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Accueil du site → Doctorat → Afrique du Sud → 2004 → The taxonomy and ecology of arbuscular mycorrhizal fungi (AMF) in agroforestry systems in Malawi

University of Pretoria (2004)

The taxonomy and ecology of arbuscular mycorrhizal fungi (AMF) in agroforestry systems in Malawi

Jefwa, Joyce Mnyazi,

Titre  : The taxonomy and ecology of arbuscular mycorrhizal fungi (AMF) in agroforestry systems in Malawi

Auteur  : Jefwa, Joyce Mnyazi,

Université de soutenance : University of Pretoria

Grade : Doctor of Philosophy PhD 2004

Description
The study was conducted in drought-prone, southern Malawi with the aim of understanding the dynamics of Arbuscular Mycorrhizal Fungi (AMF) (Glomeromycota C. Walker & Schuessler) populations in agroforestry systems. AMF species were determined using spore morphological characters. Gliricidia sepium (Jacq.) Walp and Zea mays L. intercrops were compared to maize monocrop systems to determine the variations in the diversity of AMF species and their frequency of occurrence. Similar experiments using Sesbania sesban (L) Merr. and Sesbania macrantha E Phillips & Hutch were used to establish differences across tree genera, and whether these effects would be modified by seasonal changes and the application of inorganic nitrogen and phosphorus fertilizers. Three AMF species from the research site species were evaluated for effectiveness on growth of maize, sesbania and gliricidia species. Species relative diversity indices were computed using the Shannon-Weinner method and the data was subjected to ANOVA. The species frequency of occurrence data was analysed using logistic regression. The greenhouse bioassay results were subjected to ANOVA followed by comparisons of means by Least Square Means (LSM). Five AMF species have been recorded from other parts of Africa and two were recorded for the first time in Africa. Five species were not diagnosed to species level as four had morphological features that overlapped with closely related species and one had insufficient materials. The mature stages of some species displayed similar morphological features over wide biogeographical regions. The effects of agroforestry systems were site-specific and highly dependent on the tree genera and fertility regimes. AMF species diversity responded most to the manipulation of nitrogen, which was the most deficient soil nutrient. The spores of AMF species from the site differed in their adaptations and no trend was observed in species occurrence by members of the same family or genera. Agroforestry systems influence AMF diversity with the effects varying across genera of tree and AMF species. AMF also responds to manipulation of the most deficient soil nutrient. The root morphology is among the plant characters that determine host response to AMF association. These results have great implications management of AMF symbiosis and inoculation programs.

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