AUTHOR=Wang Yixiao , Fredua-Agyeman Rudolph , Yu Zhiyu , Hwang Sheau-Fang , Strelkov Stephen E. 

TITLE=Genome-wide association study of Verticillium longisporum resistance in Brassica genotypes

JOURNAL=Frontiers in Plant Science

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1436982

DOI=10.3389/fpls.2024.1436982

ISSN=1664-462X

ABSTRACT=<p>Verticillium stripe, caused by <italic>Verticillium longisporum</italic>, presents an emerging threat to Canadian canola (<italic>Brassica napus</italic>). Initially detected in Manitoba in 2014, the presence of this pathogen has since been confirmed across western Canada. Infections by <italic>V. longisporum</italic> can result in yield losses of up to 50%, which is a cause for concern given the susceptibility of most commercial Canadian canola cultivars. The objective of this study was to screen a collection of 211 <italic>Brassica</italic> genotypes for their reactions to <italic>V. longisporum</italic>, and to use genome-wide association study (GWAS) to identify single nucleotide polymorphism (SNP) markers for resistance. The plant material consisted of 110 rutabaga (<italic>B. napus</italic> ssp. <italic>napobrassica</italic>), 35 canola, 40 <italic>Brassica rapa</italic>, and 15 <italic>Brassica oleracea</italic> accessions or cultivars, alongside 11 hosts of the European Clubroot Differential (ECD) set. These materials were screened for resistance under greenhouse conditions and were genotyped using a 19K <italic>Brassica</italic> SNP array. Three general linear models (GLM), four mixed linear models (MLM), and three GWAS methods were employed to evaluate the markers. Eleven non-commercial <italic>Brassica</italic> accessions and 9 out of 35 commercial canola cultivars displayed a low normalized area under the disease progress curve (AUDPC<sub>norm.</sub>). The non-commercial accessions could prove valuable as potential sources of resistance against <italic>V. longisporum</italic>. Forty-five SNP markers were identified to be significantly associated with <italic>V. longisporum</italic> resistance using single-SNP based GWAS analysis. In comparison, haplotype-based GWAS analyses identified 10 to 25 haplotype blocks to be significantly associated with <italic>V. longisporum</italic> resistance. Between 20% and 56% of QTLs identified by the more conventional single-SNP based GWAS analysis were also detected by the haplotype-based GWAS analysis. The overlapping genomic regions identified by the two GWAS methods present promising hotspots for marker-assisted selection in the future development of Verticillium stripe-resistant canola.</p>