Mycorrhizal Theses and Dissertations

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1999 * * * * * * * * * * * * * * * * * * * * * * *

Title : Species and speciation in the Hebeloma crustuliniforme complex.
AUTHOR: Aanen, D.K.
DEGREE: PH.D.
YEAR: 1999
INSTITUTION: Wageningen University, Subdepartment Soil Quality. The Netherlands

Title : Optimisation of the mycorrhizal infection of Cedar seedlings (Cedrus atlantica Manetti) under controlled conditions
AUTHOR: BOUKCIM, Hassan
DEGREE: PH.D.
YEAR: 1999
INSTITUTION: Ecole Nationale du Génie Rural des Eaux et des Forêts (ENGREF, Paris) & Institut National de la Recherche Agronomique (INRA, Montpellier), France
PAGES : 224
KEY-WORDS : Cedrus atlantica, Tricholoma tridentinum, Tricholoma cedrorum, Hebeloma, mycorrhization, ergosterol, fungal glucosamine, nitrate, ammonium, phosphorus, root system architecture, predisposition of roots.
Summary : The mycological inventories which were carried out in Cedar plantations of Morocco and the South of France accounted for the diversity and the specificity of the mycological flora of the Cedar plantations. Descriptions of the prospected stations made it possible to initiate a myco-ecological study by the comparison of their fungal macroflora. Isolations of mycelia were carried out from mycorrhizal basidiomata associated with Cedar trees under natural conditions. Some are specifically associated with Cedar (Tricholoma cedrorum, Tricholoma tridentinum var cedretorum, Hebeloma eburneum) contrary to others (Hebeloma sinapizans, Hebeloma hiemale, Amanita rubescens, Tricholoma terreum). The conditions of culture in vitro and the production of efficient inoculum of obtained isolates were optimised, and the capacity of these isolates to mycorrhize Cedar seedlings were demonstrated in controlled conditions, in particular for the first time for Tricholoma cedrorum and Hebeloma eburneum. The mycorrhizae obtained were described morphologically and anatomically. The effectiveness of the two forms of inoculum (" solid " and " alginate ") in the mycorrhization of young Cedar varied according to the fungal species. Satisfactory degrees of mycorrhizal infection were obtained with the isolates most studied. Beneficial effects of the mycorrhization, variables according to the fungal species, were observed on the growth of the seedlings in controlled conditions.

In order to optimise the mycorrhization of the seedlings of Cedar by improving the production of short roots receptive to infection, we studied the effect of the substrate of culture, and the form (nitrate and ammonium) and concentration of nitrogen in the fertilising solution, on the root system architecture of Cedar seedlings in a growth chamber. The result of this study showed that : (i) the use of attapulgite, alone or mixed with other mineral substrates, made it possible to obtain a better growth and ramification of Cedar root system than peat-vermiculite and, (ii) the use of nitrate 5 mM made it possible to improve the production of root growth and the branching density of the tap root compared to nitrate supplied at 0.25 mM or to ammonium. The inoculation of the seedlings by mycelium of Tricholoma cedrorum after the predisposition of the root systems, demonstrated differences in the degrees of mycorrhizal infection according to the nitrogen fertilisation. These differences cannot be explained only by the stimulation of the production of short roots. The hypothesis of anatomical modifications of the root tissues, induced by the various nitrogen solutions, was advanced and discussed. Finally, we studied the effect of phosphorus fertilisation on the mycorhization of young Cedar in an experimental nursery. The results of this study showed that the highest levels of mycorrhization of the seedlings by Tricholoma tridentinum were obtained with a solution containing 1.4 mM P combined with relatively high nitrogen and potassium concentrations, applied between the third and the eighth week after inoculation.

