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  • Author or Editor: A. Börner x
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PCR assays specific for the GA insensitive dwarfing genes (alleles) Rht-B1b and Rht-D1b were employed to study a series of additional alleles of Rht-B1 and Rht-D1 . The amplification profiles of Rht-B1b and Rht-B1d were not distinguishable from one another, whereas lines carrying Rht-B1c, Rht-B1e and Rht-B1f amplified a product analogous to that of the wild type. At the 4D locus, no discrimination was possible between Rht-D1b, Rht-D1c and Rht-D1d . As a result, the utilisation of these PCR assays is limited. Examples of the analysis of germplasm and spontaneous occurring off-types are presented.

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Quantitative trait loci (QTL) analysis was carried out with a set of 114 recombinant inbred lines (RILs) from the International Triticeae Mapping Initiative (ITMI) population of ‘W7984’ × ‘Opata 85’ to identify genomic regions controlling traits related to post-anthesis drought tolerance of wheat ( Triticum aestivum L.). In two experiments performed in Gatersleben in 2001 and 2003, the amount stem reserves mobilisation was estimated by measuring of changes in 1000-grain weight after chemical desiccation treatment. QTLs for stem reserves mobilisation (Srm) were mapped on chromosomes 2D, 5D and 7D. The mapping positions obtained in the present investigation are discussed with respect to studies on drought tolerance performed in wheat previously. QTLs for drought tolerance preferentially appeared in homoeologous regions at distal parts of the group 7 chromosomes.

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A segregation test confirmed that the genes present on chromosome 1A encoding red and black glumes are allelic to one another. Similarly, the chromosome 1D genes for smokey-grey and red glume coloration are allelic. Consensus maps of chromosomes 1A and 1D carrying Rg-A1 and Rg-D1 , respectively, were derived from extant genotypic data. The Gli-B1 associated microsatellite MW1B002 mapped 2cM proximal from Rg-B1 . The association of red glume coloration with specific MW1B002 alleles is described for a set of Russian, Albanian, Indian and Nepalese bread wheats.

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Two bread wheat crosses were used to genetically map the genes determining anthocyanin pigmentation of the anther (Pan-D1) , culm ( Pc-B1 and Pc-D1 ), leaf sheath (Pls-B1) , and leaf blade (Plb-B1, Plb-D1) . The genes cluster with Rc-1 (red coleoptile) on chromosome arms 7BS and 7DS. A germplasm panel of 37 wheat cultivars and introgression lines was tested for the presence of anthocyanin pigmentation on various plant organs, and significant correlations were established between pigmentation of the coleoptile and culm, coleoptile and leaf blade, coleoptile and anther, and anther and leaf blade.

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Cereal Research Communications
Authors: O. Tereshchenko, E. Gordeeva, V. Arbuzova, A. Börner and E. Khlestkina

Previously, it was suggested that purple grain colour was transferred to bread wheat from purple-grained tetraploid T. durum. In the current study, we demonstrated that the D genome of bread wheat ‘Purple’ carries one of two complementary genes determining purple grain colour. This gene was mapped on the short arm of chromosome 7D 2.5 cM distal to the locus Rc-D1 determining red coleoptile colour. This position is highly comparable with that of the Pp1 gene mapped earlier on the short arm of chromosome 7B in tetraploid T. durum.We suggest the Pp genes on T. durum chromosome 7B and T. aestivum chromosome 7D are orthologous. We designated them Pp-B1 and Pp-D1, respectively. Microsatellite-based genotyping of near-isogenic lines ‘i:S29Pp1Pp2PF’ and ‘i:S29Pp1Pp3P’, their recurrent (T. aestivum ‘Saratovskaya 29’) and donor (T. aestivum ‘Purple Feed’ and ‘Purple’, respectively) parents showed the presence of donor introgressions on chromosomes 2A and 7D in both near-isogenic lines. In addition to previously described purple pericarp, anthers and culms, phenotyping of these lines in the current study showed dark red coleoptile colour (with anthocyanin contents four times higher than in ‘Saratovskaya 29’ coleoptiles) and purple leaf blade and leaf sheath colour. It was concluded that each of the lines ‘i:S29Pp1Pp2PF’ and ‘i:S29Pp1Pp3P’ carry clusters of genes Rc-D1, Pc-D1, Pan-D1, Plb-D1, Pls-D1 and Pp-D1 on chromosome 7D between microsatellite markers Xgwm0044 and Xgwm0676.

