Tesis sobre el tema "Soil fungi"

The investigation of soil structural stability and soil water processes was assessed through the application of laboratory investigations and a field based analysis. The impact of an arbuscular mycorrhizal (AM) fungal exudate glomalin (a glycoprotein), proposed to be hydrophobic was assessed for a correlation with low levels of soil hydrophobicity through measures of subcritical water repellency. Initially no correlation was reported but a further temporal investigation that involved a soil inoculum detected a significant positive effect; the results indicated that a certain concentration of protein is required before an influence upon soil hydrophobicity is detected. The temporal investigation detected significant re-aggregation of previously disturbed soil; this was linked to both increases in fungal biomass and enmeshment by plant roots. Soil in the direct vicinity of plant roots showed the most significant increases in aggregated structures, indicating that plant root enmeshment was one of the predominant factors in soil aggregation. Soil water repellency was directly correlated with measures of macroaggregates (aggregates >2000 pm), indicating that increased hydrophobicity is a mechanism involved in aggregate stabilisation. Field scale sampling and analysis indicated that fertilizer applications had varied effects upon fungal populations, dependent on the particular land management applied to the soil. Undisturbed grassland where fungal biomass was likely to be the predominant microorganism present showed significant effects of fertilizer regime upon fungal biomass, with effects likely to be related to plant-fungi interactions through changes in AM fungal biomass. The influence of fertilizer regime on arable sites was less pronounced which indicated a significant influence of disturbance reducing fungal biomass and reducing the direct and indirect effects associated with fertilizer additions. The investigation of soil pore spatial distribution is essential for understanding soil processes as water flow, gas and nutrient exchanges will occur within pore space, as will many biological processes. The investigation of inter-aggregate pore space was completed upon soil aggregates < 2 mm that had been exposed to previous experimental perturbations, where increased aggregate stability, water repellency and fungal biomass were reported. A resolution of «4 pm was achieved and changes in percentage porosity and spatial pore distributions were detected as a result of direct and indirect effects of plant roots. Greatest increases in heterogeneity of pore space were reported in soil from close proximity to roots, with a reduction in this phenomenon at an increasing distance from the root zone. The mechanism proposed for these changes was localised drying from roots. The results presented provide greater understanding of controlling factors associated with soil water and stability mechanisms, along with demonstrating biologically and physically induced changes in micro and meso-scale structures as a result of different treatments. The work provides scope for further investigation of particular biological and physical factors associated with soil structural mechanisms.

The influence of root-zone temperature on the efficacy of various ectomycorrhizal fungi, i.e., their ability: (1) to colonize roots in a nursery environment, (2) to persist and colonize new roots in the field and (3) to improve the growth, nutrition, and physiology of white spruce (Picea glauca (Moench) Voss) seedlings, was examined in controlled environment experiments using water baths to regulate root-zone temperature. Eight-week-old non-mycorrhizal seedlings were inoculated with 13 different inocula (1 forest floor inoculum, 12 specific fungi), then transplanted into 6, 16, or 26°C peat:vermiculite mixes for 8 weeks. Maximum root colonization occurred at 16°C for most inocula. The 6°C mix strongly reduced mycorrhiza formation with only 8 of the 13 inocula forming any mycorrhizae during the 8-week test period. Primary infection from ectomycorrhizal propagules (spores and hyphal fragments) was reduced more than was secondary infection from established mycorrhizae; once established, all inocula colonized new roots in 6°C forest soil. Fall-lifted cold-stored seedlings infected with 8 inocula (forest floor, 7 specific fungi) were planted into 6 and 12°C forest soil mixtures with or without indigenous ectomycorrhiza inoculum. Survival and colonization of new roots by inoculant fungi was good (> 50%) for the 12-week test duration despite the significant potential for infection by indigenous inoculum. High persistence appeared to be due to successful (>75%) root colonization by the inoculant fungi in the nursery production phase, to the relative weakness of ectomycorrhizal propagules (spores and hyphal fragments) compared with live ectomycorrhizal attachments, and to the favorable pattern of lateral root egress from the container plug after planting. Colonization of new roots by established mycorrhizae showed an effect of soil temperature in the presence, but not the absence, of indigenous inoculum. Percent new root colonization by inoculant fungi was lower in the 12°C forest soil. Rapid extension of lateral roots in the 12°C soil increased the likelihood that short roots initiated near the tips of elongating roots would be infected by indigenous fungi. There was no evidence of active or passive interactive replacement between inoculant and indigenous fungi. However, Hebeloma crustuliniforme appeared to inhibit mycorrhizal formation by indigenous fungi; roots not infected by this fungus remained non-mycorrhizal. Application of slow-release fertilizer reduced new root colonization by E-strain but had no effect on colonization by H. crustuliniforme or indigenous forest floor fungi. Non-inoculated seedlings (controls) and seedlings inoculated with 5 different inocula (forest floor, 4 specific fungi) were planted in 6 and 12°C forest soil for 3 weeks. Inoculation influenced the rate at which seedlings acclimated to the 6°C soil with respect to resistance to water flow and net photosynthetic rate, but had no effect on pre-dawn stomatal conductance. Differences among inoculation treatments were related to the size and nutritional status of seedlings at the time of transplanting. Seedlings infected with Laccaria bicolor or E-strain exhibited the least decrease in resistance to water flow due to the relatively small size (dry weight, short root number) of their root systems at the time of transplanting. Net photosynthetic rate and new foliage production correlated positively with shoot N and P (% dry weight) and the proportion of total seedling N and P contained in shoot tissues at the time of planting. Non-inoculated seedlings (controls) and seedlings inoculated with forest floor or 5 specific fungi were planted in 6 and 12°C forest soil for 12 weeks. The presence of "any" mycorrhiza at the time of transplanting did not improve seedling growth under the experimental conditions (i.e., cool, acidic soils with an indigenous ectomycorrhizal fungal population). On average, mycorrhizal infection increased N and P uptake at 12°C but not at 6°C. Growth response to specific fungi was very variable with some fungi depressing seedlings growth (e.g., E-strain and H. crustuliniforme) and others strongly promoting it (forest floor inoculum, L. bicolour, Thelephora terrestris). Seedling response to the various inocula was not related to the degree of mycorrhizal infection at the time of planting nor to the source of inocula; but was associated with differences in the content and distribution of nutrients at the time of transplanting and differences in total nutrient uptake, root efficiency, nutrient-use efficiency and net photosynthetic rate after transplanting. Root efficiency was not proportional to the number of short roots per unit root or to the amount of external mycelium attached to the various mycorrhizae. Implications for applied forestry and research are discussed in the final chapter.
Forestry, Faculty of
Graduate

This thesis evaluates protocols to visualise and quantify short-term interactions between soil-borne fungi and soil. The quantification captures interactions between the ubiquitous soil saprotroph and plant pathogen Rhizoctonia solani, and a sandy loam soil, over a period of five days. The literature review provides evidence of mutual interactions between soil and fungi and highlights the lack of understanding about processes occurring at short time scales, which are crucial for modelling the complexity of soil environment. The first part of the thesis merges X-ray microtomography, image analysis and laboratory measurements to investigate the impact of short term incubation of fungi on soil water retention and soil structure at macro (whole microcosm) and micro (individual aggregate) scales. Part Two quantifies the effect of experimental variables such as aggregate-size and soil bulk-density on key descriptors of the soil pore network. Finally, a fungal growth model was used to quantify to what extent soil structure mediated by bulk-density affected fungal growth dynamics. The experimental work showed that despite high fungal biomass content there was no effect of fungal colonisation on soil structure and hydraulic properties after short-term incubation. However, it was possible to alter the geometry of soil pore space and thus influence fungal growth dynamics. This was achieved by manipulating the initial conditions of re-packed soil microcosms through variation of aggregate size and bulk density. The experimental work showed that despite high fungal biomass content there was no effect of fungal colonisation on soil structure and hydraulic properties after short-term incubation. However, it was possible to alter the geometry of soil pore space and thus influence fungal growth dynamics. This was achieved by manipulating the initial conditions of re-packed soil microcosms through variation of aggregate size and bulk density.

