Tissue-Specific Responses of Cereals to Two Fusarium Diseases and Effects of Plant Height and Drought Stress on Their Susceptibility

Multiple species of Fusarium can infect wheat and barley plants at various stages of development. Fusarium head blight (FHB) refers to the infection of spikes and developing kernels by these pathogens, and crown rot (FCR) infers to infection of the root, crown, and basal stem by Fusarium pathogens. Interestingly, most of the host genes conferring resistance to these two diseases are different in both wheat and barley, and plants’ susceptibility to these two diseases are oppositely affected by both plant height and reduced water availability. Available results do not support the hypothesis that reduced height genes have different effects on biotrophic and necrotrophic diseases. Rather, differences in temperature and humidity in microenvironments surrounding the infected tissues and the difference in the physical barriers originating from the difference in cell density seem to be important factors affecting the development of these two diseases. The fact that genes conferring resistance to Type I and Type II of FHB are different indicates that it could be feasible to identify and exploit genes showing resistance at the three distinct stages of FCR infection for breeding varieties with further enhanced resistance. The strong association between FCR severity and drought stress suggests that it should be possible to exploit some of the genes underlying drought tolerance in improving resistance to FCR.