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Various milling parameters, wet gluten content and key dough properties were analyzed for two sister lines of bread wheat with Ae. markgrafii introgressions in genetic background of cultivar Alcedo carrying a set of sub-chromosomal alien segments on chromosomes 2AS, 2BS, 3BL, 4AL and 6DL. The lines revealed higher grain vitreousness, larger particle size of flour, and higher wet gluten content in grain compared to cv. Alcedo. The flour from these lines also showed excellent water absorption and developed more resilient dough. The introgressions in the Alcedo genome caused no reduction in 1,000-grain weight. General improvement of the grain technological properties appears to be the result of introgressions into 2AS, 2BS and 3BL chromosomes. Coincidence of locations of Ae. markgrafii introgressions in chromosome with the QTLs positions for technological traits, revealed in bread wheat mapping populations, is discussed.

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The relatively copper-tolerant wheat variety Chinese Spring (recipient), the copper-sensitive variety Cappelle Desprez (donor) and their substitution lines were screened for copper tolerance in a soil pot experiment under artificial growth conditions. Chromosomes 5A, 5B, 5D and 7D of Cappelle Desprez significantly decreased the copper tolerance of the recipient variety to varying extents.  By contrast, the 6B and 3D chromosomes significantly increased the copper tolerance of Chinese Spring, suggesting that a wide range of allelic differences could be expected between wheat genotypes for this character. The significant role of homologous group 5 in copper tolerance was confirmed by testing wheat-rye substitution lines. The substitution of rye chromosome 5R (5R/5A substitution line) into a wheat genetic background significantly increased the copper tolerance of the recipient wheat genotype. The results suggest that chromosomes 5R and 5A probably carry major genes or gene complexes responsible for copper tolerance, and that the copper tolerance of wheat can be improved through the substitution of a single chromosome carrying the responsible genes. At the same time, it is also possible that the effect of homologous group 5 is not specific to copper tolerance, but that the genes located on these chromosomes belong to a general stress adaptation (frost, cold, vernalisation requirements, etc.) complex, which has already been detected on this chromosome. To answer this question further studies are needed to determine the real effect of these chromosome regions and loci on copper tolerance.

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A leaf rust resistance gene transferred from the tetraploid wheat Triticum timopheevii (Zhuk.) Zhuk. (genomic composition: A t A t GG) into common wheat Triticum aestivum L. conditioned resistance at the seedling and adult plant stages in the introgression line ‘line 842-2’. To determine chromosome location and to map the resistance gene an F 2 population from a cross between ‘line 842-2’ and susceptible wheat cultivar ‘Skala’ was developed and screened against leaf rust pathotype 77 ( Puccinia triticina Erikss.). Microsatellite markers detected introgressions of the T. timopheevii genome on chromosomes 1A, 2A, 2B, 5B and 6B of ‘line 842-2’. Linkage analysis revealed an association between leaf rust resistance and microsatellite markers located on chromosome 5B. The markers Xgwm880 and Xgwm1257 were closely linked to the resistance gene with genetic distances of 7.7 cM and 10.4 cM, respectively. Infection type tests with three leaf rust isolates resulted in different patterns of infection types of ‘line 842-2’ and ‘Thatcher’ near-isogenic line with the Lr18 gene on chromosome 5B. The data corroborated the hypothesis of the diversity of the resistance coming from T. timopheevii . The resistance gene of the introgression ‘line 842-2’ seems to be different than Lr18 and therefore it was designated LrTt2 .

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The International Triticeae Mapping Initiative (ITMI) recombinant inbred line (RIL) population was used to detect quantitative trait loci (QTL) underlying some key agronomic characters in bread wheat ( Triticum aestivum L.). Trait measurements were taken from five independent field experiments performed in Serbia. Stable across environment QTL involved in the determination of heading/flowering time and ear morphology/grain yield were detected on, respectively, chromosome arms 2DS and 4AL. These map locations are consistent with those obtained where the same population has been grown in contrasting geographical sites. However, as a result of QTL × environment interactions, not all these QTL are expressed in all environments. Nevertheless the (pleiotropic) effect on ear morphology appears to be expressed in almost all environments, and so represents a high value target for wheat improvement.

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Cereal Research Communications
Authors: S. Navakode, A. Weidner, R. Varshney, U. Lohwasser, U. Scholz and A. Börner

Barley is more sensitive than the other major cereal crops to aluminium (Al) toxicity. Here, a doubled haploid mapping population was exploited to study the inheritance of Al tolerance in barley. Quantitative trait locus (QTL) mapping was based on a genetic map constructed with genic markers. Al tolerance QTL were identified on chromosomes 2H, 3H and 4H. A sequence homology search was used to derive the putative function of the genes linked to the QTL, in order to identify potential candidate genes for Al tolerance. Some of these candidates are implicated in stress/defence responses, in particular, stress signal transduction, transcription regulation factors and cell metabolism.

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