Mapping of QTLs controlling carbon isotope discrimination in the photosynthetic system using recombinant inbred lines derived from a cross between two different rice (Oryza sativa L.) cultivars. uri icon

abstract

  • Carbon isotope discrimination (Delta) occuring in the process of photosynthesis, shows variation among rice (Oryza sativa L.) cultivars. Elucidation of specific traits associated with the extent of this discrimination under irrigated conditions may be useful to improve photosynthetic ability in rice plants. We measured leaf photosynthesis and Delta in Milyang 23 and Akihikari, and conducted quantitative trait loci (QTL) analysis on Delta at heading stage using a population of 126 recombinant inbred lines (RILs), derived from a cross between the two cultivars. While the two parental cultivars showed a similar Delta, the RILs showed a wide variation in Delta including transgressive segregation. Seven QTLs were detected for Delta; four on chromosomes 2 (two regions), 7, and 11 were those for Delta that is increased by the Milyang 23 allele, whereas the other three on chromosomes 1, 2, and 6 were those for Delta that is increased by the Akihikari allele. These results suggest that G in Milyang 23 may be discriminated through a photosynthetic process different from that in Akihikari. Milyang 23 showed a higher stomatal conductance and a higher ratio of intercellular to ambient CO2 concentration (Ci/Ca), while Akihikari showed a higher carboxylation efficiency but a lower Ci/Ca. According to the theory that a higher Ci/Ca leads to a higher Delta, the QTLs for Delta that is increased by the Milyang 23 allele might be related to a higher stomatal conductance. However, the theory provided no persuasive factors to explain the QTLs for Delta that is increased by the Akihikari allele. Plausible factors associated with these QTLs are discussed.

publication date

  • 2006
  • 2006