Genome-wide association mapping for early and late drought tolerance in a diverse barley collection

Studying drought tolerance interactions in several developmental stages to map QTL in bi-parental populations is often impossible due to low polymorphism (genetic or phenotypic) in at least one stage. A diverse spring barley collection was investigated for a genome-wide association study and extensive screenings were examined in the early and adult stages. The genotypes were selected for differences in drought tolerance. Tests in the germination and seedling stages were based on osmotic stress induced by polyethylene glycol. In the adult stage, drought tolerance was tested using a rainout shelter, a foil tunnel and with the method of chemical desiccation using potassium iodide. The spring barley collection includes wild barley, landraces and cultivars. Diversity Array Technology (DArT) markers were used for genotyping. Population structure and the extent of linkage disequilibrium (LD) were studied intensely. The genotypes were divided into wild and cultivated barley and into two- and six-row groups with different origins. The decay of LD is fast, offering a fine resolution of the identified loci. The marker-trait associations were calculated in TASSEL using different general linear and mixed linear models. The complexity of the interaction of relevant traits for drought tolerance could be seen at the genetic level. More than 200 loci were found for all the traits, and many loci were shared between the different developmental stages. Root traits were often associated with yield traits. Comparison with the literature showed many of the detected loci were involved in earlier studies, sometimes associated with different, but often with similar or the same traits. Several loci could be identified, where dehydrins may represent the causal gene. Loci for yield components over a range of different studies were also identified. The results of this study highlighted the difficulties in breeding for drought tolerance, but also showed the value of deep phenotyping and of association mapping for such a complex trait

Europe

The foregoing conclusions are broadly consistent with those expressed in the IPCC Special Report on Regional Impacts of Climate Change (1998) and the Second Assessment Report(1996). This survey incorporates much more information than previously reported, corroborating previous conclusions (with which it is broadly consistent) but extending knowledge into other sectors. It is more specific about subregional effects and includes new information concerning adaptive capacity

Locating Stable Across Environment QTL Involved in the Determination of Agronomic Characters in Wheat

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 x 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