Alternative approach to controlling citrus black spot disease
- Authors: Thabede, Jahman Thabo
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/178569 , vital:42951
- Description: Access restricted until April 2022. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Thabede, Jahman Thabo
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/178569 , vital:42951
- Description: Access restricted until April 2022. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2021
- Full Text:
- Date Issued: 2021-04
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.
- Full Text:
- Date Issued: 2019
- 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.
- Full Text:
- Date Issued: 2019
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.
- Full Text:
- Date Issued: 2019
- 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.
- Full Text:
- Date Issued: 2019
Investigating soil microbial interactions of Portulacaria afra
- Authors: Fulmaka, Aviwe
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54598 , vital:26592
- Description: Portulacaria afra commonly known as Spekboom contributes significantly to carbon sequestration and has been widely planted in degraded areas of the Eastern Cape. Approximately 50% of planted cuttings do not survive although the cause of this decline is unknown. Like many indigenous plants, Spekboom forms a symbiotic relationship with mycorrhizal fungi and the interaction with rhizobacteria may enhance and improve plant growth and establishment. This study aims to investigate these relationships which will include a survey of the arbuscular mycorrhizal (AM) fungal populations associated with Spekboom, determination of the causal agent of Spekboom decline, isolation and identification of the associated rhizobacteria and investigation of their plant growth promotion properties and assessing the ability of arbuscular mycorrhizal fungi and selected rhizobacteria to enhance establishment and growth of Spekboom. Soil and root samples from selected trial sites were used to assess AM fungal spore abundance and colonisation; isolation, characterization, and identification of rhizobacteria and determine the interaction of the microbes on Spekboom growth and tolerance to Fusarium. AM spore abundance and percentage root colonisation did not differ between the three Spekboom plots. Molecular analyses of the SSU region from the plots showed 4 families of AM fungi and were identified as Ambisporaceae, Glomeraceae, Claroideoglomeraceae and Paraglomeraceae. A suspected Fusarium pathogen was isolated and molecularly identified. Pathogenicity tests indicated reduced Spekboom growth with poor root development. Thirty four rhizobacterial isolates were tested for various plant growth promoting abilities. Of these, 6 were able to produce IAA which may promote plant root growth, 27 siderophores and 23 were phosphate solubilisers. Bacterial isolates were molecularly identified to be from various species of Bacillus, with some Arthrobacter, Enterobacter, Pseudomonas and Microbacterium. Inoculation of Spekboom cuttings with mycorrhizal fungi and selected rhizobacterial isolates significantly improved shoot height. Spekboom cuttings challenged with Fusarium and inoculated with mycorrhizal fungi and two rhizobacterial isolates significantly improved growth. The inoculation of cuttings in the nursery with mycorrhizal fungi and selected rhizobacteria is recommended prior to establishing Spekboom in the field.
- Full Text:
- Date Issued: 2016
- Authors: Fulmaka, Aviwe
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54598 , vital:26592
- Description: Portulacaria afra commonly known as Spekboom contributes significantly to carbon sequestration and has been widely planted in degraded areas of the Eastern Cape. Approximately 50% of planted cuttings do not survive although the cause of this decline is unknown. Like many indigenous plants, Spekboom forms a symbiotic relationship with mycorrhizal fungi and the interaction with rhizobacteria may enhance and improve plant growth and establishment. This study aims to investigate these relationships which will include a survey of the arbuscular mycorrhizal (AM) fungal populations associated with Spekboom, determination of the causal agent of Spekboom decline, isolation and identification of the associated rhizobacteria and investigation of their plant growth promotion properties and assessing the ability of arbuscular mycorrhizal fungi and selected rhizobacteria to enhance establishment and growth of Spekboom. Soil and root samples from selected trial sites were used to assess AM fungal spore abundance and colonisation; isolation, characterization, and identification of rhizobacteria and determine the interaction of the microbes on Spekboom growth and tolerance to Fusarium. AM spore abundance and percentage root colonisation did not differ between the three Spekboom plots. Molecular analyses of the SSU region from the plots showed 4 families of AM fungi and were identified as Ambisporaceae, Glomeraceae, Claroideoglomeraceae and Paraglomeraceae. A suspected Fusarium pathogen was isolated and molecularly identified. Pathogenicity tests indicated reduced Spekboom growth with poor root development. Thirty four rhizobacterial isolates were tested for various plant growth promoting abilities. Of these, 6 were able to produce IAA which may promote plant root growth, 27 siderophores and 23 were phosphate solubilisers. Bacterial isolates were molecularly identified to be from various species of Bacillus, with some Arthrobacter, Enterobacter, Pseudomonas and Microbacterium. Inoculation of Spekboom cuttings with mycorrhizal fungi and selected rhizobacterial isolates significantly improved shoot height. Spekboom cuttings challenged with Fusarium and inoculated with mycorrhizal fungi and two rhizobacterial isolates significantly improved growth. The inoculation of cuttings in the nursery with mycorrhizal fungi and selected rhizobacteria is recommended prior to establishing Spekboom in the field.
- Full Text:
- Date Issued: 2016
Investigating the use of Arbuscular Mycorrhizas and Plant Growth Promoting Bacteria to improve the drought tolerance of maize (Zea mays L.)
