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theses

The effect of cranberry floral wax was tested on appressorium formation rates in Colletotrichum fioriniae, a causal agent of fruit rot on cranberry (Vaccinium macrocarpon). Signaling mechanisms regulating appressorium induction vary by pathosystem, and offer potential targets for fungal control measures. Although studies have been done on close relatives, appressorium formation triggers have not been definitively identified in the C. fioriniae – cranberry system. Surface wax from flowers was extracted in chloroform and some of the chemical constituents of the wax were identified by gas-chromatography-mass spectrometry (GC-MS). Spores of C. fioriniae were incubated with surface wax or with pure identified compound from the wax to assess their effect on appressorium formation. Floral wax induced appressorium formation in as little as six hours. The methyl ester of hexadecanoic acid, a monomer of the plant biopolymer cutin, was identified as a wax component that showed strong stimulatory effects in vitro. This is significant, as it points to fungal cutinase production as a potential target of future disease management strategies on cranberry. In addition, no differences in induction iv were found between waxes extracted from resistant and susceptible host genotypes. Further, although hydrophobicity has been shown to induce appressorial formation in other pathogens, it was ruled out as a stimulus here by tests with hydrophobic paraffin wax. Waxes isolated from cranberry fruit throughout the growing season did not induce appressorium formation, though whether this is due to a lack of stimulatory compounds or the presence of inhibitors was not determined and merits further study.

ETD_6266

M.S.

Includes bibliographical references

by Joshua David Gager

doi:10.7282/T3TF006Q

ETD graduate

The author owns the copyright to this work.