Host selection and suitability of Clearfield® wheat cultivars to wheat stem sawfly (Cephus cinctus)

The wheat stem sawfly (WSS), Cephus cinctus (Hymenoptera: Cephidae), is a major pest of wheat. Yield losses from WSS result from stem boring and cutting, which causes plant lodging. Each year, WSS causes an estimated $350 million in damage to wheat producers across the Great Plains. This study evaluated host selection and suitability of Clearfield® (CL) wheat cultivars to WSS in field assays and evaluated the underlying mechanisms using metabolomics approaches. Oviposition preferences and larval infestation were monitored over two consecutive years across five wheat cultivars: one susceptible hollow-stem cultivar (Byrd), two semi-solid stem tolerant cultivars (Fortify SF and Amplify SF), and two herbicide-tolerant cultivars (Byrd CL Plus and Brawl CL Plus). Cultivars were grown in greenhouse and placed in infested wheat fields to expose them to natural WSS pressure. CL cultivars showed reduced WSS oviposition and larval infestation compared to the susceptible control, indicating potential host non-preference. In field plots, CL cultivars also showed lower rates of stem cutting. To investigate the mechanisms, we will perform TD-GC-MS, or Thermal Desorption-Gas Chromatography-Mass Spectrometry, to profile volatile compounds emitted by CL wheat cultivars that may interfere with WSS oviposition. In addition, perform GC-MS based metabolomic analysis to examine the composition of plant cuticular waxes in these cultivars. This dual approach will help uncover both volatile and surface-level chemical traits potentially involved in WSS host selection and resistance. These insights may inform strategies to mitigate WSS damage in wheat production and potentially guide the development of more resistant wheat cultivars.