Introgressive hybridization of common wheat has been and remains an efficient way for enriching its gene pool with resistance genes against environmental stress factors. In this aspect, T genome of the diploid species Amblyopyrum muticum (Boiss.) Eig. is believed to be prospective. The genome substitution amphidip loid Aurotica (AABBTT) with the A and B subgenomes from the common wheat cultivar Aurora and with the T subgenome from the indicated species is characterized by a high level of winter resistance. This trait is asso ciated in wheat with the chromosomes of the fifth homoeologous group. Using a comparative microsatellite analysis of Aurora and Aurotica DNAs, we identified nine SSR loci specific for the wheat D genome, whose primers produced different amplicons from Aurotica DNA. The latter were used in screening F 5 plants (Aurora × Aurotica) for the search of the specimens that carried the 5T chromosome or its fragments in their genomes. Among 234 plants, we detected 24 plants with disomic 5D/5T substitutions, which were the prog eny of five F 4 plants grown from two F 2 plants. A significant number of plants contained the recombinant 5D/5T chromosome. The recombination event could occur in any generation starting with F 2 .
Metabolic gene clusters (MGCs) are groups of genes involved in a common biosynthetic pathway. They are frequently formed in dynamic chromosomal regions, which may lead to intraspecies variation and cause phenotypic diversity. We examined copy number variations (CNVs) in four Arabidopsis thaliana MGCs in over one thousand accessions with experimental and bioinformatic approaches. Tirucalladienol and marneral gene clusters showed little variation, and the latter was fixed in the population. Thalianol and especially arabidiol/baruol gene clusters displayed substantial diversity. The compact version of the thalianol gene cluster was predominant and more conserved than the noncontiguous version. In the arabidiol/baruol cluster, we found a large genomic insertion containing divergent duplicates of the CYP705A2 and BARS1 genes. The BARS1 paralog, which we named BARS2, encoded a novel oxidosqualene synthase. The expression of the entire arabidiol/baruol gene cluster was altered in the accessions with the duplication. Moreover, they presented different root growth dynamics and were associated with warmer climates compared to the reference-like accessions. In the entire genome, paired genes encoding terpene synthases and cytochrome P450 oxidases were more variable than their nonpaired counterparts. Our study highlights the role of dynamically evolving MGCs in plant adaptation and phenotypic diversity.
Hybridization of wheat lines comprising fragments of alien genetic material (introgression) with common wheat cultivars is effective and widespread means of transferring alien genes into genomes of modern wheat cultivars, and remains the main method of expending genetic pool of common wheat using genes of wild relatives. Success of such transfer depends on the processes of sporo- and gametogenesis in F1 hybrids, therefore cytological assessment of this processes is obligatory. Stages of meiosis and microgametogenesis were studied on cytological preparations of spikes of F1 hybrids from reciprocal crosses of common wheat cultivars and wheat lines of introgression origin with alien genetic material from wheat wild relative Amblyopyrum muticum. Sporogenesis in F1 hybrids occurs with disorders in both male and female sexual areas. Instead of 21 closed bivalents chromosome configurations in maximal association of chromosomes in M1 PMC could contain up to 8 open bivalents, up to 12 univalents, including three- and quadrivalents. In A1 lagging chromatids were observed, and up to 5 micronuclei per cell were registered in tetrads. Quantitative characteristics of chromosome associations in M1 PMC did not differ for hybrids obtained using introgression lines as female (direct crossing) and male (reverse crossing) cross components. The difference between reciprocal crosses was detected only for the quantity of cells in tetrads with different quantity of micronuclei. F1 hybrids from direct crosses had smaller portion of cells without micronuclei, and more cells with 1-3 micronuclei compared to hybrids of reverse crosses.
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