Burkea africana Hook. (wild syringa) is an average sized leguminous tree, 10-12 m in
height occasionally reaching over 20m. This monotypic genus is dominant and codominant in Zambia, and is present throughout Africa as far north as Ethopia and west
to Nigeria, and south to South Africa especially Limpopo, North West, Gauteng and
Mpumalanga. It inhabits dry, non–calcareous sandy soils in savanna and woodlands
up to 1500 m altitude or gentle slope of 1080 m elevation. Burkea africana produces
a relatively large number of seeds, which is unusual for a resprouting species. Several
studies conducted on B. africana trees paid more attention to the medicinal attributes,
however little or nothing is known regarding the factors and dynamics that contribute
to the growth and existence of these trees, particularly because these trees grow
naturally in nutrient-poor savanna soils. Although B. africana trees have been in
existence for a very long period of time, propagating it through thinning and
transplanting of seedlings for regeneration and/ or re-establishment of seedlings to
survive until sexual maturity still remains a mystery. It is hypothesized that factors
controlling establishment and development of B. africana trees are related to microbial
activities in the soil, very complex and species specific but poorly understood. This
study aimed to identify, if there is a symbiotic relationship between the soil and
mycorhizal fungi, and rhizobium bacteria or other growth stimulating activities, in the
Burkea soils, which will accelerate and assist effective growth of B. africana trees to
reach reproductive stage and produce pods without dying.
The chemical composition of Burkea soil and non-Burkea soils was analysed using
HCl extraction method.). The results indicated the similar values (p>0.05) were
observed for all micro and macro minerals as well as total nitrogen, pH and organic
matter. However, total ions nitrate and ammonium concentration levels of Burkea soils
were higher (p<0.05) than those found in non-Burkea soils.
The use of advanced metabolomics tool using1H-NMR was used to determine and
identify soil metabolites which may be responsible for successful growth and
establishment of the Burkea africana trees. The findings of this study indicated that
metabolomic analysis showed different metabolites in the respective soils. Growth-promoting metabolites (GPM) such as trehalose and betaine were found to be in
higher concentrations in the Burkea soils. Conversely, acetate, lactate and formate,
were found in higher concentrations in the non-Burkea soils.
Furthermore, LC-MS was used to determine the soil components present in Burkea
soil as compared to non-Burkea soil using. The results indicated that a total of 22
compounds consisted of essential amino acids such as phenylalamine, threonine,
tryptophan, leucine, isoleucine and lysine; conditional essential amino acids such as
arginine, cysteine, glycine, glutamine, proline and tyrosine; non-essential amino acids
such as citruline, alinine, aspartic acids, asparagine, glutamic acid and serine;
nucleobased amino acids such as guanosine, adenine, adenosine, cytindine;
dicarboxylic acid such as fumaric acid as well as common non-proteinogenic amino
acids such as 4-hydroxyproline compounds were found in both Burkea and nonBurkea soils.
The study investigated the microbial communities in the soil where Burkea africana
trees grows successfully (Burkea soils) and how it varies from the soils where they do
not grow (non-Burkea soils). DNA was extracted from the soil and a high throughput
sequence bask local assignment search tool (BLAST) was used to analyze the
microbial diversity (bacterial and fungal) and composition found in both soils, for a
comprehensive understanding of the soil microflora. The results revealed that
Penicillum sp is prevalent in Burkea soils and was the main discriminant between the
two soils. On the contrary, non-cultured fungi, which could not be identified, dominated
the non-Burkea soils. The variances in soil composition suggests that species
supremacy play a role in the growth of B. africana trees.
Lastly, the current study investigated and also identified what attracts caterpillars
known as Cirina forda to invade and feed on B. africana trees. In addition, to
determining if there is a symbiotic relationship between the plant-growth metabolites;
growth-promoting fungi (Penicilium sp) and the caterpillars. The results of the study,
revealed that the fungus Pleurostomophora richardsiae was predominant in the leaves
of B. africana trees as well as in the caterpillars. It is proposed that Pl. richardsiae is a
volatile compound which attracts caterpillars and makes B. africana trees susceptible to caterpillars’ outbreaks. The second largest percentage of fungi found in the
caterpillars was Aspergillus nomius. / School of Agriculture and Life Sciences / Ph. D. (Agriculture)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:unisa/oai:uir.unisa.ac.za:10500/26713 |
| Date | 10 1900 |
| Creators | Nemadodzi, Lufuno Ethel |
| Contributors | Prinsloo, G., Vervoort, J. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 1 online resource (xix, 119 leaves) : color illustrations, color graphs, application/pdf |
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