Identifying novel sources of resistance to wheat stem sawfly in five wild wheat species.

BACKGROUND: The wheat stem sawfly (WSS, Cephus cinctus) is a major pest of wheat (Triticum aestivum) and can cause significant yield losses. WSS damage results from stem boring and/or cutting, leading to the lodging of wheat plants. Although solid-stem wheat genotypes can effectively reduce larval survival, they may have lower yields than hollow-stem genotypes and show inconsistent solidness expression. Because of limited resistance sources to WSS, evaluating diverse wheat germplasm for novel resistance genes is crucial. We evaluated 91 accessions across five wild wheat species (Triticum monococcum, T. urartu, T. turgidum, T. timopheevii, and Aegilops tauschii) and common wheat cultivars (T. aestivum) for antixenosis (host selection) and antibiosis (host suitability) to WSS. Host selection was measured as the number of eggs after adult oviposition, and host suitability was determined by examining the presence or absence of larval infestation within the stem. The plants were grown in the greenhouse and brought to the field for WSS infestation. In addition, a phylogenetic analysis was performed to determine the relationship between the WSS traits and phylogenetic clustering. RESULTS: Overall, Ae. tauschii, T. turgidum and T. urartu had lower egg counts and larval infestation than T. monococcum, and T. timopheevii. T. monococcum, T. timopheevii, T. turgidum, and T. urartu had lower larval weights compared with T. aestivum. CONCLUSION: This study shows that wild relatives of wheat could be a valuable source of alleles for enhancing resistance to WSS and identifies specific germplasm resources that may be useful for breeding. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Efficient curation of genebanks using next generation sequencing reveals substantial duplication of germplasm accessions.

Genebanks are valuable resources for crop improvement through the acquisition, ex-situ conservation and sharing of unique germplasm among plant breeders and geneticists. With over seven million existing accessions and increasing storage demands and costs, genebanks need efficient characterization and curation to make them more accessible and usable and to reduce operating costs, so that the crop improvement community can most effectively leverage this vast resource of untapped novel genetic diversity. However, the sharing and inconsistent documentation of germplasm often results in unintentionally duplicated collections with poor characterization and many identical accessions that can be hard or impossible to identify without passport information and unmatched accession identifiers. Here we demonstrate the use of genotypic information from these accessions using a cost-effective next generation sequencing platform to find and remove duplications. We identify and characterize over 50% duplicated accessions both within and across genebank collections of Aegilops tauschii, an important wild relative of wheat and source of genetic diversity for wheat improvement. We present a pipeline to identify and remove identical accessions within and among genebanks and curate globally unique accessions. We also show how this approach can also be applied to future collection efforts to avoid the accumulation of identical material. When coordinated across global genebanks, this approach will ultimately allow for cost effective and efficient management of germplasm and better stewarding of these valuable resources.

Chromosome Engineering Techniques for Targeted Introgression of Rust Resistance from Wild Wheat Relatives.

Hexaploid wheat has relatively narrow genetic diversity due to its evolution and domestication history compared to its wild relatives that often carry agronomically important traits including resistance to biotic and abiotic stresses. Many genes have been introgressed into wheat from wild relatives using various strategies and protocols. One of the important issues with these introgressions is linkage drag, i.e., in addition to beneficial genes, undesirable or deleterious genes that negatively influence end-use quality and grain yield are also introgressed. Linkage drag is responsible for limiting the use of alien genes in breeding programs. Therefore, a lot of effort has been devoted to reduce linkage drag. If a gene of interest is in the primary gene pool or on a homologous chromosome from species in the secondary gene pool, it can be introgressed into common wheat by direct crosses and homologous recombination. However, if a gene of interest is on a homoeologous chromosome of a species belonging to the secondary or tertiary gene pools, chromosome engineering is required to make the transfer and to break any linkage drag. Four general approaches are used to transfer genes from homoeologous chromosomes of wild relatives to wheat chromosomes, namely, spontaneous translocations, radiation, tissue culture, and induced homoeologous recombination. The last is the method of choice provided the target gene(s) is not located near the centromere where recombination is lacking or is suppressed, and synteny between the alien chromosome carrying the gene and the recipient wheat chromosome is conserved. In this chapter, we focus on the homoeologous recombination-based chromosome engineering approach and use rust resistance genes in wild relatives of wheat as examples. The methodology will be applicable to other alien genes and other crops.