in regions different from that of qRCH-10. No QTL for NSC concentration at 14 d after heading was detected between RM8201 and 8716, the region analyzed in this study. The QTLs qRCH-10 and qRCAH-10-1 for RUBisCO content would have additive effects. These QTLs for RuBisCO content and NSC concentration newly found using CSSLs and their backcross progeny F-2 population should be useful for better understanding the genetic basis of source and temporary-sink functions in rice and for genetic improvement of Koshihikari in terms of their functions.