The hypothesis that mycophagous nematodes feed on the mycelia of VAM fungi and consequently reduce the spread of vesicular-arbuscular mycorrhizal (VAM) infection in plant roots and the growth response of plants to this infection was investigated in experiments carried out under controlled environmental conditions. Preliminary experiments indicated that nematodes might be able to reduce VAM infection by Glomus clarum if they were added to soil at the same time as the fungal inoculum. However, nematodes did not affect the growth response of red clover to VAM infection even though there was an indication that nematodes may directly affect plant growth possibly by causing damage to root hairs which could facilitate the entry of pathogens. There seemed to be little effect of mycorrhizal status on the numbers of nematodes which could be recovered from the growth medium. The two standard methods used to extract nematodes in these preliminary experiments were found to give low and variable recoveries. A method which gave greater and less variable recoveries was developed and the conditions for its successful use were defined. The four species of nematodes used in this study differed in their ability to reduce the growth of a range of fungi and in their ability to increase in number as a result of feeding on these fungi. Both experimental data and a mathematical model, which was developed subsequently, showed that the suitability of a fungus as a source of nutrition could be measured by the increase in numbers of nematodes and the reduction in weight of mycelium as a result of grazing. The model therefore provided a rationale for ranking different fungi in terms of their suitability as hosts for a given species of nematode. Of the four species of nematodes, A phelenchus avenae was the most damaging to the growth of a range of fungi. However, when added at the same time as, or later than, the VAM inoculum, A. avenae had no effect on the spread of VAM infection or on the response of plants to VAM infection. The numbers of A. avenae recovered were similar in non-mycorrhizal and mycorrhizal treatments. A mathematical model was developed which simulated the spread of VAM infection and the change in numbers of nematodes with time. Close agreement between predictions of the model and experimental results was only achieved if it was assumed that the nematodes were not capable of feeding on the VAM fungus. Aphelencholdes composticola multiplied most when cultured in agar plates but grew poorly when cultured on its own in soil. When organic material (bran) colonized either by Agaricus bisporus (the nematodes preferred host) or by volunteer fungi was introduced into soil, the numbers of A. composticola increased by up to one hundred times. Neither VAM infection by G. clarum nor the mycorrhizal responses of the plant were affected by these high numbers of A. composticola, by the introduction of bran alone or by bran colonized by A. bisporus. In soil without added bran or saprotrophic fungi numbers of A. composticola were not affected by the presence of G. clarum, indicating that the available food sources in unamended soil were sparse. Mycorrhizal plants appeared to benefit more than non-mycorrhizal plants from the mineralization of phosphorus by the saprotrophic fungi. Factors which may determine the suitability of some fungi as food sources for mycophagous nematodes are discussed. The possibility that VAM fungi are immune to grazing by these nematodes is considered. Ways in which mycophagous nematodes may influence the growth of plants are also discussed.

Wheat crops are known to be devastated by infections of soil-borne pathogens, especially the fungus Gaeumannomyces graminis var. tritici (Ggt) that causes ‘take-all’. Plant growth promoting rhizobacteria (PGPR) such as Pseudomonas fluorescens have received much attention as biocontrol agents against Ggt, mainly due to their ability to produce antibiotics. The polycetide secondary antimicrobial metabolite 2,4-diacetylphloroglucinol (DAPG) is produced by a number of fluorescent pseudomonad strains and is known to suppress Ggt. Another soil microbial group which have been under investigation for their biocontrol potential against Ggt, are arbuscular mycorrhizal (AM) fungi which have the potential to out-compete Ggt and improve host plant nutrition and vigour. In this thesis, I report results from experiments that investigate interactions among AM fungi, Ggt, and DAPG-producing bacteria. A central hypothesis is that carbon flow from plants and AM fungi stimulates DAPG production. I therefore focus on interactions among AM fungi, Ggt and bacteria in vivo with wheat plants and in vitro with only fungal exudates. The synergistic co-operation of pseudomonads and AM fungi against Ggt was demonstrated and the fungal exudates (from AM and Ggt) produced both in vitro and in vivo increased DAPG production by P. fluorescens. The ecology and functioning of beneficial AM fungi was found not to be influenced by the presence of either Ggt or DAPG, highlighting the potential sustainable suppression of “take all” in wheat rhizosphere.

Arbuscular mycorrhizal fungi (AMF) can form a mutualistic symbiosis with over two-thirds of all land plants, providing phosphorus and/or nitrogen in exchange for carbon. They can have a significant effect on the surrounding soil, altering pH, water content, structure, and drainage. Important greenhouse gases (GHG) including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) can be influenced by these factors, yet to date the interactions between AMF and soil GHG fluxes are surprisingly understudied. A microcosm system was developed to study GHG fluxes in the presence and absence of AMF hyphae. A central compartment contained an AMF host plant (Zea mays L.), with two outer compartments, that either allowed (AMA) or prevented (NAMA) AMF hyphal access. Organic matter patches of dried, milled, Z. mays leaves mixed with soil were added to the outer compartments to encourage proliferation of AMF hyphae and GHG production. Soil-atmosphere fluxes of N2O, CO2 and CH4 from the outer compartments were quantified, and gas probes were developed to measure N2O concentrations within the organic matter patches. Data from a series of microcosm experiments provide evidence for AMF interactions with soil fluxes of N2O and CO2, but not CH4. Soil CO2 fluxes were found to be a useful non-invasive method for determining the presence of AMF in hyphal compartments. The N2O concentrations in organic patches decreased in AMA treatments, and a subsequent experiment demonstrated that N2O production by nitrifiers may be limited in the presence of AMF hyphae. In contrast, following harvesting, N2O fluxes from organic matter patches were higher in the AMA treatment; possibly because carbon release from severed AMF hyphae fuelled denitrification. These interactions have important implications for N cycling and sustainable agriculture. The evidence presented in this thesis suggests that AMF may play a previously unappreciated role in reducing soil-atmosphere losses of N2O.

The present study was firstly aimed at producing the AM fungal inocula by using soil-based and soil-less culture techniques, including the in-vitro axenic technique, and secondly to assess the infectivity and effectiveness of the inocula so produced in glasshouse and field conditions. Indigenous AM fungi from 5 different sites of New South Wales were successfully propagated and multiplied using the pot-culture and atomizing disc aeroponic culture techniques, and their infectivity was measured using the MPN bioassay method. The coarse and fine sand mix was proven to be very effective for the production of AM fungal inocula. The findings indicated that aeroponic culture technique is far superior to that of conventional pot-culture technique, and could possibly substitute the most commonly used pot-culture technique of AM fungal inoculum production. The ultra-sonic nebulizer technology could possibly be an alternative to conventional aeroponic systems for producing AM fungal isolates in commercial quantities. The introduction of the sheared-root inoculum of Glomus intraradices, produced by the ultra-sonic nebulizer technique, into agricultural soils can substantially reduce the intake of P-fertilizers as much as 50% of the recommended level. The study also indicated that soil phosphorus is a critical factor in limiting mycorrhizal colonization, possibly limiting mycorrhizal responses.The research suggests that various commercially produced single or 'cocktail' inocula may work on mycorrhiza dependent plants in soils where the indigenous AM flora is either not abundant and/or efficient. Furthermore, ecophysiology of the same AM species have different effects on plant growth.

Thesis (M.S.)--Southern Oregon University, 2002.
Includes bibliographical references (leaves 37-43). Also available via Internet as PDF file through Southern Oregon Digital Archives: http://soda.sou.edu. Search Bioregion Collection.

