Genome discrimination by in situ hybridization in Icelandic species of Elymus and Elytrigia (Poaceae : Triticeae)

The genome constitution of Icelandic Elymus caninus, E. alaskanus, and Elyt rigia repens was examined by fluorescence in situ hybridization using genom ic DNA and selected cloned sequences as probes. Genomic in situ hybridizati on (GISH) of Hordeum brachyantherum ssp. californicum (diploid, H genome) p robe confirmed the presence of an H genome in the two tetraploid Elymus spe cies and identified its presence in the hexaploid Elytrigia repens. The H c hromosomes were painted uniformly except for some chromosomes of Elytrigia repens which showed extended unlabelled pericentromeric and subterminal reg ions. A mixture of genomic DNA from H. marinum ssp. marinum (diploid,Xa gen ome) and H. murinum ssp. leporinum (tetraploid,Xu genome) did not hybridize to chromosomes of the Elymus species or Elytrigia repens, confirming that these genomes were different from the H genome. The St genomic probe from P seudoroegneria spicata (diploid) did not discriminate between the genomes o f the Elymus species, whereas it produced dispersed and spotty hybridizatio n signals most likely on the two St genomes of Elytrigia repens. Chromosome s of the two genera Elymus and Elytrigia showed different patterns of hybri dization with clones pTa71 and pAes41, while clones pTa1 and pSc119.2 hybri dized only to Elytrigia chromosomes. Based on FISH with these genomic and c loned probes, the two Elymus species are genomically similar, but they are evidently different from Elytrigia repens. Therefore the genomes of Iceland ic Elymus caninus and E. alaskanus remain as StH, whereas the genomes of El ytrigia repens are proposed as XXH.