No description available.

Mycorrhizal fungi are a major component of agricultural systems and play a key role in plant nutrition. Little is known about the effects of tillage practices and manuring on arbuscular mycorrhizal fungi (AMF). The purpose of this study was to evaluate the effect of soil disturbance on winter survival, development and distribution of AMF in soil and on plant nutrient uptake and productivity. This research was conducted in long-term corn plots in two soils and under controlled conditions. / A growth chamber study with field soil demonstrated that most of the fungal hyphae with mycorrhizal plants were mycorrhizal rather than saprophytic. This result was extrapolated to subsequent experiments. Soil disturbance reduced corn nutrient uptake and growth by disrupting the AMF hyphal network. Similarly, fallow periods reduced density of AMF hyphae, leading to reduced mineral nutrients uptake and plant growth. Soil disturbance was also found to severely reduce winter survival of AMF hyphae in agricultural soil. AM hyphae could survive the winter in soil, even when they were not attached to roots. Their survival however, was improved when they remained attached to roots. / Under field conditions, indigenous AMF were more abundant in no-till soil, less abundant under reduced tillage and least abundant under conventional tillage. Under all tillage systems, most of AMF hyphae were located in the top 15 cm of the soil profile suggesting that deep plowing could result in dilution of AMF propagules in the seeding zone. There was a seasonal variation in the abundance of hyphae in soil. Soil hyphae and root colonization declined after the silking stage of corn. Hyphal abundance decreased further over the winter, to reach their lowest level in the spring. / The spatial distribution of fungal hyphae in the field was not homogenous. Hyphal density was maximal directly under the corn rows and decreased linearly up to the mid-row. Marked seasonal variations in hyphal densities were observed on the row but fluctuations at mid-row were not significant suggesting that little AMF hyphae were ever present between the rows. Liquid dairy manure had little effect on the abundance of hyphae and spores.

It may be possible to tailor crop management to encourage diverse soil microbial communities and beneficial microorganisms, and produce high quality food products. Studies were carried out in 2005-2007 to evaluate the impact of spring wheat (Triticum aestivum L.) cultivar choice and crop polycultures on soil microbial communities in organic and conventional systems, and subsequent wheat quality. Five wheat cultivars were grown organically and conventionally to evaluate grain breadmaking quality and micronutrient content and their impact on the soil microbial community. Organic grain yields were roughly half of conventional yields, but quality levels were all acceptable for Canadian Western Hard Red Spring wheat. Measured soil (0-15 cm) microbial profiles (by phospholipid fatty acid analysis) differed between the two management systems, and amongst cultivars in the conventional system. The most recent cultivar in the study, AC Superb, exhibited the highest levels of fungi suggesting that breeding efforts in conventionally managed environments may have resulted in cultivating mycorrhizal dependence in that environment. In general, many of the studied grain micronutrients were greater in the organically grown wheat system, possibly due in part to decreased grain yield and smaller grain size. Maximizing grain micronutrient content through wheat cultivar choice was dependent on management system. The presence of fungi biomarkers appears to have improved uptake of Mn and Cu. Monocultures and polycultures of common annual crops were grown organically and conventionally in 2006-2007. Intercrops exhibited an ability to overyield in an organic system, largely through weed suppression, but intercrops also overyielded in a conventional system where weeds were controlled through herbicides. As intercrop complexity decreased, the instances of improved weed suppression declined. Management systems and wheat cultivars can alter the composition of the soil microbial community. Annual crop polycultures did not alter soil microbial communities in this study, but showed evidence of agronomic benefits in both organic and conventional systems. / Plant Science

No description available.

