We are interested in understanding genetic and molecular mechanisms that control disease resistance and other agronomically important traits in cereal plants. For our work we make use of the latest developments in cereal genetics and genomics to dissect phenotypes into genes, gene networks and molecular pathways.
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Durable disease resistance in cereals
Fungal diseases are one of the most serious threats in cereal production, resulting in yield losses and increased input costs for disease management. Cereal diseases are most sustainably controlled by the release and planting of durably resistant cereal cultivars. Plants have evolved an amazing repertoire of disease resistance genes to fight off attacks by fungal pathogens. Many of these resistance genes however are not very durable in the field. Often, genetically uniform cultivars are planted on large acreages which in turn fosters the selection of pathogen strains that are able to overcome cereal resistance genes. Breakdown of disease resistance in cereals has been frequently reported, sometimes only a few years after the release of a resistant cultivar.
Some resistance genes on the other hand were successfully used in breeding and agriculture for decades with no pathogen adaptation. Such resistance genes are referred to as ‘durable’ or ‘broad-spectrum’. Our group is interested in studying the genes and molecular pathways that control durable disease resistance against fungal pathogens. One of the most unique examples of a durable resistance gene is Lr34 of wheat. This gene provides durable albeit partial resistance against all strains of multiple fungal diseases. Lr34 encodes for a rare variant of an ATP-binding cassette transporter. In our group we study the exact molecular function of this unusual and remarkable resistance gene. Another wheat gene, known as Lr22a, confers broad-spectrum resistance against the fungal disease leaf rust. Lr22a was transferred into modern bread wheat from a wild wheat ancestor in the 1970s and no virulent leaf rust race against Lr22a has been reported so far. Our aim is to identify the gene responsible for the Lr22a-resistance using a map-based cloning approach. Map-based cloning in wheat was tedious in the past because of wheat’s large and complex genome. Recent technological advances in cereal genomics, including high-throughput marker platforms, genome complexity reduction and genome sequencing, allow us nowadays to significantly speed up gene cloning in wheat.
Leaf of a susceptible wheat line infected with the fungal disease leaf rust (top) compared to a wheat line carrying a broad-spectrum disease resistance gene (bottom).
In addition, we use biotechnology to improve broad-spectrum disease resistance in cereals. For example, the wheat Lr34 gene is transferrable into other cereals, including barley and rice, where it confers resistance against barley-specific and rice-specific fungal diseases, respectively.
Genebanks - treasure chests of genetic diversity for cereal improvement
During domestication and in breeding, only a limited number of plants were selected and gave rise to today’s cereals. As a consequence, modern cereal cultivars only capture a fraction of the diversity that can be found among old landraces and wild progenitors of today’s cereals. Because of this genetic bottleneck, many genes of potential agricultural importance were not introduced into modern cereal cultivars. Genebanks play a pivotal role in preserving genetic diversity by collecting, maintaining and characterizing landraces and wild cereal progenitors. With the help of modern genetics and genomics we can now tap this diversity and make it accessible for breeding. The key technological breakthroughs for this were the development of high-throughput molecular marker platforms and next-generation sequencing. Today, we can study the genetic diversity of hundreds of cereal accessions and link this diversity to phenotypes using genome-wide association studies (GWAS). In one current project we perform genetic characterization of spelt wheat (Triticum spelta), bread wheat (Triticum aestivum) and barley accessions of the Swiss National genebank using a wheat 15K SNP array and genotyping-by-sequencing. The Swiss spelt wheat collection is one the largest and most diverse in the world. In another project, we make use of the recent re-sequencing of 3,000 rice accessions to identify new broad-spectrum disease resistance genes against fungal diseases.