Abstract
Bipolaris sorokiniana is a prevalent fungal pathogen that resides in the soil and affects various parts of wheat, leading to diseases such as spot blotch, common root rot, head blight and black point. The genetic mechanisms that confer resistance in wheat against this pathogen are not completely known. In this research, 1302 wheat germplasms from around the world were evaluated for resistance to spot blotch at the seedling stage, and it was found that merely 3.8% displayed moderate or better resistance. A genome-wide association study (GWAS) employing high-density 660K single-nucleotide polymorphism (SNP) data pinpointed a segment on chromosome 1BL (621.2-674.0 Mb) containing nine SNPs that are significantly linked to spot blotch resistance, named Qsb.hebau-1BL. RNA sequencing and reverse transcription-quantitative PCR analyses demonstrated that the gene TraesCS1B02G410300, which codes for nicotinamide-adenine dinucleotide phosphate-binding oxidoreductase (TaNADPO), was markedly upregulated by B. sorokiniana. Five SNP variations were identified in the promoter region of TaNADPO in wheat lines with or without Qsb.hebau-1BL. Wheat lines that overexpressed TaNADPO exhibited increased resistance to spot blotch and higher accumulation of reactive oxygen species (ROS). In contrast, knockout EMS mutants of Triticum turgidum TdNADPO (tdnadpo-K2561, Gln125*) and TaNADPO (tanadpo-J10516796, splice donor variant) showed diminished resistance and lower ROS levels. In conclusion, TaNADPO is a key gene for resistance against B. sorokiniana, providing essential information for the development of spot blotch-resistant wheat varieties through molecular breeding techniques.