Ultramafic soils enriched in nickel, such as found in Australia and New Caledonia, are associated with unique, diverse and poorly known vegetation communities. Re-establishment of these highly specific ecosystems is still a challenge for Ni mining companies. Ultramafic vegetation communities are the outcome of a long evolution process resulting in their adaptation to the extreme soil conditions found on ultramafic outcrops. Mycorrhizal fungi, a very common plant symbiont, are generally thought to be beneficial to plants in other ecosystems, providing plants with phosphorus and even promoting metal tolerance in plants in some cases. We examined the hypothesis that mycorrhizal fungi may contribute to the survival of plants in ultramafic soil conditions. Bandalup Hill, an ultramafic outcrop enriched in Ni (South West of Western Australia) was selected to assess the contribution of mycorrhizal fungi to ultramafic plants. Soil constraints, in particular the degree of Ni toxicity, were assessed at two sites with ultramafic soils within the outcrop. Total metal, nutrient, DTPA extractable Ni and available P were measured in soil while Ni, Ca and Mg were tested in the soil solution. In addition, nutrients and metals were analyzed in shoots of some plant species occurring at each site: Eucalyptus flocktoniae, Melaleuca pomphostoma, Melaleuca coronicarpa and Hakea verucosa. Topsoils in Bandalup Hill and plant shoots had high levels of Ni, and very low levels of P, K and N. Variation in DTPA extractable Ni between sites reflected the variation in shoot Ni level of E. flocktoniae and M. pomphostoma. Variations in soil solution Ni levels reflected variations in shoot Ni levels of M. coronicarpa and H. verucosa between sites. The germination requirements of the plant species used to assess the soil constraints was assessed. Species selected included Eucalyptus flocktoniae, Melaleuca coronicarpa, and Hakea verucosa. Seeds of E. flocktoniae and M. coronicarpa had a higher germination rate if pre-treated with smoke water, while no pre-treatment was required to germinate H. verucosa seeds. The unusual germination requirement of E. flocktoniae and M. coronicarpa involve complex chemical signals that may be present in the soil when the conditions are more favorable for plant establishment. Such unusual germination requirement may represent an adaptation to the hostile conditions of the ultramafic soils of Bandalup Hill. The mycorrhizal association and root characteristics of the selected plant species was also assessed after 8 weeks of growth in undisturbed ultramafic topsoil cores from Bandalup Hill. Roots of these species (including H. verucosa from a previously designated non-mycorrhizal family, Proteaceae) were associated with mycorrhizal fungi. Roots of E. flocktoniae and M. coronicarpa were colonized by both arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (ECM), while roots of H. verucosa only contained some AM fungal structures. All species had high shoot to root ratios and their root characteristics reflected their association with mycorrhizal fungi. Based on the previous observations, uninoculated and inoculated E. flocktoniae seedlings were grown for 10 to 16 weeks in sand amended with Ni at 0, 0.2, 1 and 2.3 mg/kg. Mycorrhizal inoculum consisted of spores of Pisolithus sp. (ECM) or a mix of AMF spores and colonized root fragments, both originating from Bandalup Hill. Another inoculum consisted in Pisolithus sp. spores from a site with ultramafic soils in New Caledonia. Inoculation with AM and ECM fungi from Bandalup Hill was beneficial to E. flocktoniae. Benefits consisted mainly of a reduction of Ni shoot translocation at the highest Ni soil level. At 1 mg/kg soil Ni, E. flocktoniae exhibited a certain degree of tolerance to Ni. A substantial increase in growth and nutrient uptake with Pisolithus sp. from Western Australia was also observed. The contribution of AM fungi from Bandalup Hill to E. flocktoniae, M. coronicarpa, H. verucosa, and Trifolium subterraneum (clover) was then examined in ultramafic soil from Bandalup Hill.Steaming of ultramafic soil increased the availability and plant uptake of P. Consequently, uninoculated seedlings grew better, and inoculation with AM fungi decreased the growth of native plant species but did not affect their shoot Ni concentration. The presence of AM fungi increased the concentration of P in shoots of native plants species. Inoculation had no effect on the growth and nutrient content of subterranean clover. As mining activities have the potential to reduce the infectivity of AM fungi in topsoils, the effect of disturbance and storage practices on the AM infectivity of ultramafic topsoils collected in summer or winter from Bandalup Hill was investigated. Disturbance consisted in passing topsoil through a 2mm seive and cutting roots into 1cm fragments. Disturbed topsoil was then stored at room temperature in pots that were either sealed from the atmosphere or left open, and pots were maintained at field capacity. E. flocktoniae seedlings were planted in undisturbed and disturbed topsoil just after topsoil collect and then after 3, 6 and 9 months of topsoil storage. AM fungi present in the topsoil collected in summer was less susceptible to initial disturbance than AM fungi present in topsoil collected during winter. Also, storage of topsoil in sealed pots watered to field capacity was more detrimental to its infectivity than storage of topsoil in dry conditions. Mycorrhizal fungi can contribute to the survival of some native plant species in the ultramafic soils of Bandalup Hill and they may represent another strategy to improve the success of Ni mine revegetation. However, such contribution may not be the unique avenue for native plants to survive in ultramafic soils of Bandalup Hill.