Thesis (MSc)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: Mucoralean fungi are mostly saprotrophs that are frequently encountered in soil habitats. Using an isolation temperature of circa 25°C, other workers obtained these fungi from a wide diversity of geographical areas in southern Africa. However, it is known that psychrotolerant mucoralean fungi, able to grow at 25°C as well as at 5°C, occur in pristine Alti Mountain Grassland. Nothing is known about the diversity of these psychrotolerant soil fungi in other vegetation types of South Africa. Consequently, in this study, the psychrotolerant fungal taxa and numbers in soil from a vineyard and from pristine Mountain Fynbos were determined using an incubation temperature of 4°C and a complex isolation medium. The latter contained agar, malt extract, peptone, yeast extract, penicillin and streptomycin sulphate. Soil samples were analysed in late summer, autumn and mid-winter. It was found that, for the samples taken in late summer and autumn, the diversity of mucoralean species in the soil differed between fynbos and vineyard. In winter however, no significant difference was detected between the Shannon's diversity indices of mucoralean species in the soil samples taken from the two habitats. It was found that in both soil types, the percentage mucoralean fungi on the plates increased from summer to winter. In addition, the numbers of detectable Morlierella subgenus Morlierella on the plates were higher in winter than in late summer. The diversity of mucoralean species obtained during winter in fynbos and vineyard soil was significantly less than the diversity of these species in Alti Mountain Grassland soil. To determine if the Morlierella subgenus Morlierella isolates from the fynbos and vineyard soil, and those obtained from Alti Mountain Grassland, differ in the ability to grow at low temperatures, the radial growth rate on malt extract agar at 4°C and BOC was determined for each isolate. The results indicate that not only did seasonal changes occur in the taxa within Morlierella subgenus Morlierella, but that the isolates dominating the soil in different seasons also differed in the ability to grow at low temperatures. The percentage of isolates that had reached greater colony diameters after B days of incubation at 4°C, was higher for the isolates obtained in the cold wet month of July than for those obtained in the warmer dryer month of February. Similar results were obtained with the radial growth experiments conducted at BOC. The Morlierella subgenus Morlierella isolates obtained in winter from fynbos and vineyard soil showed less variation in low temperature growth rate than the isolates of this taxon obtained in winter from Alti Mountain Grassland soil during a previous study. This variation corresponds to the greater number (20) of Morlierella subgenus Morlierella species found in the grassland soil. Altogether only seven species of this subgenus was detected during the present study in the fynbos and vineyard soil samples. It was speculated that this difference in diversity between the fynbos and vineyard isolates, and the grassland isolates obtained in a previous study, might have been as a result of differences in the habitat or the enumeration methods used. The phylogenetic relationship between different psychrotolerant isolates of Morlierella subgenus Morlierella originating from the soil of the fynbos, vineyard and Alti Mountain Grassland, was subsequently determine through comparison of ITS regions, within ribosomal RNA repeats. Consequently, 45 psychrotolerant Morlierella subgenus Morlierella isolates originating from the three soil habitats was compared on the basis ITS 1 nucleotide sequence composition and radial growth rate at 4°C. Phylogenetic analyses showed that the isolates could be grouped into two clusters correlating with the ability to grow at low temperatures. Each cluster was further subdivided into two subgroups. It was found that except for one subgroup and the reference strain occurring in another subgroup, all the subgroups contain isolates originating from a single soil habitat. Therefore, the ITS 1 sequence of these fungi seems to indicate the original habitat and ability to grow at low temperatures. This correlation of the ITS sequence with the ecological habitat of a fungus has also been observed by other workers for other fungal groups.
AFRIKAANSE OPSOMMING: Mucoraliese fungi is meestal saprotrofe wat dikwels in grondhabitatte aangetref word. Deur gebruik te maak van 'n isolasietemperatuur van circa 25°C, het ander werkers dié fungi van 'n wye verskeidenheid geografiese gebiede in suidelike Afrika verkry. Dit is egter bekend dat die psigrotolerante mucoraliese fungi, wat in staat is om by 2SoC en ook by SaC te groei, in ongeskonde Alti Berg-Grasland voorkom. Niks is egter bekend oor die diversiteit van dié psigrotolerante grondfungi in ander veldtipes van suidelike Afrika nie. Die psigrotolerante fungustaksa en -getalle in grond van 'n wingerd en van ongeskonde Berg Fynbos is gevolglik in dié studie bepaal deur gebruik te maak van 'n inkubasietemperatuur van 4"C en 'n komplekse isolasiemedium. Laasgenoemde het agar, moutekstrak, peptoon, gisekstrak, penisillien en streptomisiensulfaat bevat. Grondmonsters is in die laatsomer, herfs en midwinter geanaliseer. Daar is 'n verskil gevind tussen die diversiteit van die mucoraliese spesies in die grond van fynbos en dié van wingerd in die monsters wat in die laatsomer en midwinter geneem is. In die winter is daar egter geen beduidende verskil gevind tussen die Shannon diversiteitsindekse van mucoraliese spesies in die grondmonsters wat uit die twee habitatte getrek is nie. In albei grondtipes is daar gevind dat die persentasie mucoraliese fungi op die plate toegeneem het van somer tot winter. Daarby was die aantal waarneembare Morlierella subgenus Morlierella op die plate meer in die winter as in die laatsomer. Die diversiteit van mucoraliese spesies wat in die winter uit fynbos- en wingerdgrond verkry is, was beduidend minder as die diversiteit van dié spesies in Alti Berg-Grasland grond. Om te bepaal of die Morlierella subgenus Morlierella isolate van die fynbos- en wingerdgrond en dié van Alti Berg-Grasland van mekaar verskil ten opsigte van hul vermoë om by lae temperature te groei, is die radiale groeitempo op moutekstrak by 4"C en aoc vir elke isolaat bepaal. Die resultate dui aan dat daar nie alleen seisoenale veranderinge in die taksa binne Morlierella subgenus Morlierella voorkom nie, maar dat die isolate wat tydens verskillende seisoene uit die grond verkry is, ook ten opsigte van hul groeivermoë by lae temperature van mekaar verskil. Die persentasie isolate wat groter kolonie diameters bereik het ná B dae inkubasie by 4°C, was hoër vir die isolate van die koue, nat Juliemaand as vir dié wat in die warmer en droër Februariemaand verkry is. Soortgelyke resultate is verkry met radiale groei-eksperimente wat by BOC gedoen is. Die MortierelIa subgenus MortierelIa isolate wat in die winter uit fynbos- en wingerdgrond verkry is, het In kleiner variasie in hul groeitempo by lae temperature getoon as die isolate in dié takson wat tydens 'n vorige studie in die winter uit Alti Berg-Grasland grond verkry is. Dié variasie stem ooreen met die groter aantal (20) MortierelIa subgenus MortierelIa spesies wat in die graslandgrond gevind is. Slegs sewe spesies van dié subgenus is gedurende die huidige studie in die fynbos- en wingerdgrondmonsters waargeneem. Daar is gespekuleer dat dié verskil in diversiteit tussen die fynbos- en wingerdisolate en die graslandisolate van die vorige studie die gevolg mag wees van verskille tussen die habitat of die enumerasiemetodes wat gebruik is. Die filogenetiese verwantskap tussen verskillende psigrotolerante isolate van MortierelIa subgenus MortierelIa uit die grond van die fynbos, wingerd en Alti Berg-Grasland, is vervolgens bepaal deur 'n vergelyking van interne getranskribeerde spasieerder (ITS) areas, binne ribosomale RNS herhalings. Daar is gevolglik 45 psigrotolerante MortierelIa subgenus MortierelIa isolate uit die drie grondhabitatte met mekaar vergelyk op grond van die basis ITS 1 nukleotied opeenvolgingsamestelling en radiale groeitempo by 4°C. Filogenetiese analises het die isolate in twee groepe verdeel op grond van hul vermoë om by lae temperature te groei. Elke groep is verder in twee subgroepe verdeel. Daar is gevind dat behalwe vir een subgroep en die verwysingstam wat in 'n ander subgroep voorgekom het, elkeen van die subgroepe bestaan het uit isolate wat van 'n enkele grond habitat verkry is. Dit wil dus voorkom of die ITS 1 opeenvolging van dié fungi 'n aanduiding gee van die oorspronklike habitat en die vermoë om by lae temperature te groei. Dié korrelasie tussen die ITS opeenvolging en die ekologiese habitat van 'n fungus is ook deur ander werkers vir ander fungusgroepe waargeneem.

