The Fusarium Head Blight Pathosystem

Abstract

Fusarium Head Blight (FHB), or scab, is a fungal disease affecting many smallgrain cereals, but is of most importance on wheat and barley (Nelson et al. 1981). FHB reduces kernel weight and consequently grain yield. The germination rate and seedling vigour are reduced when the seeds are infected. The fungus digests proteins and starch and the use of infected kernels generates technical problems because enzymes and yeast growth are inhibited by by-products of the fungus that prevent bread production (Becthel et al. 1985, Saric et al. 1997). Metabolites produced by Fusarium species are also the cause of ‘gushing’ of beer. However, of primary concern, is the contamination of grain with mycotoxins produced by several of the species associated with FHB. Several of these compounds have been shown to be harmful to human and animal health. Yield losses caused by FHB may reach 50–60% (Miller and Trenholm 1994, Windels 2000). In Paraguay, weather conditions in 1972–1975 favoured Fusarium and Septoria epidemics that together accounted for losses up to 70%. In the USA, yield losses and damage caused by FHB was estimated to be about $3 billion in the 90’s and $220 million in the Canada (Windels 2000). Damages were also reported in China: FHB may affect up to 7 millions ha and 2.5 million tonnes of grain may be lost in epidemic years. In Minnesota, the disease has had an impact on cropping patterns, between 1992 and 1998 the amount of land planted to wheat decreased of 31% (Windels 2000).