GWAS revealed a novel resistance locus on chromosome 4D for the quarantine disease Karnal bunt in diverse wheat pre-breeding germplasm

This study was initiated to identify genomic regions conferring resistance to Karnal Bunt (KB) disease in wheat through a genome-wide association study (GWAS) on a set of 179 pre-breeding lines (PBLs). A GWAS of 6,382 high-quality DArTseq SNPs revealed 15 significant SNPs (P-value <10(-3)) on chromosomes 2D, 3B, 4D and 7B that were associated with KB resistance in individual years. In particular, two SNPs (chromosome 4D) had the maximum R-2 values: SNP 1114200 vertical bar F vertical bar 0-63:T >C at 1.571 cM and R-2 of 12.49% and SNP 1103052 vertical bar F vertical bar 0-61:C > A at 1.574 cM and R-2 of 9.02%. These two SNPs displayed strong linkage disequilibrium (LD). An in silico analysis of SNPs on chromosome 4D identified two candidate gene hits, TraesCS4D02G352200 (TaNox8; an NADPH oxidase) and TraesCS4D02G350300 (a rhomboid-like protein belonging to family S54), with SNPs 1103052 vertical bar F vertical bar 0-61:C > A and 1101835 vertical bar F vertical bar 0-5:C > A, respectively, both of which function in biotic stress tolerance. The epistatic interaction analysis revealed significant interactions among 4D and 7B loci. A pedigree analysis of confirmed resistant PBLs revealed that Aegilops species is one of the parents and contributed the D genome in these resistant PBLs. These identified lines can be crossed with any elite cultivar across the globe to incorporate novel KB resistance identified on 4B.