Department of Agronomy and Plant Genetics, 411 Borlaug Hall, 1991 Upper Buford Circle University of Minnesota, St. Paul, MN 55108, U.S.A.
Fusarium head blight (FHB), caused primarily by Fusarium graminearum, decreases grain yield and quality in wheat and barley. Disease severity, deoxynivalenol (DON), fungal biomass, and transcript accumulation were examined in a wheat near-isogenic line pair carrying either the resistant or susceptible allele for the chromosome 3BS FHB-resistance quantitative trait locus (Fhb1). Fhb1 restricts spread of disease symptoms but does not provide resistance to initial infection or initial DON accumulation. Wheat exhibits both induction and repression of large sets of gene transcripts during F. graminearum infection. In addition, a difference in the general timing of transcript accumulation in plants carrying either the resistant or susceptible allele at the Fhb1 locus was detected, and 14 wheat gene transcripts were detected that exhibited accumulation differences between the resistant and susceptible alleles. These results indicate that these may be host responses that differentiate the resistant from the susceptible interaction. Comparative analysis of the wheat--F. graminearum and the barley--F. graminearum interactions revealed a large set of conserved transcript accumulation patterns. However, we also detected gene transcripts that were repressed in wheat but not in barley. Based on the disease symptoms, transcript accumulation data, and comparative analysis of the barley and wheat host response to F. graminearum infection, we developed an integrated model for the interactions of wheat and barley with F. graminearum.