During co-evolution with pathogens plants have evolved a multigenic, broad-acting basal defence system that is triggered by highly conserved pathogen-associated molecular patterns (PAMPs). PAMP-triggered immunity (PTI) is the most important mechanism of quantitative host- as well as nonhost resistance. In many cultivars, however, PTI is often not very efficient against major host pathogens due to poor combinations of favourable alleles (QTL).

BARLEY-fortress is an international research consortium for the targeted exploitation of basal defence genes in barley with the aim to introgress and engineer broad and durable pathogen resistance into this major crop. In a combined marker-assisted backcrossing and transgenic approach in two German elite varieties of spring barley, valuable haplotypes of functionally validated genes of PTI are introgressed from landraces or wild barley, and selected combinations of genes are being used for stacked over-expression or RNAi. Transgene stacking is strongly facilitated and speeded up by creating a triple over-expression cassette based on pathogen-induced promoters of three different barley HvGER4 genes. The transgene locus driven by GER4 is allowing local over-expression in pathogen-attacked epidermis of cereals including barley, wheat and maize and will be valuable to engineer resistance against powdery mildew, scald, net blotch, spot blotch, rice (cereal) blast, and possibly Fusarium head blight. Special emphasis is put on the improvement of penetration resistance via re-inforcing cell walls of attacked tissue by a series of genes that have been identified by project partners during the last years (RNAi) and that are involved in targeted secretion, cell-wall synthesis/re-modelling and crosslinking. Additional genes derived from previous GABI-projects should also be included for stacked over-expression and RNAi. Plant resistance is analysed in the greenhouse (transgenes) and field (backcrossing) by microscopic and macroscopic assays using tools of automated pattern recognition. Promising genotypes will be further analysed by genome-wide transcript profiling and by cell-wall analysis.

Results from BARLEY-fortress are expected to generate new knowledge about cell-wall based defense in grasses, and to be directly useful in barley breeding.  We also expect the results to be transferrable to wheat and rye due of close phylogenetic relatedness of the three Triticeae crops and because mechanisms of PAMP-triggered immunity were found to be highly conserved.