- Authors: Moore, Nicolle Maureen
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54587 , vital:26591
- Description: Maize (Zea mays L.) is a direct staple food crop in Africa and remains an essential component of global food security, with maize crops accounting for over 60% of the total harvested area of annual food crops. Stress caused by drought and high soil salinity limits crop growth and productivity more than any other single environmental factor, with grain yield reductions up to 76% depending on the severity of the drought and the plant growth stage. Arbuscular mycorrhizal (AM) fungi and Plant Growth Promotion Rhizobacteria (PGPR) have previously been shown to improve tolerance of plants to drought stress through a number of chemical and physiological processes. The aim of this investigation was to determine whether mycorrhizal fungi and rhizobacteria adapted to drought and saline conditions and possessing plant growth promoting (PGP) traits were able to stimulate plant growth responses when applied to Zea mays seeds growing under greenhouse conditions Bacterial isolates selected were tolerant to concentrations of NaCl up to 600 mM and maintained 50% growth at low water potentials (-1.44 MPa). They were positive for Indole Acetic Acid (IAA) production, phosphate solubilisation and secretion of siderophores. Bacterial isolates showing plant growth promoting potential were identified using 16S rDNA gene sequencing as Achromobacter xylosoxidans strains A8 and C54 and Klebsiella oxytoca strain M1. Mixed inoculum was prepared from indigenous communities of mycorrhizas in soils sampled from the Cerebos Salt Pan and the Kalahari Desert. Mycorrhizal diversity was investigated using 454-Pyrosequencing which revealed that the community composition was dominated by species in the Ambispora, Glomus and Paraglomus genera with a rare component represented by species in the Redeckera, Archaeospora and Geosiphon genera. Microscopic examination of plant roots at the end of the trial revealed the presence of diagnostic mycorrhizal structures within the root cells, confirming that colonization was successful. Plant growth response to microbial inoculation was assessed by monitoring changes in plant photosynthetic capacity over the duration of a 7 week pot trial. A significant difference in photosynthetic and biomass data was observed between drought and well-watered groups but no mycorrhizal or bacterial treatment effect was evident within the groups, despite the high levels of colonization by mycorrhizas. These results suggest that the beneficial effects of mycorrhizal colonization may be primarily attributed to improved nutrient and mineral uptake in conditions where nutrients are limiting, resulting in improved growth. The improved growth may then have secondary effects on the plant‟s ability to withstand drought. Having controlled for nutrient deficiency, it was not evident in this study that mycorrhizal fungi were able to stimulate a change in plant physiology and confer drought tolerance under the conditions imposed.
- Full Text:
- Date Issued: 2016
- Authors: Moore, Nicolle Maureen
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54587 , vital:26591
- Description: Maize (Zea mays L.) is a direct staple food crop in Africa and remains an essential component of global food security, with maize crops accounting for over 60% of the total harvested area of annual food crops. Stress caused by drought and high soil salinity limits crop growth and productivity more than any other single environmental factor, with grain yield reductions up to 76% depending on the severity of the drought and the plant growth stage. Arbuscular mycorrhizal (AM) fungi and Plant Growth Promotion Rhizobacteria (PGPR) have previously been shown to improve tolerance of plants to drought stress through a number of chemical and physiological processes. The aim of this investigation was to determine whether mycorrhizal fungi and rhizobacteria adapted to drought and saline conditions and possessing plant growth promoting (PGP) traits were able to stimulate plant growth responses when applied to Zea mays seeds growing under greenhouse conditions Bacterial isolates selected were tolerant to concentrations of NaCl up to 600 mM and maintained 50% growth at low water potentials (-1.44 MPa). They were positive for Indole Acetic Acid (IAA) production, phosphate solubilisation and secretion of siderophores. Bacterial isolates showing plant growth promoting potential were identified using 16S rDNA gene sequencing as Achromobacter xylosoxidans strains A8 and C54 and Klebsiella oxytoca strain M1. Mixed inoculum was prepared from indigenous communities of mycorrhizas in soils sampled from the Cerebos Salt Pan and the Kalahari Desert. Mycorrhizal diversity was investigated using 454-Pyrosequencing which revealed that the community composition was dominated by species in the Ambispora, Glomus and Paraglomus genera with a rare component represented by species in the Redeckera, Archaeospora and Geosiphon genera. Microscopic examination of plant roots at the end of the trial revealed the presence of diagnostic mycorrhizal structures within the root cells, confirming that colonization was successful. Plant growth response to microbial inoculation was assessed by monitoring changes in plant photosynthetic capacity over the duration of a 7 week pot trial. A significant difference in photosynthetic and biomass data was observed between drought and well-watered groups but no mycorrhizal or bacterial treatment effect was evident within the groups, despite the high levels of colonization by mycorrhizas. These results suggest that the beneficial effects of mycorrhizal colonization may be primarily attributed to improved nutrient and mineral uptake in conditions where nutrients are limiting, resulting in improved growth. The improved growth may then have secondary effects on the plant‟s ability to withstand drought. Having controlled for nutrient deficiency, it was not evident in this study that mycorrhizal fungi were able to stimulate a change in plant physiology and confer drought tolerance under the conditions imposed.
- Full Text:
- Date Issued: 2016
Host relations of Kalaharituber pfeilii (Henn.) Trappe & Kagan-Zur
- Authors: Ntshakaza, Pamella
- Date: 2014
- Subjects: Ascomycetes -- Kalahari Desert , Medicinal plants -- Kalahari Desert , Edible fungi -- Kalahari Desert , Truffles -- Kalahari Desert , Desert plants -- Kalahari Desert , Mycorrhizas -- Kalahari Desert , Stipa -- Kalahari Desert
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4167 , http://hdl.handle.net/10962/d1020888
- Description: Kalaharituber pfeilii (Henn.) Trappe & Kagan-Zur commonly known as the “Kalahari truffle” is a desert truffle species identified from the Kalahari region of southern Africa. Two other species, Eremiomyces echinulatus (Trappe & Marasas) Trappe & Kagan-Zur and Mattirolomyces austroafricanus (Trappe & Marasas) Trappe & Kovacs are also known to occur in other parts of southern Africa. Truffles are hypogeous fruiting bodies of Ascomycetes, important to humans for their nutritional value and medicinal characteristics. These truffles are known as desert truffles as they prefer to occur under arid or semi-arid conditions characteristic of deserts. Truffle development depends on the presence of a mycorrhizal host, associated microorganisms as well as soil and climatic characteristics. It has been suggested that K. pfeilii has a suspected broad plant host range which includes herbaceous to woody trees and shrubs. However, these relationships have not been verified. Indigenous people of the Kalahari believe that truffles are found under grasses. In the Kalahari, truffle fruiting bodies are often found entangled in Stipagrostis ciliata (Desf.) De Winter var. capensis (Trin. & Rupr.) De Winter roots. S. ciliata, also known as the tall bushman-grass, is the most common grass found in the Kalahari. The objective of this study was to provide conclusive evidence that S. ciliata var. capensis is a host of the Kalahari truffle. Truffle fruiting bodies and grass roots from where the truffles were found were collected from Upington, South Africa. The fruiting bodies were identified by observing their morphological characteristics using the ‘Keys of Truffle genera’. All observed physical properties were similar to those of K. pfeilii and further identification was done using molecular techniques. DNA was extracted from the fruiting bodies, mycelial cultures, rhizosheaths and from the S. ciliata var. capensis grass roots, which were then amplified using the specific K. pfeilii specific primers TPF3 and TPR1 and sequenced. The obtained sequence results confirmed that the collected fruiting bodies were those of the K. pfeilii and the molecular techniques also confirmed that K. pfeilii DNA was present in the S. ciliata var. capensis rhizosheath and root cells. Microscopy showed an ectendomycorrhizal association between K. pfeilii and S. ciliata var. capensis. Mycorrhizal resynthesis experiments were conducted to establish this mycorrhizal association in-vitro. They were unsuccessful because of the structure of the grass and the availability of contaminants. And more...
