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Control of Botrytis cinerea on post-harvested blueberry (Vaccinium corymbosum L.) fruit

Auda, Ahmed Abbas (2021) Control of Botrytis cinerea on post-harvested blueberry (Vaccinium corymbosum L.) fruit. PhD thesis, Murdoch University.

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Blueberries (Vaccinium corymbosum L.) are cultivated worldwide due to their important commercial value and the health benefits of the fruit. Botrytis cinerea is a highly destructive horticulture pathogen with a host range of 1400 plant species, including blueberry. Worldwide its management costs billions of dollars annually. Biosecurity controls require that international shipments of products be pest-free, which is increasingly difficult due to the ban of key pesticides. Instead, biological control strategies can be used to manage postharvest fruit pathogens. Surveys on postharvest blueberry in Western Australia were conducted to assess the fungal species associated with fruit decay and their pathogenicity. The fungi isolated were Botrytis cinerea, Alternaria alternata, Cladosporium cladosporioides, Penicillium brevicompactum, Epicoccum nigrum, Aureobasidium pullulans, Diaporthe australafricana, a Verticillium sp., and a Ceriporia sp. Botrytis cinerea, A. alternata, C. cladosporioides A. pullulans, and D. australafricana were pathogens. The other four were not. Two methods were used to evaluate the eight fungi as putative antagonists against B. cinerea. Firstly, each antagonist was screened for direct antagonism against B. cinerea on half-strength potato dextrose agar (PDA). Secondly, the involvement of secondary metabolites was evaluated by growing each antagonist on a dialysis membrane placed on the surface of half PDA for four days before removing the membrane and placing B. cinerea in the centre of the PDA plates and monitoring its growth. E. nigrum was found to be the most effective antagonist, followed by Verticillium sp., the Ceriporia sp. and A. pullulans using both methods. The eight putative antagonists were then screened for their ability to produce non-volatile organic compounds (NVOCs) in the presence and absence of B. cinerea using direct immersion solid-phase microextraction (DI-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The metabolic analysis by GC-MS confirmed that there were unique compounds identified from all eight fungi, such as E. nigrum producing more of these than the others. Future studies are required to determine if any of these compounds can be used to control B. cinerea as a postharvest pathogen of blueberry. This study has improved our understanding of postharvest blueberry pathogens in Australia. The results will help refine current B. cinerea postharvest management and develop more efficient and environmentally friendly control strategies.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Agricultural Sciences
Supervisor(s): Hardy, Giles, Ren, Yonglin and Agarwal, Manjree
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