Reorganization of wheat and rye genomes in octoploid triticale (\xd7\xa0Triticosecale)

Anna Kalinka,Magdalena Achrem

doi:10.1007/s00425-017-2827-0

Abstract

Main conclusionThe analysis of early generations of triticale showed numerous rearrangements of the genome. Complexed transformation included loss of chromosomes, t-heterochromatin content changes and the emergence of retrotransposons in new locations. This study investigated certain aspects of genomic transformations in the early generations (F5 and F8) of the primary octoploid triticale derived from the cross of hexaploid wheat with the diploid rye. Most of the plants tested were hypoploid; among eliminated chromosomes were rye chromosomes 4R and 5R and variable number of wheat chromosomes. Wheat chromosomes were eliminated to a higher extent. The lower content of telomeric heterochromatin was also found in rye chromosomes in comparison with parental rye. Studying the location of selected retrotransposons from Ty1-copia and Ty3-gypsy families using fluorescence in situ hybridization revealed additional locations of these retrotransposons that were not present in chromosomes of parental species. ISSR, IRAP and REMAP analyses showed significant changes at the level of specific DNA nucleotide sequences. In most cases, the disappearance of certain types of bands was observed, less frequently new types of bands appeared, not present in parental species. This demonstrates the scale of genome rearrangement and, above all, the elimination of wheat and rye sequences, largely due to the reduction of chromosome number. With regard to the proportion of wheat to rye genome, the rye genome was more affected by the changes, thus this study was focused more on the rye genome. Observations suggest that genome reorganization is not finished in the F5 generation but is still ongoing in the F8 generation.

Highlights

Synthetic allopolyploids are most often obtained by interspecific or intergeneric hybridization, followed by chromosome doubling in hybrids
Transformations of parental genomes in newly formed allopolyploids are a multidimensional phenomena, difficult to capture both in time and space
It is difficult to identify all levels of genomic changes, and very erroneous conclusions can be drawn from partial analyses

Summary

Introduction

Synthetic allopolyploids are most often obtained by interspecific or intergeneric hybridization, followed by chromosome doubling in hybrids. Certain phenomena that accompany the naturally occurring allopolyploidization could be distinguished thanks to the possibility of creating such synthetic allopolyploids. The diploidization processes proceed differently and have a different nature in individual allopolyploid species (Liu and Wendel 2002). The genomic response to allopolyploidization is species-specific. There are virtually no changes and parental genomes remain unchanged. For most allopolyploids, largescale modifications of the emerging hybrid genome have been demonstrated. These transformations often occur in a relatively short period of time, immediately after the hybridization and/or polyploidization (Teutonico and Osborn 1994; Wendel et al 1995)

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