- Full Text:
- Date Issued: 2014
- Authors: Ntshakaza, Pamella
- Date: 2014
- Subjects: Ascomycetes -- Kalahari Desert , Medicinal plants -- Kalahari Desert , Edible fungi -- Kalahari Desert , Truffles -- Kalahari Desert , Desert plants -- Kalahari Desert , Mycorrhizas -- Kalahari Desert , Stipa -- Kalahari Desert
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4167 , http://hdl.handle.net/10962/d1020888
- Description: Kalaharituber pfeilii (Henn.) Trappe & Kagan-Zur commonly known as the “Kalahari truffle” is a desert truffle species identified from the Kalahari region of southern Africa. Two other species, Eremiomyces echinulatus (Trappe & Marasas) Trappe & Kagan-Zur and Mattirolomyces austroafricanus (Trappe & Marasas) Trappe & Kovacs are also known to occur in other parts of southern Africa. Truffles are hypogeous fruiting bodies of Ascomycetes, important to humans for their nutritional value and medicinal characteristics. These truffles are known as desert truffles as they prefer to occur under arid or semi-arid conditions characteristic of deserts. Truffle development depends on the presence of a mycorrhizal host, associated microorganisms as well as soil and climatic characteristics. It has been suggested that K. pfeilii has a suspected broad plant host range which includes herbaceous to woody trees and shrubs. However, these relationships have not been verified. Indigenous people of the Kalahari believe that truffles are found under grasses. In the Kalahari, truffle fruiting bodies are often found entangled in Stipagrostis ciliata (Desf.) De Winter var. capensis (Trin. & Rupr.) De Winter roots. S. ciliata, also known as the tall bushman-grass, is the most common grass found in the Kalahari. The objective of this study was to provide conclusive evidence that S. ciliata var. capensis is a host of the Kalahari truffle. Truffle fruiting bodies and grass roots from where the truffles were found were collected from Upington, South Africa. The fruiting bodies were identified by observing their morphological characteristics using the ‘Keys of Truffle genera’. All observed physical properties were similar to those of K. pfeilii and further identification was done using molecular techniques. DNA was extracted from the fruiting bodies, mycelial cultures, rhizosheaths and from the S. ciliata var. capensis grass roots, which were then amplified using the specific K. pfeilii specific primers TPF3 and TPR1 and sequenced. The obtained sequence results confirmed that the collected fruiting bodies were those of the K. pfeilii and the molecular techniques also confirmed that K. pfeilii DNA was present in the S. ciliata var. capensis rhizosheath and root cells. Microscopy showed an ectendomycorrhizal association between K. pfeilii and S. ciliata var. capensis. Mycorrhizal resynthesis experiments were conducted to establish this mycorrhizal association in-vitro. They were unsuccessful because of the structure of the grass and the availability of contaminants. And more...
- Full Text:
- Date Issued: 2014
Investigating the role of mycorrhizal fungi and associated bacteria in promoting growth of citrus seedlings
- Authors: Sitole, Phumeza
- Date: 2014
- Subjects: Mycorrhizal fungi , Citrus -- South Africa , Citrus -- Diseases and pests -- Biological control -- South Africa , Fungi as biological pest control agents , Bacteria , Phytophthora , Pythium , Indoleacetic acid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4111 , http://hdl.handle.net/10962/d1013033
- Description: South Africa is the world's second largest exporter of fresh citrus and is ranked 14th in citrus production. Fungal pathogens such as Phytophthora and Pythium cause economic losses as a result of root rot and brown rot. Mycorrhizal fungi are specialized members of the fungal community forming a mutualistic relationship with plant roots. Mycorrhizal fungal structures are known to associate with other soil microorganisms and these may contribute to improved plant growth. A diverse group of bacteria that interact with the mycorrhizal fungi are known as Mycorrhizal Helper Bacteria (MHB). The aim of this study was to investigate the role of arbuscular mycorrhiza and associated bacteria isolated from spores and determine whether they had any plant growth promoting potential. A total of 19 bacteria were isolated from arbuscular mycorrhizal spores and were molecularly identified as belonging to several Bacillus, Micrococcus, Onchrobactrum and Staphylococcus sp. All bacterial isolates were tested for plant growth promotion abilities. One Bacillus isolate was able to solubilise phosphate. Four isolates Micrococcus sp, Micrococcus leteus, Ochrobacterum sp and Ochrobacterum antropi were able to produce Indole Acetic Acid and three isolates showed potential to reduce growth of Phytophthora nicotianae, P. citrocola and P. citrophthora in in vitro plate cultures. Further tests using culture supernatants of the Bacillus sp, Micrococcus sp and Bacillus cereus confirmed their ability to inhibit or reduce growth of the three Phytophthora species in a 96 well bioassay. Bacillus sp and Bacillus cereus were able to inhibit Phytophthora spp by 95 to 100 % and Micrococcus spp was able to decrease pathogen growth by 60 to 94 %. These bacterial isolates were further evaluated for plant growth promoting abilities on citrus rough lemon seedlings alone or in combination with arbuscular mycorrhizal inoculum. Bacterial and mycorrhizal inoculants influence the increase in shoot and root biomass. Bacillus cereus in combination with mycorrhizal inoculum significantly increased seedling shoot to root ratio while root biomass was significantly increased with mycorrhizal inoculation. Due to the short duration of the trial mycorrhizal colonisation could not be assessed. It is evident that selected combinations of bacteria and mycorrhizal fungi could promote citrus seedling growth and potentially improve seedling health. Further studies under nursery conditions are recommended.
