Rice Genetics IV - IRRI books - International Rice Research Institute

ABNipponbare × KasalathF 2QTL analysisF 1BC 1 F 1BC 3 F 1× NipponbareMarker-assistedselection (MAS)BC 1 F 2 × NipponbareSingle-seedMASdescent methodBC 2 F 1 × NipponbareMASMAS× Nipponbare12 3 4 5 6 7 8 9 10 11 12Hd9 Hd11Hd3Hd13Hd5Hd8Hd1 Hd4Hd10Hd12Hd2Hd7Hd6BC 3 F 2BC 3 F 3BC 3 F 4BC 4 F 1BC 1 F 5MASQTL analysisBC 4 F 2BC 4 F 3Detection of additional QTLsFine mapping of QTLsSelection of near-isogenic linesFig. 2. Plant materials used to detect QTLs and chromosomal locations of QTLs controllingheading date. (A) Mapping populations derived from a cross between Nipponbare and Kasalath.QTL mapping was performed by using F 2 , BC 1 F 5 , and BC 3 F 2 lines. Fine mapping and selection ofnear-isogenic lines were conducted using advanced backcross progeny. (B) A high-density RFLPlinkage map showing chromosomal locations of putative QTLs (Hd1–Hd13) for heading date.neously, cannot be used for the precise mapping of one of multiple QTLs. Moreover,determination of the true genetic action of the QTL is more difficult because the geneticparameters of a given QTL are often affected by the segregation of other QTLs.In plant genetics, NILs developed by backcrossing have been widely used to performaccurate genetic analysis because the segregating populations obtained fromcrossing NILs and their recurrent parents simplify genetic variation by excluding extra-geneticfactors. To obtain an answer to the main question about QTLs—Does aQTL represent a single locus or multiple loci?—we performed fine mapping of a QTLas a single Mendelian factor using advanced backcross progeny. So far, we have shownthat 9 of 13 QTLs for heading date could be mapped precisely on the RFLP linkagemap as single factors (Yamamoto et al 1998, 2000, H.X. Lin and M. Yano, unpublisheddata). Only one chromosomal region could be dissected into two factors withdifferent functions in the control of heading (L. Monna and M. Yano, unpublisheddata).230 Yano