Soil samples were incubated on agar precolonised by different 'host' fungi for detection of presumptive mycoparasites. In a survey of 34 British soils, only Pythium oligandrum, Gliocladium roseum group, Trichoderma spp, and Papulaspora sp. were detected routinely, from 19, 34, 30 and 27 soils respectively; all soils contained more than one mycoparasite, 3 soils had two detectable types, 20 contained three types and 11 contained all four detectable types. The choice of host fungus strongly influenced the efficiency of detection of mycoparasites: Fusarium culmorum was best for P. oligandrum, Rhizoctonia solani for Trichoderma spp., and Botrytis cinerea for Papulaspora sp., but G. roseum (and G. atrum and G.fimbriatum) grew well from soil on colonies of Trichoderma aureoviride, R. solani or B. cinerea. The incidence of detection in replicate samples indicated that a range of host-colonised agar plates are needed to determine the spectrum of presumptive mycoparasites in a soil. Competition between these mycoparasites affected the success of detection because incorporation of metalaxyl into B. cinerea-colonised agar plates prevented growth by P. oligandrum and enhanced the growth of Papulaspora sp. from soil samples. Baiting of soils only partly increased the efficiencies of detection: for Trichoderma spp, when soil was baited with cellulose film precolonised by R. oryzae, and for Papulaspora sp. when the bait was cellulose film or mature, dried wheat leaves, precolonised by Humicola grisea. Agar precolonised by F. culmorum was used to detect apparent changes in soil populations of P. oligandrum, using a most probable number method based on serial dilution of soil samples with sand. The addition of dried, mature wheat flag leaves or fresh, green grass leaves to soil enhanced the detectable populations for at least 280 days, although the effect of grass leaves was found only after a second supplement at 150 days. A metalaxyl-tolerant population of P. oligandrum, added to soil as oospores, was still detectable after 240 days when soil samples were placed on F. culmorum-colonised agar containing metalaxyl.

Bibliography: leaves 71-79. Almost 80 percent of plant taxa develop vesicular-arbuscular mycorrhizae (VAM) which are symbiotic associations between plant roots and soil fungi. The fungi are biotropic-obligate symbionts. Identification of VAM fungi is currently based on spore characteristics. Molecular techniques provide tools for better and more accurate identification of species, as well as for the examination of genetic variability occuring between individual spores of a single species.

Thesis (MSc)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Numerous workers studied the impact of pollutants and agricultural chemicals, containing heavy metals such as copper (Cu), on soil microbes. It was found that elevated soil Cu levels do have a detrimental effect on soil bacterial populations however the filamentous fungi seemed to be less affected. Most of these studies were conducted in soils containing already relatively high Cu levels and the effect of this heavy metal on the nonfilamentous fungi (i.e. yeasts) was never investigated. The aim of this study was therefore to determine the impact of elevated Cu levels on filamentous fungi and yeasts occurring in soils containing relatively low natural Cu levels. A synthetic selective medium containing glucose as carbon source, thymine as nitrogen source, vitamins, minerals and chloramphenicol as anti-bacterial agent (TMV-agar), was used to enumerate ascomycetous and basidiomycetous Cu resistant yeasts in a sample of virgin soil containing ~ 2ppm Cu. Media that were used to enumerate Cu resistant filamentous fungi were malt extract agar, malt extract agar with streptomycin sulfate, maltyeast- extract-peptone agar with chloramphenicol and streptomycin sulfate, benomyl–dichloran-streptomycin medium for the enumeration of hymenomycetous fungi and two selective media for the isolation of mucoralean fungi. Cu resistant fungi able to grow on all of the above mentioned solid media supplemented with 32 ppm Cu occurred in the soil sample. To obtain an indication of the level of Cu tolerance of fungi present in this soil sample, a number of fungal isolates were screened for the ability to grow on a series of agar plates, prepared from glucose-glutamate-yeast extract agar, containing increasing concentrations of Cu. It was found that filamentous fungi and yeasts that were able to grow on this agar medium containing up to 100 ppm Cu were present in the soil. A series of soil microcosms was subsequently prepared from the soil sample by experimentally contaminating the soil with increasing amounts of copper oxychloride, were after fungal populations in the microcosms, including Cu resistant fungi, were monitored using plate counts. At the end of the incubation period, after 245 days, fungal biomass in the microcosms was compared by determining the concentrations of the fungal sterol, ergosterol, inthe soil. Generally, Cu had little impact on the numbers of filamentous fungal colony forming units on the plates, as well as on the ergosterol content of the soil. The numbers of filamentous fungi in the soil, including the Mucorales and hymenomycetes, seemed to be less affected by the addition of copper oxychloride than the numbers of soil yeasts able to grow on TMV-agar. The focus of the next chapter was on the response of yeasts in different soils to elevated levels of Cu in the soil. TMV-agar was used to enumerate yeasts in soil microcosms prepared from four different soil samples, which were experimentally treated with copper oxychloride resulting in Cu concentrations of up to 1000 ppm. The selective medium supplemented with 32 ppm Cu was used to enumerate Cu resistant yeasts in the microcosms. The results showed that the addition of Cu at concentrations ≥ ~1000 ppm did not have a significant effect on total yeast numbers in the soil. Furthermore, it was found that Cu resistant yeasts were present in all the soil samples regardless of the amount of Cu that the soil was challenged with. At the end of the incubation period, yeasts in the microcosms with zero and ~1000 ppm additional Cu were enumerated, isolated and identified using sequence analyses of the D1/D2 600-650bp region of the large subunit of ribosomal DNA. Hymenomycetous species dominated in the control soil, while higher numbers of the urediniomycetous species were found in the soil that received Cu. These observations suggest that urediniomycetous yeasts may play an important role in re-establishing overall microbial activity in soils following perturbations such as the addition of Cu-based fungicides.
AFRIKAANSE OPSOMMING: Vele navorsers het al die impak van besoedelingstowwe en landbouchemikalieë wat swaarmetale soos koper (Cu) bevat, op grond-mikrobes bestudeer. Dit is gevind dat verhoogde Cu vlakke ‘n nadelige effek het op grond-bakteriese populasies, maar dat die filamentagtige fungi geneig is om minder geaffekteer te word. Meeste van hierdie studies is gedoen met gronde wat alreeds relatief hoë Cu vlakke bevat het en die effek van hierdie swaarmetaal op die nie-filamentagtige fungi (d.i. giste) is nooit ondersoek nie. Die doel van hierdie studie was dus om die impak van verhoogde Cu vlakke op filamentagtige fungi en giste in gronde, wat natuurlike lae vlakke van Cu bevat, te bepaal. ‘n Sintetiese selektiewe medium wat glukose as koolstofbron, timien as stikstofbron, vitamiene, minerale asook chloramfenikol as anti-bakteriese agent bevat (TMV-agar), is gebruik om askomisete en basidiomisete Cu weerstandbiedende giste in ‘n monster ongeskonde grond, bevattende ~ 2dpm Cu, te tel. Media wat gebruik is om Cu weerstandbiedende filamentagtige fungi te tel, was mout-ekstrak agar, moutekstrak agar met streptomisiensulfaat, benomiel-dichloran-streptomisien medium vir die tel van hiemenomiseetagtige fungi en twee media vir die isolasie van mukoraliese fungi. Cu-weerstandbiedende fungi wat op al die bogenoemde media, aangevul met 32 dpm Cu, kon groei, het in die grondmonster voorgekom. Om die mate van Cu-weerstandbiedendheid van fungi wat in die grondmonster voorkom, te bepaal, is ‘n getal fungus-isolate op agarplate, voorberei met glukose-glutamaat-gis ekstrak agar, bevattende verhoogde konsentrasies Cu, nagegaan. Daar is gevind dat daar filamentagtige fungi en giste in die grond voorkom wat die vermoë het om op media bevattende 100 dpm Cu te groei. ‘n Reeks grond mikrokosmosse is dus voorberei vanaf die grondmonster deur om dit eksperimenteel te kontamineer met verhoogde hoeveelhede koper oksichloried, waarna die fungus-populasies asook die Cu-weerstandbiedende fungi in die mikrokosmos gemoniteer is deur middel van plaattellings. Aan die einde van die inkubasie periode, 245 dae, is die fungus biomassa in al die mikrokosmosse bereken deur die konsentrasie van die fungus sterool ergosterool te bepaal en dit met mekaar te vergelyk. Oor die algemeen het Cu min impak ten opsigte van diegetal filamentagtige fungi kolonie vormende eenhede die plate, asook op die ergosterool inhoud van die grond gehad. Dit wil voorkom of die getal filamentagtige fungi in die grond, insluitende die Mucorales en die hymenomisete, minder geaffekteer is deur die toediening van koperoksichloried as die aantal grondgiste wat op die TMV-agar kan groei. Die fokus van die volgende hoofstuk was dus op die reaksie wat giste in verskillende grondtipes gehad het op verhoogde Cu in die grond. TMV-agar is gebruik om die getal giste te bepaal in die grond mikrokosmosse van die vier verskillende grondmonsters, wat voorberei is deur om dit eksperimenteel met koper oksikloried te kontamineer tot en met Cu konsentrasies van 1000 dpm. Die selektiewe medium wat gesupplementeer is met 32 dpm Cu, is gebruik om Cu weerstandbiedende giste in die mikrokosmosse te bepaal. Die resultate toon dat die toevoeging van Cu by konsentrasies ≥ ~1000 dpm nie enige beduidende effek op die totale gis getalle gehad het nie. Daar is ook gevind dat daar Cu weerstandbiedende giste in die grond monsters voorkom gekom het ten spyte van die hoeveelheid Cu wat tot die grond toegevoeg is. Aan die einde van die inkubasie periode is die giste wat die die mikrokosmosse bevattende nul en ~1000 dpm Cu getel, geïsoleer en geïdentifiseer deur gebruik te maak van DNA volgorde bepaling van die D1/D2 600-650 bp areas geleë in die groter subeenheid van die ribosonale DNA. Hymenomisete spesies het in die grond kontrole gedomineer, terwyl hoër getalle uredinomisete spesies in die grond met addisionele Cu gevind is. Die resultate dui daarop dat uredinomisete giste dalk ‘n belangrike rol kan speel in die hervestiging van die oorwegende mikrobiese aktiwiteit in grond na skoktoestande soos die aanwending van Cu-gebaseerde fungisiede.

