Hessian fly tolerance increases yield in elite durum wheat cultivars Svevo and Soft Svevo.

Insect resistance is critical for wheat crop sustainability and global food security. The dependence on innate plant resistance to prevent significant yield losses caused by Hessian fly (Mayetiola destructor), a major pest, could be detrimental in the event of severe infestation due to evolution of virulent biotypes. Wheat tolerance offers an alternate and viable strategy, as it minimizes selection pressure on pest populations with no plant yield penalty. Despite its lucrative attributes, the mechanisms governing tolerance are unknown. Here, we dissect Hessian fly tolerance-associated plant responses in two elite wheat (Triticum turgidum subsp. durum) cultivars, Svevo and Soft Svevo. Both exhibited dual phenotypes, harboring live and dead larvae, with phenotypic and molecular characteristics intermediate between resistant and susceptible plants. Although 75-96% of larvae survived on the infested tolerant plants, yields increased significantly by 14% over uninfested plants. Survival of the primary Hessian fly-infested stems was a key trait positively influencing yield (+31%) in the tolerant plants. The live larvae completed their life cycle producing viable adult Hessian flies. We further identified a positive correlation between caffeic acid levels and tolerance, suggesting a priming role in plant survival, associated with increased yield. Our finding provides the first comprehensive integrative physiological and metabolic characterization of Hessian fly tolerance advancing prospects for deploying tolerance with major implications for wheat productivity.