Browsing by Author "Ndaba, Nkosinathi Sthembiso"

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    Trichoderma as a functional fungal group in the rhizosphere of maize and wheat under conservation and conventional agricultural practices
    (Stellenbosch : Stellenbosch University, 2021-12) Ndaba, Nkosinathi Sthembiso; Jacobs, Karin; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: The contribution of agriculture in South Africa to the economy, is one of those major drivers of employment in South Africa. The two most produced commercial crops in SA are maize and wheat. In chapter one, the importance of these crops and the effect of farming practices such as conventional and conservation agriculture were briefly compared and discussed. Furthermore, the importance of microorganisms in agriculture as well as their role in various biological processes that occurs in soil are briefly discussed. Particular attention was given to the role of Trichoderma spp. as they interact and form relationships with other soil organisms. This was followed by a brief discussion on the taxonomic history of Trichoderma spp. and the application of Trichoderma spp. in the industrial and agricultural sectors. Chapter two is the first of three research chapters and discussed the isolation and identification of Trichoderma species from wheat soil in the Western Cape. All isolates in this chapter were collected from agricultural soil only. The identification and classification of species was primarily based on macro features and amplification of internal transcribed spacer (ITS) regions. Thereafter, the final identification was done by combining two markers (ITS and Elongation factor 1 alpha (TEF1)). Ninety-one (91) strains of Trichoderma spp. which resolved into seven species that were identified as T. virens, T. saturnisporum, Trichoderma sp., T. gamsii, T. koningiopsis, T. velutinum, and T. spirale. It was also reported that T. gamsii was the predominant species. In addition, crop rotation practices resulted in a higher number of strains and species when it is compared with the monoculture practices. Chapter three is similar to Chapter 2 and focuses on the identification of Trichoderma species, on maize from different geographical areas in KwaZulu-Natal and the Free State. Soil samples were collected from sites with crop rotation as well as monoculture practices. From isolations, 337 strains were recovered from maize soil representing 11 Trichoderma species. Seven species have been isolated previously in South Africa. However, five species namely, T. velutinum, T. rifaii, T. paratroviride, T. neokoningii and T. peberdyi are being reported for the first time in South Africa. Distribution of the species significantly differed between crop rotation and monoculture practices, with crop rotation sites resulting in a higher number of species than monoculture practices. Furthermore, T. gamsii and T. hamatum were the most abundant species isolated. In chapter four the potential functions of different strains were investigated. The results suggest that each certain function in Trichoderma spp. could be strain specific. This chapter determined the abilities of Trichoderma strains to solubilize phosphate and produce indole acetic acid. These two metabolic factors (solubilization of phosphate and production of indole acetic acid) were evaluated because it is known that they could be used for primary identification of species that might have the capacity to improve plant growth. Findings indicated that the majority of strains were able to solubilize phosphate and pH reduction play a vital role in this case. T. koningiopsis NNC066 solubilized the maximum amount of phosphate whereas Trichoderma sp. K4 solubilized the least amount of phosphate. Moreover, no strains were able to produce indole acetic acid (IAA) in the absence of tryptophan (L-TRP). Although, the amendments of the media with L-TRP, enabled all strains to produce the IAA where maximum amount obtained at 41.90 µg/ml by T. gamsii NNC019, while the least amount was at 0.30 µg/ml by Trichoderma sp. K1.