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The homothallic behaviour and other nuclear patterns of Armillaria luteobubalina isolates from the coastal dune system and eucalyptus wandoo woodland in South-Western Australia

Dunne, Christopher P. (1999) The homothallic behaviour and other nuclear patterns of Armillaria luteobubalina isolates from the coastal dune system and eucalyptus wandoo woodland in South-Western Australia. Honours thesis, Murdoch University.


Armillaria luteobubalina Watling & Kile is a common and destructive primary pathogen in a number of plant species. The pathogen is widely distributed in the wet sclerophyll forest, dry sclerophyll forest and woodland, and the coastal dune system in south-western Australia. The current study was conducted to _determine the nuclear behaviour during the life cycle and the spatial distribution of genotypes within disease centres. Basidiomes were collected from two disease centres: one in the coastal dune system; and the other from the Eucalyptus wandoo Blakey woodland. Monosporous isolates, putative diploid isolates and gill tissue were obtained from the basidiomes. Overall, 71 and 173 monosporous and diploid isolates, respectively, across the two sites. A preliminary study with streptomycin and lactic acid to enhance the recovery of non-contaminated basidiospores was conducted. In order to determine the ploidy and nuclear arrangement during different stages of the life cycle, the isolates and gill tissue were stained with orecein, 4', 6-diaminodino-phenylindol, phloxine or trypan blue. Additionally, mycelial interactions were utilised to describe the spatial distribution of genotypes at both disease centres by pairing haploid-haploid, diploid haploid and diploid-diploid. Additionally, the identity of the collected basidiomes were confirmed by interspecific pairings of vegetative isolates.

The results of this investigation clearly demonstrate that the addition of streptomycin had no adverse effects on basidiospore gennination and was used successfully to isolate monosporous isolates. Additionally, 4°C was the optimum temperature for the long-term storage of viable spores.

A. luteobubalina was shown to be amphithallic and to produce binucleate (8.45 %) and uninucleate (91.55 %) basidiospores. The results provide evidence that the variation in the nwnber of sterigmata between basidia is responsible for the incorporation of two nuclei within the basidiospores. The heterothallic life cycle of A luteobubalina begins with the germination of a haploid basidiospore to produce a haploid mycelium. The mating of two compatible monokaryotic isolates produce a vegetative diploid. The vegetative diploid persists until it undergoes a somatic nuclear reduction within the subhymenium, prior to basidium formation and subsequent basidiospore production.

The mating interactions demonstrated that the Trigg disease centre is dominated by one diploid genotype, compared to 2 diploid genotypes at the Pykes road disease site. During the intraspecific pairing of monokaryotic and diploid isolates, 5 A and 6 B alleles were identified.

The study demonstrates for the first time: the vegetative diploid stage in the secondary mycelia; a somatic haploidisation occurs within the basidia; and the pseudohomothallic behaviour of A. luteobubalina.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Notes: A digital copy of this thesis is not available. Your library can request a copy from Murdoch University Library via Document Delivery. A fee applies to this service.
Supervisor(s): Hardy, Giles, Shearer, Bryan and Tommerup, Inez
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