- Full Text:
- Date Issued: 2014
- Authors: Sitole, Phumeza
- Date: 2014
- Subjects: Mycorrhizal fungi , Citrus -- South Africa , Citrus -- Diseases and pests -- Biological control -- South Africa , Fungi as biological pest control agents , Bacteria , Phytophthora , Pythium , Indoleacetic acid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4111 , http://hdl.handle.net/10962/d1013033
- Description: South Africa is the world's second largest exporter of fresh citrus and is ranked 14th in citrus production. Fungal pathogens such as Phytophthora and Pythium cause economic losses as a result of root rot and brown rot. Mycorrhizal fungi are specialized members of the fungal community forming a mutualistic relationship with plant roots. Mycorrhizal fungal structures are known to associate with other soil microorganisms and these may contribute to improved plant growth. A diverse group of bacteria that interact with the mycorrhizal fungi are known as Mycorrhizal Helper Bacteria (MHB). The aim of this study was to investigate the role of arbuscular mycorrhiza and associated bacteria isolated from spores and determine whether they had any plant growth promoting potential. A total of 19 bacteria were isolated from arbuscular mycorrhizal spores and were molecularly identified as belonging to several Bacillus, Micrococcus, Onchrobactrum and Staphylococcus sp. All bacterial isolates were tested for plant growth promotion abilities. One Bacillus isolate was able to solubilise phosphate. Four isolates Micrococcus sp, Micrococcus leteus, Ochrobacterum sp and Ochrobacterum antropi were able to produce Indole Acetic Acid and three isolates showed potential to reduce growth of Phytophthora nicotianae, P. citrocola and P. citrophthora in in vitro plate cultures. Further tests using culture supernatants of the Bacillus sp, Micrococcus sp and Bacillus cereus confirmed their ability to inhibit or reduce growth of the three Phytophthora species in a 96 well bioassay. Bacillus sp and Bacillus cereus were able to inhibit Phytophthora spp by 95 to 100 % and Micrococcus spp was able to decrease pathogen growth by 60 to 94 %. These bacterial isolates were further evaluated for plant growth promoting abilities on citrus rough lemon seedlings alone or in combination with arbuscular mycorrhizal inoculum. Bacterial and mycorrhizal inoculants influence the increase in shoot and root biomass. Bacillus cereus in combination with mycorrhizal inoculum significantly increased seedling shoot to root ratio while root biomass was significantly increased with mycorrhizal inoculation. Due to the short duration of the trial mycorrhizal colonisation could not be assessed. It is evident that selected combinations of bacteria and mycorrhizal fungi could promote citrus seedling growth and potentially improve seedling health. Further studies under nursery conditions are recommended.
- Full Text:
- Date Issued: 2014
Screening of entomopathogenic fungi against citrus mealybug (Planococcus citri (Risso)) and citrus thrips (Scirtothrips aurantii (Faure))
- FitzGerald, Véronique Chartier
- Authors: FitzGerald, Véronique Chartier
- Date: 2014
- Subjects: Entomopathogenic fungi , Citrus mealybug -- South Africa -- Eastern Cape , Citrus thrips -- South Africa -- Eastern Cape , Citrus -- Diseases and pests , Citrus mealybug -- Biological control , Citrus thrips -- Biological control , Biological pest control agents , Scanning electron microscopy , Mycoses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4166 , http://hdl.handle.net/10962/d1020887
- Description: Mealybugs (Planococcus citri) and thrips (Scirtothrips aurantii) are common and extremely damaging citrus crop pests which have proven difficult to control via conventional methods, such as chemical pesticides and insect growth regulators. The objective of this study was to determine the efficacy of entomopathogenic fungi against these pests in laboratory bioassays. Isolates of Metarhizium anisopliae and Beauveria bassiana from citrus orchards in the Eastern Cape, South Africa were maintained on Sabouraud Dextrose 4% Agar supplemented with Dodine, chloramphenicol and rifampicin at 25°C. Infectivity of the fungal isolates was initially assessed using 5th instar false codling moth, Thaumatotibia leucotreta, larvae. Mealybug bioassays were performed in 24 well plates using 1 x 107 ml-1 conidial suspensions and kept at 26°C for 5 days with a photoperiod of 12 L:12 D. A Beauveria commercial product and an un-inoculated control were also screened for comparison. Isolates GAR 17 B3 (B. bassiana) and FCM AR 23 B3 (M. anisopliae) both resulted in 67.5% mealybug crawler mortality and GB AR 23 13 3 (B. bassiana) resulted in 64% crawler mortality. These 3 isolates were further tested in dose-dependent assays. Probit analyses were conducted on the dose-dependent assays data using PROBAN to determine LC₅₀ values. For both the mealybug adult and crawlers FCM AR 23 B3 required the lowest concentration to achieve LC₅₀ at 4.96 x 10⁶ conidia ml-1 and 5.29 x 10⁵ conidia ml-1, respectively. Bioassays on adult thrips were conducted in munger cells with leaf buds inoculated with the conidial suspensions. Isolate GAR 17 B3 had the highest mortality rate at 70% on thrips while FCM AR 23 B3 resulted in 60% mortality. Identification of the isolates, FCM AR 23 B3, GAR 17 B3 and GB AR 23 13 3, were confirmed to be correct using both microscopic and molecularly techniques. ITS sequences were compared to other sequences from GenBank and confirmed phylogenetically using MEGA6. Mealybug infection was investigated using scanning electron microscopy, mycosis was confirmed but the infection process could not be followed due to the extensive waxy cuticle. These results indicate that there is potential for the isolates FCM AR 23 B3 and GAR 17 B3 to be developed as biological control agents for the control of citrus mealybug and thrips. Further research would be required to determine their ability to perform under field conditions.