TITLE: BELOW GROUND BIOLOGY OF BOTRYCHIUM PUMICOLA (OPHIOGLOSSACEAE) (ASCOMYCETES, GEMMAE, ROOT FUNGI, OREGON)
AUTHOR: CAMACHO, FRANCISCO JOAQUIN
DEGREE: PH.D.
YEAR: 1999
INSTITUTION: OREGON STATE UNIVERSITY; 0172
ADVISER: Adviser: STELLA COAKELY
SOURCE: DAI, VOL. 60-06B, Page 2450, 00132 Pages
DESCRIPTORS: BIOLOGY, BOTANY; BIOLOGY, ECOLOGY
ABSTRACT: Botrychium pumicola Coville is a rare fern with extant populations in Klamath, Lake and Deschutes counties, of central Oregon. It grows on subalpine pumice ridges and lower montane lodgepole pine forest openings on pumice-rich soils. The goal of this research was to better understand the below ground biology of B. pumicola. Detailed examination of the subterranean structures of B. pumicola revealed sporophytic gemmae attached to the stem. Developing gemmae are a non-photosynthesizing stage in the life cycle of this plant and are presumed to depend on mycorrhzial fungi for their nutrition. Population genetic analysis of B. pumicola using inter-simple sequence repeats (ISSR) suggests that the gemmae do not disperse far from the parent plant. Examination of the endophytic fungal structures in the roots of B. pumicola reveal arbuscular mycorrhziae and a high abundance of septate hyphae. To better characterize the root fungi, the internal transcribed spacer region of fungal ribosomal DNA (ITS) was amplified from root DNA by the polymerase chain reaction (PCR). The ITS amplicon was cloned and sequenced in order to characterize the different fungi in a root segment. Arbuscular mycorrhizal-like sequences were of low abundance in these clone libraries, whereas the dominant fungal group were ascomycetes. The most frequent fungi in these clone libraries are two commonly isolated sterile ascomycetes.

TITLE: COMPARISONS OF NO-TILLAGE AND CONVENTIONAL COTTON (GOSSYPIUM HIRSUTUM L.) WITH EVALUATIONS OF MYCORRHIZAL ASSOCIATIONS
AUTHOR: FLINT, ERNEST HILMON, JR.
DEGREE: PH.D.
YEAR: 1999
INSTITUTION: MISSISSIPPI STATE UNIVERSITY; 0132
ADVISER: Major Professor: GLOVER B. TRIPLETT
SOURCE: DAI, VOL. 60-05B, Page 1924, 00087 Pages
DESCRIPTORS: AGRICULTURE, AGRONOMY; AGRICULTURE, SOIL SCIENCE
ABSTRACT: Increased yield of cotton (Gossypium hirsutum L.) has been observed with no- tillage following winter wheat cover (NT) compared with conventional tillage (CT); however, the reasons for NT benefits remain unclear. The objectives of these studies were to document differences in plant growth between the two tillage systems, and to investigate possible interactions between vesicular-arbuscular mycorrhizal (VAM) fungi and cotton plant performance. Two primary questions were addressed. First, how much benefit is provided cotton by the NT system as compared with CT? Second, do VAM fungi contribute to increased yield of cotton?

Growth and maturity of cotton were influenced by tillage. Cotton plants were 25 percent taller and had developed 12 percent more nodes in NT soil than in CT soil by the final measurement date of July 6, 1996. Although there was no direct proof that VAM contributed to the improvements in growth and maturation, observations were consistent with such a role. First, there was greater growth in NT soil as could be promoted by a vast hyphal network, while other soil differences between NT and CT could have been involved. Plants in NT soil had significantly more colonizaiton sites per centimeter of root than in CT soil. Nylon mesh surrounding roots in both tillage systems contained greater numbers and length of VAM hyphae in NT soil than in CT soil.

Cotton plants which emerge in NT soil and were transferred in soil cores to CT soil grew no better than those emerging in CT soil, and plants which emerged in CT soil and were transferred to NT soil grew as well as plants which emerged in NT soil. Plants in NT soil under field conditions continued rapid growth during an extended dry period while growth of plants in CT soil was significantly decreased even though NT plants were larger and had grater stomatal conductivity and transpiration rates. More 32P and was absorbed from NT soil from which roots were excluded, indicating hyphal absorption. Cotton plants also absorbed more 15N from NT soil than from CT soil.

