Defense genes and pathways in Fusarium crown rot susceptible and partially-resistant Australian wheat seedlings responding to Fusarium culmorum infection

Fusarium crown rot causes considerable losses to wheat production in parts of the United States and Australia. Australian wheat germplasm has been the best source of resistance to Fusarium crown rot caused by F. pseudograminearum. In order to understand the mechanism of resistance to Fusarium crown rot caused by F. culmorum, a transcriptional study using the Affymetrix wheat chip was done to compare the partially-resistant Australian line '2-49' to the susceptible Australian wheat variety ‘Puseas’ at ten days post-inoculation. Genes determined to be significantly different in expression levels were identified in four categories: 2-49 inoculated versus 2-49 non-inoculated, Puseas inoculated versus Puseas non-inoculated, 2-49 inoculated versus Puseas inoculated and 2-49 non-inoculated versus Puseas non-inoculated. Five candidate genes, oxalate oxidase, chitinase 1, glycosyltransferase, WIR1, and a stress-related protein were selected for further expression characterization at one, five, and ten days post-inoculation using quantitative real-time RT-PCR. The quantitative real-time RT-PCR results confirmed the microarray results and showed that differential expression in these genes was due to differences in genetic background, inoculation response, or the interaction of both factors. These genes are being investigated for their roles in the resistance response of 2-49 using a viral-induced gene silencing (VIGS) study and pathways analysis. An understanding of how 2-49 prevents F. culmorum spread throughout the seedling will greatly improve our understanding of resistance to fungal invasion in wheat.