Optimizing Dothistroma septosporum infection of Pinus radiata and the development of red-band disease : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Genetics at Massey University, Palmerston North, New Zealand

Barron, Naydene

Optimizing Dothistroma septosporum infection of Pinus radiata and the development of red-band disease : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Genetics at Massey University, Palmerston North, New Zealand

dc.contributor.author	Barron, Naydene
dc.date.accessioned	2017-12-13T22:53:42Z
dc.date.available	2017-12-13T22:53:42Z
dc.date.issued	2006
dc.description.abstract	The filamentous fungus Dothistroma septosporum infects pine species throughout the world causing red-band disease, one of the most serious diseases of conifer species. In NZ, a clonally derived asexual strain of D. septosporum was identified in 1964, and has spread throughout the country. There are conflicting accounts on the environmental conditions required for infection, which has lead to difficulties in optimizing a laboratory-based system for infection. The pathogen is spread naturally through rain-splashed inoculum of conidiospores from mature stromata that have erupted through the pine needle tissue. Diseased needles become necrotic, often with a red band due to the mycotoxin dothistromin produced by the hyphae. Dothistromin has the chemical structure of a difuranoanthraquinone and shows similarity to the aflatoxin precursor, versicolorin B produced by Aspergillus parasiticus. The role of dothistromin in pathogenicity has not yet been determined, although experiments have shown injecting toxin into pine needles results in the characteristic red band lesion. In this study it was found that fluctuating temperature (16°C/24°C), a 12 h diurnal cycle (white and ultraviolet light), high relative humidity and continuous moisture are conditions conducive to development of red-band disease on inoculated pine trees in an artificial environment. A higher rate of infection was obtained using pine seedlings as opposed to pine cuttings, and using a spore suspension containing a yeast extract. A dothistromin minus mutant was able to infect pine needles, indicating that dothistromin is not a pathogenicity factor, though it may be a virulence factor. The use of GFP-expressing isolates allowed the initial infection process to be monitored with both wild type and mutant isolates. Additionally, a PCR-based diagnostic procedure to confirm infection was developed. The production of aflatoxin by Aspergillus species is regulated by nutritional parameters and extracellular pH, which affect both growth and aflatoxin gene expression. D. septosporum similarly has enhanced growth at acidic pH, but it does not appear that pH has a strong influence on physiological processes as toxin biosynthesis and gene expression do not appear to be pH regulated. Different carbon and nitrogen sources also affect the morphology of D. septosporum.	en_US
dc.identifier.uri	http://hdl.handle.net/10179/12497
dc.language.iso	en	en_US
dc.publisher	Massey University	en_US
dc.rights	The Author	en_US
dc.subject	Dothistroma septosporum	en_US
dc.subject	Genetics	en_US
dc.subject	New Zealand Pinus radiata	en_US
dc.subject	Diseases and pests	en_US
dc.title	Optimizing Dothistroma septosporum infection of Pinus radiata and the development of red-band disease : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Genetics at Massey University, Palmerston North, New Zealand	en_US
dc.type	Thesis	en_US
massey.contributor.author	Barron, Naydene
thesis.degree.discipline	Genetics	en_US
thesis.degree.grantor	Massey University	en_US
thesis.degree.level	Masters	en_US
thesis.degree.name	Master of Science (M. Sc.)	en_US