Homoeologous metaphase I (Ml) associations in hybrids between durum wheat and its wild allotetraploid relatives Aegilops neglecta, Ae. triuncialis and Ae. ventricosa have been characterized by a genomic in situ hybridization procedure that allows simultaneous discrimination of A, B and wild species genomes. Earlier results in equivalent hybrids with the wild species Ae. cylindrica and Ae. geniculata have also been considered to comparatively assay the Ml pairing pattern of the durum wheat x

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... lops interspecific combinations more likely to occur in nature. The general picture can be drawn as follows. A and B wheat genomes pair with each other less than the 2 wild constituent genomes do in any of the hybrid combinations examined. Interspecific wheat-wild associations account for 60-70% of total Ml pairing in all hybrids, except in that derived from Ae. triuncialis, but the A genome is always the wheat partner most frequently involved in Ml pairing with the wild homoeologues. Hybrids with Ae. cylindrica, Ae. geniculata and Ae. ventricosa showed similar reduced levels of Ml association and virtually identical Ml pairing patterns. However, certain recurrent differences were found when the pattern of homoeologous pairing of hybrids from either Ae. triuncialis or Ae. neglecta was contrasted to that observed in the other durum wheat hybrid combinations. In the former case, a remarkable preferential pairing between the wild species constituent genomes U' and C* seems to be the reason, whereas a general promotion of homoeologous pairing, qualitatively similar to that observed under the effect of the phlc mutation, appears to occur in the hybrid with Ae. neglecta. It is further discussed whether the results reported here ca n be extrapolated to the corresponding bread wheat hybrid combinations.