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The genus Bromus subgen. Festucaria is a widespread Old World and New World taxon having genomes A, B and L, distinguished cytogenetically. Stebbins (1981) suggested that evolution in Bromus went from the small genomes A and B to the large genome L. Thus, Old World species with genomes A and B could be ancestral to New World species with genome L. To test this hypothesis we carried out RAPD analysis of a representative group of species from subgen. Festucaria. RAPD band patterns enabled resolution of 13 species after excluding the species-specific bands with high/moderate support. The basal position of Bromus variegatus M. Bieb. - an Old World species presumably having a B genome - in relation to some New World species with the genome L confirmed Stebbins' hypothesis of its ancestry in relation to the Old World species. The group of high bootstrap support, B. cappadocicus Boiss. et Balansa-B. erectus Huds.-B. riparius Rehm., with genome A. and a distinctly xerothermic ecological profile, was related to a New World species with genome L, B. auleticus Trin. ex Nees, pointing to their presumably common evolutionary history.
Extensive genetic variations of low-molecular-weight glutenin subunits (LMW-GS) and their coding genes were found in the wild diploid A- and D-genome donors of common wheat. In this study, we reported the isolation and characterization of 8 novel LMW-GS genes from Ae.longissima Schweinf. & Muschl., a species of the section Sitopsis of the genus Aegilops, which is closely related to the В genome of common wheat. Based on the N-terminal domain sequences, the 8 genes were divided into 3 groups. A consensus alignment of the extremely conserved domains with known gene groups and the subsequent cluster analysis showed that 2 out of the 3 groups of LMW-GS genes were closely related to those from the В genome, and the remaining was related to those from A and D genomes of wheat and Ae. tauschii. Using 3 sets of gene-group-specific primers, PCRs in diploid, tetraploid and hexaploid wheats and Ae. tauschii failed to obtain the expected products, indicating that the 3 groups of LMW-GS genes obtained in this study were new members of LMW-GS multi-gene famailies. These results suggested that the Sitopsis species of the genus Aegilops with novel gene variations could be used as valuable gene resources of LMW-GS. The 3 sets of group-specific primers could be utilized as molecular markers to investigate the introgression of novel alien LMW-GS genes from Ae. longissima into wheat.
Tetraploid rye was crossed with different tetraploid triticale lines. The F₁ generation of tetraploid rye × tetraploid triticale hybrids was backcrossed with 4x rye. After backcrossing, all BC₁-F₁ plants were subjected to open pollination, whereas in the BC₁-F₂ generations only plants with wheat chromosomes in their karyotypes were open-pollinated. Substitution, addition and addition-substitution lines of wheat chromosomes in tetraploid rye were isolated from the F₂ and F₃ of BC₁. In 60 plants of BC₁-F₂, 59 chromosomes from the A genome and 9 from the B genome of wheat were recovered. The wheat chromosomes were monosomic except for five plants which were disomic, viz. 1A and 5A in two plants each, and a translocated 3AS/5AL in one plant. In 235 BC₁-F₃ plants, 174 wheat addition and substitution chromosomes were found, 143 from the A genome and 31 from the B genome. All wheat chromosomes except 3A from the A genome and four chromosomes from the B genome - 2B, 3B, 5B and 7B were recovered. The number of substitutions ranged from one to four per plant, only two plants having four. In the group of addition plants the number of added wheat chromosomes ranged from one to two, and in the case of addition-substitution plants — from two to four. Wheat chromosomes occurred in monosomic form, except 10 plants. Six substitution plants were disomic for 1 A, 2A, 5A, 7A, 2B and 3B, respectively. One was disomic for 1A and 5A in two addition plants. Two addition-substitution plants were double disomic: 1A and 5A - in one, and 1A and 3B in the other. In the BC₁-F₃ generation, 23 different translocations were found, four of which occurred between wheat chromosomes and the remaining 19 - between wheat and rye chromosomes. Translocated chromosomes were monosomic, except four plants. Two of them were disomic for 3AS/4RL, one for 4AS/4RS and one for 7AS/7RS. The fertility of both addition and substitution plants ranged from 0 to 38.0 seeds/spike, regardless of the chromosome number, with a mean of 9.61 seeds/spike. Plants with 28 chromosomes showed singnificantly higher fertility than plants with 29 and more chromosomes, except additoion plants with chromosomes 5A and 5B. The analysis of the influence of particular wheat chromosomes on plant fertility showed that both substitution and addition plants with chromosome 6A had the highest average fertility, while plants with chromosome 2B in substitution lines as well as plants with chromosome 2A in addition and addition-substitution lines had the lowest fertility.
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