[Truncated abstract] Genus Burkholderia encompasses a diverse collection of bacteria that inhabit rhizospheres throughout the world. Species can provide beneficial returns for eukaryotes, such as nitrogen fixation and nodule formation in plants and biocontrol of cropping systems. Burkholderia members can also cause disease in various animals, fungi and plants. These seemingly conflicting characteristics point to the capacity of Burkholderia spp. to interact with diverse eukaryotes. Within terrestrial ecosystems, Burkholderia spp. must negotiate favourable outcomes with both the primary producers and the primary decomposers, namely plants and fungi. It is these ongoing negotiations which govern many rhizosphere processes and lead to niche differentiation for Burkholderia spp. This research set out to design an in vitro model for investigating Burkholderiaeukaryote interactions. Surface and cellular interactions between Burkholderia spp. and both plants and fungi were then investigated. Specifically, mechanisms of adherence and invasion of plant and fungal cells were studied. The Burkholderia spp. B. vietnamiensis and B. pseudomallei were applied to mycorrhizal fungus spores as well as to several plant species. Bacterial inoculation had varying effects on germination of plant and fungal dormant forms. B. vietnamiensis-inoculation consistently increased Gigaspora decipiens spore germination, while B. pseudomallei produced no significant change. The effect of B. vietnamiensis on Acacia colei seed germination was density dependant, resulting in either increases or decreases in seed germination rates. ... Detection of B. pseudomallei in surface waters and soils was improved by the use of a rapid on-site molecular method. The related species B. thailandensis and B. ubonensis were also cultured from northern Western Australia. Mycorrhizal spores were isolated from soils of melioidosis-endemic regions. Burkholderia spp., including B. pseudomallei and B. vietnamiensis were detected in extracts of these mycorrhizal spores. Therefore, associations of Burkholderia spp. with mycorrhizal spores extend beyond the in vitro setting. These studies have increased our understanding of several specific interactions between Burkholderia spp. and eukaryotes of the rhizosphere. Common themes in adherence and invasion have emerged. Burkholderia spp. are able to closely associate with eukaryotes and to gain access to protected niches. Such access helps to explain the persistence of these bacteria in the environment during periods of desiccation and nutrient limitation.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 120-141).

