Wheat Research

Priming for resistance against Fusarium graminearum
Dr. Rajagopal Subramaniam and Dr. Charles Nasmith, Agriculture and Agri-Food Canada

Fusarium graminearum is the causal agent of several serious cereal crop diseases including Fusarium Head Blight of wheat (FHB). In 1996, Ontario’s wheat industry experienced the worst epidemic on record, resulting in a total loss between $100 and $200 million due to FHB. While the fungus itself contributes to affects on cereal crop physiology due to disease, the associated trichothecene mycotoxins affect the quality of the grain and present a toxic hazard to both animal and human consumers.

Work performed in Dr. Gopal Subramaniam’s laboratory has focused on understanding mycotoxin production in F. graminearum (Fg), and has led to the characterization of a fungal strain compromised in the production of trichothecene mycotoxins, and therefore drastically reduced pathology symptoms. This disarmed mutant strain has an important trichothecene regulator gene (Tri6) removed.

Interestingly, we have found that the removal of this gene not only reduces the expression of mycotoxin genes, but also affects genes involved in the fungus’ survival such as carbon and nitrogen acquisition. Members of the Subramaniam Laboratory also have experience with the use of low virulence strains in order to control virulent disease through ‘priming’ for resistance (specifically using low virulent strains to control the causal agent of Dutch elm disease, Ophiostoma novo-ulmi).

Figure a: Harmless strain priming followed by wild type fusarium application.

Figure B: No application of harmless strain, only infected with wild type of fusarium.

We have combined these two experiences, and have shown that ‘priming’ can work as a bio-control. Point inoculating an Fg sensitive variety of wheat (Roblin) with the Fg mutant strain (priming) and then subsequently inoculating with the Fg wild type strain reduces Fg symptoms compared to the mock controls. We are presently comparing the Tri6 Fg mutant with other promising ‘priming’ candidates.

We are also looking at more resistant wheat varieties such as Wuhan I, Nuybai, and Sumai3. Since priming causes a specific response from the plant host, testing more resistant varieties may provide a stronger priming response, and thereby better disease control. Along with bio-control, ‘priming’ can assist in identifying genes that are involved in resistance, information invaluable to breeders looking for targeted Fg resistant material. These findings will therefore address both practical and basic research applications, in order to combat this devastating disease.