AN EFFICIENT SCREENING FOR TERMINAL DELETIONS AND TRANSLOCATIONS OF BARLEY CHROMOSOMES ADDED TO COMMON WHEAT

As a prerequisite to determine physical gene distances in barley chrom osomes by deletion mapping, a reliable, fast and inexpensive approach was developed to detect terminal deletions and translocations in indiv idual barley chromosomes added to the chromosome complement of common wheat. A refined fluorescence in situ hybridization (FISH) technique s ubsequent to N-banding made it possible to detect subtelomeric repeat sequences (HvT01) on all 14 chromosome arms of barley. Some chromosome arms could be distinguished individually based on the number of FISH signals or the intensity of terminal FISH signals. This allowed the de tection and selection of deletions and translocations of barley chromo somes (exemplified by 7H and 4HL), which occurred in the progeny of th e wheat lines containing a pair of individual barley chromosomes (or t elosomes) and a single so-called gametocidal chromosome (2C) of Aegilo ps cylindrica. This chromosome is known to cause chromosomal breakage in the gametes in which it is absent. Terminal deletions and transloca tions in barley chromosomes were easily recognized in metaphase and ev en in interphase nuclei by a decrease in the number of FISH signals sp ecific to the subtelomeric repeat. These aberrations were verified by genomic in site hybridization. The same approach can be applied to sel ect deletions and translocations of other barley chromosomes in wheat lines that are monosomic for the Ae. cylindrica chromosome 2C.