Genome discrimination and chromosome pairing in the Hordeum chilense × Aegilops tauschii amphiploid
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Tritordeum (X Tritordeum Ascherson et Graebner) is a synthetic amphiploid belonging to the Triticeae tribe, which resulted from crosses between Hordeum chilense and wheat. It presents useful agronomic traits that could be transferred to wheat, widening its genetic basis.
In situ hybridisation with total genomic DNA from H. chilense and cloned, repetitive DNA sequences (pTa71 and pAs1) probes were used to discriminate the parental origin of all chromosomes, to analyse the chromosome pairing and to identify the chromosomes in pollen mother cells (PMCs) at metaphase I of the tritordeum line HT251 (HchHchDD, 2n = 4x = 28).
The H. chilense total genomic DNA and the ribosomal sequence pTa71 probes, allowed the unequivocal discrimination of the 14 chromosomes of Hch genome-origin and the 14 chromosomes of D genome-origin.
Chromosome pairing analysis revealed meiotic irregularities such as reduced percentage of PMCs with complete homologous pairing, high frequency of univalents, most of H. chilense-origin and a reduced frequency of intragenomic multivalents from both genomes. The H. chilense genome revealed high meiotic instability.
After individual chromosome identification at metaphase I with the pAs1 probe, we found the occurrence of pairing between chromosomes of different homoeology groups. The possible interest of the tetraploid tritordeum in the improvement of other Triticeae species is also discussed.
Key WordsAegilops tauschii Hordeum chilense in situ hybridisation meiotic pairing tritordeum
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