TITLE: EFFECTS OF INTERACTIONS BETWEEN ARBUSCULAR MYCORRHIZAL FUNGI AND RHIZOBIUM LEGUMINOSARUM ON PEA AND LENTIL (TRIPARTITE SYMBIOSIS, LEGUMES, PISUM SATIVUM, LENS ESCULENTA)
AUTHOR: JOHNNY, LISET LIZZY
DEGREE: PH.D.
YEAR: 1999
INSTITUTION: THE UNIVERSITY OF SASKATCHEWAN (CANADA); 0780
ADVISER: Adviser: J. J. GERMIDA
SOURCE: DAI, VOL. 60-07B, Page 3027, 00263 Pages
DESCRIPTORS: AGRICULTURE, AGRONOMY; AGRICULTURE, PLANT CULTURE; BIOLOGY, MICROBIOLOGY
ISBN: 0-612-37892-6
ABSTRACT: Legumes form tripartite symbioses with arbuscular mycorrhizal fungi (AMF) and rhizobia which influence plant productivity. This study assessed factors that influence the tripartite symbioses between AMF, Rhizobium leguminosarum bv. viceae and pea (Pisum sativum L.) or lentil (Lens esculenta L.), in order to determine if specific combinations of AMF and rhizobia enhanced plant productivity. A survey of soil and plant samples from 12 field sites in Saskatchewan indicated that AMF activity (i.e., number of spores and root colonization) was higher under lentil (n = 7) than pea (n = 5) crops. The efficacy of commercial rhizobia inoculants, reference strains and isolates obtained from root nodules of field-grown pea and lentil was assessed under gnotobiotic conditions. Some strains significantly increased the shoot dry weight and shoot N content of plants, whereas other strains varied in their effectiveness. Effective and ineffective rhizobia strains were selected for co-inoculation studies with AMF in a growth chamber. Results suggest that specific AMF+rhizobia combinations enhanced plant growth and yield. Furthermore, effective AMF can enhance the performance of inferior rhizobia and vice versa.

A subsequent study determined the influence of soil-P levels on the tripartite symbiosis. Application of P fertilizer did not alter pea response to either AMF+rhizobia combination, but significantly increased the yield and nutrition of co-inoculated lentil plants. Furthermore, inoculation of pea or lentil with rhizobia or rhizobia+AMF combinations yielded growth equivalent to or better than 20 ppm. of P fertilizer. Selected spore wall bacteria (SWB) isolated from ANF spores stimulated or inhibited the germination of NT4 spores in vitro. The stimulatory SWB enhanced growth and ANF root colonization of NT4-inoculated pea plants, whereas the inhibitory SWB had no effect. However, in the presence of the rhizobia strain LX43, this trend was reversed. My research showed that interactions between AMF, rhizobia and the legume host were specific, and that microsymbiont efficacy, soil-P level, and SWB can alter the outcome of the tripartite symbioses. Therefore, it is important to assess the effect of AMF-rhizobia-legume interactions in the development of commercial inoculants for enhancing legume productivity. (Abstract shortened by UMI.)

TINA JONSSON: Ectomycorrhizal Root Communities in Spruce Forests, studied in Relation to N-deposition and Liming. Licentiate thesis, Microbial Ecology, Lund University, Sweden.

TITLE: CHANGES OF THE NATIVE MYCORRHIZAL POPULATION IN A COLOMBIAN OXISOL AND ITS IMPACT ON LAND PRODUCTIVITY (ZEA MAYS, PHYTOLACCA RIVINOIDES)
AUTHOR: PENA-VENEGAS, CLARA PATRICIA
DEGREE: M.S.
YEAR: 1999
INSTITUTION: STATE UNIVERSITY OF NEW YORK COL. OF ENVIRONMENTAL SCIENCE & FORESTRY; 0213
ADVISER: Major Professor: JAMES J. WORRALL
SOURCE: MAI, VOL. 37-05, Page 1390, 00103 Pages
DESCRIPTORS: AGRICULTURE, SOIL SCIENCE; AGRICULTURE, AGRONOMY; BIOLOGY, ECOLOGY
ABSTRACT: After native forests are cleared, good crop productivity is possible for a limited period of time, leading to further deforestation. Mature and regenerating forests were compared in terms of soil composition, arbuscular mycorrhiza (AM) composition, and productivity, in order to determine the role of AM in soil productivity. Forests studied were similar in soil composition but regenerating forests contained more AM propagules and native root infection.

Productivity was estimated as field growth of maize (Zea mays), a mycorrhiza-dependent species, and Phytolacca (Phytolacca rivinoides), a mycorrhiza-independent species. Also, soil from each plot was pasteurized, half of the sample was inoculated with the native AM population, and soils were planted with maize and Phytolacca under greenhouse conditions. In field plots, maize from regenerating forests showed significantly higher root infection than that from mature forests. Results from greenhouse conditions suggest that maize in mature forest soils have greater need of mycorrhizas than in regenerating forest soils. Phytolacca had neither root infection nor significant differences in growth.

A dynamic AM population model is proposed in which clear- cutting of natural vegetation decreases their number and natural regeneration of cut areas increases them until the forest matures and AM populations drop to a stable level.

