Chromosome elimination and introgression following somatic hybridization between bread wheat and other grass species

The timing and influencing factor of donor chromosome elimination and introgression in somatic hybrids involving bread wheat (Triticum aestivum L.) was investigated by sampling fusion products made between bread wheat and four different donor species. Genomic in situ hybridization experiments showed that both events in the main occurred within 12-15 days of the fusion. Over 70 % of the elimination events had taken place before the first mitotic interphase. Pre-treating the donor protoplasts by either gamma or UV irradiation showed that the severity of exposure affected the likelihood of chromosome elimination and introgression. More donor chromosome elimination and less introgression occurred when donors were phylogenetically more distant, such as annual meadow grass (Poaannua) or maize (Zea mays), than phylogenetically closer donors such as tall wheatgrass [Agropyron elongatum (Thinopyrum elongatum)] or Haynaldia villosa. The interaction effect between donor species and irradiation time significantly affected the chromatin behaviors during somatic hybridization. Besides, the polyploid A. elongatum behaved differently from diploid H. villosa, even though these two species are phylogenetically equidistant from wheat.