Recently, four novel genes named Pinb-2, with 57–60% sequence similarity with wild-type allele Pinb-D1a coding for grain-hardness related puroindoline B have been shown to occur on homoeologous group 7 chromosomes in bread wheat (Triticum aestivum). In the present report, T. monococcum ssp. monococcum (Am genome) revealed a Pinb-2 gene with a poly-G tract and an in-frame TAG stop codon at the 5′ terminus of the coding DNA sequence. The stop codon was observed in 53 accessions of different geographic origins, suggesting that Pinb-2 in ‘monococcum’ wheat is unlikely to be expressed. By contrast, the coding DNA sequence of Pinb-2 in T. urartu (Au genome) was found to be 99% identical to its counterpart on chromosome 7AL in bread and durum (T. turgidum ssp. durum) wheat. Moreover, a sequence very similar to “urartu” Pinb-2 was found in tetraploid wheat T. timopheevii and hexaploid wheat T. zhukovskyi. This latter species exhibited an additional Pinb-2 pseudogene inherited from T. monococcum. The results are discussed in relation to the lineage of T. zhukovskyi and the potential role of Pin-b2 on kernel texture.
Authors:M. Megyeri, A. Farkas, M. Varga, G. Kovács, M. Molnár-Láng, and I. Molnár
Megyeri, M., Mikó, P., Molnár, I., Kovács, G. (2011): Development of synthetic amphiploids based on Triticum turgidum × T. monococcum crosses to improve the adaptability of cereals. Acta Agron. Hung. , 59 , 267
High-molecular-weight glutenin subunits (HMW-GSs) are important seed storage proteins associated with bread-making quality in common wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD). Variation in the Glu-A1x locus in common wheat is scare. Diploid Triticum monococcum ssp. monococcum (2n = 2x = 14, AmAm) is the first cultivated wheat. In the present study, allelic variations at the Glu-A1mx locus were systematically investigated in 197 T. monococcum ssp. monococcum accessions. Out of the 8 detected Glu-A1mx alleles, 5 were novel, including Glu-A1m-b, Glu-A1m-c, Glu-A1m-d, Glu-A1m-g, and Glu-A1m-h. This diversity is higher than that of common wheat. Compared with 1Ax1 and 1Ax2*, which are present in common wheat, these alleles contained three deletions/insertions as well as some single nucleotide polymorphism variations that might affect the elastic properties of wheat flour. New variations in T. monococcum probably occurred after the divergence between A and Am and are excluded in common wheat populations. These allelic variations could be used as novel resources to further improve wheat quality.
Authors:I. Garbus, M. Díaz, B. Stamova, and V. Echenique
The diploid wheat Triticum monococcum (2n = 2x = 14, AmAm) constitutes an excellent and simplified model to study wheat genome expression since it has lower genome complexity compared to polyploid wheat species.The analysis of a collection of near 10,000 ESTs obtained from two libraries of T. monococcum (TM011XXX and TM043E1X) and one from T. monococcum ssp. aegilopoides (TM046E1X), lead to 2246, 1843 and 2405 unigenes, respectively. The unigenes from each library were individually analyzed through the Blast2Go interface revealing higher identity compared to EST databases. However, a low percentage of sequences showed significant similarity with Triticum databases, reflecting that several novel Triticum expressed genes have been identified in these libraries. The sequences annotation and classification under GO categories showed similar distribution for the three libraries, but differences were identified in some subcategories.When a virtual unique library was constructed including the sequences from the three libraries, seventeen genes were found to be over-expressed between reproductive and vegetative tissues and thirty-five showed genotype-specific expression. These differentially expressed genes included several regulatory proteins and some unreported sequences. Some of these differentially expressed genes were validated by qRT-PCR. The exploration for specific polymorphisms allowed the identification of several SNPs.These EST libraries constitute a valuable tool for the assessment of active metabolic pathways in vegetative and reproductive tissues in diploid wheat species. A more detailed assessment of expression profiles of genotypes with spring and winter growth habits would allow the identification of the transcriptomic strategies developed under the pressure of these antagonistic growth conditions.
As regards wheat varieties constituting a natural ploid series the issue of analysing diploid, tetraploid and hexaploid species is tropical since ancient varieties can play significant roles in contemporary agriculture as well. Seventeen winter wheat varieties, out of which 2 diploid varieties carried genome A, 9 diploidic types had genomes AB, two varieties had genomes AG and four varieties were hexaploid ones with genomes ABD, were analysed from the point of view of their amino acid compositions. The amino acid contents of Asp, Thr, Ser, Glu, Gly, Ala, Cys, Val, Met, Ile, Leu, Tyr, Phe, His, Lys, Arg, Pro (a total of 17) were determined in the varieties listed above.It has been found that the amino acid contents of the grains genotype AA
exceeded the amino acid content of
in respect of all the amino acids analysed in this experiment, with Glu being the only exception. In comparison with the
wheat, essential amino acid contents showed a similarly favourable picture in the diploidic varieties mentioned. As regards type AB tetraploid varieties excesses of 13–16%, in comparison to the
wheat, were found in essential amino acid contents. The amounts of non-essential amino acids in all the winter wheat varieties showed decreases irrespective of the ploid level.What concerns the total amino acid content, all the winter wheat varieties with the exception of
(AB) contained less amino acid than the
wheat. All the monocarbonic acid and aromatic as well as heterocyclic amino acid contents of the wildly growing
(A) and the grown
(A) (with polaric, apolaric R groups, diamino radicles) exceeded the same contents of
. The value of the monoamino-dicarbonic acid, however, was lower in our experiment.
Authors:N. Daskalova, S. Doneva, Y. Stanoeva, I. Belchev, and P. Spetsov
Four amphiploid lines (SHW) based on T. monococcum (Tm) and T. boeoticum (Tb) were crossed to T. durum varieties to generate 13 combinations. Field germination and winter survival of hybrid plants in F2 were assessed. Among all crosses, those with SHW8A-Tb and SHW9A-Tm showed highest field germination but with different degrees of spike fragility. The variation on seed number and weight per main spike was studied in F4–6 from SHW8ATb/ Progres and SHW5A-Tb/Severina crosses after individual selection for these traits. Ten lines with durum phenotype from the former and three genotypes with dicoccum plant shape from the latter cross were developed. SDS-PAGE indicated the presence of HMW-GS 1Ax2*+1Aynull subunits in four lines, among which 1Ax2* was inherited from T. boeoticum acc.110 through SHW8A-Tb. Most of the selected genotypes possessed γ-gliadin45, which was relating to good end-use quality. Powdery mildew testing showed that all progenies resulted from the SHW8A-Tb/Progres were susceptible to 12 races of the pathogen, while three lines derived from the SHW5A-Tb/Severina cross behaved differently: G32 expressed resistance to six, G33 to 2, and G34 to 5 races. The selected genotypes from crosses involving SHW with T. boeoticum exhibited good breeding performance compared to tetraploid wheat parents, and might be of breeding interest to further research.