Host plant resistance genes for fusarium head blight: Sources, mechanisms, and utility in conventional breeding systems

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.)], also known as scab, is a destructive disease of wheat (Triticum aestivum L; T. turgidum L. var durum) and barley (Hordeum vulgare L.). Host resistance has long been considered the most practical and effective means of control, but breeding has been hindered by a lack of effective resistance genes and by the complexity of the resistance in identified sources. This paper will provide an overview of progress in developing host plant resistance for FHB, primarily in the USA, by review of the sources of resistance in wheat and barley, and their utilization in breeding programs. Although there are no reported sources of immunity, considerable genetic variability exists for resistance in both wheat and barley. Sources of resistance in durum, however, are limited. The strategy of breeding programs is to recombine different types and sources of resistance steadily through traditional breeding strategies. To facilitate selection, artificial inoculation techniques are used in both the field and greenhouse. This enables breeders to select simultaneously for resistance and desirable agronomic characteristics. Incremental increases in resistance are being reported in hexaploid wheat and to a lesser extent in barley and durum wheat. It is anticipated that the development of molecular markers will improve the efficiency of developing FHB wheat and barley cultivars.