Two factorial greenhouse experiments were performed to determine the effects of four arbuscular mycorrhizal fungi (AMF) species (Glomus arenarium, Funneliformis caledonius, F. mosseae, and Rhizophagus irregularis) and a root endophyte (Piriformospora indica) on four ‘day-neutral’ strawberry (Fragaria × ananassa Duch.) cultivars (‘Albion’, ‘Charlotte’, ‘Mara des Bois’, and ‘Seascape’), and mixed-AMF species (R. irregularis + F. mosseae) on cv. ‘Seascape’, under salt conditions (0-200 mM NaCl). In its biomass, ‘Seascape’ was more tolerant to salinity than the other cultivars. Cultivars responded differently to fungal inoculation as to salinity. G. arenarium had a negative effect on plant growth and ‘Mara des Bois’ responded negatively to inoculation. Among the remaining inoculants and cultivars, fungal-symbiosis was beneficial to growth. R. irregularis alleviated the symptoms of salt stress and improved fruit quality to a higher degree than the other AMF species and the root endophyte. Our results support the use of bio-inoculants in salty horticultural areas.

Two factorial greenhouse experiments were performed to determine the effects of four arbuscular mycorrhizal fungi (AMF) species (Glomus arenarium, Funneliformis caledonius, F. mosseae, and Rhizophagus irregularis) and a root endophyte (Piriformospora indica) on four ‘day-neutral’ strawberry (Fragaria × ananassa Duch.) cultivars (‘Albion’, ‘Charlotte’, ‘Mara des Bois’, and ‘Seascape’), and mixed-AMF species (R. irregularis + F. mosseae) on cv. ‘Seascape’, under salt conditions (0-200 mM NaCl). In its biomass, ‘Seascape’ was more tolerant to salinity than the other cultivars. Cultivars responded differently to fungal inoculation as to salinity. G. arenarium had a negative effect on plant growth and ‘Mara des Bois’ responded negatively to inoculation. Among the remaining inoculants and cultivars, fungal-symbiosis was beneficial to growth. R. irregularis alleviated the symptoms of salt stress and improved fruit quality to a higher degree than the other AMF species and the root endophyte. Our results support the use of bio-inoculants in salty horticultural areas.

Triclosan (TCS) is an antimicrobial compound found in several types of common household products. After being washed down the drain, TCS will then end up in the local watershed. Although numerous studies have been conducted to evaluate the fate and effects of TCS in aquatic environments, there have been no studies evaluating the role arbuscular mycorrhizal fungi (AM) play in a plants response to TCS exposure. Three species of wetland plants native North Texas were inoculated with AM spores and exposed to 0, 0.4 g/L and 4.0 g/L TCS concentrations. Root morphology of E. prostrata and S. herbacea showed AM and exposure responses. S. herbacea produced the greatest amounts biomass and TCS bioaccumulation, in all but one treatment. It also displayed opposing results to E. prostrata in measures of root length, root surface area, relative root mass, relative shoot mass and shoot:root ratio. TCS root tissue concentrations increased with increased exposures for both E. prostrata and S. herbacea. Even though E. prostrata had the lowest levels in each measure of biomass production, it had the highest amount of root TCS bioaccumulation in the AM inoculated 4.0 g/L treatment. H. laevis was between the other two species in terms of biomass production, and did not demonstrate any exposure or inoculation effects in morphology or TCS accumulation. Overall, no clear patterns were detected, which highlights the fact that further study is required to completely understand the effects compounds like TCS can have on plant community structure, and ultimately ecosystem function.

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No description available.

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The goal of this study was to evaluate the effect of controlled burns, drought and the presence of arbuscular mycorrhizal fungi (AMF) on a dry coastal grassland in Hawai'i Volcanoes National Park. Two introduced African grasses, Hyparrhenia rufa thatching grass, and Melinis repens - Natal redtop, along with one indigenous grass Heteropogon contortus - pili grass composed most of the cover at the study sites. The response of the grasses to fire, AMF infection potential of the soil, and in situ seedling AMF infection were monitored in the field for three years from 1997 to 2000 at Keauhou, Ka'aha, and Kealakomo in Hawai'i Volcanoes National Park. A greenhouse experiment compared the competitive ability of the three grasses with or without AMP inoculation or water stress. The population dynamics of the three grasses were modeled based on their responses to fire, AMF infection, competition and water. At low fire intensities Heteropogon and Hyparrhenia had similar high survival rates while Melinis had a low survival rate. At higher fire intensities all species had low survival rates. The fire decreased the AMF infection potential of the soil at Kaaha, but in situ seedlings AMF infection levels remained high and not statically between the burned and unburned Kaaha sites. In the greenhouse portion of this study Heteropogon biomass increased in response to AMF infection while the other two species did not respond positively to infection. These results suggest that AM fungi increase the growth of the native species, thereby decreasing the impact of competition from two co-occurring alien grasses. When population dynamics were modeled to include the effects of fire, drought and AMF, Melinis and Hyparrhenia produced more biomass in the simulations than the native grass Heteropogon. Drought and AMF decreased the difference in biomass production between the species but did not reverse the competitive ranking of the species.