Four arbuscular mycorrhizal (AM) fungal isolates (Glomus sp.) from disparate edaphic conditions were screened for effects on whole -plant transpiration of juvenile 'Volkamer' lemon (Citrus volkameriana Ten. and Pasq.) plants of similar shoot mass and canopy leaf area. Mycorrhizal and non -mycorrhizal plants were grown in 8 -liter containers for 2.5 months under well- watered conditions before subjection to three consecutive soil drying episodes of increased severity (soil moisture tensions of -0.02 [still moist], -0.06 [moderately dry], and -0.08[dry] MPa respectively). Whole plant transpiration measurements were made on the last day of each soil drying episode and measurements were repeated on the first and second days after re- watering, when soil profiles were moist. The percent root length colonized by AM fungi differed among isolates. Three AM fungal isolates, Glomus sp. 25A, Glomus mosseae (Nicol. & Gerde.) Gerde. & Trappe 114C, and Glomus intraradices Schenck & Smith FL 208-3 increased root length and subsequently increased lemon plant water use. Conversely, plants inoculated with Glomus mosseae 51C did not enhance lemon plant root length nor improve plant water use compared with nonmycorrhizal control plants. Inoculating citrus with AM fungi that promote root extension may reduce plant water deficit stress under field conditions.

This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.

Fungi are key components in forest ecosystems, being involved in decomposition of plant biomass and the cycling of nutrients in forest soils. Despite their importance little is understood about the influence forest management practices, such as long-term prescribed burning and forest conversion are having on soil fungal communities. Part of the work described in this thesis investigated the effects of long-term repeated prescribed burning on the total soil fungal community, the diversity of mycelial communities of ectomycorrhizal fungi and the influence of biennial prescribed burning on the cellulolytic soil fungal community using stable isotope probing techniques. The influence of long-term repeated prescribed burning on soil fungal communities was investigated through a series of studies conducted at Peachester State Forest, Queensland, Australia. This site has been the centre of a long-term repeated prescribed burning experiment, established since 1972, consisting of plots subjected to biennial, quadrennial or no burning. Denaturing gradient gel electrophoresis (DGGE) was used to show that long-term prescribed burning significantly altered the total fungal community structure in the top 10 cm of soil, when compared with unburned plots. Hyphal ingrowth bags, used to target ectomycorrhizal (ECM) mycelia in soil, along with DGGE analysis, indicated that profiles of the soil fungal community from 2 yr burn plots significantly differed from those of the 4 yr burn and unburned plots. Following analysis of clone assemblages from the different burn regimes, results indicated that this difference reflected an altered ECM fungal community composition. 13C stable isotope probing (SIP), following the incubation of soil with 13C labelled cellulose, and DGGE analysis was found to significantly alter the active fungal community in the upper 10cm of soil at Peachester State Forest. Fewer active fungi in the 2 yr burn plots were found to have incorporated 13C compared to the unburned plots, strongly suggesting that the activities of cellulolytic fungi were negatively affected by the 2 yr burning treatment. The thesis also incorporated work that assessed the effect of forest conversion from native eucalypt to Pinus elliottii plantation on the soil fungal community at Beerburrum State Forest, Queensland, Australia. ITS and 18S RNA and DNA were used, along with terminal restriction fragment length polymorphism (T-RFLP) and DGGE analysis, indicating that total and active fungal communities differed significantly between the native eucalypt forest and first rotation P. elliottii plantation. This suggested that the conversion from native eucalypt forest to P. elliotti plantation significantly altered the soil fungal community at the Beerburrum site.

The present study was firstly aimed at producing the AM fungal inocula by using soil-based and soil-less culture techniques, including the in-vitro axenic technique, and secondly to assess the infectivity and effectiveness of the inocula so produced in glasshouse and field conditions. Indigenous AM fungi from 5 different sites of New South Wales were successfully propagated and multiplied using the pot-culture and atomizing disc aeroponic culture techniques, and their infectivity was measured using the MPN bioassay method. The coarse and fine sand mix was proven to be very effective for the production of AM fungal inocula. The findings indicated that aeroponic culture technique is far superior to that of conventional pot-culture technique, and could possibly substitute the most commonly used pot-culture technique of AM fungal inoculum production. The ultra-sonic nebulizer technology could possibly be an alternative to conventional aeroponic systems for producing AM fungal isolates in commercial quantities. The introduction of the sheared-root inoculum of Glomus intraradices, produced by the ultra-sonic nebulizer technique, into agricultural soils can substantially reduce the intake of P-fertilizers as much as 50% of the recommended level. The study also indicated that soil phosphorus is a critical factor in limiting mycorrhizal colonization, possibly limiting mycorrhizal responses.The research suggests that various commercially produced single or 'cocktail' inocula may work on mycorrhiza dependent plants in soils where the indigenous AM flora is either not abundant and/or efficient. Furthermore, ecophysiology of the same AM species have different effects on plant growth.
Doctor of Philosophy (PhD)

Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains viii, 72 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 61-64).

