2019 ASHS Annual Conference

Fusarium wilt, a soil-borne disease caused by the fungal pathogen Fusarium oxysporumsp. fragariae, poses a serious risk to strawberry (Fragaria × ananassa) production in many parts of the world. We previously described a dominant gene (Fw1) that confers resistance to Fusarium wilt. Here, we describe fine-scale genetic and physical mapping of the Fw1 locus, and the development of high-throughput DNA markers for marker-assisted selection of Fw1 alleles. The genomic segment harboring Fw1 was narrowed down to less than 5 Mb on chromosome Fvb2-4 in a genome-wide associate study (GWAS). GWAS was facilitated by the availability of a high-quality octoploid reference genome, whole-genome shotgun resequencing of susceptible and resistant genotypes, and the development of 49,000 and 850,000-single nucleotide polymorphism (SNP) genotyping arrays. DNA sequences for the SNP probes on these arrays are sub-genome specific and anchored to the octoploid reference genome. We identified hundreds of DNA variants in the haploblock harboring the Fw1 locus. To facilitate marker-assisted selection, several co-dominant sub-genome specific Kompetitive Allele Specific PCR (KASP) genotyping assays were developed both, for SNPs tightly linked to Fw1 and for SNPs flanking the candidate region. These KASP assays define a 4.2 Mb candidate region on chromosome 2-4 and accurately predict Fw1 genotypes in segregating populations. We are currently screening 2,000 segregating progenies to select recombination events within the candidate haploblock, with the goal of identifying candidate genes for Fw1.