- Full Text:
- Date Issued: 2014
- Authors: FitzGerald, Véronique Chartier
- Date: 2014
- Subjects: Entomopathogenic fungi , Citrus mealybug -- South Africa -- Eastern Cape , Citrus thrips -- South Africa -- Eastern Cape , Citrus -- Diseases and pests , Citrus mealybug -- Biological control , Citrus thrips -- Biological control , Biological pest control agents , Scanning electron microscopy , Mycoses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4166 , http://hdl.handle.net/10962/d1020887
- Description: Mealybugs (Planococcus citri) and thrips (Scirtothrips aurantii) are common and extremely damaging citrus crop pests which have proven difficult to control via conventional methods, such as chemical pesticides and insect growth regulators. The objective of this study was to determine the efficacy of entomopathogenic fungi against these pests in laboratory bioassays. Isolates of Metarhizium anisopliae and Beauveria bassiana from citrus orchards in the Eastern Cape, South Africa were maintained on Sabouraud Dextrose 4% Agar supplemented with Dodine, chloramphenicol and rifampicin at 25°C. Infectivity of the fungal isolates was initially assessed using 5th instar false codling moth, Thaumatotibia leucotreta, larvae. Mealybug bioassays were performed in 24 well plates using 1 x 107 ml-1 conidial suspensions and kept at 26°C for 5 days with a photoperiod of 12 L:12 D. A Beauveria commercial product and an un-inoculated control were also screened for comparison. Isolates GAR 17 B3 (B. bassiana) and FCM AR 23 B3 (M. anisopliae) both resulted in 67.5% mealybug crawler mortality and GB AR 23 13 3 (B. bassiana) resulted in 64% crawler mortality. These 3 isolates were further tested in dose-dependent assays. Probit analyses were conducted on the dose-dependent assays data using PROBAN to determine LC₅₀ values. For both the mealybug adult and crawlers FCM AR 23 B3 required the lowest concentration to achieve LC₅₀ at 4.96 x 10⁶ conidia ml-1 and 5.29 x 10⁵ conidia ml-1, respectively. Bioassays on adult thrips were conducted in munger cells with leaf buds inoculated with the conidial suspensions. Isolate GAR 17 B3 had the highest mortality rate at 70% on thrips while FCM AR 23 B3 resulted in 60% mortality. Identification of the isolates, FCM AR 23 B3, GAR 17 B3 and GB AR 23 13 3, were confirmed to be correct using both microscopic and molecularly techniques. ITS sequences were compared to other sequences from GenBank and confirmed phylogenetically using MEGA6. Mealybug infection was investigated using scanning electron microscopy, mycosis was confirmed but the infection process could not be followed due to the extensive waxy cuticle. These results indicate that there is potential for the isolates FCM AR 23 B3 and GAR 17 B3 to be developed as biological control agents for the control of citrus mealybug and thrips. Further research would be required to determine their ability to perform under field conditions.
- Full Text:
- Date Issued: 2014
Interactions of arbuscular mycorrhizal fungi and spore-associated bacteria
- Authors: Ridsdale, Carmen Jane
- Date: 2013
- Subjects: Mycorrhizal fungi , Host plants , Bacteria
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4159 , http://hdl.handle.net/10962/d1018269
- Description: Arbuscular mycorrhizal (AM) fungi are naturally occurring in roots of terrestrial plants. AM fungi are capable of benefiting the host plant through various mechanisms such as enhanced nutrient supply, alleviation of environmental stress and inhibition of plant fungal pathogens. AM fungal spore-associated bacteria have been previously isolated and shown to have plant growthpromoting (PGP) abilities by several authors. Some bacterial isolates are able to promote AM fungal colonisation of host plants and are known to be mycorrhizal helper bacteria (MHB). This study focused on the isolation of AM fungal spore-associated bacteria, characterization of the isolates according to plant growth promoting abilities and evaluation of their potential to enhance plant growth and mycorrhizal colonisation. AM fungi were extracted from soils sampled from natural indigenous forest sources, raspberry (Rubus idaeus cv. Heritage) and strawberry (Fragaria ananassa) farms in South Africa and from a raspberry (Rubus idaeus cv. Autumn Bliss) plantation in Argentina. A total of 52 sporeassociated bacteria were isolated from the external and internal surfaces of AM fungal spore morphotypes from the two countries. The bacterial isolates were evaluated for their PGP abilities such as phosphate solubilisation, indole-3-acetic acid production, ammonia production and inhibition of the fungal pathogens Fusarium oxysporum and Phythophthora nicotianae through mechanisms such as siderophore and/ or hydrolytic enzyme production. A total of 23 bacterial isolates from both South Africa and Argentina showing the most potential to be PGP, were identified molecularly as belonging to the genera Acinetobacter, Alcaligenes, Bacillus, Microbacterium, Micrococcus, Serratia and Staphylococcus. The ability of ten selected bacterial isolates showing multiple PGP capacity were evaluated for their plant growth promotion and mycorrhizal colonisation enhancement ability on raspberry (Rubus idaeus cv. Meeker). Significant differences in increased shoot and root dry weights were shown by the treatments compared to the uninoculated control. The highest increase in shoot and root dry weights were shown by South African (Bacillus mycoides) and Argentinean (Alcaligenes faecalis) isolates. AM fungal colonisation was significantly enhanced by the South African (Bacillus mycoides) and Argentinean (Micrococcus luteus) isolates compared to the AM fungal singly inoculated control.
- Full Text:
- Date Issued: 2013
- Authors: Ridsdale, Carmen Jane
- Date: 2013
- Subjects: Mycorrhizal fungi , Host plants , Bacteria
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4159 , http://hdl.handle.net/10962/d1018269
- Description: Arbuscular mycorrhizal (AM) fungi are naturally occurring in roots of terrestrial plants. AM fungi are capable of benefiting the host plant through various mechanisms such as enhanced nutrient supply, alleviation of environmental stress and inhibition of plant fungal pathogens. AM fungal spore-associated bacteria have been previously isolated and shown to have plant growthpromoting (PGP) abilities by several authors. Some bacterial isolates are able to promote AM fungal colonisation of host plants and are known to be mycorrhizal helper bacteria (MHB). This study focused on the isolation of AM fungal spore-associated bacteria, characterization of the isolates according to plant growth promoting abilities and evaluation of their potential to enhance plant growth and mycorrhizal colonisation. AM fungi were extracted from soils sampled from natural indigenous forest sources, raspberry (Rubus idaeus cv. Heritage) and strawberry (Fragaria ananassa) farms in South Africa and from a raspberry (Rubus idaeus cv. Autumn Bliss) plantation in Argentina. A total of 52 sporeassociated bacteria were isolated from the external and internal surfaces of AM fungal spore morphotypes from the two countries. The bacterial isolates were evaluated for their PGP abilities such as phosphate solubilisation, indole-3-acetic acid production, ammonia production and inhibition of the fungal pathogens Fusarium oxysporum and Phythophthora nicotianae through mechanisms such as siderophore and/ or hydrolytic enzyme production. A total of 23 bacterial isolates from both South Africa and Argentina showing the most potential to be PGP, were identified molecularly as belonging to the genera Acinetobacter, Alcaligenes, Bacillus, Microbacterium, Micrococcus, Serratia and Staphylococcus. The ability of ten selected bacterial isolates showing multiple PGP capacity were evaluated for their plant growth promotion and mycorrhizal colonisation enhancement ability on raspberry (Rubus idaeus cv. Meeker). Significant differences in increased shoot and root dry weights were shown by the treatments compared to the uninoculated control. The highest increase in shoot and root dry weights were shown by South African (Bacillus mycoides) and Argentinean (Alcaligenes faecalis) isolates. AM fungal colonisation was significantly enhanced by the South African (Bacillus mycoides) and Argentinean (Micrococcus luteus) isolates compared to the AM fungal singly inoculated control.
