Genetically well-characterized mapping populations are a key tool for rapid and precise localization of quantitative trait loci (QTL) and subsequent identification of the underlying genes. In this study, a set of 73 introgression lines (S42ILs) originating from a cross between the spring barley cultivar Scarlett (Hordeum vulgare ssp. vulgare) and the wild barley accession ISR42-8 (H. v. ssp. spontaneum) was subjected to high-resolution genotyping with an Illumina 1536-SNP array. The array enabled a precise localization of the wild barley introgressions in the elite barley background. Based on 636 informative SNPs, the S42IL set represents 87.3% of the wild barley genome, where each line contains on average 3.3% of the donor genome. Furthermore, segregating high-resolution mapping populations (S42IL-HRs) were developed for 70 S42ILs in order to facilitate QTL fine-mapping and cloning. As a case study, we used the developed genetic resources to rapidly identify and fine-map the novel locus thresh-1 on chromosome 1H that controls grain threshability. Here, the recessive wild barley allele confers a difficult to thresh phenotype, suggesting that thresh-1 played an important role during barley domestication. Using a S42IL-HR population, thresh-1 was fine-mapped within a 4.3cM interval that was predicted to contain candidate genes involved in regulation of plant cell wall composition. The set of wild barley introgression lines and derived high-resolution populations are ideal tools to speed up the process of mapping and further dissecting QTL, which ultimately clears the way for isolating the genes behind QTL effects.
The objective of the study was to test the feasibility of coexistence between genetically modified (GM) and non-GM maize under real-life agronomical conditions. GM hybrid maize with the event MON810 (Bt maize) was drilled at 30 sites in fields surrounded by near isogenic conventional maize, although only 27 sites could be finally evaluated. Field sizes of Bt maize varied between 0.3 and 23 ha, and the flowering period of the Bt and conventional maize was synchronous. At some sites, different planting dates of GM and non-GM maize or an earlier ripening conventional maize were tested in additional strips to obtain altered flowering and thereby reduce cross-pollination. The overlapping of flowering periods was successfully avoided only at two sites where non-GM maize was planted 25 or 28 days later. During harvest, samples were taken from the conventional maize in strips at distances of 0-10, 20-30, and 50-60 m to the Bt maize fields to assess the GM DNA content as a function of distance. Sampled materials included chaffed plant material intended for silage (18 sites), grains (eight sites), or crushed husks and cobs (one site). Wind effects were taken into account by sampling in all four compass directions. Quantitative PCR was used to detect the event specific MON810 DNA sequence in sampled materials. The analysis was conducted by two certified independent diagnostic testing companies selected in a pre-test. Taking averages over all compass directions and the two laboratories no samples collected beyond 10 m had levels of GM above the threshold of 0.9 %. In conclusion, the data indicate that coexistence of GM and conventional maize is possible under real-life large-scale agronomical conditions. Levels of GM DNA in harvested grain resulting from outcrossing can be managed to levels below 0.9 % by simply planting 20 m of conventional maize as a pollen barrier between adjacent fields.
An Aegilops turcomanica‐typical gliadin was discovered in sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE) patterns of ethanol‐soluble seed proteins from wheat lines Tr. 476, 482 and 492, which had been derived from a direct cross of Ae. turcomanica and Triticum aestivum and which revealed powdery mildew resistance due to a putative Ae. turcomanica‐introgression. This Ae. turcomanica‐derived gliadin was tested for its suitability as biochemical marker. For this purpose, doubled‐haploid lines were produced via anther culture from crosses of Tr. 482 and Tr. 492 with actual winter wheat cultivars and breeding lines. Until now, 173 lines with Ae. turcomanica‐gene(s) have been selected from 297 doubled haploid wheat lines.
The post-anthesis development of growing maize kernels is strongly affected by heat stress. The maize cultivar ''Spezi'' was used to quantify this effect in kernels from 14 days after flowering until maturity. Day/night temperature of control plants was 25/20°C. Stress of 40/25°C was given for seven days or continuously up to maturity. Kernels were analysed weekly for dry matter and extractable DNA. In addition the ploidy levels and the DNA content in intact cell nuclei were determined by flow cytometry. The dry matter reduction started immediately after heat treatment and reached, at maturity, 40% for temporary heat stress and 60% for permanent heat stress. The reduction of extractable DNA started later and was not as extensive. Endopolyploidy was found in all kernel tissues, namely embryo, endosperm and pericarp. In endosperm, 3C nuclei reached their maximum number at approximately 14-17 days, and cells with higher ploidy levels between 21 and 26 days after flowering. Later on 6C nuclei were dominant. The DNA content in intact cells of the endosperm reached a maximum 21 days after flowering. This maximum was lower for heat stress variants and decreased more rapidly. Heat stress can vary from year to year under field conditions. Since heat stress changes the ratio between embryo and endosperm DNA in the direction of a higher portion of embryo DNA at maturity, this has an influence on the measured content of GM DNA from GM pollen transfer into conventional maize fields.
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