HIGH-RESOLUTION RFLP MAPPING OF THE FERTILITY RESTORATION (RF3) GENE AGAINST TRITICUM-TIMOPHEEVI CYTOPLASM LOCATED ON CHROMOSOME 1BS OF COMMON WHEAT

Near-isogenic lines of alloplasmic wheat for the Rf3 gene controlling fertility restoration against the cytoplasm of Triticum timopheevi wer e developed by successive backcrossing of Chinese Spring to the F-1 pl ants between (timopheevi)-CS (male sterile) and T. spelta (carrying Rf 3). The resultant three BC3F1 plants were self-pollinated so as to obt ain 125 BC3F2 progenies. Using this population, we precisely mapped th e Rf3 gene on the short arm of wheat chromosome 1B (1BS) of the RFLP l inkage map. The Rf3 gene was localized at a position 1.2 cM and 2.6 cM distant from Xcdo388 and Xabc156, respectively. The genetic distances of Rf3 from Nor and Gli-BI were calculated to be 22.3 cM and 18.6 cM, respectively, supporting previous data. Estimation of the physical di stance of the region suggets that the Rf3 gene resides within 500 kbp from the adjacent RFLP markers. The marker order of the genetic map co rresponded to that of the cytological map, except for the position of Xbcd98. Comparison between genetic and cytological maps clearly shows that RFLP markers are unevenly distributed throughout the chromosome a rm, and recombinations took place unequally in the chromosome arm.