Poster

Ahmed Charif^1,2, Navin Shrestha^1,2, Tatiana Danilova¹, Katherine Frels², Stephen Wegulo³, 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, University of Nebraska, Lincoln, NE 68583, USA
Corresponding Author: Xiwen Cai, xiwen.cai@usda.gov

Charif, Ahmed

acharif2@unl.edu

Fusarium head blight (FHB), caused mainly by Fusarium graminearum, is a major threat to durum wheat (Triticum turgidum ssp. durum) without an effective native source of resistance. Fhb7, derived from Thinopyrum elongatum and encoding a glutathione S-transferase that detoxifies trichothecene mycotoxins (DON), offers a route to improve durum resistance. We transferred the Fhb7^The2 allele from the hexaploid donor WGC002 into three winter durum lines, AC25-1013, AC25-1026, and AC25-1037, by marker-assisted backcrossing and developed BC₂F₃ introgression lines homozygous for Fhb7^The2. We evaluated the introgression lines and their recurrent parents in the greenhouse by single-spikelet point inoculation and in the field with corn-spawn inoculation at Lincoln, Nebraska. FHB severity was scored as the percentage of infected spikelets at 14 and 21 days post-inoculation (dpi) in the greenhouse and field. In the greenhouse, recurrent parents reached 69.1-76.0% severity at 14 dpi and 90.5-96.1% at 21 dpi, whereas Fhb7^The2 lines remained at 7.7-10.1% and 14.1-19.0% with a reduction of 85.4-89.9% and 80.0-84.4%, respectively (P < 0.001 for all comparisons). Disease in the introgression lines was largely confined to the inoculated and adjacent spikelets, indicating strong resistance to fungal spread (Type II resistance). In the field, Fhb7^The2 lines showed 22.3-26.0% severity compared with 65.4-68.8% for the recurrent parents, a reduction of 61.4-67.1% (P < 0.05). The smaller field effect is consistent with the combined assessment of initial infection and spread under variable environmental conditions. The effect of Fhb7^The2 was similar across the three genetic backgrounds in both environments, indicating stable expression in winter durum. These results demonstrate that Fhb7^The2 provides substantial and consistent FHB resistance in durum wheat and that the BC₂F₃ introgression lines represent valuable breeding germplasm. Selected lines will be advanced to BC₄F₃ to recover a greater proportion of the recurrent parent background while maintaining the resistance introgression. Advanced lines will be evaluated across multiple environments and assessed for DON accumulation and agronomic performance to further define the breeding value of Fhb7^The2.

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