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

Authors: Peirce, Erika; EVERS, BYRON - Bayer Cropscience; RAUPP, JOHN - Kansas State University; Guttieri, Mary; POLAND, JESSE - King Abdullah University Of Science And Technology; AKHUNOV, EDUARD - Kansas State University; BROECKLING, COREY - Colorado State University; HALEY, SCOTT - Colorado State University; MASON, ESTEN - Colorado State University; NACHAPPA, PUNYA - Colorado State University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2024
Publication Date: 2/6/2024
Citation: Peirce, E.S., Evers, B., Raupp, J.W., Guttieri, M.J., Poland, J., Akhunov, E., Broeckling, C., Haley, S., Mason, E., Nachappa, P. 2024. Identifying novel sources of resistance to wheat stem sawfly in five wild wheat species. Pest Management Science. https://doi.org/10.1002/ps.8008.
DOI: https://doi.org/10.1002/ps.8008

Interpretive Summary: The wheat stem sawfly (WSS) is a devastating pest of wheat crops. Sawfly larvae cut through stems of wheat plants, causing them to bend or break and then fall to the ground. Wheats with the solid stem trait better resist the sawfly larvae but may yield less than wheats with hollow stems, and the solidness trait can be inconsistent. New sources of resistance to WSS are critically needed by breeders developing wheat cultivars for regions where the sawfly is endemic. We evaluated 91 different accessions of five species, including common wheat (Triticum aestivum) and five wild wheat species (Triticum monococcum, T. urartu, T. turgidum, T. timopheevii, and Aegilops tauschii). We measured how attractive each accession was to the sawfly (host selection) and how well the sawfly larvae grew in each accession (host suitability) by exposing greenhouse-grown plants to sawflies in wheat fields. The sawflies laid eggs in the stems, and we counted the eggs in each stem to assess host selection. We later dissected the wheat stems to see if sawfly larvae were present, a measure of host suitability. Some wild wheat species (Ae. tauschii, T. turgidum, and T. urartu) had fewer sawfly eggs and larvae than others (T. monococcum and T. timopheevii). The sawfly larvae that did grow in T. monococcum, T. timopheevii, T. turgidum, and T. urartu also were smaller than those that grew in common wheat (T. aestivum). Wild relatives of wheat, therefore, can be a valuable source of new resistance for breeders working to minimize economic loss to wheat stem sawfly.

Technical Abstract: 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. While solid-stem wheat genotypes can effectively reduce larval survival, they may have lower yields than hollow-stem genotypes and show inconsistent solidness expression. Due to 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. When we weighed the larvae within stems of T. monococcum, T. timopheevii, T. turgidum, and T. urartu, these larvae had lower larval weights than those of 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.