Plant & Animal Genome VI Conference Plant & Animal Genome VI Conference
W92
Rice Genome Research Program, National Institute of Agrobiological Resources/Institute of the Society for Techno-innovation of Agriculture, Forestry and Fisheries, Tsukuba, Ibaraki 305, Japan
Genes controlling heading date in rice were mapped using several types of
progeny derived from a cross between a japonica variety, Nipponbare,
and an indica variety, Kasalath. Eleven quantitative trait loci
(QTLs) with large and small effects were identified. So far, five QTLs have
been mapped precisely as single Mendelian factors by combining the use of
advanced backcross progeny and ordinal linkage mapping based on progeny
tests. Seven near-isogenic lines (NILs) of QTLs were also developed by
marker-aided selection from backcross progeny. These NIL-QTLs allowed us to
identify the function of detected QTLs, such as photoperiod sensitivity or
basic vegetative growth, by measurement of days to heading under various
controlled-day-length conditions. Combining two or more QTLs into the
genetic background of Nipponbare allowed us to investigate epistatic gene
interactions among QTLs. We could also identify yeast artificial chromosome
clones carrying some of the detected QTLs that control photoperiod
sensitivity by the high-resolution and fine-scale mapping of these QTLs.
Cosmid contigs of the genomic regions spanning these QTLs are under
construction. Some candidate cosmid clones have been used in the genetic
complementation analysis based on transformation. To facilitate the
identification of genes at QTLs, we also developed a new cosmid vector that
allows us to do Agrobacterium-mediated transformation of rice.