Cloning and mapping of chromosome-specific DNA markers in crops

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Repeated DNA sequences cloned from Agropyron intermedium (2n=42, E1E1E2E2XX) enabled to identify the Ag.intermedium chromosomes in the common wheat genome by Southern and in situ hybridization.Two repetitive DNA clones not hybridized to the total genomic DNA of Triticum aestivum cv.Chinese Spring (CS) were screened from the MboI-digested genomic DNA library of Ag.intermedium. The clone pTA100 hybridized to the 350bp tandem repeated family defined by digestion with EcoO109I.The clone pTA100 showed homology with the EcoO109I-380 bp tandem repeated family of rye (TOMITA et al.1993) which belonged to the 350 bp family or rye (BEDBROOK et al.1980, APPELS et al.1986) . the clone pTA28 hybridized to four kinds of repeated fragments, 6800 bp, 6200 bp, 3600 bp and 1850 bp defined by digestion with EcoO109I.The clone pTA100 used as a probe did not exhibit hybridization signals based on both genomic Southern and chromosomal in situ analysis for the amphiploid AgCS (2n=56, AABBDDEE) between CS (2n … More =42, AABBDD) and Ag.elongatum (2n=14, EE) . This finding indicated that the pTA100 family was absent in the E genome. However, the clone pTA100 hybridized to the terminal regions of the ten pairs of chromosomes in Ag.intermedium. These results indicated that at least three pairs of chromosomes belonged to the E1 or E2 genomes and the segments of the hybrid region in these chromosomes must have originated from the X genome.The clone pTA100 was used as a probe for Southern hybridization to seven kinds of Wheat-Ag.intermedium chromosome addition lines. The 350bp tandem patterns were observed in the addition lines A,B,C and D,while no hybridization was observed in the remaining three addition lines. Moreover, based on chromosomal in situ analysis the clone pTA100 hybridized to each terminal region of the short arm of added chromosome A,the long arm of added chromosome B and both arms of added chromosomes C and D.As the added chromosomes C and D differed in their arm rotios, it was possible to distinguish these four added chromosomes from each other by the ISH site of the clone pTA100. The three kinds of added chromosomes A,B and D showing the ISH site of the clone pTA100 and faint C-bands may have originated from the X genome of Ag.intermedium. Less