Genetic Analysis of Water Use Efficiency in Rice (Oryza sativa L.) at the Leaf Level

Carbon isotope discrimination (Delta C-13) is considered as an index of leaf-level water use efficiency, an important objective for plant breeders seeking to conserve water resources. We report in rice a genetic analysis for Delta C-13, leaf structural parameters, gas exchange, stomatal conductance, and leaf abscisic acid (ABA) concentrations. Doubled haploid and recombinant inbred populations, both derived from the cross IR64 x Azucena, were used for quantitative trait locus (QTL) analysis following greenhouse experiments Delta C-13 QTLs on the long arms of chromosomes 4 and 5 were colocalized with QTLs associated with leaf blade width, length, and flatness, while a QTL cluster for Delta C-13, photosynthesis parameters, and ABA was observed in the near-centromeric region of chromosome 4. These results are consistent with phenotypic correlations and suggest that genetic variation in carbon assimilation and stomatal conductance contribute to the genetic variation for Delta C-13 in this population.