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The host-pathogen relationship between apple and trametes versicolor and factors affecting host susceptibility

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Kile, G. A (1971) The host-pathogen relationship between apple and trametes versicolor and factors affecting host susceptibility. PhD thesis, University of Tasmania.

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Abstract

Examination of a large number of apple trees infected with Trametes
versicolor, indicated that the fungus was a facultative parasite which
caused a white rot of the sapwood. Papery bark was a distinctive but
non-specific external symptom of the disease. The development of papery
bark was influenced by seasonal and nutritional conditions and was not a
reliable indicator of susceptibility of trees to T, versicolor. Discoloration of the sapwood always occurred in advance of fungal
colonisation and decay. The formation of discolored wood involved the
loss of starch and nuclei from ray and xylem parenchyma and the eventual
necrosis of these cells. Necrotic cells were filled with a brown
amorphous material which appeared to be oxidised phenolics. In young
wood, ray and xylem parenchyma formed polysaccharide wound gum which was
deposited in the vessels of the sapwood-discolored wood transition zone.
The levels of K, Ca, Mg, moisture, pH, neutral solvent extractable
materials and phenolics in discolored wood, differed from those in the
adjacent sapwood. Bacteria were present in discolored wood in advance
of the fungus. Discoloration was a non-specific response of the sapwood to
mechanical or pethological stimuli. In vitro decay tests indicated that
discolored wood was more resistant to decay than normal sapwood. Discoloration
of the wood and gum formation therefore appeared to be an
active host resistance mechanism to fungal penetration and decay. The
host reaction to wounding was related to the physiological cycle of the
tree and with age cells lost the ability to synthesise wound gum and reduced
amounts of extraneous material were formed in the ray and xylem
parenchyma. Evidence indicated that the resistance of young apple
sapwood to colonisation and decay by T. versicolor was due to its vital
nature and ability to elaborate an effective fungal inhibitory barrier.
The susceptibility of living wood to fungal decay increased with age, due
to a natural decline in host resistance.

Item Type: Thesis (PhD)
Keywords: Trametes versicolor, Apples
Copyright Holders: The Author
Copyright Information:

Copyright 1971 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.) - University of Tasmania, 1971. Bibliography: l. 214-229

Date Deposited: 19 Dec 2014 02:26
Last Modified: 09 May 2017 06:19
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