ITEMS FROM GERMANY

 

INSTITUT FÜR PFLANZENGENETIK UND KULTURPFLANZENFORSCHUNG (IPK)

Corrensstraße 3, 06466 Gatersleben, Germany.

 

Assessment of SNP haplotypes of the puroindoline b gene for grain hardness in European wheat varieties by Pyrosequencing. [p. 31]

X.Q. Huang and M.S. Röder.

Grain hardness is one of the most important quality characteristics of bread wheat and has a profound effect on milling, baking and the quality of the end product. Grain hardness is reported to result from either a failure to express puroindoline a (Pina) or single nucleotide mutations in puroindoline b (Pinb). For the first time, we have developed two SNP assays for identification of the seven Pinb alleles using Pyrosequencing technology (Huang and Röder 2005). The hardness genotypes of German wheat cultivars available confirmed the reliability and validation of the SNP assays developed for the Pinb locus. SNP haplotypes for 493 European wheat cultivars at the Pinb gene locus are presented at http://pgrc.ipk-gatersleben.de/puroindoline.

Reference.

 

Dissection of QTL for grain weight into single Mendelian genes. [p. 32]

M.S. Röder and X.Q. Huang.

In previous research, the advanced backcross strategy was applied for the first time in wheat in order to introduce and map QTL from unadapted germ plasm via synthetic wheat lines. In the BC2F2 winter wheat population 'Prinz/W-7984', a total of 40 putative QTL for agronomic and plant morphologic characters were mapped (Huang et al. 2003). In the BC2F2 winter wheat population' Flair/XX86', a total of 57 putative QTL were identified and mapped (Huang et al. 2004). In order to test the stability of the detected QTL, the BC2 population 'Prinz/W-7984' was advanced to BC3 and reëvaluated in the field for QTL. Among the characters, total grain yield, heading date, plant height, number of tillers (spikes)/area, and 1,000-kernel weight, the 1,000-kernel weight turned out to be the most stable character. Of eight QTL for 1,000-kernel weight detected in the BC2 of 'Prinz/W-7984', five QTL were detected in the BC3 at similar mapping positions on chromosomes 2D, 4D, 7B (two QTL), and 7D. Coinciding mapping positions of QTL for 1,000-kernel weight among the two BC2 populations 'Prinz/W-7984' and 'Flair/XX86' were detected for chromosomes 2A, 2D, and 7D. For further verification and fine mapping of the respective QTL, both mapping populations were advanced to BC4, and the resulting NILs currently are being used to develop segregating F2-populations.

References.

 

Salt tolerance. [p. 32]

A. Börner, A. Bálint, U. Lohwasser, M.S. Röder, A. Weidner, G. Badridze, and E.K. Khlestkina.

Fifty-four winter and 32 spring bread wheat and 18 different tetraploid accessions (T. durum subsp. dicoccum and subsp. polonicum) from Georgia were tested for salt tolerance at the germination stage. In addition, several Georgian endemics were investigated under salt-stress conditions, among them 25 hexaploid (T. aestivum subsp. macha and T. zhukovskyi) and 16 tetraploid (T. turgidum subsp. carthlicum, T. karamyschevii, and T. timopheevii subsp. timopheevii) accessions. Tests were made with three different sodium chloride solutions (1 %, 1.5 %, and 2 %) and distilled water as control.

In general the hexaploid species showed a higher salt tolerance compared to the tetraploids. The Georgian endemic winter wheat T. aestivum subsp. macha exhibited a better tolerance under salt stress conditions than both winter and summer T. aestivum accessions. Because of an increased inability to elongate shoots in 2 % sodium chloride, the hexaploid wheats from Georgia were considered as moderately salt tolerant.

Within the tetraploid accessions, no large differences with respect to salt tolerance were observed. Compared to T. turgidum subsp. dicoccum and T. turgidum subsp. durum, the endemic T. turgidum subsp. carthlicum accessions showed the best development under salt-stress conditions.