- Full Text:
- Date Issued: 2013
Ericoid mycorrhizal fungi and potential for inoculation of commercial berry species (Vaccinium corymbosium L.)
- Authors: Bizabani, Christine
- Date: 2011
- Subjects: Ericaceae , Mycorrhizas , Fynbos
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4136 , http://hdl.handle.net/10962/d1016127
- Description: Ericaceous plants are the richest growth form of the fynbos vegetation of South Africa. The fynbos is characterized by highly leached acidic soils, low mineral nutrients and climatically it is a winter rainfall and dry summer region. Ericoid mycorrhizal fungi associate with Erica species enhancing their ability to access essential nutrients for survival under unfavourable growth conditions. The aim of this study was to select local Ericaceae plant species and to isolate, identify and characterize the ericoid endophytes and assess these isolates as potential inocula for commercial berry species. Two ericaceous plants Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth. were identified from the Mountain Drive area of Grahamstown, Eastern Cape. Root staining was used to confirm the mycorrhizal status of both plants. Hyphal coils typical of ericoid association were observed within the epidermal cells of the hair roots under a light microscope. The endophytes were successfully isolated in pure culture on 2% malt extract agar (MEA) and modified Fontana medium. Cultural morphology and microscopy were used for initial identification. Two slow growing isolates were selected. These isolates were further subjected to molecular identification; extracted DNA was amplified using ITS1 and ITS4 fungal primers. The rDNA gene internal transcriber spacer (ITS) was then sequenced and analyzed by comparison to sequences in the GenBank. On the basis of percentage sequence identity Lachnum Retz. species and Cadophora Lagerb. & Melin species were identified as the ericoid endophytes of E. cerinthoides and E. demmissa respectively. The optimum growth parameters of the fungal isolates were determined in 2% MEA incubated at varying temperatures and pH. It was established that both species had optimum growth at 27⁰C and pH 5. The Ericaceae species are sometimes found in metal contaminated sites were ericoid fungi have been proved to alleviate toxicity of their host. The fungal isolates were grown in increasing concentration of Cu²⁺ and Zn²⁺ in 2% MEA. The growth of Lachnum species decreased with increasing Zn²⁺ ions above 2.7 mM while Cadophora species showed a change in morphology and also decreased in growth with increased ion concentration. However there were no significant differences recorded in the growth of Cadophora and Lachnum species on increasing Cu²⁺ concentration. Lachnum and Cadophora isolates were formulated into a semi solid inoculum and inoculated onto micropropagated Vaccinni corymbosum L. plantlets of 5 different varieties. Colonization was low for all varieties, Elliott and Brightwell varieties recorded the highest colonization of 35% and 31% respectively. Lachnum species infected roots showed potential ericoid structures while the Cadophora inoculated plantlets had hyphal coils within the cortical cells typical of ericoid mycorrhizas. Inoculation significantly enhanced the shoot growth of Brightwell and Elliott varieties. The Chandler variety inoculated with Lachnum species showed improved shoot dry weight. The Bluecrop and Elliott varieties inoculated with Cadophora and Lachnum accumulated more root biomass. All inoculated Bluecrop plantlets had an improved canopy growth index. Brightwell plantlets inoculated with Lachnum species also had an enhanced canopy growth index. The growth responses were variable within varieties and between varieties. Treatments with the Cadophora and Lachnum have shown potential in the promotion of growth of the Blueberry species. The findings indicate the need to conduct trials under conditions which simulate the commercial growth conditions so as explore the optimum potential of the isolates.
- Full Text:
- Date Issued: 2011
- Authors: Bizabani, Christine
- Date: 2011
- Subjects: Ericaceae , Mycorrhizas , Fynbos
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4136 , http://hdl.handle.net/10962/d1016127
- Description: Ericaceous plants are the richest growth form of the fynbos vegetation of South Africa. The fynbos is characterized by highly leached acidic soils, low mineral nutrients and climatically it is a winter rainfall and dry summer region. Ericoid mycorrhizal fungi associate with Erica species enhancing their ability to access essential nutrients for survival under unfavourable growth conditions. The aim of this study was to select local Ericaceae plant species and to isolate, identify and characterize the ericoid endophytes and assess these isolates as potential inocula for commercial berry species. Two ericaceous plants Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth. were identified from the Mountain Drive area of Grahamstown, Eastern Cape. Root staining was used to confirm the mycorrhizal status of both plants. Hyphal coils typical of ericoid association were observed within the epidermal cells of the hair roots under a light microscope. The endophytes were successfully isolated in pure culture on 2% malt extract agar (MEA) and modified Fontana medium. Cultural morphology and microscopy were used for initial identification. Two slow growing isolates were selected. These isolates were further subjected to molecular identification; extracted DNA was amplified using ITS1 and ITS4 fungal primers. The rDNA gene internal transcriber spacer (ITS) was then sequenced and analyzed by comparison to sequences in the GenBank. On the basis of percentage sequence identity Lachnum Retz. species and Cadophora Lagerb. & Melin species were identified as the ericoid endophytes of E. cerinthoides and E. demmissa respectively. The optimum growth parameters of the fungal isolates were determined in 2% MEA incubated at varying temperatures and pH. It was established that both species had optimum growth at 27⁰C and pH 5. The Ericaceae species are sometimes found in metal contaminated sites were ericoid fungi have been proved to alleviate toxicity of their host. The fungal isolates were grown in increasing concentration of Cu²⁺ and Zn²⁺ in 2% MEA. The growth of Lachnum species decreased with increasing Zn²⁺ ions above 2.7 mM while Cadophora species showed a change in morphology and also decreased in growth with increased ion concentration. However there were no significant differences recorded in the growth of Cadophora and Lachnum species on increasing Cu²⁺ concentration. Lachnum and Cadophora isolates were formulated into a semi solid inoculum and inoculated onto micropropagated Vaccinni corymbosum L. plantlets of 5 different varieties. Colonization was low for all varieties, Elliott and Brightwell varieties recorded the highest colonization of 35% and 31% respectively. Lachnum species infected roots showed potential ericoid structures while the Cadophora inoculated plantlets had hyphal coils within the cortical cells typical of ericoid mycorrhizas. Inoculation significantly enhanced the shoot growth of Brightwell and Elliott varieties. The Chandler variety inoculated with Lachnum species showed improved shoot dry weight. The Bluecrop and Elliott varieties inoculated with Cadophora and Lachnum accumulated more root biomass. All inoculated Bluecrop plantlets had an improved canopy growth index. Brightwell plantlets inoculated with Lachnum species also had an enhanced canopy growth index. The growth responses were variable within varieties and between varieties. Treatments with the Cadophora and Lachnum have shown potential in the promotion of growth of the Blueberry species. The findings indicate the need to conduct trials under conditions which simulate the commercial growth conditions so as explore the optimum potential of the isolates.
