Intergenomic translocations of polyploid oats (genus Avena) revealed by genomic in situ hybridization

Wild and cultivated hexaploid oats share the same genomes (AACCDD) and disp lay a considerable level of interspecific variation in both plant and chrom osome morphology. The GISH was utilized to detect the interspecific genomic compositions in four hexaploid and two tetraploid oats using total genomic DNA of Avena eriantha (a C-genome diploid) as probe. Intergenomic transloc ations between A/D and C-genome chromosomes were frequently observed in hex aploid and tetraploid species. In the hexaploid, two pairs of A/D genome se gments on C-genome chromosome (A/D-C) translocation and four to six pairs o f C-genome segments on A/D genome chromosome (C-A/D) translocation were cle arly identified whilst the number of A/D-C translocations was constant amon g species. In the tetraploid A. maroccana (AACC), a pair of A-C and four pa irs of C-A translocations were observed. Moreover, the A/D translocation se gments on chromosome 5C was detected only in A. byzantina and A. maroccana, whilst A/D-C translocations were observed on the 1C and 7C of A. sativa, A . fatua and A. sterilis. A. byzantina did however also carry the 1C rearran gement. This result shows that A. byzantina has retained a similar genomic constitution to the tetraploid ancestor of hexaploid oats, A. maroccana. Th ree pairs of A-C translocations were detected only in A. murphyi (AACC), an d two pairs of those were the 1C and 7C as well as the three hexaploid spec ies except A. byzantilza.