Synthesis of bridging hybrids in the process of introduction of diploid wheat genomes into hexaploid wheat
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Wild related species are a useful reservoir of valuable genes for widening the genetic base of wheat and for the reduction of the vulnerability of wheat cultivars to pathogens, fungal diseases and environmental hazards. In this work, the action of prezygotic and postzygotic incrossability barriers was characterized, determining the possibilities of direct introduction of Am - genome from Triticum monococcum and D-genome from Triticum. tauschii into T. aestivum cultivars, with elimination of commonly performed bridging hybridisation with tetraploid wheat. As gene recipient parents, Polish cultivars of hexaploid wheat cv. Omega, cv. Igna (spring) and cv. Tercja (winter) were used. Application of wheat cultivars as female parents in hybridisation with T. tauschii yielded a very low percentage of effective pollination (0-1.2%). In reciprocal crosses prezygotic incompatibility barriers were more weakly expressed, and percentages of effective pollination (i.e. pollination which initiates the first steps of seed development) were from 28.3 to 32.4. The ability to form callus on MS medium with standard for areals concentration of growth regulators (i.e. 1 mg dcm-3 IAA and 1.0 mg dcm-3 kinetine) was positively correlated with F1 plants regeneration rate. Introduction of Am - genome into common wheat cultivars can be performed exclusively using T. monococcum as a male parent because of pollen sterility caused by T. monococcum cytoplasm in hybrid progeny. After pollination of T. aestivum stigmas with pollen of T. monococcum the frequency of effective pollination was 1.2-4.9%. The most important factor influencing the results of in vitro culture was the lethality of young seedlings, caused by postzygotic gene incompatibility.
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W. Sodkiewicz, Instytut Genetyki Roslin, Polska Akademia Nauk, ul. Strzeszynska 34, 60-479 Poznan, Poland, e-mail: email@example.com