S. Cloutier, T. Edwards, C. Zheng, H. M. Booker, T. Islam, K. Nabetani, H. R. Kutcher, O. Molina, F. M. You

Theoretical and Applied Genetics; January 2024; vol.137; Article 27

Key message

Fine-mapping of a locus on chromosome 1 of fax identifed an S-lectin receptor-like kinase (SRLK) as the most likely candidate for a major Fusarium wilt resistance gene.

Abstract

Fusarium wilt, caused by the soil-borne fungal pathogen Fusarium oxysporum f. sp. lini, is a devastating disease in fax. Genetic resistance can counteract this disease and limit its spread. To map major genes for Fusarium wilt resistance, a recombinant inbred line population of more than 700 individuals derived from a cross between resistant cultivar ‘Bison’ and susceptible cultivar ‘Novelty’ was phenotyped in Fusarium wilt nurseries at two sites for two and three years, respectively. The population was genotyped with 4487 single nucleotide polymorphism (SNP) markers. Twenty-four QTLs were identifed with IciMapping, 18 quantitative trait nucleotides with 3VmrMLM and 108 linkage disequilibrium blocks with RTM-GWAS. All models identifed a major QTL on chromosome 1 that explained 20–48% of the genetic variance for Fusarium wilt resistance. The locus was estimated to span~867 Kb but included a~400 Kb unresolved region. Whole-genome sequencing of ‘CDC Bethune’, ‘Bison’ and ‘Novelty’ produced~450 Kb continuous sequences of the locus. Annotation revealed 110 genes, of which six were considered candidate genes. Fine-mapping with 12 SNPs and 15 Kompetitive allele-specifc PCR (KASP) markers narrowed down the interval to~69 Kb, which comprised the candidate genes Lus10025882 and Lus10025891. The latter, a G-type S-lectin receptor-like kinase (SRLK) is the most likely resistance gene because it is the only polymorphic one. In addition, Fusarium wilt resistance genes previously isolated in tomato and Arabidopsis belonged to the SRLK class. The robust KASP markers can be used in marker-assisted breeding to select for this major Fusarium wilt resistance locus.

See https://link.springer.com/article/10.1007/s00122-023-04528-2

Fig.1: Distribution and correlation of the Fusarium wilt severity scores in flax (Linum usitatissimum) for the five site-years, means and best linear unbiased predictor (BLUP) values. Distributions of each dataset are on the diagonal. Correlations among datasets are illustrated below the diagonal and correlation values are above it. The site-years are Saskatoon 2019, 2020 and 2021, and Morden 2019 and 2021. FW_mean and FW_BLUP are the means and BLUP values of the Fusarium wilt severity scores across all five site-years in a recombinant inbred line (RIL) population derived from a cross between ‘Bison’ and ‘Novelty’. *** P value < 0.001