Molecular Breeding Using a Major QTL for Fusarium Head Blight Resistance in Wheat

The difficulties of breeding for Fusarium head blight (caused by Fusarium graminearum Schwabe [teleomorph: Gibberella zeae]) resistance, a quantitatively inherited fungal disease, caused us to initiate a marker-assisted selection (MAS) approach to accelerate our gains from selection. Although MAS for simply inherited traits has become commonplate in many plant breeding programs, there are few examples of its application with quantitatively inherited traits. Several barriers to MAS for a quantitative trait locus (QTL) must be addressed before it can be integrated into a breeding program, including (i) its efficiency or gain compared to phenotypic selection; (ii) the usefulness of markers in breeding-relevant populations; and (iii) the cost, throughput, and expertise required. We identified a major QTL, Fhb1, for Fusarium head blight resistance in wheat (Triticum aestivum L.) and validated its effect in an additional mapping population and near-isogenic lines developed from segregating lines in our breeding program. The effect of this QTL was large and consistent enough to justify complementing our extensive phenotypic screening efforts for this disease with MAS for this major QTL. Fhb1 is located in a highly polymorphic region, and we developed highly diagnostic markers while fine mapping this QTL. The establishment of the USDA-ARS Regional Small Grains Genotyping Centers has dramatically increased our capabilities to apply MAS by providing access to high-throughput DNA extraction and genotyping equipment. Because a limited number of induvidual can be can be subjected to MAS, we use a process of retrospective breeding to identify those populations that are most likely to produce cultivar candidates. More efficient DNA extraction technologies and marker platforms will allow us to fully implement MAS in breeding programs.