Mapping and marker development of the rye-derived Hessian fly resistance gene H25 in wheat.

Hessian fly (HF), Mayetiola destructor (Say), is a serious pest of wheat (Triticum aestivum L.) worldwide. Using resistance genes from alien sources is a promising strategy for developing HF-resistant cultivars. The HF resistance gene H25 in the wheat line KS92WGRC20 was originally transferred from chromosome 6R of rye (Secale cereale L.) into the proximal region of the long arm on wheat chromosome 4A. However, the introgressed 6R segment has not been characterized and diagnostic markers for H25 have been lacking, limiting its use in breeding programs. This study developed a population of 188 recombinant inbred lines (RILs) from Jagger × KS92WGRC20 and analyzed the population using single-nucleotide polymorphism (SNP) markers generated by genotyping-by-sequencing (GBS). Phenotypic segregation analysis and gene mapping confirmed H25 as the sole HF resistance gene in KS92WGRC20. Two kompetitive allele-specific PCR (KASP) markers, K6R_316905104 and K6R_316905114, were converted from GBS-SNPs and validated in two wheat diversity panels, one with 203 winter wheat accessions from the major US wheat growing areas and the other containing 38 wheat lines that carry various known HF resistance genes. In addition, a gel-based dominant PCR marker was also developed. Moreover, a genomic region spanning 310-480 Mb was proposed as a putative introgressed segment of chromosome 6R based on analysis of GBS data from the RIL population using the rye Lo7 as reference genome. Together, these results provide practical molecular tools and new insights into the 6R introgression carrying H25, facilitating its efficient deployment in wheat breeding programs.