Mycorrhizal Theses and Dissertations

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2006 * * * * * * * * * * * * * * * * * * * * * * *

Title: 
The role of arbuscular mycorrhizal fungi in pasture colonization by the tropical forest tree species Terminalia amazonia
Authors: 
Aldrich-Wolfe, Laura
Keywords:  T-RFLP; forest regeneration; Coto Brus; arbuscular mycorrhiza; Urochloa; Terminalia; Glomus; seedling establishment
Issue Date: 
29-Aug-2005
Abstract: 
At three sites in Siete Colinas, Coto Brus, Costa Rica, I examined differences in composition of arbuscular mycorrhizal (AM) fungi between forest fragments and pastures, and consequences of these differences for seedling establishment in pastures by the tropical forest tree Terminalia amazonia. I estimated species composition of AM fungi through spore counts from field soils and greenhouse cultures. The AM fungal community differed between forest and pasture. While some AM fungi were common in both habitats, others were abundant in one and rare or absent in the other. To assess the importance of the change in community composition for pasture colonization by T. amazonia, I planted seedlings inoculated with either forest or pasture soil in forest and pasture, and compared survivorship, growth, and root colonization by AM fungi. Seedlings inoculated with forest soil experienced lower mortality, and greater initial growth rates and colonization by AM fungi, than seedlings inoculated ...
URL: 
http://hdl.handle.net/1813/2179
Appears in Collections:
Theses and Dissertations (CLOSED)
Cornell University

Author: Rachid BOUAMRI
Title: Diversity and seasonal variation of arbuscular mycorrhizal fungi associated with Phoenix dactylifera L. in Tafilalet Date palm grove
Degree: Ph. D.
Language: French
Year: 2006
Institute: Moulay Ismaïl University, Morocco.
Supervisor:
- Prof. M.N. SERRHINI, Ecole Nationale d'Agriculture de Meknes, Morocco
- Prof. A BENNANI, Moulay Ismaïl University, Morocco
Email: bouamrir@yahoo.fr
ABSTRACT
A survey of arbuscular mycorrhizal fungi (AMF) diversity in date palm rhizosphere was undertaken in ten palm groves located along the Ziz valley (Tafilalet, south-west Morocco). Four parameters retained were the root colonization intensity, the root colonization frequency, the spore density and specific richness. The mean frequency and the mean intensity of root colonization reached 72 and 43% respectively. There was no significant difference in the frequency of root colonisation by AM fungi between season but the significant difference in root colonization were observed between seasons; maximum root colonization levels occurred during winter and Spring and minimum levels in summer (July). The AMF colonization levels of field date palm ! roots were found to be negatively correlated with soil phosphorus content (r2 = -0, 64). The spore density varied from 238 to 1840 spores/10g of soil. The significant difference in spore density was observed between season. Higher spore density were found during Spring and summer and decreased during autumn and winter.
      Fifteen AMF species belonging to three genera were detected in the 10 studied sites from field and/or trap cultures. Detected species were Glomus mosseae, Glomus constrictum, Glomus fasciculatum, Glomus intraradices, Glomus etunicatum! , Glomus macrocarpum, Glomus aggregatum, Glomus sp1, Glomus sp2, Scutellospora gregaria, Scutellospora sp1 Scutellospora sp2, Acaulospora sp1, Acaulospora sp2, and Acaulospora sp3. The number of sporulating species was significantly higher in April with 15 species detected and attained its minimum during winter with only 7 detected species. Species richness at each of the individual sampling sites ranged from 4 to 10 fungal species. The effectiveness of two native AM fungi (Glomus mosseae and Glomus sp) isolated from the rhizosphere of Phoenix dactylifera were used as inoculants for co! rn (Zea mays) and sorghum (Sorghum vulgare).Two AM isolates from International culture collection of (Vesicular) arbuscular mycorrhizal, namely G. intraradices and G. mosseae, were also used as reference inocula. The native G. mosseae and the reference Glomus mosseae were the most effective improving growth and shoot phosphorus concentration of corn and sorghum plants among the other isolates tested. The shoot biomass in mycorrhizal plants of sorghum increased by 203% compared with those of the non mycorrhizal plants. Whereas, in mycorrhizal plant of corn, the shoot biomass increased by 163% and 278% respectively compared with those of the non mycorrhizal plants. The native Glomus mosseae was more effective at taking up phosphorus from soil. The phosphorus content improvement was 120% and 157% respectively in corn and sorghum plants. However, the native Glomus sp was less effective than other isolate at enhancing growth and taking up phosphorus from soil.
Mots clés : diversity, Seasonal variation, arbuscular mycorrhizal, Phoenix dactylifera, Tafilalet, Morocco,
RESUME
Une étude de la diversité des champignons mycorhiziens à arbuscules dans la rhizosphère du palmier dattier a été menée dans dix sites le long de la vallée de Ziz (palmeraie de Tafilalet, Sud-Est du Maroc). Les paramètres considérés sont la colonisation des racines du palmier dattier, la densité des spores et la richesse spécifique. Les fréquences et les intensités moyennes de colonisation sont de 72% et 43%, respectivement. Les fréquences de colonisation ne montrent pas de différences significatives entre les saisons, quant aux intensités de mycorhization, les différences sont significatives. Les valeurs les plus importantes ont été enregistrées dans les prélèvements effectués durant les saisons d'hiver et de printe! mps. L'intensité moyenne de mycorhization est corrélée négativement avec la teneur en phosphore assimilable dans le sol (r2 = - 0,64). La densité des spores varie entre 238 et 1.840 spores/ 100 g de sol, selon les sites. Elle varie significativement selon les saisons. Une densité moyenne de 800 spores/100g de sol a été enregistrés en printemps et en été contre 400 spores / 100g de sol en automne et en hiver. Quinze espèces de champignons mycorhiziens à arbuscules ont été répertoriées dans l'ensemble des sites étudiés : Glomus mosseae, G. fasciculatum, G. constrictum, G. aggregatum, G. macrocarpum, G. etunicatum, G. intraradices, Glomus sp1, Glomus sp2, Acaulospora sp1, Acaulospora sp2, Acaulospora sp3, Scutellospora gregaria, Scutellospora sp1 et Scutellospora sp2. Leur fréquence d'apparition ainsi que leur taux de sporulation varient en fonction des sites et des saisons. Les quinze espèces ont été détectées dans les prélèvements effectués au printemps. Seuls sept parmi elles ont pu être isolées à partir des prélèvements effectués en hiver. La richesse spécifique varie de 4 à 10 espèces selon les sites.
      Deux souches parmi les 15 isolées (Glomus mosseae et Glomus sp.) ainsi que deux autres de référence, fournies par l'INVAM (Glomus mosseae et Glomus intraradices) ont été considérées dans un essai d'évaluation de l'efficience de ces souches sur deux plantes mycotrophes (Zea mays et Sorghum vulgare). Les deux souches Glomus mosseae autochtone et celle de référence ont assuré les meilleurs taux de croissance et teneurs en phosphore les plus élevées chez les plants mycorhizés. En effet, chez le sorgho, l'amélioration de la biomasse sèche dépasse 203% pour les deux souches. Chez le maïs, cette amélioration est d'environ 163% pour la souche locale et de 278% pour la souche de référence. Les gains en phosphore assimilable les plus importants ont été enregistrés chez les plants mycorhizés par la souche locale ; il est de 120% chez le maïs et dépasse les 15! 7% chez le sorgho. Quant à la seconde souche locale, Glomus sp, elle a montré des effets moindres par rapport aux premières souches aussi bien sur la croissance que sur la nutrition phosphatée des deux plantes hôtes testées.
Mots clés : diversité, variation saisonnière, champignons mycorhiziens à arbuscules, Phoenix dactylifera, Tafilalet, Maroc