Made available in DSpace on 2014-06-11T19:35:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-09-23Bitstream added on 2014-06-13T20:26:13Z : No. of bitstreams: 1 scabora_mh_dr_ilha.pdf: 1356809 bytes, checksum: 1945cc637998450974f2829ff790aafa (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Com a construção da barragem da Usina Hidrelétrica de Ilha Solteira (SP), ocorreu a degradação do solo, expondo o subsolo e dando origem às áreas de empréstimo. Com o objetivo de melhor compreender a associação entre fungos micorrízicos arbusculares (FMA) e espécies arbóreas na recuperação de áreas degradadas, foram avaliados a produção de esporos e a diversificação das comunidades de FMA nativos após inoculação em dez espécies arbóreas nativas do cerrado, implantadas em duas áreas, uma vegetada com pastagem e outra com subsolo exposto, bem como avaliar a ocupação destas por espécies herbáceas co-ocorrentes e as alterações da fertilidade do solo ao longo de quatro anos de revegetação. O experimento foi conduzido na Fazenda de Ensino, Pesquisa e Extensão da Universidade Estadual Paulista, Faculdade de Engenharia, Campus de Ilha Solteira, localizada no município de Selvíria-MS. O delineamento experimental foi o fatorial 2x4x10 em blocos, ou seja, duas áreas (pastagem e subsolo exposto), quatro anos e 10 espécies arbóreas, com quatro repetições, sendo cada repetição constituída por cinco plantas. Após a instalação do experimento, amostras do solo e do subsolo foram coletadas na profundidade de 0- 0,10 cm, no 1, 2, 3 e 4o ano e utilizadas para avaliação das características químicas e das comunidades de FMA. O número de esporos, a riqueza de espécies, a diversidade e a equabilidade foram comparados e relacionados com as propriedades químicas do solo e com a ocupação das espécies herbáceas co-ocorrentes. Houve incrementos nos teores de matéria orgânica ao longo do anos na área de subsolo. Na diversificação de FMA foram identificadas 52 espécies, das quais 19 pertencem ao gênero Glomus, 14 pertencem à Acaulospora, 10 à Scutellospora, seis à Gigaspora... / Due the construction of the Ilha Solteira Hydroelectric plant (SP), soil degradation has occurred, exposing the subsoil and giving rise to the “soil landing” areas. In order to better understand the association between arbuscular mycorrhizal fungi (AMF) and tree species in the recovery of degraded areas, were assessed the spores production and diversification of native communities of AMF by evaluating ten species of cerrado native tree after the inoculation, introduced in two areas, one vegetated with grass and the other with exposed subsoil, as well as, by evaluating the occupation by the co-occurring plant species and changes in soil fertility, over the four years of restoration. The experiment was conducted at the Education, Research and Extension Farm of the UNESP-Universidade Estadual Paulista, Engineering Faculty, Ilha Solteira Campus, located in the city of Selvíria-MS. The experimental design was a complete randomized block design in a 2 x 4 x 10 factorial, i.e., two areas (pasture and subsoil exposed), four years and 10 tree species, with four replicates, each replicate consisting of five plants. The soil and subsoil, sampled at the depth of 0 to 0.10 m, after 12, 24, 36 and 48 months after the experiment installation, were used to evaluate the soil chemical and AMF communities characteristics... (Complete abstract click electronic access below)

Resumo: Com a construção da barragem da Usina Hidrelétrica de Ilha Solteira (SP), ocorreu a degradação do solo, expondo o subsolo e dando origem às áreas de empréstimo. Com o objetivo de melhor compreender a associação entre fungos micorrízicos arbusculares (FMA) e espécies arbóreas na recuperação de áreas degradadas, foram avaliados a produção de esporos e a diversificação das comunidades de FMA nativos após inoculação em dez espécies arbóreas nativas do cerrado, implantadas em duas áreas, uma vegetada com pastagem e outra com subsolo exposto, bem como avaliar a ocupação destas por espécies herbáceas co-ocorrentes e as alterações da fertilidade do solo ao longo de quatro anos de revegetação. O experimento foi conduzido na Fazenda de Ensino, Pesquisa e Extensão da Universidade Estadual Paulista, Faculdade de Engenharia, Campus de Ilha Solteira, localizada no município de Selvíria-MS. O delineamento experimental foi o fatorial 2x4x10 em blocos, ou seja, duas áreas (pastagem e subsolo exposto), quatro anos e 10 espécies arbóreas, com quatro repetições, sendo cada repetição constituída por cinco plantas. Após a instalação do experimento, amostras do solo e do subsolo foram coletadas na profundidade de 0- 0,10 cm, no 1, 2, 3 e 4o ano e utilizadas para avaliação das características químicas e das comunidades de FMA. O número de esporos, a riqueza de espécies, a diversidade e a equabilidade foram comparados e relacionados com as propriedades químicas do solo e com a ocupação das espécies herbáceas co-ocorrentes. Houve incrementos nos teores de matéria orgânica ao longo do anos na área de subsolo. Na diversificação de FMA foram identificadas 52 espécies, das quais 19 pertencem ao gênero Glomus, 14 pertencem à Acaulospora, 10 à Scutellospora, seis à Gigaspora... