Authors: Ahmed Charif 1,2, Fang Wang (1,20, Tatiana Danilova 1, Gang Li 1, Navin Shrestha 1,2, Yueqiang Leng 3, Shaobin Zhong 3, Zhao Jin 4, Deanna Funnell-Harris 1, Katherine Frels 2, Stephen Wegulo 5, Jeffrey Boehm Jr. 1,2, Andrew Green 4, Steven Xu 6, and Xiwen Cai 1,2
1. USDA-ARS, Wheat, Sorghum & Forage Research Unit, Lincoln, NE 68583, USA
2. Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE 68583, USA
3. Department of Plant Pathology, North Dakota State University, Fargo, ND 58108, USA
4. Department of Plant Sciences, North Dakota State University, Fargo, ND 58108, USA
5. Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583, USA
6. USDA-ARS, Crop Improvement and Genetics Research Unit, Western Regional Research Center, Albany, CA 94710, USA
Corresponding Author: Xiwen Cai, xiwen.cai@usda.gov
Presenting Author: Ahmed Charif
Abstract
Wheat breeding for Fusarium head blight (FHB) resistance has been limited by the shortage of resistance genes and the complexity of the current resistance sources in terms of inheritance and interaction with environments. The discovery, characterization, and deployment of novel resistance genes in wheat, especially in durum wheat, has been a major research priority in the FHB community. We transferred a novel Thinopyrum elongatum (2n=2x=14, EE)-derived FHB resistance gene Fhb7The2 to wheat through a wheat-Th. elongatum 7B-7E translocation (7BS·7BL-7EL) by genomics-enabled chromosome engineering and developed an FHB-resistant germplasm containing Fhb7The2, which was released as PI 702949 to the public in 2023. Obvious deleterious effects have not been observed with the Th. elongatum chromosome segment of the 7B-7E translocation in the germplasm. PI 702949 has been distributed to most, if not all, of the USWBSI-funded wheat FHB breeding programs, and to USDA-ARS, CIMMYT, and many private breeding companies in the US and other countries. Also, we developed diagnostic PCR allelic competitive extension (PACE) markers specific for Fhb7The2, which have largely increased the efficacy and throughput of Fhb7The2 introgression and deployment in US wheats. More recently, we have incorporated Fhb7The2 into elite HRSW, HRWW, and spring and winter durum genotypes for FHB-resistant germplasm/variety development by marker-assisted backcrossing breeding. Three HRSW introgression lines containing Fhb7The2 were developed and evaluated for FHB resistance in the FHB nurseries at Lincoln, NE and Fargo, ND and greenhouses in 2023 and 2024. They consistently exhibited FHB resistance significantly better than their recipient parents under all field and greenhouse environments and had similar agronomic performance as their respective parents. In addition, we have developed a number of HRWW and spring and winter durum introgression lines containing Fhb7The2, which have been evaluated for FHB resistance in the field and greenhouse. All of the Fhb7The2 introgressions significantly outperformed their recipient parents on FHB resistance under all environments. In summary, the wild grass-derived FHB resistance gene Fhb7The2confers significant resistance in both common and durum wheat backgrounds and the alien translocation involving wheat chromosome 7B does not result in obvious deleterious effects on the overall agronomic performance of the introgressions. The monogenic nature of Fhb7The2 in wheat backgrounds dramatically improves its utility and efficacy in marker-assisted breeding pipelines. The deployment of Fhb7The2 in different classes of US wheats will strengthen and diversify their resistance to FHB and reduce the economic losses caused by the disease in wheat production.