BREEDING FOR HEAD BLIGHT (FUSARIUM SPP.) RESISTANCE IN WHEAT: DEVELOPMENT OF A MYCOTOXIN-BASED SELECTION METHOD OF SEEDLINGS
It was decided to start a Fusarium resistance breeding program in cooperation with Austrian breeders to improve the FHB resistance of their breeding material. In order to decrease the amount of field inoculations, a study was carried out to develop a simple laboratory method to examine FHB resistance of wheat breeding material. In literature several methods are described to select plants with increased level of disease resistance using toxic metabolites produced by Fusarium as selection agent. The toxins produced by plant pathogens can be classified into two categories: host-specific and nonhost-specific, on the basis of selective phytotoxicity to compatible and noncompatible hosts. A host-specific toxin selectively damages only those plant varieties that are susceptible to the pathogens. Both F. graminearum and F. culmorum produce several nonhost-specific toxins, the most important of which are the trichothecenes deoxynivalenol (DON) and 3-acetyldeoxynivalenol. They probably play a role in the aggressiveness of the pathogen and promote disease development and colonization (Snijders and Krechting, 1992). These trichothecenes inhibit eukaryotic protein synthesis by blocking the peptidyl transferase step (Carter et al., 1980). It has been reported that plants tolerant to these toxins have an increased resistance to FHB (Snijders and Krechting, 1992). Either crude toxic metabolite extracts (Lijuan et al., 1991; Fadel and Wenzel, 1993) or highly purified toxins have been used (Wakulinski, 1989; Wang and Miller, 1988). Selection was carried out at the level of germinating seeds and seedlings (Shimada and Otani, 1990; Wakulinski, 1989), callus (Lijuan et al., 1991), coleoptiles (Wang and Miller, 1988) or microspores (Fadel and Wenzel, 1993). Good correlations between in vitro tests and FHB resistance have been reported (Wang and Miller, 1988; Wakulinski, 1989; Lijuan et al., 1991).