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Due the construction of the Ilha Solteira Hydroelectric plant (SP), soil degradation has occurred, exposing the subsoil and giving rise to the "soil landing" areas. In order to better understand the association between arbuscular mycorrhizal fungi (AMF) and tree species in the recovery of degraded areas, were assessed the spores production and diversification of native communities of AMF by evaluating ten species of cerrado native tree after the inoculation, introduced in two areas, one vegetated with grass and the other with exposed subsoil, as well as, by evaluating the occupation by the co-occurring plant species and changes in soil fertility, over the four years of restoration. The experiment was conducted at the Education, Research and Extension Farm of the UNESP-Universidade Estadual Paulista, Engineering Faculty, Ilha Solteira Campus, located in the city of Selvíria-MS. The experimental design was a complete randomized block design in a 2 x 4 x 10 factorial, i.e., two areas (pasture and subsoil exposed), four years and 10 tree species, with four replicates, each replicate consisting of five plants. The soil and subsoil, sampled at the depth of 0 to 0.10 m, after 12, 24, 36 and 48 months after the experiment installation, were used to evaluate the soil chemical and AMF communities characteristics... (Complete abstract click electronic access below) / Orientador: Ana Maria Rodrigues Cassiolato / Coorientador: Rosilaine Carrenho / Banca: Katia Luciene Maltoni / Banca: Franscisco Maximino Fernandes / Banca: Daniela Tiago da Silva Campos / banca: Waldeamar Zangaro Filho / Doutor

Arbuscular mycorrhizas (AM) are mutually beneficial symbiotic associations between the roots of plants and certain Zygomycetous fungi. The role of AM fungi in coastal sand dunes has been explored in many parts of the world, though little work has been conducted in South African dune systems. This study aimed to investigate the presence and extent of mycorrhizal colonisation of a coastal sand dune in South Africa. The roots of five plant species (Scaevola plumieri, Arctotheca populifolia, Ipomoea pes-caprae, Ehrharta villosa and Chrysanthemoides monilifera) were sampled along a foredune profile at Old Woman's River in the Eastern Cape. These roots were assessed for the percentage mycorrhizal colonisation they supported. Spores extracted from the rhizosphere sand of each plant species were counted and identified to genus level. Results were related to seasonality and the position of the plants along the profile. All plant species were found to be mycorrhizal. Percentage colonisation ranged from 0-92%, depending on plant species and season. Mycorrhizal colonisation was generally highest in the winter months, and especially so in I pes-caprae and E. villosa. The extent of various mycorrhizal structures in root tissue varied between plant species. Spore numbers ranged from 0-48 spores 100g-1 sand with highest numbers occurring in winter. S. plumieri and A. populifolia were associated with greatest spore abundance. Four fungal genera (Glomus, Acaulospora, Scutellospora and Gigaspora) were identified. Distribution of these genera showed seasonal variations between plant species. A bioassay, using Sorghum, was conducted to test the inoculum potentials of sand from the Scaevola hummock and the IpomoealEhrharta dune. Highest percentage colonisation occurred in plants grown in the Scaevola sand, which also had the lowest root and shoot measurements. The bioassay confirmed that AM propagules are present and viable, even in the mobile sand of the foredune. This study showed that mycorrhizal colonisation and spore numbers varied seasonally, but that the extent of this was dependent on plant species. The position of plants along the foredune profile tended to be less important than plant species. It is thought that the growth cycle and rooting system of each plant species determines seasonal cycles and abundance of AM fungi. Variation within fungal populations probably also impacts on this. Knowledge of the presence and distribution of AM fungi in this system paves the way for more detailed studies which need to examine the role of these endophytes in South African sand dunes.