Retroelement Insertional Polymorphisms, Diversity and Phylogeography within Diploid, D-genome Aegilops tauschii (Triticeae, Poaceae) Sub-taxa in Iran
1 Department of Biology, University of Leicester, Leicester LE1 7RH, UK
2 Department of Biology, University of Isfahan, Isfahan, Iran
* For correspondence. E-mail phh4{at}le.ac.uk
Received: 5 September 2007 Returned for revision: 22 January 2008 Accepted: 27 February 2008
Background and Aims: The diploid goat grass Aegilops tauschii (2n = 2x = 14) is native to the Middle East and is the D-genome donor to hexaploid bread wheat. The aim of this study was to measure the diversity of different subspecies and varieties of wild Ae. tauschii collected across the major areas where it grows in Iran and to examine patterns of diversity related to the taxa and geography.
Methods: Inter-retroelement amplified polymorphism (IRAP) markers were used to analyse the biodiversity of DNA from 57 accessions of Ae. tauschii from northern and central Iran, and two hexaploid wheats.
Key Results: Eight IRAP primer combinations amplified a total of 171 distinct DNA fragments between 180 and 3200 bp long from the accessions, of which 169 were polymorphic. On average, about eight fragments were amplified with each primer combination, with more bands being amplified from accessions from the north-west of the country than from other accessions.
Conclusions: The IRAP markers showed high levels of genetic diversity. Analysis of all accessions together did not allow the allocation of individuals to taxa based on morphology, but showed a tendency to put accessions from the north-west apart from others regions. It is speculated that this could be due to different activity of retroelements in the different regions. Within the two taxa with most accessions, there was a range of IRAP genotypes that could be correlated closely with geographical origin. This supports suggestions that the centre of origin of the species is towards the south-east of the Caspian Sea. IRAP is an appropriate marker system to evaluate genetic diversity and evolutionary relationships within the taxa, but it is too variable to define the taxa themselves, where more slowly evolving morphological, DNA sequence or chromosomal makers may be more appropriate.
Key words: Aegilops squarrosa, Aegilops tauschii, biodiversity, fertile crescent, IRAPs, phylogeography, plant breeding, retrotransposons, Triticum
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