| Results and Discussion Segregation analysis of F2 generation, when crossing alloplasmic lines with both marker lines, has shown, as a whole, digenic control of awnedness trait and monogenic control of glume hairiness trait. At the same time there is observed a strong cytoplasm effect on segregation in some combinations of crosses. Cytoplasms Ae. kotschyi. Ae. ventricosa and Ae. crassa 6X show segregation distortion for awnedness - awnlessness trait when using MS63 line as a pollen parent (Table 1). In these crosses a part of awned plants was greatly reduced in F2. Cytoplasms of Ae. squarrosa and Ae. comosa induced sharp increase of a part of hairy glume plants. When using another marker - K31362, the effect of the cytoplasms on segregation was different (Table 2). Cytoplasms of T. aestivum and Ae. squarrosa increased considerably awned plant rate, cytoplasms of Ae. cylindrica and Ae. kotschyi decreased it. Cytoplasms of Ae. juvenalis and Ae. vavilovii changed segregation for glume hairiness character in the direction of decreasing the part of hairy plants. Though germination of F2 plants in various crossing combinations was different (Table 1 and 2) one couldn't suppose that the reason of segregation change was due to selective mortality of definite combinations of genotypes and cytoplasms as no high negative correlations was revealed between germination and segregation change (r = 0.319 and 0.211 for crossing with MS-63 marker and r = -0.234 and 0.076 for crossing with K31326 marker). At least germination change is not a single and major reason for observed segregation shifts. Both pollen parents have identical and allelic marker genes, nevertheless different numerical segregation ratio is observed with the same cytoplasms. It can be assumed that cytoplasm effect on segregation is due to different gamete survival or different probability of gamete participation in fertilization depending on cytoplasm and genes linked with markers. Summarizing data obtained in the present and the previous papers (DAVYDENKO 1984, 1985) one can come to the conclusion that segregation shifts may be observed for diverse traits having different chromosomal localization. Different cytoplasms are "chromosome specific" as they can prefer gametes carrying one of two chromosomes depending on genes located on them. It is interesting that cytoplasmic effect on sister chromatid exchange frequency was also "chromosome specific" and "locus specific" (LUGININ et al. 1987). Probably specificity of nuclear cytoplasmic effects is a general property becoming apparent both at a plant phenotype level and at individual chromosome and locus level. In any case the obtained data are evidence of the great cytoplasm influence on changes of definite allele rates in plant populations. These facts give ground for speculations about change orientation of nuclear genes frequency by cytoplasmic background change, what was, probably, of great importance in evolution of Triticinae tribe and other higher plants and may be important in selection and breeding processes of crop plants. The author is grateful to Prof. TSUNEWAKI K. for kind presentation of alloplasmic wheat lines seeds. |
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