Sanders, Donald W. The University of Manitoba, March, 2017. The effect of preceding crop on soybean (Glycine max) grain yield, mycorrhizal colonization, and biological nitrogen fixation. Major Professor:Yvonne Lawley. Manitoba has seen a twenty-fold increase in soybean acres seeded since 2000, with over 1.6 million acres seeded in 2016. This change presents unique opportunities and challenges to improve crop rotations in Manitoba. This experiment studied the effect of four crop sequences on soybean yield, mycorrhizal colonization, and biological nitrogen fixation. In the first year of this experiment, spring wheat, canola, corn and soybeans were grown at three sites in Manitoba (Carman, Portage la Prairie, and Kelburn). In the second year, soybeans were grown on these same plots as a test crop. This two-year sequence of crops was done twice at each site, in 2012-13 and 2013-14. To determine mycorrhizal colonization, root samples were collected at the V3 stage and then analyzed microscopically for mycorrhizal infection. Nitrogen fixation was estimated using the natural abundance method using soybeans collected at the R5 and R6 stage and canola as a reference crop. Soybean following soybean had significantly higher grain yield than all other crop sequences at one site year, and significantly lower grain yield than all other crop sequences at another site year. There were no other differences in soybean test crop yield between crop sequences. Crop sequence significantly affected mycorrhizal colonization. Soybean following canola had significantly lower mycorrhizal colonization than soybean following soybean or corn. Soybean following spring wheat also had significantly lower mycorrhizal colonization than soybean following soybean or corn. Soil test phosphorus levels also significantly affected mycorrhizal colonization, with increasing soil phosphorus resulting in decreased mycorrhizal colonization. Crop sequence significantly affected biological nitrogen fixation. Soybean following soybean or corn often had significantly greater biological nitrogen fixation than soybean following spring wheat or canola. Soil test nitrate levels affected biological nitrogen fixation, with increasing soil nitrate resulting in decreased biological nitrogen fixation. Soil test nitrate levels were affected by the carbon to nitrogen ratio of the preceding crop, with a higher carbon to nitrogen ratio associated with decreased soil nitrate. These results indicate that although there is often not a yield penalty associated with specific rotations, crop sequence has a strong impact on mycorrhizal colonization and biological nitrogen fixation. The soil organisms associated with those processes affect soil phosphorus uptake and nitrogen fixation. Producers should consider the importance of crop rotation when seeking to maximize productivity through symbiotic processes with mycorrhizae and nodule forming bacteria. / May 2017

In this thesis I investigated the mutualism between Kunzea ericoides (kanuka) and two groups of soil fungi, ectomycorrhizae (ECM) and arbuscular mycorrhizae (AMF). Mycorrhizal mutualisms, which are considered globally ubiquitous, are poorly understood over changing abiotic gradients. A field survey of K. ericoides assessed how the relationship with the soil fungi varieties altered over a hydrologic gradient. Arbuscular mycorrhizal colonisation was significantly improved by increasing rainfall levels and amount of surrounding kanuka, and negatively affected by increasing altitude. Ectomycorrhizal colonisation was not significantly affected by any measured variables and remained relatively constant across all circumstances, suggesting that it is the preferred fungal mutualist for this tree species. A glasshouse experiment was done to measure the effect of ECM inoculation on the growth and water usage of K. ericoides over varying moisture availability. The seedlings were planted in soil inoculated with both ECM and AMF (experimental) or AMF only (control) and then grown under varying levels of water stress. The experiment was replicated with two soil types, with soil from beneath adult manuka (Leptospermum scoparium) and soil from beneath adult kanuka (K. ericoides). ECM colonisation significantly increased as soil moisture decreased for both soil types. ECM inoculation also increased the root:shoot ratio, and drastically decreased water usage under drought conditions. There were some soil effects as the seedlings grown in manuka-soil achieving greater biomass than seedlings grown in kanuka-soil. This is possibly due to presence of pathogens or some type of legacy competition which the seedlings would experience growing near conspecifics. Overall, K. ericoides formed a dominant mutualism with ectomycorrhizae. These two both thrive in dry environmental conditions and have a suite of complementing abilities which possibly allow K. ericoides to expand it range into these dry habitat types. The increased benefit of these mutualisms at the hydrologic range limit of the species supports the importance of biotic interaction mediating environmental stress. Understanding the effects and response of mycorrhizal mutualisms are especially significant considering current climate change issues in New Zealand and worldwide.

The availability of ectomycorrhizal fungi (ECMF) to conifer seedlings above the present treeline is likely related to the presence of alternate ECMF host plants, including Betula glandulosa, Arctostaphylos alpina, and Salix herbacea. The ECMF inoculum potential of soils from above treeline that either supported (host) or lacked (non-host) an alternate host plant was assessed by growing Picea mariana as ECMF bait seedlings in field-collected soils under controlled conditions. Seedlings became colonized when grown in both host and non-host soils, but ECMF percent colonization, richness, and diversity were higher for those grown in host soils. The ECMF community in Arctostaphylos host soils was most similar to the community in forest soils. Seedling growth varied among the different soil types, but was mainly influenced by percent ECMF colonization and soil nutrients. Alternate ECMF host plants will likely act as important sources of fungal inoculum, potentially improving conifer seedling establishment and growth.