Identifikation von QTLs für trockenstress-induzierte Blattseneszenz in Wildgerstenintrogressionslinien und Elitegersten (IZN-Projekt)

Leaf senescence is the last step in leaf development and is characterized by degradation processes. At the onset of leaf senescence photosynthesis is down regulated and valuable resources are recycled for re-use in other parts of the plant. This process can be induced by internal factors like age and phytohormones, but also by external stress conditions, e.g. drought stress. Stress-induced leaf senescence is a major cause of loss in yield and recent investigations prove that the process of leaf senescence is closely linked to drought stress tolerance. In the project we aim at the identification of QTLs (quantitative trait loci) for drought stress induced leaf senescence using two sets of germplasm. These are a unique set of wild barley introgression lines (ILs) and a set of European elite barley varieties. The genetically characterized ILs possess marker-defined chromosomal segments of the wild barley accession ISR42-8 and, by this, enables to utilize the genetic potential of the wild species. The cultivar set represents modern barley varieties grown during the last 40 years in Europe and genotypes of the Spanish barley core collection (SBCC). Both sets will be tested under early drought conditions in green house experiments and under rainout shelters in the field, respectively. For phenotype studies the course of stress-induced leaf senescence will be followed using senescence parameters like chlorophyll content and photosystem II efficiency measured by non-destructive techniques. In order to detect QTLs for drought tolerance combined with delayed leaf senescence, the presence of line x phenotype associations will be tested for both germplasm collections. In addition, in those lines showing the most extreme alterations in the course of drought stress induced senescence the stress induced senescence process will also be analyzed on a molecular level. For this, expression of candidate genes of drought stress and leaf senescence will be analyzed by quantitative Real-Time PCR. Using the expertise and infrastructures of all cooperating groups, exotic and elite alleles for drought stress tolerance will be identified and the more tolerant lines will be used directly for breeding. As a long-term goal, the three groups plan to pin-point the genetic background of drought tolerance and leaf senescence by identifying the genes involved in these processes and by further molecular studies of their function.