Marker-assisted selection for Fusarium head blight resistance in wheat

The cultivation of wheat varieties resistant to Fusarium head blight (FHB) is recognized as one of the most important components to diminish losses due to this disease. Although there is no known immunity to this disease in wheat germplasm, considerable improvements in genetic resistance have been achieved by concentrated breeding efforts that have relied primarily upon repeated field and greenhouse-based screening. DNA markers are a relatively new technology that can be used to increase breeding progress, especially for traits such as FHB that are difficult to select for under field conditions and that are controlled by multiple genes. Marker-assisted selection (MAS) uses markers to select for particular DNA segments that are genetically linked to genes that provide incremental resistance to FHB. One particular gene, designated Fhb1, provides a 20-25% average reduction in FHB symptoms. This gene and its associated markers have been validated in numerous breeding programs and is widely used to more precisely breed for resistance. About a dozen other genes affecting FHB reaction have been identified, but they have smaller and more inconsistent effects compared with Fhb1. Nevertheless, breeders are discovering which of these markers can be combined with Fhb1 in their genetic backgrounds to enhance resistance. The establishment of the USDA-ARS Regional Small Grains Genotyping Centers and similar facilities around the world have increased the capacity for wheat breeders to utilize this powerful technology. More efficient DNA extraction technologies and marker platforms will allow breeders to more fully implement MAS in the future.