- Full Text:
- Date Issued: 2011
Interaction between arbuscular mycorrhizal fungi and soil microbial populations in the rhizosphere
- Authors: Ike-Izundu, Nnenna Esther
- Date: 2008
- Subjects: Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3962 , http://hdl.handle.net/10962/d1004021 , Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Description: This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.
- Full Text:
- Date Issued: 2008
- Authors: Ike-Izundu, Nnenna Esther
- Date: 2008
- Subjects: Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3962 , http://hdl.handle.net/10962/d1004021 , Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Description: This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.
- Full Text:
- Date Issued: 2008
The development of a putative microbial product for use in crop production
- Authors: Gumede, Halalisani
- Date: 2008
- Subjects: Agricultural productivity , Agriculture -- Economic aspects , Microbial products , Bacterial diseases of plants , Biological pest control agents , Lettuce -- Diseases and pests , Crops -- Nutrition , Bacillus (Bacteria) , Phytopathogenic microorganisms -- Control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3945 , http://hdl.handle.net/10962/d1004004 , Agricultural productivity , Agriculture -- Economic aspects , Microbial products , Bacterial diseases of plants , Biological pest control agents , Lettuce -- Diseases and pests , Crops -- Nutrition , Bacillus (Bacteria) , Phytopathogenic microorganisms -- Control
- Description: The challenges faced by the agricultural sector especially around improving production yields using environmentally friendly solutions have received market attention. Biological intervention can range from application of biological products to enhance the nutritional value of crops or to control plant pathogens. Biostart, a biological product that demonstrated growth enhancement when applied in lettuce crops is currently in the market. The product is comprised of a consortium of bacterial isolates (Bacillus licheniformis, Brevibacillus laterosporus and Bacillus laterosporus) but the contribution of the individual isolates to growth enhancement had not been elucidated. Green house experiments on lettuce seedlings with individual and mixed treatments were commissioned to determine such contribution. There was either no or marginal growth enhancement observed in the experiments. The results showed that the product was effective as a consortium and not as individual isolates. Further isolation and screening for potential Bacilli with antifungal properties was undertaken. An isolate identified as Bacillus subtilis that demonstrated inhibition against a wide spectrum of fungi, and especially the phytopathogenic Verticillium dahliae and Fusarium oxysporum, was successfully identified. The isolate was cryo-preserved and cultivated to significant levels at bench scale. A characterized comparison of different putative products with known systematic fungicide showed potential application even of heat treated products. The product showed control V. dahliae when tested in green houses with potatoes and tomatoes as test crops. This isolate has been targeted for further development as a biological control product.
- Full Text:
- Date Issued: 2008
- Authors: Gumede, Halalisani
- Date: 2008
- Subjects: Agricultural productivity , Agriculture -- Economic aspects , Microbial products , Bacterial diseases of plants , Biological pest control agents , Lettuce -- Diseases and pests , Crops -- Nutrition , Bacillus (Bacteria) , Phytopathogenic microorganisms -- Control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3945 , http://hdl.handle.net/10962/d1004004 , Agricultural productivity , Agriculture -- Economic aspects , Microbial products , Bacterial diseases of plants , Biological pest control agents , Lettuce -- Diseases and pests , Crops -- Nutrition , Bacillus (Bacteria) , Phytopathogenic microorganisms -- Control
- Description: The challenges faced by the agricultural sector especially around improving production yields using environmentally friendly solutions have received market attention. Biological intervention can range from application of biological products to enhance the nutritional value of crops or to control plant pathogens. Biostart, a biological product that demonstrated growth enhancement when applied in lettuce crops is currently in the market. The product is comprised of a consortium of bacterial isolates (Bacillus licheniformis, Brevibacillus laterosporus and Bacillus laterosporus) but the contribution of the individual isolates to growth enhancement had not been elucidated. Green house experiments on lettuce seedlings with individual and mixed treatments were commissioned to determine such contribution. There was either no or marginal growth enhancement observed in the experiments. The results showed that the product was effective as a consortium and not as individual isolates. Further isolation and screening for potential Bacilli with antifungal properties was undertaken. An isolate identified as Bacillus subtilis that demonstrated inhibition against a wide spectrum of fungi, and especially the phytopathogenic Verticillium dahliae and Fusarium oxysporum, was successfully identified. The isolate was cryo-preserved and cultivated to significant levels at bench scale. A characterized comparison of different putative products with known systematic fungicide showed potential application even of heat treated products. The product showed control V. dahliae when tested in green houses with potatoes and tomatoes as test crops. This isolate has been targeted for further development as a biological control product.
