Performance Story: New sources of resistance to fusarium head blight in spring wheat
PI: Dr. Randy Kutcher, University of Saskatchewan
Fusarium head blight (FHB) is a serious disease of wheat across western Canada, causing substantial yield and quality losses. As well as reduced yields, the disease can also result in downgrading or complete crop loss due to high toxin content in the grain. FHB creates a management challenge because highly resistant wheat varieties are not available and fungicides do not provide complete FHB control. Therefore, a priority of pathology and breeding programs in Canada and in the US is to find new sources of resistance. This can be achieved by screening existing collections of germplasm or creating new, exotic, sources of resistance by novel means.
In this project, we aimed to identify wheat germplasm with new sources of FHB resistance by screening two large wheat collections in our Fusarium disease nursery at Saskatoon in 2016 and 2017. The project began with an evaluation of 4,000 wheat accessions from the Plant Gene Resource of Canada (PGRC) collected worldwide. The FHB disease incidence and severity were assessed for each line. As a result, 400 lines with the lowest FHB incidence and severity were selected for genome-wide association study (GWAS) to identify novel genes/or quantitative trait locus (QTLs) associated with FHB resistance. GWAS identified QTLs associated with FHB incidence on chromosomes 1B, 2B, 7A and 7B, and for FHB severity on chromosomes 1A, 1B, 2B, 3A, 3D, 4A, 5A, 5B and 6A.
In addition to the PGRC panel of accessions, 412 lines were evaluated from a synthetic hexaploid wheat (AABBDD genome) association mapping (SHW AM) panel, which was created by crossing durum wheat (tetraploid, AABB genome) with Aegilops tauschii (goatgrass, the progenitor of bread wheat; diploid, DD genome), at the International Wheat Research Centre in Mexico (CIMMYT). Thirty-eight SHW consistently showed low incidence and severity (comparable to the resistant check Sumai3) across biological replications and multi-year testing in the field. All 38 lines also had low DON accumulation. Greenhouse evaluation of Type II resistance of these 38 lines identified two lines with very strong resistance. These lines will be useful in the development of FHB-resistant wheat germplasm and populations for the discovery of novel FHB resistance. GWAS analysis of the SHW AM, identified QTLs for FHB incidence and severity in 2016 and 2017. Seven high-priority QTLs, on chromosomes 2A, 2D, 3B, 5A, 5D, 7B and 7D were selected, and Kompetitive allele-specific PCR (KASP) markers flanking these QTLs were developed for use in marker-assisted selection (MAS).
In a new SWDC funded 3-year project, we are continuing to further investigate the genetic structure of these new resistance sources and adding additional phenotyping data on the resistance of the most promising lines. With advanced genomic and phenotyping tools, the next project aims to explore novel FHB resistances within these lines and identify genetic determinants contributing to novel FHB resistance. Eventually, we will identify markers linked to different FHB resistance types and select donor lines with complementary FHB resistance components to introgress into desirable breeding material. The knowledge, germplasm and markers generated from this project will accelerate breeding cycles and benefit the wheat industry.