Wild Relative Introgression Toolbox: Unlocking homoeologous recombination for accelerated gene transfer into wheat
Project Summary:
Modern wheat breeding has significantly narrowed the genetic diversity of elite cultivars, limiting resilience against rapidly evolving biotic and abiotic stresses. Wild relatives of wheat harbor valuable alleles for disease resistance, pest tolerance, yield stability, heat tolerance, drought tolerance, and salinity tolerance; however, efficient transfer of these traits into elite wheat backgrounds remains a major challenge. The principal biological barrier is the Ph1 locus on chromosome 5B, which suppresses homoeologous recombination (HR) between wheat and related species. Although the ph1b mutant partially releases this suppression, recombination frequency remains low, largely restricted to distal chromosomal regions, and frequently results in transfer of large alien chromosomal segments associated with linkage drag. Research conducted at the Wheat Genetics Resource Center (WGRC) demonstrated that chromosome 5Mg from Aegilops geniculata dramatically enhances homoeologous recombination when combined with ph1b. This system can increase recombination frequency by up to ~100-fold in targeted introgression systems and promotes recombination across distal, interstitial, and proximal chromosomal regions, thereby enabling transfer of smaller and more precisely defined alien chromatin segments. Despite these advances, several major gaps remain unresolved. Major gaps remain unresolved regarding whether the ph1b + 5Mg system can consistently enhance recombination across diverse Triticeae species with varying levels of genomic divergence. In addition, there is currently no user-friendly bioinformatics platform specifically designed to track alien introgressions and design donor-specific SNP markers across diverse Triticeae genomes. This project will address these limitations by developing a comprehensive Wild Relative Introgression Toolbox integrating advanced recombination systems, introgression germplasm, and genomic tools. Specifically, the project will 1) Develop genome-wide introgression libraries from diverse Triticeae donor species using the optimized ph1b + 5Mg recombination system to generate novel alien introgression resources for wheat improvement. 2) Investigate homoeologous recombination behavior, crossover distribution, and introgression stabilization using existing genome-wide introgression libraries and other available introgression resources developed under the optimized ph1b + 5Mg system, and determine their relationship with genomic divergence among Triticeae species.3) Utilize genomic data generated from the newly developed genome-wide introgression libraries together with existing genomic resources available in the WGRC to develop a user-friendly online bioinformatics platform for donor-specific SNP marker design, introgression mapping, and tracking of alien chromatin across Triticeae species. The resulting toolbox will accelerate precise gene transfer from wild relatives into elite wheat backgrounds and provide foundational resources for climate-resilient wheat breeding.
