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Genetic structure of Albizia gummifera and its local adaptation to the associated arbuscular mycorrhiza

Nantongo, Judith. 2008 Genetic structure of Albizia gummifera and its local adaptation to the associated arbuscular mycorrhiza. Makerere University, Department of Forest Biology & Ecosystems Management, Masters Thesis, 61pp.

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Abstract/Summary

The aim of this study was to assess genetic structure and local adaptation of Albizia gummifera to associated mycorrhiza using three populations from Uganda, Kenya and Madagascar. Using variation in chloroplast DNA sequences, estimates of genetic diversity and differentiation were obtained. Local adaptation of A. gummifera to the associated mycorrhiza was investigated by planting seed from different A. gummifera provenances into soils inoculated with soil microbial samples from respective local sites. In addition, the stability of inoculum was tested by comparing the performance of fresh and stored soils as inoculum. Four weeks after seedling emergence, height measurements were initiated and continued for six weeks. Mycorrhizas in the soil inoculum were identified using direct microscopic observation. Genetic data were analysed using GENALEX while greenhouse data were analysed using GENSTAT. The results showed that the species is genetically diverse with 14 cpDNA haplotypes identified (hTOT = 0.803), with Uganda showing most diversity (h =0813) and Kenya the least (h =0.398). Although the majority of variation was distributed within populations (75%), significant population differentiation was observed (ΦPT = 0.249, p > 0.01) and each population contained private haplotypes: Uganda (5), Madagascar (3) and Kenya (1). Greatest genetic distance was observed between Kenya and Madagascar (2.711). The lowest distance was observed between Uganda and Kenya (0.298). The diversity of the mycorrhizal community varied between sites with Ugandan fresh soils being more diverse than Kenyan fresh soils. For the old soils, fungal diversity was highest in Kenya, followed by Madagascar and then Uganda. Based on the growth performance measurements, there was no evidence of adaptation of A. gummifera provenances to local mycorrhizas though plant performance for inoculated plants was higher than that of the control. From the study, it appears that the specific kind of fungi the A. gummifera plants are exposed to is not important, although they benefit from the exposure. The tree populations seem to have genetically differentiated and transferring them to sites outside their own may pose a genetic threat. More research is however needed to ascertain adaptive differences of A. gummifera to abiotic and other biotic factors, the suitable founding genetic diversity and other factors that may affect introductions. The exact mycorrhizas that colonise the plants also need to be identified.

Item Type: Publication - Thesis (Masters)
Programmes: CEH Programmes pre-2009 publications > Biodiversity > BD01 Conservation and Restoration of Biodiversity
CEH Sections: Watt
Additional Keywords: Albizia, molecular, mycorrhiza, chloroplast
NORA Subject Terms: Agriculture and Soil Science
Biology and Microbiology
Ecology and Environment
Date made live: 16 Jul 2008 10:52
URI: http://nora.nerc.ac.uk/id/eprint/3096

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