Drought has serious impact on the stability and fertility of soil systems, but the consequences for soil microbes and functioning remain unclear. Major soil carbon (C) and nitrogen (N) cycling processes such as microbial biomass C (MBC) and N (MBN), respiration, carbon use efficiency (CUE), extracellular enzyme (EE) activity, gross N mineralization (GNM), and N retention were explored in response to drought, biocides and fertilizer treatments in a seminatural Australian grassland soil. Results showed that the abundances and activities of fungi and bacteria across seasons were responsible for larger variations of CUE compared to drought, and more fungi in dry summer with greater investment in C for EEs production reduced CUE. To investigate their effects on these processes, an initial meta-analysis showed that most biocides had significant negative effects on MBC and MBN, and mixed effects on soil respiration and N cycles. As biocide addition can temporarily increase C and N to surviving microbes, a laboratory experiment was conducted using common fungicides and bactericides. Biocides addition to soil can result in unwanted temporary increases in C and N supply to surviving microbes due to a pulse in microbial necromass, and where biocides can directly be used as sources of C and N. To overcome this issue, the effect of labeled substrate with and without biocides additions in a controlled drought treatment were further investigated. Under drought, fungi produced oxidative enzymes and appeared to be more important in decomposing recalcitrant C substrate than bacteria. Further, drought effects on GNM and plant N uptake were not in synchrony, and compost addition can reduce N loss with drought compared to mineral fertilizers. Finally, this research provides and improved understanding of the links between microbes and soil dynamics with continuing drought stress to overcome the potential rates of soil degradation in grasslands of Australia.

Thesis (M.S.)--Southern Oregon University, 2005.
"A thesis submitted to ... Southern Oregon University in partial fulfillment of the requirements for the degree of Master of Science ..." Includes bibliographical references (leaves 101-109). Also available via Internet as PDF file through Southern Oregon Digital Archives: http://soda.sou.edu. Search Bioregion Collection.

Com a resultat de les activitats humanes, la contaminació deguda a productes químics alliberats al medi s’ha convertit en un problema global, essent una amenaça real per a l’activitat humana. La contaminació pot afectar qualsevol compartiment de l’ecosistema. Els hidrocarburs derivats del petroli, on s’inclouen els hidrocarburs policíclics aromàtics (HAPs), són contaminants que afecten de manera particular el sòl. Actualment existeixen diverses tècniques per a la restauració d’emplaçaments contaminats, inclosa la bioremediació. La micorremediació, àrea de coneixement en què s’emmarca la tesi, ha guanyat atenció en els últims anys ja que és una tècnica ambientalment respectuosa. Aquest treball presenta els resultats de les investigacions prèvies al desenvolupament d’un tractament de bioremediació de sols contaminats per hidrocarburs policíclics aromàtics mitjançant el fong ligninolític Trametes versicolor. Els resultats de l’esmentada investigació es presenten en tres apartats diferenciats. El primer es centra en la producció de biomassa del fong per a posteriors aplicacions en processos de bioremediació. Es divideix en dues seccions: • La primera es basa en la producció de biomassa en cultiu submergit. Els experiments es van centrar en formular un medi definit de cultiu de baix cost que permetés obtenir nivells elevats de biomassa, en la morfologia desitjada (pellets). El reactor fluïditzat per polsos d’aire amb control de pH va resultar ser el més adequat. La producció s’escalà a un bioreactor de 10 litres. • La segona secció analitza la colonització del fong sobre suports lignocel·lulòsics provinents de residus agrícoles per a posterior aplicació en el sòl. La selecció dels millors substrats per a la colonització es va basar en el nivell de biomassa (ergosterol), la producció de lacasa i la capacitat de degradar naproxè en 24 hores. Es va demostrar que el fong era capaç de colonitzar el sòl tant en condicions estèrils com en no estèrils mantenint, en tot cas, la capacitat degradativa. El segon apartat es centra en la degradació d’hidrocarburs policíclics aromàtics pel fong. Es divideix en tres seccions: • La primera es basa en la selecció d’un surfactant per a la degradació de HAPs en medi líquid, essent el millor el surfactant no iònic Tween 80. Es va poder demostrar la capacitat degradativa de diversos HAPs en medi líquid; tant en experiment per separat com en mescles. Així mateix, també es va demostrar que en les condicions de cultiu l’enzim lacasa podia degradar alguns dels compostos. • La segona secció fa referència a la identificació de productes intermediàris de degradació d’HAPs. També es va estudiar la capacitat de degradació d’aquests intermediaris per part del fong. • En la tercera secció es van provar diferents sistemes de degradació en sòl, on el bioslurry es presenta com el més efectiu en termes d’eficàcia de degradació. Es va poder comprovar que en les biopiles airejades el fong va tenir problemes derivats del rang termofílic assolit. El darrer apartat es basa en la degradació dels HAPs de la creosota. Es divideix en dues seccions: • La primera es centra en la degradació dels HAPs de la fracció aromàtica de la creosota. Es van estudiar diferents sistemes i es va determinar que el fong era més eficient en degradació en biopiles. En cultius submergits, medi líquid i slurry, el fong era efectiu en la degradació d’HAPs de baix pes molecular però no en aquells d’alt pes molecular. Es va observar l’efecte inhibitori sobre Trametes tant dels compostos addicionals afegits junt amb la creosota com en augmentar la concentració de HAPs. ! • La segona secció és fruit de la col·laboració amb el Laboratori de Biotecnologia Ambiental de l’Institut de Microbiologia de l’Acadèmia de les Ciències de la República Txeca de Praga. S’estudià l’efecte de la interacció del fong amb la població microbiana del sòl durant processos de bioremediació d’HAPs en sòl.! El treball experimental s’ha dut a terme en el “Grup de degradació de contaminants industrials i valorització de residus” del Departament d’Enginyeria Química de la UAB. L’objectiu general de recerca del grup és el desenvolupament de processos biotecnològics per a degradar compostos xenobiòtics difícilment degradables per tractaments convencionals.
Como consecuencia de las actividades humanas, la contaminación debida a productos químicos liberados en el medio se ha convertido en un problema global, siendo una amenaza real para la actividad y la salud de los seres vivos. La contaminación puede afectar a cualquier compartimento del ecosistema. Concretamente, los hidrocarburos derivados del petróleo son contaminantes que afectan de manera particular al suelo, entre los cuales destacan los hidrocarburos policíclicos aromáticos (HPAs). Actualmente existen diversas técnicas para la restauración de emplazamientos contaminados por estos compuestos. Cabe destacar que en los últimos años la comunidad científica ha centrado especialmente los esfuerzos en el campo de la micorremediación (área de conocimiento donde se enmarca la presente tesis) dado que se trata de una técnica ambientalmente respetuosa. El trabajo presenta los resultados de las investigaciones previas al desarrollo de un tratamiento de bioremediación de suelos contaminados por hidrocarburos policíclicos aromáticos mediante el hongo ligninolítico Trametes versicolor. Los resultados de la mencionada investigación se presentan en tres apartados diferenciados. El primero se centra en la producción de biomasa del hongo para posteriores aplicaciones en procesos de bioremediación. Se divide en dos secciones: • La primera se basa en la producción de biomasa en cultivo sumergido. Los experimentos se centraron en formular un medio de cultivo definido de bajo coste que permitiera obtener niveles elevados de biomasa, en la morfología deseada (pellets). El reactor fluidizado por pulsos de aire con control de pH resultó ser el más adecuado. La producción se escaló a un bioreactor de 10 litros. • La segunda sección analiza la colonización del hongo sobre soportes lignocelulósicos provenientes de residuos agrícolas para posterior aplicación en el suelo. La selección de los mejores sustratos para la colonización se basó en el nivel de biomasa (ergosterol), la producción de lacasa y la capacidad de degradar naproxeno en 24 horas. Se demostró que el hongo era capaz de colonizar el suelo tanto en condiciones estériles como no estériles manteniendo, en todo caso, la capacidad degradativa. El segundo apartado se centra en la degradación de hidrocarburos policíclicos aromáticos por el hongo. Se divide en tres secciones: • La primera se basa en la selección de un surfactante para la degradación de HPAs en medio líquido, siendo el surfactante no iónico Tween 80 aquel que dio mejores resultados. Se pudo demostrar la capacidad degradativa de diversos HPAs en medio líquido; tanto en experimentos por separado como en mezclas. Asimismo, también se demostró que en las condiciones de cultivo la enzima lacasa podía degradar algunos de los compuestos. • La segunda sección hace referencia a la identificación de productos intermediarios de degradación de HPAs. También se estudió la capacidad de degradación de estos intermediarios por parte del hongo. • En la tercera sección se probaron diferentes sistemas de degradación en suelos, donde el bioslurry resultó el más efectivo en términos de eficacia de degradación. Se pudo comprobar que en las biopilas aireadas el hongo tuvo problemas derivados del rango termofílico alcanzado. El último apartado se basa en la degradación de los HPAs de la creosota. Se divide en dos secciones: • La primera se centra en la degradación de los HPAs de la fracción aromática de la creosota. Se estudiaron diferentes sistemas y se determinó que el hongo era más eficiente en degradación en las biopilas. En cultivos sumergidos, medio líquido y slurry, el hongo era efectivo en la degradación de HPAs de bajo peso molecular pero no en aquellos de alto peso molecular. Se observó el efecto inhibitorio sobre Trametes versicolor tanto de los compuestos adicionales añadidos junto con la creosota como al aumentar la concentración de HPAs. • La segunda sección es fruto de la colaboración con el Laboratorio de Biotecnología Ambiental del Instituto de Microbiología de la Academia de las Ciencias de la República Checa en Praga. Se estudió el efecto de la interacción del hongo con la población microbiana del suelo durante procesos de bioremediación de HPAs en suelos. El trabajo experimental se ha llevado a cabo en el "Grupo de degradación de contaminantes industriales y valorización de residuos" del Departamento de Ingeniería Química de la UAB. El objetivo general de investigación del grupo es el desarrollo de procesos biotecnológicos para degradar compuestos xenobióticos difícilmente degradables mediante tratamientos convencionales.
As a result of human activities pollution aroused as a global concern due to improper release of chemicals into the environment. Contamination represents a real threat to humans and can affect any ecosystem compartment. Petroleum hydrocarbons affect typically soil, including polycyclic aromatic hydrocarbons (PAHs). Several conventional clean-up techniques are available for site restoration, including bioremediation. Mycoremediation, attained interest in the last decades as it is assumed to be an environmental-friendly technique. This work shows the results of the basic research previous to the development of a polycyclic aromatic hydrocarbons polluted soil bioremediation treatment by means of the white rot fungus Trametes versicolor. The results of the mentioned research are presented in three differentiated sections. The first section focuses on the fungal biomass production for posterior applications in bioremediation processes. It is divided into two subsections: • The first part focuses on biomass production of in submerged cultures. The experiments were aimed at formulating a low-cost defined medium to obtain high amounts of biomass, in the preferred morphology (pellets). The air-pulsed fluidized bioreactors equipped with pH control were the most appropriate. The production was scaled-up to a 10 liters bioreactor. • The second part analyzes the fungal colonization of lignocellulosic supports for further application in soil. The selection of the optimal substrate for colonization based on active biomass amounts, laccase production and the capacity to degrade naproxene in 24 hours. It was demonstrated that the fungus was capable of colonizing soil both under sterile and non-sterile conditions maintaining, in any case, the degradative capacity. The second section focuses on the fungal ability to degrade polycyclic aromatic hydrocarbons. It is ddivided into three subsections: • The first part focuses on the selection of an optimal surfactant for PAHs degradation in liquid medium, obtaining the best results with the non-ionic surfactant Tween 80. The degradation of several PAHs by T. versicolor in liquid medium was demonstrated; both in individual-PAHs experiment as well as in PAHs-mixtures. Likewise, it was also demonstrated that under culture conditions laccase might degrade some of the studied compounds. • The second section includes the identification of PAHs metabolites arising from degradation. The fungal degradation capacity of these intermediates was also examined. • In the third section different degradation systems of were tested for soil treatment, the bioslurry resulted as the most effective in terms of degradation efficiency. It was checked out that in aerated biopiles, the fungus had problems derived from attaining termophilic ranges. The last section deals with the creosote-PAHs degradation. It is divided into two subsections: • The first part focuses on the fungal PAHs-degradation of the creosote aromatic fraction. Different systems were studied and it was determined that the fungus was more efficient at degrading PAHs in biopiles approach. In submerged cultures, liquid medium and slurry, the fungus was effective at degrading low-molecular-weight PAHs but not those of high-molecularweight. It was also observed inhibitory effects on Trametes due to the additional compounds present in creosote as well as when increasing the total PAHs concentration. • The second section is a result of the collaboration with the Laboratory of Environmental Biotechnology in the Institute of Microbiology, which belongs to the Academy of Sciences of the Czech Republic (Prague). The effect on PAHs removal during the interaction between soil microbial population and white-rot fungi during soil bioremediation processes was studied. The experiments have been carried out in the "Group of degradation of industrial pollutants and valuation of waste" from the Department of Chemical Engineering in the UAB. The main research motivation of the group is to develop specific biotechnological processes to degrade xenobiotic compounds that are scarcely degraded by conventional treatments.