Title: Alternative tomato farming system practices and their influence on the persistence and infectivity of Arbuscular Mycorrhizal fungi and other fungal root endophytes.
Author: Rasmann, Christopher
Email: chris.rasmann@ars.usda.gov
Language: English
Year: 2006
Department: University of Florida, Department of Plant Pathology
Supervisor: Adviser: Graham, James H.   Co-adviser: Chellemi, Daniel O
Abstract: Farming practices are known to significantly impact arbuscular mycorrhizal (AM) fungi, as well as other soil microbial communities in agroecosystems. The effects of highly divergent land management strategies on the incidence and infectivity of AM fungi and other fungal endophytes were evaluated in a 5-year cropping systems study at the USDA ARS Header Canal farm site in Ft. Pierce, FL. Two treatments, the conventional and disk fallow systems, represented farming practices considered to be detrimental to AM fungal populations. The remaining three treatments, the organic, bahia pasture and weed fallow systems, used practices thought to be more conducive to the presence of AM fungi. In December of year four and five of the study, tomato rhizosphere soil and fibrous roots of tomato were collected. Roots were cleared, stained and examined for colonization by AM fungi and other fungal endophytes. Rhizosphere soil was assayed for infection potential of AM and other root endophytic fungi based on maize seedling colonization at the five-leaf stage. Tomato roots and rhizosphere soil from year five were also analyzed for AM fungal biomass using a fatty acid biomarker 16:1ω5c. Sudangrass trap cultures were set up to determine abundance and diversity of AM fungal spore morphotypes. Of all investigated agricultural practices, phosphorus (P) fertilization and soil disturbance had the greatest influences on AM fungal infectivity and abundance. All plots had very high levels of available soil P, which resulted in low levels of colonization across treatments. The bahia pasture system was the only treatment without regular extensive soil mixing, and these plots had the highest level of field root colonization by AM fungi. Field roots were more heavily colonized by fungal endophytes other than AM fungi in all treatments; tomato plants from organic plots, though, were unique in encouraging colonization by Microdochium bolleyi.
Populations of root-associated AM fungi and other fungal root endophytes were positively correlated in all studies. Hurricane-associated flooding and a shortened growing season played a role in reducing the infection potential in all treatments except for the organic plots in year five compared to year four. The levels of primary inoculum were maintained in organic plots, apparently through improved soil quality which resulted in decreased resistance to root development. Areas under active disturbance in disk fallow plots had the lowest levels of primary inoculum, but recovery to levels comparable to less disturbed treatments occurred after a single season of host root growth. Diversity of AM fungal morphotypes was typical of agricultural fields, with at least 11 species present across treatments. Glomus spp. were the dominant spore type recovered in all treatments.
Url: Full text: http://purl.fcla.edu/fcla/etd/UFE0017800

