Host plant resistance genes for Fusarium head blight: I. Sources, mechanisms, and utility in conventional breeding systems. Crop Sci

ABSTRACT source of complete resistance is known, and current sources provide only partial resistance.Fusarium head blight (FHB), caused by Fusarium graminearum The United States Department of Agriculture (USDA)Schwabe [teleomorph Gibberella zeae (Schwein.)], also known as scab, is a destructive disease of wheat (Triticum aestivum L; T. tur- currently ranks FHB as the worst plant disease of wheat gidum L. var durum) and barley (Hordeum vulgare L.). Host resis- and barley since the stem rust (caused by Puccinia gram-tance has long been considered the most practical and effective means inis Pers.:Pers.) epidemics of the 1950s (Wood et al., of control, but breeding has been hindered by a lack of effective 1999). FHB epidemics have been documented in 26 resistance genes and by the complexity of the resistance in identified states and five Canadian provinces. Yield losses in wheat sources. This paper will provide an overview of progress in developing since 1990 have exceeded 13 Tg (500 million bushels)host plant resistance for FHB, primarily in the USA, by review of with economic losses estimated at $2.5 billion (Windels,the sources of resistance in wheat and barley, and their utilization 2000). Wheat yields in 1993 were reduced by about 50%in breeding programs. Although there are no reported sources of in northeastern North Dakota and 40 % in northwesternimmunity, considerable genetic variability exists for resistance in both wheat and barley. Sources of resistance in durum, however, are lim- Minnesota compared with 1992 (National Agricultural ited. The strategy of breeding programs is to recombine different Statistics Service, 1993–1999). In barley, losses hav