- Full Text:
- Date Issued: 2008
Isolation, propagation and rapid molecular detection of the Kalahari truffle, a mycorrhizal fungus occurring in South Africa
- Authors: Adeleke, Rasheed Adegbola
- Date: 2007 , 2013-04-03
- Subjects: Truffles -- Kalahari Desert , Fungi -- Identification , Mycorrhizal fungi -- South Africa , Edible fungi -- South Africa , Mushroom culture -- South Africa , Fungi -- Cultures and culture media -- South Africa , Truffles -- South Africa , Truffles -- Lifecycles , Mycorrhizal fungi -- Lifecycles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3889 , http://hdl.handle.net/10962/d1002951 , Truffles -- Kalahari Desert , Fungi -- Identification , Mycorrhizal fungi -- South Africa , Edible fungi -- South Africa , Mushroom culture -- South Africa , Fungi -- Cultures and culture media -- South Africa , Truffles -- South Africa , Truffles -- Lifecycles , Mycorrhizal fungi -- Lifecycles
- Description: Terfezia pfeilii is an edible mycorrhizal fungus that thrives in the Kalahari Desert of southern Africa. It is best known by desert dwellers for its flavour and as a source of nutrition. Although the genus Terfezia is generally regarded as being an ectomycorrhizal mycobiont, the exact mycorrhizal type formed by T. pfeilli and its' associated host plants remains uncertain. Discovery of the host plants for T. pfeilii would first be required in order to further investigate the life cycle and cultivation of this truffle. This study focussed on the isolation of mycelia from the ascocarp, optimising the growth conditions of the mycelial cultures, rapid molecular identification of T. pfeilii, investigation of potential helper bacteria and mycorrhizal synthesis experiments. T. pfeilii ascocarps were harvested from the Spitskop Nature Reserve in Upington, South Africa. Ascocarps were successfully identified using both morphological and molecular methods. Despite the delayed growth mostly caused by contaminating microorganisms, the isolation of T. pfeilii mycelia culture was successful. Molecular techniques were used to confirm the identity of the pure culture. Further studies were conducted on ways to improve the growth conditions of the mycelial culture on Fontana medium. An optimum temperature of 32°C, the addition of Bovine Serum Albumin as a nitrogen source and a pH of 7.5 significantly improved the growth of T. pfeilii in vitro. A rapid PeR-based molecular method was developed to speed up the identification of T. pfeilii. Specific primers that can exclusively amplify the ITS region of T. pfeilii were designed and used to identify both the ascocarps and the mycelial culture. The specificity of these primers was confirmed by their inability to amplify DNA from the isolates of contamining fungi obtained during the isolation process. Molecular comparison was made to confirm the reclassification of South African samples of T. pfeilii as Kalaharituber pfeilii as proposed by Ferdman et al.,(2005). However, in this study, the name T. pfeilii has been retained. A total of 17 bacterial isolates were obtained from the fruiting bodies of T. pfeaii and these were tested for stimulation of mycelial growth in vitro, indole production and phosphate solubilising capabilities. Bacterial isolates that showed potential to be Mycorrhization Helper Bacteria (MHB) were identified as Paenibacillus sp., Bacillus sp. and Rhizobium tropici. Selected plant seedlings were inoculated with T. pfeilii cultures or ascocarp slurry in order to re-establish the mycorrhizal association. After 8 months, light microscopy observations revealed an endomycorrhizal type association between Cynodon dactylon and T. pfeilii. This was confirmed with molecular analysis using specific T. pfeilii ITS primers. After 15 months, molecular methods confirmed Acacia erioloba as another host plant. These results have provided essential information paving the way for further investigation into the life cycle and biology of the Kalahari truffle. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2007
- Authors: Adeleke, Rasheed Adegbola
- Date: 2007 , 2013-04-03
- Subjects: Truffles -- Kalahari Desert , Fungi -- Identification , Mycorrhizal fungi -- South Africa , Edible fungi -- South Africa , Mushroom culture -- South Africa , Fungi -- Cultures and culture media -- South Africa , Truffles -- South Africa , Truffles -- Lifecycles , Mycorrhizal fungi -- Lifecycles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3889 , http://hdl.handle.net/10962/d1002951 , Truffles -- Kalahari Desert , Fungi -- Identification , Mycorrhizal fungi -- South Africa , Edible fungi -- South Africa , Mushroom culture -- South Africa , Fungi -- Cultures and culture media -- South Africa , Truffles -- South Africa , Truffles -- Lifecycles , Mycorrhizal fungi -- Lifecycles
- Description: Terfezia pfeilii is an edible mycorrhizal fungus that thrives in the Kalahari Desert of southern Africa. It is best known by desert dwellers for its flavour and as a source of nutrition. Although the genus Terfezia is generally regarded as being an ectomycorrhizal mycobiont, the exact mycorrhizal type formed by T. pfeilli and its' associated host plants remains uncertain. Discovery of the host plants for T. pfeilii would first be required in order to further investigate the life cycle and cultivation of this truffle. This study focussed on the isolation of mycelia from the ascocarp, optimising the growth conditions of the mycelial cultures, rapid molecular identification of T. pfeilii, investigation of potential helper bacteria and mycorrhizal synthesis experiments. T. pfeilii ascocarps were harvested from the Spitskop Nature Reserve in Upington, South Africa. Ascocarps were successfully identified using both morphological and molecular methods. Despite the delayed growth mostly caused by contaminating microorganisms, the isolation of T. pfeilii mycelia culture was successful. Molecular techniques were used to confirm the identity of the pure culture. Further studies were conducted on ways to improve the growth conditions of the mycelial culture on Fontana medium. An optimum temperature of 32°C, the addition of Bovine Serum Albumin as a nitrogen source and a pH of 7.5 significantly improved the growth of T. pfeilii in vitro. A rapid PeR-based molecular method was developed to speed up the identification of T. pfeilii. Specific primers that can exclusively amplify the ITS region of T. pfeilii were designed and used to identify both the ascocarps and the mycelial culture. The specificity of these primers was confirmed by their inability to amplify DNA from the isolates of contamining fungi obtained during the isolation process. Molecular comparison was made to confirm the reclassification of South African samples of T. pfeilii as Kalaharituber pfeilii as proposed by Ferdman et al.,(2005). However, in this study, the name T. pfeilii has been retained. A total of 17 bacterial isolates were obtained from the fruiting bodies of T. pfeaii and these were tested for stimulation of mycelial growth in vitro, indole production and phosphate solubilising capabilities. Bacterial isolates that showed potential to be Mycorrhization Helper Bacteria (MHB) were identified as Paenibacillus sp., Bacillus sp. and Rhizobium tropici. Selected plant seedlings were inoculated with T. pfeilii cultures or ascocarp slurry in order to re-establish the mycorrhizal association. After 8 months, light microscopy observations revealed an endomycorrhizal type association between Cynodon dactylon and T. pfeilii. This was confirmed with molecular analysis using specific T. pfeilii ITS primers. After 15 months, molecular methods confirmed Acacia erioloba as another host plant. These results have provided essential information paving the way for further investigation into the life cycle and biology of the Kalahari truffle. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2007
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