Molecular Cytogenetic Characterization of Eb‐Genome Chromosomes in Thinopyrum bessarabicum Disomic Addition Lines of Bread Wheat

Abstract

Thinopyrum bessarabicum (2n=2x=14, EbEb=JJ) is recognized for its high tolerance to soil salinity and the scab disease caused by Fusarium graminearum. Seven Triticum aestivum/T. bessarabicum disomic addition lines (2n=44=21′′ ABD + 1′′ Eb) developed at the International Maize and Wheat Improvement Center were assayed. Genomic in situ hybridization (GISH) showed that six of the seven were true disomic alien addition lines, whereas one was a duplication‐translocation addition line in which four‐fifths of the additional chromosome was an alien chromosome segment and one‐fifth was a wheat chromosome segment. Using AFLP fragments amplified from 32 selective primer pairs, 389 fragments were assigned to T. bessarabicum chromosomes. The duplication‐translocation addition line had no unique AFLP fragments but shared 25 fragments with the 7Eb addition line, indicating that the translocation chromosome probably involved the 7Eb rather than the 3Eb, as originally described. The presumed 6Eb addition line was determined to have a pair of 4Eb chromosomes. Thus, the 3Eb and 6Eb addition lines are missing. At present, there are 48 AFLP markers for 1Eb, 67 for 2Eb, 39 for 4Eb, 59 for 5Eb, and 54 for 7Eb. In addition, two RAPD markers for 1Eb, two for 2Eb, six for 4Eb, one for 5Eb, and three for 7Eb were identified. Sixty‐eight AFLP markers were present in the amphidiploid but absent in all tested disomic addition lines, making them putative markers for 3Eb and/or 6Eb. Also, 50 AFLP and six RAPD markers occur in at least five Eb chromosomes. These molecular markers, when used in conjunction with GISH, will be useful in identifying the two missing Eb addition lines and in monitoring the introgression of Eb chromosomal segments into wheat.