Hybrids involving wheat relatives and autotetraploid Triticum umbellulatum

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Abstract
Genomic analysis based on chromosome pairing is perhaps the most reliable method of determining the major evolutionary pathways in allopolyploid series. Difficulties can arise when genomes have become modified, since then they will not correspond exactly to the genomes used as analysers. Some resolution of this type of problem is possible when the interpretation of meiotic data is enhanced by numerical methods. However, providing conclusive evidence of which chromosomes are pairing rather than just how many remains a problem unless specific chromosomes can be recognized. One possible solution is to make hybrids between natural polyploids and autotetraploids of the putative diploid progenitors. The recognition of specific pairing patterns in such hybrids will provide substantial evidence of which chromosomes are pairing at metaphase I. Hybrids between an autotetraploid Triticum umbellulatum and the natural U-genome polyploids T. kotschyi, T. neglecta, T. ovatum, T. macrochaetum, T. columnare, T. triunciale, and T. juvenale demonstrate that the U-genome of most of them is very closely related to the U-genome of the diploid T. umbellulatum. The U-genome in four hybrids in two accessions of T. ovatum does differ from its diploid progenitor, T. columnare shows some heterogeneity, and T. juvenale may show differentiation.Key words: autotetraploid, evolution, genome analysis, Triticum species, pivotal–differential evolution.