Tetraploid wheat (Triticum turgidum) lines from the United States as a source of Hessian fly (Mayetiola destructor) resistance

Deploying resistant wheat cultivars is the most economical and environment-friendly strategy to manage the devastating effects of the dipteran pest, Hessian fly (Hf; Mayetiola destructor). Currently, 37 Hf resistance genes have been identified to combat the 18 Hf genotypes documented so far. However, the Hf populations adapt rapidly to overcome the newly deployed resistance genes within a few years of release resulting in development of virulent Hf biotypes and breakdown of plant resistance. Identification of new and novel sources of resistance offers breeders additional resources that can be included in the breeding programmes to develop elite Hf-resistant cultivars. In the current study, we screened 374 wheat (tetraploid and hexaploid) accessions originating from different regions of the United States and identified three tetraploid (Triticum turgidum) pasta wheat lines, one originating from North Dakota (PI 639869) and two from Minnesota (PI 352398 and CItr 15710) exhibiting ≥95% resistance to Hf biotype L at 20°C. Further, the wheat cultivar PI 352398 showed 100% resistance to six additional Hf genotypes including biotypes B, C, D, O, GP and vH13. The lines PI 639869 and CItr 15710 also showed >70% resistance with most biotypes, except against biotype GP with the former and biotype B with the latter. Interestingly, a few plants from these two cultivars exhibited putative tolerance to these biotypes where the plants showed normal growth but harboured white, live larvae and showed cell permeability that was intermediate in levels between Hf-infested resistant and susceptible wheat. Additionally, since the increase in environmental temperatures to 25–30°C also negatively impacts Hf resistance, the three T. turgidum (PI 639869, PI 352398 and CItr 15710) cultivars were evaluated for Hf resistance at 30°C. None of the wheat cultivars were resistant to Hf biotype L at 30°C indicating a temperature-dependent breakdown of resistance and are therefore not suitable for geographical regions with higher environmental temperatures. Taken together, these three wheat lines represent additional sources of Hf resistance that can be leveraged by breeders for developing durable elite lines.