The nature and occurrence of mycorrhizal associations, with particular reference to the anatomy, carbohydrate physiology, plant mineral nutrition and occurrence of ectomycorrhizae (ECM), is discussed. The ecology and forest relations of Picea sitchensis - the Sitka spruce concludes the literature review. Identification of areas of good and poor Sitka growth on related soils and the quantification of their ECM status, investigation of the effect of phosphate addition to Sitka seedlings in pots, subsequent and changes to their ECM status, and the effects of soluble aluminium on phosphate nutrition of Sitka seedlings, the collation of results and relation back to the field situation were carried out as experimental work. Field sites were identified and described in terms of geology, soils, field ECM status, forest productivity and nutrient status. Three pot experiments were carried out. The 1st investigated the effects of phosphate application on ECM Sitka seedlings in soil from the field sites; the 2nd investigated the effects of phosphate application to ECM and non-mycorrhizal (NM) seedlings in compost; and the 3rd investigated the affects of application of Al-citrate to ECM and NM seedlings in compost containing high and low levels of phosphate. The results obtained were described and discussed in the context of a model of the factors affecting plant response to the soil environment. The field ECM development representing a considerable drain on the carbohydrate economy of the field sites was to some extent duplicated in the greenhouse. The possible decrease in importance of this drain was illustrated by phosphate application, but was increased by addition of Al-citrate. A previously unrecorded ECM-enhanced uptake of Manganese was reported. The importance of phosphate in the soils under discussion was emphasised, and possible further work suggested.

Thesis (Ph.D.)--University of Western Sydney, 2007.
A thesis submitted to the University of Western Sydney, College of Health and Science, Centre for Plant and Food Science, in fulfilment of the requirements for the degree of Doctor of Philosophy. Includes bibliographical references.

