albrecht.serfling@julius-kuehn.de

claudia.breitkreuz@julius-kuehn.de

jasper.kroessmann@julius-kuehn.de

mathieu.deblieck@gmx.de

anne-kathrin.pfrieme@julius-kuehn.de

andreas.stahl@julius-kuehn.de

Two of the most important fungal pathogens in wheat, leaf rust (Puccinia triticina) and stripe rust (Puccinia striiformis), develop races through mutation that lead to the breakdown of vertical resistances, benefit from climate change and increasing CO2 content in the atmosphere. During evaluation projects, which include phenotyping at different environments distributed over Europe, around 15,000 wheat genotypes and genetic resources from the secondary gene pool with regard to their resistance against those rusts have been investigated.

To take the diversity of rust populations into the account, racial composition by virulence/avirulence pattern were investigated genetically and by wheat differential sets. Around 30 races in populations were detected. Only 13 out of 54 leaf rust resistances (Lr-genes) and 9 out of 33 stripe rust resistances (Yr-genes) are effective but as mostly vertical resistances vulnerable to be broken down. Therefore, a core collection of 800 genetic diverse wheat genotypes was selected to identify effective and more durable resistances reliably by a high-throughput phenotyping system.

The heritability across seedling high-throughput investigations and field trials could be estimated with h2=0.77 and between field trials in six environments with h2=0.7 (stripe rust) and h2=0.92 (leaf rust). Based on on 49,646 markers from SNP-chip analysis, GBS approaches and genome sequencing data together with BLUES based on phenotyping data, GWAS was performed. Six highly significant new leaf rust and four stripe rust associations in genome regions, not associated with known resistances could be identified.

Already known resistance loci containing Yr-genes and Lr-genes were excluded from analysis based on marker information from NILs, e.g. Yr10 on chromosome 1B, Yr17 on chromosome 2B or Yr6 on chromosome 7B, and Lr22b on chromosome 2D. A subset of 200 genotypes, registered in last 50 years in Germany was investigated under elevated CO2 concentrations. The results gave hint, that infection pressure by rusts is increased and some of commonly used vertical resistances are less effective under an elevated CO2 concentration.

This should be taken into account for future analysis of resistances. From the investigated secondary gen pool in a T. monococcum accession, a prehaustorial, race independent nearly non-host resistance as a candidate for a future durable resistance in wheat could be identified. The genetic background is a berberine bridge enzyme-like protein and differs from the vertical resistance based on NBS-Lrr genes, common in wheat.

Genotypes carrying such unknown resistances are now usable as breeding material together with closely linked or gene specific markers to accelerate the breeding process of resistant elite cultivars in the future.