Author: Anna CARAFA
Title: A morphological and molecular analysis of endophytic associations of liverworts with glomeromycotean fungi
Degree: Ph. D.
Language: Italian
Year: 2006
Institute: Seconda Università degli Studi di Napoli, Italy.
Supervisor: - Prof. R. Ligrone, Dipartimento di Scienze ambientali, SUN, Caserta, Italy
Email: anna.carafa@unina2.it
ABSTRACT:
Light and electron microscopy of a wide range of liverwort taxa has shown that endophytic associations with aseptate fungi are widespread in Marchantiopsida and Metzgeriidae and, with the noteworthy exceptions of the early divergent taxa Treubia and Haplomitrium (Carafa et al. 2003; Duckett et al. 2006), exhibit much the same morphology and developmental pattern. The fungus penetrates the thallus through the rhizoids and colonizes the internal parenchyma, forming intracellular coils and arbuscules. The infection is entirely intracellular, with fungal hyphae crossing directly through the cell walls. The cytology of fungal colonization is basically the same as in arbuscular mycorrhizas (AM) in higher plants (Bonfante-Fasolo 1984) and reflects a high level of compatibility between the host plant and fungus. Large thick-walled fungal swellings are common in mature parts of the thallus. As reported for the vesicles in AMs, these structures accumulate abundant lipid and probably function as storing and/or perennating organs (Bonfante-Fasolo 1984). Fungal infection in Haplomitrium is restricted to chlorophyll-less subterranean axes and the fungus is mostly confined to the epidermal cells, that are penetrated directly by external hyphae. In Treubia the fungus penetrates the photosynthetic thallus through clefts between epidermal cells and forms an intra- and intercellular infection that is far more highly differentiated than any of the fungal associations described to date in liverworts (Duckett et al. 2006). Besides intracellular arbuscules and/or coils, the fungus in Treubia and Haplomitrium forms prominent thin-walled swellings that, unlike the vesicles in other liverworts and in AMs, rapidly degenerate and collapse. Fungal colonization in Marchantia induces the loss of autofluorescence in host cell walls. Immunogold labelling with monoclonal antibodies has shown that fungal penetration is not associated with callose deposition and that the interfacial material ensheathing the intracellular hyphae contains the same epitopes present in the host cell walls. Moreover, in Marchantia and Conocephalum fungal penetration induces the deposition of a new wall layer that is heavily labelled by CCRCM1, whilst very little labelling was observed in uninfected cells with this antibody. Phylogenetic analyses based on the sequences of fungal 18 S rDNA from five liverwort taxa showed that in all cases the fungal endophytes were members of the Glomeromycota (i.e. the same fungal group that forms AMs in higher plants) and fell into the Glomus group A (Schübler et al. 2001) except for Monoclea, whose endophyte was related to Acaulospora. The results provide experimental support to the hypothesis that the association with glomeromycotean fungi is a primitive condition (plesiomorphy) of liverworts (Kottke & Nebel 2005). Taking account of the Glomeromycota as the most ancient lineage of mycorrhizal fungi (Schübler et al. 2001) and liverworts as basal in land plant phylogenies (Shaw & Renzaglia 2004), it appears likely that liverwort associations with glomeromycotean fungi are the most primitive plant/fungus symbiosis described to date.

Author: Dr. Anurag Yadav
Title: Studies on artificial co-inoculation of oak seedlings with some ectomycorrhizal fungi and mycorrhizosphere bacteria
Degree: Ph. D.
Language: English
Year: 2003
Institute:Department of Microbiology, Gurukula Kangri University, Haridwar (U.A.)-249404, India.
Supervisor: Dr. R.C. Dubey
Email: anuragyadav@rediffmail.com