A pesquisa sobre bactérias diazotróficas associadas à cultura do trigo tem demonstrado a necessidade de associar bactérias eficientes a genótipos responsivos ao nitrogênio, os quais mais se beneficiariam dessa associação. Em um experimento com parcelas subdivididas instalado em condições de campo, em Mococa (SP), empregando os tratamentos: 3 doses de N (0, 60 e 120 kg ha -1 ) x 3 genótipos de trigo (IAC-24, ITD-19 e IAC-355), foi avaliada a ocorrência de microrganismos diazotróficos endofíticos em raízes desinfestadas superficialmente, utilizando-se 3 meios de cultivo distintos, NFb, semi-específico para Azospirillum spp, JNFb, semi-específico para Herbaspirillum spp., e LGI-P, semi-específico Gluconacetobacter diazotrophicus. O genótipo IAC-355 apresentou a menor quantidade de bactérias diazotróficas endofíticas. Além disso, para este genótipo, houve um ajuste linear ascendente da quantidade de bactérias diazotróficas com o aumento na quantidade de N adicionada, o que comprova a influência do genótipo da planta na associação com essas bactérias. Nenhuma bactéria pertencente aos gêneros Azospirillum ou Herbaspirillum foi isolada do genótipo IAC-355. Nas condições estudadas, não foi identificado nenhum isolado de Gluconacetobacter diazotrophicus nas raízes do trigo. Foram obtidos 8 isolados do gênero Azospirillum e 12 do gênero Herbaspirillum. Esses isolados foram testados "in vitro", no genótipo do qual foram originalmente isolados. Todos os isolados testados no genótipo ITD-19 causaram maior crescimento radicular que a testemunha e apenas 1 isolado de Herbaspirillum sp. propiciou aumento significativo do teor de N na parte aérea. A colonização micorrízica no genótipo IAC-355 foi maior que nos demais genótipos independente da dose de N, comprovando a influência do genótipo na colonização. A colonização micorrízica se correlacionou com a massa da matéria seca, e com o teor e a quantidade acumulada de P e N na parte aérea, assim como com a produtividade. A atividade da biomassa microbiana foi alterada na ausência de N, obtendo-se correlação entre o qCO2 e a relação Cmic:Corg, indicando que na ausência de N, houve perdas de C no solo cultivado com o genótipo IAC-24, enquanto que na presença do IAC-355, houve maior eficiência na utilização do C do solo pelos microrganismos. Na contagem de bactérias nitrificadoras obteve-se um ajuste linear ascendente em relação à quantidade de N adicionada, provavelmente devido à maior disponibilidade de substrato. A quantidade de microrganismos nitrificadores se correlacionou com a massa da matéria seca, e com o teor e a quantidade acumulada de N na parte aérea, assim como com a produtividade. A interação FMA-bactéria diazotrófica não propiciou benefícios para cultura do trigo. A interação FMA-bactéria diazotrófica demonstrou ser bastante especifica. As plantas associadas a Glomus, quando em presença dos isolados bacterianos apresentaram maior crescimento, acúmulo e aproveitamento dos nutrientes. Confirmou-se que o fungo micorrízico realmente é um agente transmissor de bactérias diazotróficas endofíticas, sendo que Acaullospora causou maior colonização radicular. As plantas dos tratamentos em que somente a bactéria foi inoculada apresentaram o dobro da produção de matéria seca, da quantidade acumulada e do índice de eficiência de utilização de N e P na parte aérea em relação à testemunha. A especificidade da interação planta-bactéria diazotrófica associativa indica que é possível obter benefícios desta associação, explorando bactérias e cultivares locais.
The research on diazotrophic bacteria associated to wheat has demonstrated the need to associate efficient bacteria to N-responsive genotypes, which would be more benefited from this association. A field experiment was carried out in Mococa, state of São Paulo-Brazil, with 3 genotypes of wheat (IAC-24, ITD-19 and IAC-355) under 3 nitrogen doses (0, 60 e 120 kg ha -1 ). The occurrence of diazotrophic bacteria was evaluated in three media, namely, NFb semi-specific for Azospirillum spp., JNFb semi-specific for Herbaspirillum spp., and LGI-P semi-specific for Gluconacetobacter diazotrophicus, using surface-sterilized roots. Regardless the nitrogen dose, the population of diazotrophic bacteria established poorly in the genotype IAC-355, but the infection increased with the addition of nitrogen for the same genotype, proving the influence of the host genotype for its association with these bacteria. Azospirillum spp. or Herbaspirillum spp. could not be isolated from the surface-sterilized roots of IAC-355. In the field experiment G. diazotrophicus was not found in any of the wheat-genotype roots. It was obtained 12 Herbaspirillum spp. isolates and 8 Azospirillum spp isolates. These strains were tested under gnotobiotic conditions, using the genotype from which they had been originally isolated. Inoculated ITD-19 plants showed an increase in root length, even though, only one strain showed a significant increase on shoot N accumulation. In the genotype IAC-355 mycorrhizal colonization was higher, proving the influence of the plant genotype. Mycorrhizal colonization showed significant correlation to shoot dry matter, shoot N and shoot P concentration and accumulation, as well as to the grain yield. In the absence of added N, the activity of microbial biomass was affected. The correlation between the qCO2 and biomass C-to-N ratio, showed that in absence of N, soil-C loss under IAC-24 cultivation, but a greater efficiency in the use of the soil-C by the microorganisms under IAC-355 cultivation. The populations of nitrifying bacteria increased with N addition, probably due to the N-rich substrate availability. The nitrifying bacteria showed significant correlation to shoot dry matter, shoot N concentration and accumulation, as well as to grain yield. There was no benefit from the AMF-diazotrophic bacteria co-inoculation on wheat plants. The specificity of AMF-diazotrophic bacteria interaction was demonstrated, it was confirmed that AMF indeed is a transmitting agent of endophytic diazotrophic bacteria, Acaullospora caused higher endophytic-bacteria root colonization. Plants inoculated with single strain doubled shoot dry matter, shoot N and P concentration and accumulation as compared to the control. Plant-bacteria interaction specificity demonstrates the possibility of getting benefits from this association by exploring both bacterial strains and plant genotypes from the same location.

Effects of fungi and overstory composition on tree seedling survival and growth were investigated in closed canopy upland forests in the coastal plain of South Carolina. Seedlings of Quercus alba, Cornus florida and Pinus taeda were planted in the understory of two forest types -naturally regenerated hardwood and planted pine. Fungal species composition and biomass were experimentally manipulated with a treatment of the fungicide captan. In contrast with other studies conducted in different systems (sand dune, grassland, and old field), the effects of soil fungi were minor in a closed canopy forest. Only Q. alba showed a significant response to the fungicide (p < 0.05) treatment with increased growth. Overstory composition had no significant effect on growth or survival for any of the species. Both of the commercially desirable species (Q. alba and P. taeda) had reasonable survival ( @ 60%). Both also maintained positive, though modest, growth. This suggests that an advance regeneration pool could be established successfully by artificial regeneration.
Master of Science

Thesis (M.S.)--West Virginia University, 2004.
Title from document title page. Document formatted into pages; contains vii, 57 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Fungi are thought to be one of the most diverse groups of organisms in the Arctic. They drive mineral and energy cycles and influence the occurrence of other organisms as mutualists (mycorrhizae, endophytes, lichens), decomposers and pathogens. Nevertheless, information on fungal biodiversity and distribution patterns in relation to environments across the Arctic is still sparse. Molecular methods were used to examine the diversity and community structures of ectomycorrhizal fungi (EMF) associated with two principal arctic host plants, Salix arctica and Dryas integrifolia, as well as total soil fungal communities of adjacent disturbed and undisturbed areas of patterned-ground features across the five bioclimatic subzones (A-E) of the North American Arctic. Key findings include the following: (1) More diverse fungal communities had been observed than previously known. These communities encompass nearly all fungal phyla and included all fungal guilds. However, a few species-rich fungal families dominated these fungal communities. (2) Surprisingly, species richness did not decline with latitude. (3) The most abundant fungal taxa were widely distributed in and beyond the Arctic. Yet root (EMF) and soil fungal communities showed niche preferences in regard to bioclimatic subzones. Furthermore, disturbed and undisturbed patterned ground features harbored different soil fungal communities with the exception of the coldest subzone A. In contrast, EMF community composition was not affected by host plant identity. (4) Fungal communities in the warmest subzone E were distinct from the other arctic subzones and the majority of taxa matched fungi from the boreal forest. (5) Key drivers of fungal community and guild composition along the bioclimatic gradient included regional climate, pH as well as vegetation composition and productivity across the subzones. At the local scale of patterned-ground features, fungal communities were correlated with vegetation composition and microclimate. With a warming climate, I would expect an enhanced colonization of patterned-ground features by vascular plants that would then affect fungal community structure not only at the species level, but also at the level of fungal guilds. In particular I would expect increases in fungi that are symbiotic with plants and a northward shift of both plant and fungal taxa.