Quantitative PCR and histopathological investigations of cereal tissues during infection by the crown rot pathogen Fusarium pseudograminearum

Quantitative PCR and histopathological investigations of cereal tissues during infection by the crown rot pathogen Fusarium pseudograminearum

Crown rot of wheat is a significant cause of yield losses in
many wheat producing countries, particularly Australia
where the predominant cause is the fungus Fusarium
pseudograminearum. Other cereals such as durum wheat and barley can also be affected. Partial resistance has been
identified in a small number of wheat lines, such as 2-49
and Sunco, but the mechanisms of resistance shown by these lines have not been identified. Using quantitative PCR
based on fungal translation elongation factor α DNA we
have established that fungal biomass in partially resistant
genotypes is reduced compared to susceptible genotypes in
both seedling and adult cereal tissues. Histopathological
examination of infection and colonisation of seedling and
adult tissues, using the fluorescent dye solophenyl flavine,
has not revealed any differences in tissue responses
between partially resistant and susceptible host tissues,
although there is a significantly slower spread of the fungus in the tissues of resistant genotypes. Infection is initiated predominantly through the stomata of surface-inoculated leaf sheaths. Colonisation of expanded stems frequently originates in the parenchymatous hypoderm, which
becomes highly discoloured. Early infection of pith
parenchyma cells is also frequent. Vascular tissues become
colonised by anthesis and this occurs more rapidly in
susceptible genotypes. Occlusion of large xylem vessels was
rare during moderate infections while infection of phloem
sieve tube elements is common.

Not reportable (poster paper).