Wheat yellow mosaic virus (WYMV) poses a significant threat to global autumn-sown wheat production. Growing wheat varieties with WYMV resistance is the most effective strategy for disease control. In this study, we fine-mapped a major WYMV resistance gene Ym5 (previously designated as QYm.njau-5A.1) in the Japanese wheat variety Xifeng. We delimited Ym5 to a 4.6 Mb linkage block (534.6–539.2 Mb in chromosome 5A) by genome-wide association study of 266 wheat accessions (excluding those carrying Ym1). Comparative genomic analyses revealed that resistant haplotypes, shared by Xifeng and European line ArinaLrFor, represent a putative alien introgression from Triticum monococcum. Twelve InDel and one KASP markers were developed and confirmed as diagnostic. Twenty-four recombinants were identified from a Xifeng × Yangmai 158 F₂ population consisting of 6882 individuals, and Ym5, flanked by markers ARI_106 and ARI_218, was narrowed down to a 1.1 Mb interval (534.8–535.9 Mb in ArinaLrFor). The use of Ym5 in Chinese breeding programs was traced to two sources: Xifeng and Australian variety Quality. Further investigation showed Ym5 introgression conferred no obvious yield penalty.

Fusarium head blight (FHB) is a serious fungal disease that affect small grain cereals, causing significant wheat (Triticum aestivum L.) yield and quality losses globally. Breeding disease-resistant wheat varieties is key to address FHB-related challenges, but its progress is delayed by traditional methods due to the small-scale, laborious and relatively subjective nature of manual assessment. This study presents a new approach that combines ultralow-altitude drone phenotyping with an optimized You Only Look Once (YOLO) model to examine FHB in wheat, enabling us to perform large-scale and automated symptomatic analysis of this disease. We first established an Open FHB (OFHB) training dataset, consisting of 4867 diseased and 106,801 healthy spikes collected from 132 commercial breeding lines during FHB progression. Then, a deep learning model called YOLOv8-WFD was trained for detecting healthy and diseased spikes, followed by an adaptive Excess Green method to identify symptomatic regions and thus FHB-related traits on spikes. To study resistance levels, we employed an unsupervised SHapley Additive exPlanations (SHAP) method to pinpoint key traits between 10 and 20 d after inoculation (DAIs), resulting in the classification of 423 varieties trialed during the 2023–2024 growing seasons into four resistance levels (i.e., highly and moderately susceptible, and moderately and highly resistant), which were highly correlated with field specialists’ evaluations. Finally, we derived disease developmental curves based on measures of key traits during 10–20 DAI, quantifying varietal disease progression patterns over time. To our knowledge, this work represents a significant advancement in large-scale disease phenotyping and automated analysis of FHB in wheat, providing a valuable toolkit for breeders and plant researchers to assess resistance levels, select disease-resistant varieties, and understand dynamics of the fungal disease.

Fusarium head blight (FHB) threatens wheat production worldwide. Utilization of FHB resistant varieties is the most effective solution for disease control. Owing to the limited sources of FHB resistance, mining of novel resistance genes is crucial. Here, we report an FHB resistance gene from a wild wheat relative species, Roegneria ciliaris and developed FHB resistant germplasm containing this gene. Wheat-R. ciliaris disomic addition line DA3S^c showed enhanced type Ⅱ FHB resistance compared to its sister line 3S^c-Null without chromosome 3S^c, indicating that the resistance was contributed by the addition of 3S^c. The resistance gene on 3S^c was validated using F₂ and F_2:3 populations derived from the cross between DA3S^c and susceptible Aikang 58 (a susceptible cultivar), demonstrating that the lines with 3S^c had significantly enhanced FHB resistance compared to the individuals without 3S^c. This was the second resistance gene identified in R. ciliaris, designated FhbRc2. To transfer FhbRc2 to common wheat, we produced a double-monosomic chromosome population by crossing DA3S^c with the Chinese Spring nulli-tetrasomic line N3DT3B. Eight alien chromosome lines containing 3S^c were identified using genomic/fluorescence in situ hybridization and 3S^c-specific marker analysis. Only the lines carrying the long arm of 3S^c conferred FHB resistance, further locating FhbRc2 on 3S^cL. A compensating wheat-R. ciliaris Robertsonian translocation line T3DS·3S^cL harboring FhbRc2 is developed and provides a potential genetic resource in wheat breeding for enhanced FHB resistance.