 

Copper tolerance. [p. 32-33]

Using different genetic stocks, loci for copper tolerance were mapped on the homoeologous group 5 of wheat.

Chromosome 5A. Single-chromosome, recombinant inbred lines for chromosome 5A, originating from a cross between the substitution lines Chinese Spring/T. aestivum subsp. spelta 5A and Chinese Spring/Cheyenne 5A, were mapped using microsatellite markers and screened in the greenhouse for copper tolerance. A region influencing Cu tolerance was found on the long arm of chromosome 5A. The role of this region was reinforced by screening Chinese Spring homozygous deletion lines for chromosome 5AL.

Chromosome 5B. Single-chromosome, recombinant inbred lines for chromosome 5B, originating from a cross between Chinese Spring and a Chinese Spring/Cheyenne 5B substitution line, were mapped using microsatellite markers and screened in the greenhouse for copper tolerance. A minor QTL affecting Cu-tolerance was identified on the long arm of chromosome 5B close to the centromere, which was nearly in the same position as the the QTL influencing Cu tolerance mapped earlier in the ITMI mapping population.

Chromosome 5D. Screening Chinese Spring 5DL homozygous deletion lines for copper tolerance, the locus affecting Cu tolerance was mapped on the telomeric end of chromosome 5DL. In the ITMI mapping population, the greatest effect for Cu tolerance was found in another region of chromosome 5D, however, the deletions used for this analysis are far from this region and, therefore, not suitable to find effects located there.

 

Preharvest sprouting/dormancy. [p. 33]

A set of 85 Triticum aestivum cultivar Chinese Spring-Ae. tauschii introgression lines developed at IPK Gatersleben was cultivated under greenhouse conditions in 2004. The lines were evaluated for the domestication traits preharvest sprouting and dormancy (germination) in order to discover the influence of the D genome on these traits. Single-chromosome introgression lines offer the study of QTL specific for individual chromosomes. From the results of other mapping populations, no indication was evident for an influence of the D genome. However, a major QTL could be found for dormancy on the long arm of chromosome 6D and additionally a minor QTL on the short arm of chromosome 6D. No QTL could be localized for preharvest sprouting. To verify the detected QTL, a replication of the tests will be done under field conditions in 2005.

 

Geographical mapping of morphological/color traits. [p. 33]

Using the morphological classification system applied in the Gatersleben genebank for hexaploid wheat, it became possible to divide the collection in respect to the presence or absence of single morphological traits. The characters presence/absence of awns, awn color, glume color, presence/absence of hairs on glumes, presence/absence of inflate spike type, spike density, grain color, stem filling, and presence/absence of ligules were considered. Combining the morphological data with the data of the countries of origin the global distributions of the traits were estimated. Whereas some traits (presence/absence of awns, awn color, glume color, presence/absence of hairs on glumes, and stem filling) occur preferentially in certain geographical regions, others (presence/absence of inflate spike type, spike density, grain color, and presence/absence of ligules) seem to be randomly distributed.

 

Classification of tetraploid wheat. [p. 33]

A total of 99 accessions belonging to 13 tetraploid wheat species were analyzed together with Kamut wheat using 28 wheat microsatellite markers (WMS) mapped on the A and B genomes of hexaploid wheat (two/chromosome). In total, 453 alleles were detected. The average PIC value was 0.80. Genetic similarity values between accessions were used to produce a dendrogram. Major groups of accessions reflecting taxonomical groups were distinguishable. Kamut wheats were found in one cluster together with three accessions of T. turgidum subsp. polonicum and three accessions of T. turgidum subsp. durum, which were originated from Turkey, Iraq, Iran, and Israel. We concluded that Kamut is a product of a hybridization between T. turgidum subsp. durum and T. turgidum subsp. polonicum which took place in the area of the Fertile Crescent.

 

Publications. [p. 33-35]