Identification of alien chromosomes in a series of Allium fistulosum - A-cepa monosomic addition lines by means of genomic in situ hybridization

Genomic in situ hybridization (GISH) was used to identify alien chromosomes in a series of eight different Allium fistulosum - A. cepa monosomic addit ion lines. Biotin-labeled total genomic DNA from shallot (A. cepa L. Aggreg atum group) was used as a probe together with an excess amount: of unlabele d blocking DNA from the recipient plant, Japanese bunching onion (A. fistul osum L.). Probe hybridization sites were detected by FITC-conjugated avidin and anti-avidin antibody using an epifluorescence microscope. In each mito tic metaphase cell of all the eight types of monosomic addition lines, the alien chromosomes were successfully discriminated from other 16 A. fistulos um chromosomes. Furthermore, no clear exchanges of chromosome segments betw een A. cepa and A. fistulosum were observed. This finding indicates that in each addition line an entire (unrecombined) A. cepa chromosome is present in an integral diploid background of A. fistulosum.