The illusion of progress: why most introgressions from wild Triticeae fail to improve wheat agronomically

The progressive narrowing of the genetic base of bread wheat (Triticum aestivum L.) threatens yield gains and stress resilience under climate change. Wild Triticeae species are widely viewed as a vital source of adaptive diversity, yet despite decades of research and the discovery of numerous genes and introgression lines, only a tiny fraction has delivered validated agronomic benefits. Because introgression from the secondary gene pool (Aegilops spp.) follows distinct genetic rules, this review deliberately focuses on more distant genera within the tertiary gene pool. This review critically dissects that disconnect, revealing a systematic "illusion of progress." We demonstrate how methodological biases-particularly reliance on surrogate traits under controlled conditions and insufficient multi-environment validation-interact with genetic constraints such as linkage drag, polygenic architecture, and segment instability to inflate early-stage promise while suppressing field-level reproducibility. By contrasting successful and unsuccessful introgressions, we identify the conditions essential for translational impact: major-effect loci, minimal linkage drag, stable expression across environments, and rigorous field testing. To bridge the lab-to-field gap, we advocate for agronomically relevant phenotyping, precision introgression including genome editing, integration with genomic selection, and a fundamental shift from reporting gene-level discoveries to demonstrating measurable yield performance. This work provides a conceptual framework for evaluating introgression outcomes and offers actionable strategies to improve the efficiency of exotic gene transfer in wheat breeding, thereby addressing a central challenge in plant breeding and food security.