Fusarium head blight (FHB) poses a significant threat to winter wheat cultivation. Resistance breeding programs rely heavily on a limited number of larger-effect FHB resistance QTL that have been identified, mapped, associated, and well-characterized with nearby markers. In addition, smaller-effect (background) resistance QTL may contribute moderate levels of “native” resistance, yet these QTL are generally poorly characterized. The overall resistance of a genotype is determined by the combined action of characterized as well as uncharacterized resistance QTL. FHB resistance can be improved by integrating, known larger-effect QTL through marker-aided introgression into genotypes with significant background resistance. This study aimed to identify and utilize well-adapted, advanced hard red winter wheat breeding lines with useful background FHB resistance QTL. A diallel trial consisting of 11 parents and 55 non-reciprocal F₁ hybrids was tested for Type II FHB resistance in a replicated greenhouse experiment. Data were first analyzed following the Griffing analysis. Significant differences were detected among entries for disease severity (DS), general combining ability (GCA), and specific combining ability (SCA). The ratio of GCA:SCA effects suggested that additive QTL effects were of primary importance. The Hayman analysis provided additional information on the genetic nature of the resistance QTL. Eight F₁ hybrids with the lowest DS resulted from crosses among the best general combiners. F₂ of the latter crosses were compared in a second-greenhouse FHB trial to identify possible transgressive segregates. An arbitrary threshold DS of 14% was used to select a manageable number of the most promising F₂ plants for continued line development.  

Keywords: Combining ability, Griffing design, Hayman analysis, Native resistance, Resistance breeding