Horticulture: Development of Fusarium wilt resistance in celery and understanding of pathogen virulence factors to underpin UK and EU biosecurity

This project will identify new sources of plant resistance to Fusarium wilt of celery caused by the newly emerged race 4 of Fusarium oxysporum f.sp. apii (Foa) within a celery diversity set provided by Tozer Seeds using a rapid artificially inoculated plant bioassay in the glasshouse. As Foa4 affects coriander, the response of selected coriander varieties will also be assessed. Existing genome sequence data and SNP profiles for each celery accession will be subjected to genome wide association studies (GWAS) to identify SNPs linked to resistance, and genome sequence in the region of significant associations explored for candidate resistance genes. This will allow future development of molecular markers for accelerated breeding of resistant celery cultivars. Genome sequencing of several isolates of the most significant races of Foa (race 2 and race 4) and an Fo isolate from coriander will allow comparison with existing Foa genomes to assess synteny and gene complement of conserved core chromosomes and variable accessory chromosomes which harbour genes involved in host / race specific virulence. Effector gene profiling using an existing pipeline will identify key differences in virulence gene complement between Foa races and all other sequenced Fo f.spp. while also providing targets for development of race specific RT-PCR diagnostics. These can then be used in a biosecurity context to detect the pathogen in the field and in imported plants and seeds. Overall, the project will provide the first important steps for breeding celery cultivars resistant to Fusarium wilt as well as a rapid specific test for Foa4 and other races. These outcomes will therefore benefit celery breeders, producers and consumers as well as plant health agencies by mitigating the biosecurity risk of the pathogen.