An integrated approach for identification and characterization of novel sources of resistance to wheat stem sawfly in wild wheat species

Project Summary:
Photo Credit: Kathleen Hanson

Wheat stem sawfly (WSS, Cephus cinctus) has long been considered the most important pest of wheat in the northern Great Plains of North America. In recent years, damage from WSS has expanded to areas of Nebraska, Wyoming, and Colorado. Solid stem varieties have been shown to be effective by reducing larval survival. However, the solid-stemmed varieties are not preferred by growers because of yield drag compared to hollow-stemmed varieties and inconsistent solidness expression. Given the limited sources of resistance to WSS, there is a need to evaluate diverse wheat genetic resources for additional alleles that can enhance development of WSS-resistant varieties.

As part of our previously funded grant (8/1/2019-7/31/2021), we screened 60 wheat lines from six wild wheat species using the cone-tainer method and found that Aegilops tauschii and Triticum turgidum dicoccoides consistently had fewer eggs and fewer infested stems. In the next phase of the grant, we screened 143 wild wheat introgression lines that included Ae. tauschii and T. turgidum as part of their pedigree (8/1/2021-7/31/2023). In 2022, we found that several of these lines had low egg numbers and larval infestation and an average solid stem score of 7 (Score of 5=hollow, 25=solid). This suggests potentially novel non-solid stem resistance alleles that can be leveraged to combat WSS. The 2023 data is currently being analyzed.

Moving forward, we propose to continue screening wild wheat introgression lines from wild emmer and Ae. tauschii resistant families screened in 2022 and 2023, and new introgression germplasm based on Ae. speltoides, Haynaldia villosa, and Ae. ventricose. In the long-term, the research we propose will lead to the identification of novel sources of WSS resistance that can be bred into desired wheat varieties.