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  • Author or Editor: M. Röder x
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We report the application of wheat microsatellites (GWM) for the investigation of Aegilops species carrying C and Ugenomes. Overall, 89 microsatellite markers located in A, B and D genomes of bred wheat were used for the analysis of Ae. cylindrica Host. (CCDD) and Ae. triuncialis L. (UUCC). Ae. tauschii Coss. (DD) was included as a control of amplification of the D-genome markers. Twelve, eleven and seven of the A-genome-specific markers produced amplification fragments in Ae. cylindrica, Ae. triuncialis and Ae. tauschii , respectively. The level of amplification of the B-genome markers was similar in all investigated species and amounted to 60–65%. The markers of the D genome showed a significantly higher polymorphism level among Ae. tauschii accessions than among those of Ae. cylindrica . Twenty-one microsatellite markers revealing polymorphism in Ae. cylindrica and Ae. triuncialis can be used as a markers for discrimination of C and U genomes. The results of microsatellite analysis were used to estimate genetic relationships among the Aegilops species. The dendrogram distinguished all Aegilops accessions and clustered them into three groups according to their species classification. There was no strong relation between the molecular data of the studied accessions and their geographical region of origin. Obtained data could be utilized for characterization and assessing genetic diversity of wild wheat relatives with C and U genomes.

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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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Abstract  

The - and -radiolysis of cyclohexane, cycloheptane and cyclooctane was investigated in the absence and presence of iodine scavenger. Comparison of the distributions of products formed revealed considerable differences between - and -radiolysis, and the decomposition of strainless cyclohexane and strained cycloheptane and cyclooctane.

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Abstract  

The - and -radiolysis of cyclopentane were compared in the presence and absence of iodine scavenger. The G-values of the main hydrocarbon products, cyclopentene and bicyclopentyl are 2.22 and 0.56 molecule/100 eV in -radiolysis and 3.25 and 1.23, respectively, in -radiolysis. During high LET -irradiation the yields of products formed by a radical mechanism are much smaller (G=1.18) than in -radiolysis (G=2.68), whereas unimolecular cyclopentene formation is hardly influenced by LET (G=1.8 and 1.6, respectively).

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Mapping of quantitative trait loci (QTL) was carried out in a set of 114 RILs of the International Triticeae Mapping Initiative (ITMI) mapping population under salt stress. Seedling population was grown during 8 days, under salt treatment (Hoagland’s ½ strength + 110 mM NaCl, EC 12.4 mS/cm) and normal treatment (Hoagland’s ½ strength, EC 0.9 mS/cm). We calculated starch degradation, measuring the dry weight of the grains on the 4th, 6th and 8th days of culturing. Formation of biomass was calculated measuring leaf and root length on the 4th, 6th and 8th days of culture. Interval mapping resulted in 13 QTLs, 2 major QTLs (LOD> 3) and 11 minors QTLs (LOD> 2). A total of 10 QTLs were associated with saline treatment and 3 QTLs at normal treatment. The data show that a high percentage of QTLs were in chromosomes 2B (3, 23.0%), and 1A (3, 23.0%), followed by 4D (2, 13.6%).

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Quantitative Trait Loci (QTL) mapping was carried out in a set of 114 lines of the International Triticeae Mapping Initiative (ITMI) mapping population for null nitrogen fertilization during two agricultural cycles. We quantified phenologic parameters (days to: ear emergency time, flowering time) and components of yield (number of plants and ears, plant height, leaf area, length and weight of ear, spikelet number, number and total weight of grains and by third in the ear, weight of thousand grains and total yield). Interval mapping resulted of 138 QTLs, of which 47 were catalogued as major QTLs (LOD ≥ 3.0) and 91 as minor QTLs (LOD 2.0 >0 2.9). The QTLs were distributed in 14 of the 21 chromosomes of wheat. The data showed that a high percentage of QTLs were in chromosomes 2D (49 or 35.5%), followed by 5A (22 or 15.9%), 1B (10 or 7.2%).

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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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Genotypes with various Vp-1B alleles perform different levels of pre-harvest sprouting (PHS) tolerance. In this study, 217 white-grained wheat cultivars, including 75 landraces, 39 historical cultivars, and 103 modern cultivars from five major regions of China, were examined to characterize the diversity of the Viviparous-1B ( Vp-1B ) locus associated with PHS tolerance. Four Vp-1B alleles were identified, three ( Vp-1Ba , Vp-1Bb and Vp-1Bc ) of which were previously reported in Chinese wheat cultivars. A new allele, Vp-1Be , was identified in the PHS tolerant landrace Hongheshangtou. Sequence analysis showed that Vp-1Be had an insertion of a 4-bp fragment, two SNPs, and a deletion of an 83-bp fragment compared with the nucleotide sequence of Vp-1Ba (AJ400713), all located in the third intron. Vp-1Be shared 97.80% similarity with the nucleotide sequence of AJ400713. The frequencies of Vp-1Ba , Vp-1Bb , and Vp-1Bc were 36.0%, 5.3%, and 57.3% in landraces; 23.1%, 7.7%, and 69.2% in historical cultivars; and 52.4%, 0%, and 47.6% in current cultivars, respectively.

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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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This contribution is based on an extensive literature review of student dropout in Europe, which was carried out by a research group of the Danish Clearinghouse for Education in cooperation with an international expert group in 2012/2013. The review served to answer three basic questions: What is dropout? Why does it occur? What can be done to reduce or prevent it? Only empirical studies were included in the review and altogether 44 studies were included. The article points out that student dropout is a more complex and multidimensional issue than most people think and that it is important to distinguish between formal dropout (i.e., leaving university studies altogether before degree completion) and transfer (i.e., changing subject and/or institution). The review summarizes and discusses the main results of the 44 studies included in terms of nine dimensions: (a) study conditions at university, (b) academic integration at university, (c) social integration at university, (d) personal efforts and motivations for studying, (e) information and admission requirements, (f) prior academic achievement in school, (g) personal characteristics of the student, (h) sociodemographic background of the student, and (i) external conditions. The conclusions provide an answer to the three questions posed above and include recommendations for further research, university leadership, and policymakers.

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