There are many health issues surrounding Alberta’s forests today and for the future. Health impacts of diseases, pests and climate change are currently being predicted in order to implement new management ideas and solutions, and identify specific research needs. This study examines state of the art knowledge on the current impacts of Armillaria root disease (ARD) (Armillaria spp.) in Alberta’s boreal forest region. It also assesses the biology and structure of the disease within this region to predict the extent to which the boreal forest may be impacted. In the next 50 years, both Armillaria ostoyae (Romag.) Herink and Armillaria sinapina Bérubé & Dessureault will become more of a problem, due to climate change and the current mature state of Alberta’s forests. A. sinapina, as a less-pathogenic but more opportunistic species, is predicted to be more prevalent that A. ostoyae, since the former will flourish when there are environmental stresses. Management practices will require research and evaluation of the use of alternative native tree species that have a higher resistance to the Armillaria species within Alberta and the impacts of such alternatives to the forestry industry and community structure. Future research is also essential to determine if one promising biological control agent and fungus, Hypholoma fasciculare (Huds. ex. Fr.), will be a viable and cost effective method to control Armillaria species within Alberta.

We report here the use of RAPD-PCR (Random Amplified Polymorphic DNA - Polymerase Chain Reaction) to identify segregating loci in the haploid progeny of an Armillaria ostoyae basidiocarp and the construction of the first genetic linkage map of this fungus, one of the causal species of Armillaria Root Disease. Upon screening 75 RAPD primers, 18 were found to identify a total of 43 loci segregating with a 1 : 1 Mendelian ratio. These loci were analysed for linkage among 58 monospore progeny. The map constructed with Mapmaker (LOD = 3.0, r = 0.38) was confirmed by GMendel (LOD = 1.5, r = 0.38). This map arranged 30 loci into 6 linkage groups and 4 linkage pairs. Thirteen markers remained unlinked. Using the Kosambi mapping function the linked loci accounted for approximately 450 cM and the genome was estimated to be 1600 cM. This preliminary map covers approximately 28% of the A. ostoyae genome.

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Thesis (Ph. D.)--Memorial University of Newfoundland, 1997. / Restricted until November 1998. Bibliography: leaves 189-206.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1926. / Typescript. With this is bound: Histological studies of resistance in tobacco to Thielavia basicola / George H. Conant. Reprinted from American journal of botany, vol. 14, no. 8 (Oct. 1927), p. 457-480, plates LVII-LXII. Includes bibliographical references (leaves 41-45).

A number of techniques were used to obtain a variety of bacterial and fungal species antagonistic to Pythium - F group in hydroponic systems. Isolations were made from roots of ‘escape’ lettuce plants in a commercial hydroponic gravel system as well as Pythium mycelium exposed to the hydroponic solution. Seventy four bacterial and eighteen fungal isolates were obtained and were screened for in vitro activity against Pythium by means of the dual culture method. Twenty-two bacterial isolates rendered between 10.8 and 48 % inhibition and ten fungal isolates rendered between 24.3 and 54 % inhibition of Pythium mycelial growth. Potential biocontrol agents were screened in a static aquaculture system on butterhead lettuce seedlings in the greenhouse prior to evaluation in a re-circulating gravel bed hydroponic system in the greenhouse and field, for both growth promoting and biocontrol ability. Significant increases of between 689 % and 922 % in total fresh yield were obtained from plants preventatively treated with isolates JH49, JH41, JH83, JM6R and JM16W. The eight best performing isolates were further evaluated for biocontrol activity against Pythium as well as growth promotion on butter head lettuce in a re-circulating gravel bed hydroponic system in the greenhouse. Significant increases of 1.5 % - 63.5 % and 0.9 % - 38.8 % in total fresh yield were obtained from plants evaluated for growth promotion and Pythium control, respectively. Based on their performance five of the eight isolates were selected for evaluation in a re-circulating gravel bed hydroponic field system. Treatment with Pseudomonas fluorescens and Bacillus subtilis significantly increased fresh leaf weight of lettuce plants in comparison with the untreated control indicating effective suppression of Pythium. Of the isolates that were previously evaluated against Pythium wilt and root rot of lettuce in a hydroponic system (Chapters 2 and 3), 6 bacteria and 2 fungi were most effective. The following possible modes of action of these isolates, were investigated, namely competition, production of inhibitory substances and induced resistance. The root colonizating ability of the isolates was also assessed. Competition between the isolates and the pathogen were confirmed by testing for siderophore and hydrolytic enzyme production. Five of the isolates produced siderophores much faster than the rest, demonstrating that these isolates were able to take-up iron from the media at a faster rate, thus indicating a significant competitive ability. Antibiotic production by the isolates was confirmed in vitro by means of the dual culture technique. Of the eight isolates screened, only one isolate showed in vitro inhibition of the pathogen. This result was confirmed by a TLC assay, where fluorescent bands were formed by the same isolate, indicating the presence of phenolic compounds. These compounds were separated by HPLC. Analysis of total soluble and cell wall phenolic levels in Pythium infected and non-infected plants treated and untreated with the biocontrol isolates did not render conclusive results. Three of the eight isolates were able to colonize 100% of the lettuce roots. / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2008. / Microbiology and Plant Pathology / unrestricted

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Revised 02/2015; Originally published: 2000. / The most important disease of woody dicotyledonous plants in Arizona is Phymatotrichopsis root rot (Cotton or Texas root rot) caused by a unique and widely distributed soil-borne fungus, Phymatotrichopsis omnivora. The fungus is indigenous to the alkaline, low-organic matter soils of the southwestern United States and central and northern Mexico.