Browsing by Author "Abrahams, Malikah"

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    Screening and evaluation of bacteria for the biological control of Botrytis cinerea on Vitis vinifera
    (University of the Western Cape, 2024) Abrahams, Malikah
    Agriculture plays a significant role in food security and the economic sector. However, the agriculture industry is threatened by plant pathogenic microorganisms, with fungi accounting for 42% of plant diseases. Botrytis cinerea is the most notable of all plant pathogenic fungi. B. cinerea is notoriously known to cause grey mould or grey rot in grapevine (Vitis vinifera), which threatens viticulture. Chemical fungicides have been used to control it for many years, however, chemical fungicides have negative effects on the environment and human health. In addition, excessive use of chemical fungicides and the polycyclic nature of B. cinerea led to the development of resistant strains, making it difficult to control. Alternative methods have been investigated to control B. cinerea, such as using microorganisms as biological control agents (BCAs). Therefore, researchers have been searching for BCAs that can control B. cinerea. This study aimed to test bacterial isolates for antifungal activity against B. cinerea and investigate their modes of action, which can aid in preventing grey mould in grapes. The dual-culture assay was used as a preliminary screening method to test antifungal activity against three B. cinerea strains (IWBT FF1, IWBT FF2, and B05.10). The bacterial isolates were identified using 16S rRNA gene sequencing. Various experiments assessed the modes of action behind the inhibitory activity, including testing for cell wall degrading enzymes (glucanases, proteases, chitinases), evaluating competition for space and nutrients via siderophore production on chrome-azurol S agar, and conducting an in vivo assay on wounded grape berries. Antibiosis was evaluated by assessing the effect of the cell-free supernatant on the development of B. cinerea strains. Additionally, polymerase chain reaction (PCR) was used to detect genes related to cyclic lipopeptide (CLP) synthesis, and liquid chromatography-mass spectrometry was used to determine if CLPs were expressed.