DRRW Pre-breeding efforts:CIMMYTCornell Univ.CSIROEIARICCI-Tel Aviv Univ.Kansas State Univ.Univ. of AdelaideUC-DavisUniv. of the Free StateUniv. of MinnesotaUniv. of SydneyUSDA-ARSWashington State Univ.
Why do we need a better toolbox? Speedand support replacement of rust susceptible varieties with varieties based on complex resistance - globally Increase diversity of resistance and promote durable resistance Enablestewardship of resistance sources in a manner never before possible
What tools are needed?A well-surveyed resistance gene landscape Additional, useful, sources of resistance Effective gene pyramids DNA markers and supporting information for robust selection/diagnostics Good germplasm
Deploying COMPLEX resistanceSeedling/All-stage 3 or more effective R genes combinedAdult plant/Slow-rusting 3 or more effective APR genes combined
COMPLEX resistance % Rust Severity Susceptible 100 80 1 to 2 APR genes 60 or 1+ race-specific gene 40 2 to 3 APR genes or 1+ race-specific gene 20 4 to 5 APR genes 0 or 1+ race-specific gene 0 10 20 30 3+ 40 50 Day of Epidemic This is the goal!
Ug99-family Resistance Loci(circa 2008) Red genes are translocations or show reduced recombination Green genes are APR loci Black genes have normal recombination Sr1A.1R Sr27 Sr21 Sr35 Sr26 Sr22 Sr131A 2A 3A 4A 5A 6A 7A Sr39 Sr2 Sr40 Sr37 Sr281B 2B 3B 4B 5B 6B 7B Sr33 Sr32 Sr45 Sr42 Sr44 Sr50 Sr25 Sr29 Sr431D 2D 3D 4D 5D 6D 7D Alien introgression with linkage drag
Ug99-family Resistance Loci(2012) Red genes are translocations or show reduced recombination Green genes are APR loci Black genes have normal recombination SrTr129 Sr1A.1R Sr27 Sr21 Sr35 QTL Sr26 Sr22 SrTm4 Sr52 QTL SrND643 Sr13 Sr151A 2A 3A 4A 5A 6A 7A Sr39 Sr2 Sr40 Sr12 QTL QTL QTL SrWeb/ Sr37 Gabo 56 QTL QTL Sr28 Sr56 Lr46 Sr471B 2B 3B 4B 5B 6B 7B Sr1662 Sr33 Sr32 Sr57 Sr45 Sr51 Sr42 Sr44 Sr46 Sr50 SrAt6D SrAt7D Sr53 Sr25 SrSha7 Sr55 SrC Sr29 Sr431D 2D 3D 4D 5D 6D 7D
Sources of Ug99 resistanceGene Chrom. Origin NotesTemporary DesignationsSrSha7SrCSrNini 6DSSrND643 4ALConsistent QTL (by association mapping or bi-parental mapping)1A, 1B, CIMMYT germplasm via2B, 3D, bi-parental and AM4A, 5B, approaches6B, 7A,7B
Several additional sources andbetter tools are coming (frommany directions):A few DRRW project examples
Discovery from wheat relatives Introgression, allelism tests, mapping , chromosome engineering Aegilops species, wild tetraploids, Da sypyrum villosum Association mapping
Cytogenetic improvement Thinopyrum intermedium- Group 2
Marker developmentSequencing, 9000 SNP, 90,000K SNPplatforms accelerating progress Consolidated/standardized/dense90,000 SNP genotyping ~160 Sr resistance sources from USDA-ARS ~90 Lr resistance sources from USDA-ARS ~400 Yr resistance sources from USDA-ARS Washington State Numerous populations by 9K or 90KMap-based cloning (Sr33, Sr35, others)
Linkage Block DevelopmentRecombininglinked loci toenhancestewardshipand breedingease
So what? Therehas never been a more opportune time for the international community to embrace strategic deployment and responsible stewardship of our genetic resources for durable stem rust control … ……before we lose tools that we can’t afford to replace.