Arbuscular mycorrhizal fungi as a bio-indicator of soil health under agricultural management practices in South Africa
- Authors: Sekgota, Wendy Maphefo
- Date: 2019
- Subjects: Soils -- Quality -- South Africa , Soil fertility -- South Africa , Fungi in agriculture -- South Africa , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Fungi -- Spores , Soils -- Agricultural chemical content
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/72161 , vital:30011
- Description: This study investigated the activity of arbuscular mycorrhizal (AM) fungi as a potential biological indicator of soil health under conventional and conservation agricultural management in South Africa. An experimental trial consisting of three replicates plots under conventional and reduced tillage subdivided into twelve treatments of six crops and two fertilizer inputs was assessed over four growing seasons for various AM fungal parameters such as spore density, most probable number (MPN) of propagules percentage root colonisation and easily extractable glomalin (EEG). Cropping combinations were maize monoculture; maize soybean rotation; maize cowpea rotation; maize cowpea intercropping; maize oats intercropping and maize vetch intercropping. Resident AM fungal spore numbers and EEG protein levels were very low and no root colonization was recorded in the first two growing seasons. These findings prompted the need for the inoculation of the study site in the third growing season with a commercial AM fungal product (MycorootTM). Spore numbers, EEG concentrations and percentage root colonisation increased 8 weeks after inoculation but were significantly reduced in the fourth growing season that was not inoculated. MPN infectivity increased with inoculation particularly under conventional tillage and maize monoculture. Resident spore taxa were morphologically identified into three genera Gigaspora, Scutellospora, and Glomus. For the first two growing seasons, the maize roots were heavily colonized by a pathogenic fungus after mycorrhizal inoculation no evidence of pathogenic fungi was observed. In the fourth growing season which did not receive inoculation, root colonization started to decline. Reduced tillage, high fertilizer input combined with maize cowpea rotation (MC) and maize hairy vetch intercropping (Mv) had a significant effect (P = 0.01) on AM fungal spore numbers. Cropping systems and high fertilizer input had a significant effect on EEG concentrations in the second growing season. Overall, fertilizer application and crop type had implications for mycorrhizal activity. The soil health status in this study site was deemed low as measured by the impaired mycorrhizal activity due to agricultural management practices. Field inoculation combined with classical and molecular tools could provide a more realistic assessment of the effect of agricultural management practices on AM fungi as potential bioindicators of soil health. Therefore, AM fungi could be used as bioindicators of soil health under agricultural management practices in South African soil conditions.
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Biological properties and interactions of Kalaharituber pfeilii
- Authors: Krele, Viwe
- Date: 2019
- Subjects: Kalaharituber pfeilii , Pezizales -- South Africa , Desert plants -- South Africa , Truffle culture -- South Africa , Plant biochemical genetics , Enzymes -- Analysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/72257 , vital:30022
- Description: Dessert truffles are seasonal macro fungi and have been identified in several parts of the world including South Africa. The first part of the present study dealt with the assessment of the biologically active compounds of the Kalahari truffles found in the Northern Cape of South Africa. Truffles extracts (methanol, ethanol, aqueous) were investigated for their antimicrobial properties towards Gram-positive and Gram-negative bacteria. The results demonstrated that the truffle extracts tested had no inhibitory effects against the bacterial isolates. The truffle mycelial growth was also noted to be ineffective against the selected bacteria. The bacteria tested in the present study showed some antagonistic effects against the fungus. Cultures of K. pfeilii were also screened for enzyme production including amylase, protease, cellulose, and laccase. Evaluation of the potential of K. pfeilii mycelia to produce these industrially and economically important enzymes demonstrated both amylase and protease activity. However, for laccase and cellulose, no activity was detected. The second part of the present study aimed at optimizing biomass production by K. pfeilii in liquid culture media. FF Microplate containing 95 discreet carbon sources were employed to test for substrate utilization. Blanked readings above 0.1 were regarded as positive for utilization, and 4 substrates were selected as potential substrates and were included in liquid media. Media was evaluated for mycelial biomass production. Of the carbon sources tested sucrose proved to be the most suitable for supporting mycelial growth. The third part of the current study included investigating the diversity of microbial communities colonizing the rhizosheath of Stipagrostis ciliata var. capensis (the host plant of K. pfeilii) and these were identified by means of next-generation sequencing using Illumina Miseq. Bioinformatics tools were utilized in analyzing the data. Actinobacteria were found to be the most dominant bacterial phylum, followed by unclassified bacteria, Proteobacteria, and Acidobacteria. The top 25 sequences were selected and clustered into bacterial OTUs (at 97% threshold) which were assigned into 1 phylum (Actinobacteria), 1 family (Geodermatophilaceae) and 23 genera. This phylum is well known for its secondary metabolites. Streptomyces sp. was the most frequently encountered genus. The results from this study necessitate further investigations with regards to the function and evolution of fungal-bacterial associations. Wheather these bacteria have a contribution towards the truffle development, it is still not confirmed.
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