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Background: Wild relatives have substantial impacts on the resistance of wheat to biotic and abiotic stresses. The genetic diversity of these wild varieties can be employed to widen the wheat gene pool by introducing wild allele introgression and genome structure variations. The powdery mildew resistance gene Pm13 was derived from the wheat wild relative species Aegilops longissima (S1S1, 2n = 2x = 14) and was transferred into wheat chromosome 3BS over 30 years. Until recently, it has not been widely used in wheat breeding, possibly because of the linkage drag associated with Pm13 introgression or poor alien segment compensation to 3BS. Results: In this study, translocations between the Pm13 introgression and wheat homoeologous A, B and D chromosomes were developed by using a wheat ph1b mutant. The 3Sl (3B) substitution line was hybridized with the CS nullisomic-tetrasomic line N3AT3B, and then F1 was hybridized with the CSph1b mutant. Individuals homozygous for the ph1b mutant carrying the alien chromosome 3Sl were identified from the segregating populations via molecular markers and cytological analysis. Whole-arm recombinant translocations T3SlS.3AL and T3SlS.3BL and small recombinant translocations T3SlS-3AS.3AL, T3SlS-3BS.3BL and T3DS-3SlS-3DS.3DL carrying Pm13 introgression were subsequently identified via molecular cytological analysis. Furthermore, 4 disomic T3SlS-3BS.3BL recombinants carrying the homozygous Pm13 introgression were identified. All the translocations were nearly immune to powdery mildew. Conclusions: Our results provide novel alien homoeologous Pm13 translocations for improving powdery mildew resistance in wheat and insights into the interactions between different wheat genomes and alien chromosome segments. [ABSTRACT FROM AUTHOR]

Background: Aegilops tauschii is the donor of the bread wheat D genome. Based on spike morphology, the taxon has conventionally been subdivided into ssp. tauschii and ssp. strangulata. The present study was intended to address the poor match between this whole plant morphology-based subdivision and genetic relationships inferred from genotyping by fluorescence in situ hybridization karyotyping a set of 31 Ae. tauschii accessions. Results: The distribution of sites hybridizing to the two probes oligo-pTa-535 and (CTT)10 split the Ae. tauschii accessions into two clades, designated Dt and Ds, which corresponded perfectly with a previously assembled phylogeny based on marker genotype. The Dt cluster was populated exclusively by ssp. tauschii accessions, while the Ds cluster harbored both ssp. strangulata and morphologically intermediate accessions. As a result, it is proposed that Ae. tauschii ssp. tauschii is restricted to carriers of the Dt karyotype: their spikelets are regularly spaced along the rachis, at least in the central portion of their spike. Accessions classified as Ae. tauschii ssp. strangulata carry the Ds karyotype; their spikelets are irregularly spaced. Based on this criterion, forms formerly classified as ssp. tauschii var. meyeri have been re-designated ssp. strangulata var. meyeri. Conclusions: According to the reworking of the taxon, the bread wheat D genome was most probably donated by ssp. strangulata var. meyeri. Chromosomal differentiation reveals intra-species taxon of Ae. tauschii. Ae. tauschii ssp. tauschii has more distant relationship with breed wheat than ssp. strangulata and can be used for breeding improving effectively. [ABSTRACT FROM AUTHOR]

Background: The formation of an allopolyploid is a two step process, comprising an initial wide hybridization event, which is later followed by a whole genome doubling. Both processes can affect the transcription of homoeologues. Here, RNA-Seq was used to obtain the genome-wide leaf transcriptome of two independent Triticum turgidum × Aegilops tauschii allotriploids (F1), along with their spontaneous allohexaploids (S1) and their parental lines. The resulting sequence data were then used to characterize variation in homoeologue transcript abundance., Results: The hybridization event strongly down-regulated D-subgenome homoeologues, but this effect was in many cases reversed by whole genome doubling. The suppression of D-subgenome homoeologue transcription resulted in a marked frequency of parental transcription level dominance, especially with respect to genes encoding proteins involved in photosynthesis. Singletons (genes where no homoeologues were present) were frequently transcribed at both the allotriploid and allohexaploid plants., Conclusions: The implication is that whole genome doubling helps to overcome the phenotypic weakness of the allotriploid, restoring a more favourable gene dosage in genes experiencing transcription level dominance in hexaploid wheat.