TITLE: Root activity in Scots pine dominated stands assessed by isotopic methods.
AUTHOR: Plamboeck AH
SOURCE: Acta Universitatis Agriculturae Sueciae Silvestria. 1999, No. 112, 57 pp.;
LANGUAGE: English
ABSTRACT: This thesis summarizes the results of 4 studies in Scots pine (Pinus sylvestris) stands in Sweden. The 4 papers describing these 4 studies are included at the end of this publication; all are by Plamboeck in association with other authors, and 2 are already published, and 2 are presented as manuscripts. In the first 2 studies, the dynamic adaptation of water and nutrient uptake in Scots pine was assessed by isotopic methods in an irrigation and desiccation experiment. The unsaturated hydraulic conductivity of the mineral soil explained 76% of the water uptake distribution from the soil profile. Water and cations (134Cs and 22Na) were taken up in higher amounts from the upper soil layers on the irrigated plots than on desiccated plots. No correlation was found between the fine root distribution and uptake in either treatment. In the third study, natural variations in stable carbon isotope ratios were used to study root C turnover in a boreal mixed forest. Carbon used for root growth seemed to originate from photosynthesis in the previous year. The overstorey Scots pine had the highest root_delta13C. The other abundant conifer, Norway spruce (Picea abies), displayed wide temporal variation in delta13C, while the understorey birch (Betula pendula) had consistently and clearly lower delta13C than the pine. No differences in the delta13C of roots with depth were found for any of the species. The fourth study, natural variations in stable carbon isotope ratios were used to study the trophic status of fungi and host_origin carbon in mycorrhizal fungi in mixed forests. Mycorrhizal fungi specific to overstorey and understorey tree species displayed the same differences in delta13C as did the roots and foliage of the host trees. The many promiscuous mycorrhizal fungi, associated with and connecting several tree hosts, were calculated to receive 57_100% of their carbon from overstorey trees. Thus overstorey trees also support, partly or wholly, the nutrient absorbing mycelia of their understorey competitors. The prospects for survival and maintenance of understorey species may increase because of this C support from overstorey trees.
DE: cations_; desiccation_; boreal_forests; irrigated_stands; mixed_forests; mycorrhizal_fungi; nutrient_uptake; plant_nutrition; photosynthesis_; temporal_variation; understorey_; water_uptake; plant_water_relations; roots_; hydraulic_conductivity; soil_water; spatial_distribution; root _systems; nutrition_physiology; plant_physiology; mycorrhizas_

TITLE: VARIACION EN EL PORCENTAJE DE COLONIZACION DE MICORRIZAS ARBUSCULARES ASOCIADAS A CAPPARIS CYNOPHALLOPHORA L. Y TABEBUIA HETEROPHYLLA (DC.) BRITTON EN LA VEREDA CUEVA DEL BOSQUE ESTATAL DE GUANICA, PUERTO RICO
AUTHOR: ROBLES-TORRES, ROXANNE
DEGREE: M.S.
YEAR: 1999
INSTITUTION: UNIVERSITY OF PUERTO RICO, MAYAGUEZ (PUERTO RICO); 0553
ADVISER: Director: FLAVIO PADOVANI
SOURCE: MAI, VOL. 37-06, Page 1773, 00046 Pages
DESCRIPTORS: BIOLOGY, MICROBIOLOGY; BIOLOGY, ECOLOGY; AGRICULTURE, FORESTRY AND WILDLIFE
ABSTRACT: Mycorrhizas are mutualistic associations between certain fungi and the roots of vascular plants. They are classified in two general types: ectomycorrhizas and endomycorrhizas. The arbuscular mycorrhizas are the most studied endomycorrhiza type because of their wide distribution. The present work is the first study of arbuscular mycorrhizas at Cueva Trail of the coastal habitat of the Guamica Dry Forest, Puerto Rico. The objectives of this work were to: determine if arbuscular mycorrhizas are present in the native plants Capparis cynophallophora L. and Tabebuia heterophylla (DC.) Britton; determine if there are variations in the percentage of colonization between a cleared area and an undisturbed area; establish if the variation in percentage of colonization observed is influenced by abiotic factors such as soil temperature, pH and humidity. Sampling was performed from March 1998 to January 1999. Roots were cleared and stained according to Kormanik et al. with changes in the established times. Percentage of colonization was determined using the protocol by Ambler and Young. It was observed that C. cynophallophora and T. heterophylla associate to arbuscular mycorrhizas. There was no significant difference in the percentage of colonization between the species. However, the percentage of colonization differed significantly between the cleared and the undisturbed areas, being noticeably higher in the cleared area. The percentage of colonization diminished as the soil temperature got higher, and it increased as the soil humidity rose. The effect of pH on percentage of colonization was not significant. The results show that percentage of colonization exhibits a seasonal pattern.