[Comparative cytological and molecular analysis of introgressive common wheat lines containing genetic material of...

A total of 40 introgressive lines of common wheat (2n = 42) Triticum aestivum L x T. timopheevii Zhuk., resistant to brown rust and partly to powdery mildew, were examined. Based on cytological analysis of meiosis in pollen mother cells (PMC), hybrid lines were subdivided into two groups characterized by either stable or unstable meiosis. In cytologically stable lines, chromosome configuration at the MI stage of meiosis was mostly bivalent (21II) with small proportion of defect cells (almost 10%), which at most contained two univalents (20II + + 21). Cytologically unstable group was comprised of the lines, containing high proportions of cells with abnormal chromosome pairing in meiotic PMC, as well as the cells with multivalents, and the lines containing aneuploid plants. Localization of the T. timopheevii fragments performed with the use of SSR markers showed that the lines with unstable meiosis were characterized by higher numbers of introgressions compared to stable lines. The influence of certain chromosomes of T. timopheevii on chromosome pairing stability was also demonstrated. In cytologically unstable lines, the increased frequency of 2A substitutions along with the high frequency of introgression of T. timopheevii genetic material into chromosome 7A was observed. Multivalents were scored in all cases of introgression in chromosome 7A. It was suggested that the reason for the genome instability in hybrid forms lied in insufficient compensating ability of certain T. timopheevii chromosomes and/or their parts, involved into recombination processes.