Abstract:
Fusarium ear blight (FEB) is a disease of wheat and small grain cereals,
caused by the fungi Fusarium culmorum and Fusarium graminearum. The
disease causes premature bleaching of spikelets and shrivelling of the grain can
result in a direct yield loss. Mycotoxins such as deoxynivalenol produced by the
fungus can reduce grain quality. Breeding for resistant wheat cultivars is
considered one of the best control options. Previously identified resistance has
been reported in the Chinese genotype Sumai 3.
The principal aim of this project was to identify novel sources of
resistance to FEB. Twenty four wheat genotypes were evaluated for resistance
to FEB in this project. Molecular markers linked to previously identified QTL
from Sumai 3 conferring resistance were used to confirm their absence in the
genotypes under investigation, and revealed that none of the genotypes under
investigation contained all of the QTL for resistance. Field trials conducted over
two years screening for resistance demonstrated that, although not statistically
similar to Sumai 3, levels of disease were below 10% in some of the Chinese
genotypes. Follow up experiments using reporter strains of Fusarium
graminearum explored the accumulation of fungal biomass and the expression
of the gene Tri5, which is essential for DON biosynthesis. Fungal biomass
levels were not significantly different between genotypes; however expression
of the Tri5 gene was significantly lower in the genotype Alsen.
A previously developed wheat leaf seedling bioassay was also explored.
Scanning electron microscopy revealed the presence of fungal hyphae in
advance of the visible lesion during the infection course of F. culmorum.
Inoculation with a Tri5 mutant strain of F. graminearum demonstrated that a
lack of mycotoxin production altered the lesion type. This project has
successfully identified potential novel resistance mechanisms and the future
prospects for the control of this disease are discussed.
