Fungi associated with stored wheat grain in Australia: Isolation, identification and characterisation

• Main Author: Barkat, Eman
• Other Authors: Bayliss, Kirsty, Hardy, Giles, Ren, Yonglin
• Format: Thesis
• Language: English
• Published: 2016
• Subjects: Cryptococcus victoriae
• Online Access: https://researchrepository.murdoch.edu.au/id/eprint/34990/

Fungal contamination of stored grain is a major concern because it can cause economic losses and potential human and animal health issues. The aims of this study were to: determine the effects of temperature, grain moisture content and length of storage on survival of fungi associated with stored wheat grain in Australia; compare the efficacy of a range of methods for isolating, identifying and characterizing fungi in stored wheat grain in Australia; and assess the potential of using volatile organic compounds for detecting fungi associated with stored wheat grain in Australia. It was demonstrated that fungi could be isolated from apparently healthy wheat grain for up to six months when stored at recommended or slightly higher than recommended moisture contents and temperatures. Spoilage fungi associated with wheat grain from across Australia were isolated and identified and included the genera Alternaria, Aspergillus, Aureobasidium, Cladosporium, Drechslera, Fusarium, Mucor, Nigrospora, Penicillium, Rhizopus, Setosphaeria, Stemphylium, Ulocladium, Epicoccum and an unidentified species from the Hypocreales. The genus Eutiarosporella was also recorded and a new species, Eutiarsporella pseudotritici-australis sp. nov. described. The most frequently isolated genus was Alternaria. Next generation sequencing was used to identify fungi that were not isolated using traditional methods and detected the presence of the human pathogens Cryptococcus macerans and Cryptococcus victoriae. It was also demonstrated that that some fungal species produce volatile organic compounds including cyclooctasiloxane hexadecamethyl- (CAS 556-68-3) from Alternaria alternata, pentadecane (CAS 629-62-9) from A. infectoria and naphthalene (CAS 91-20-3) in grain colonised by Cladosporium herbarum. This research has contributed new knowledge regarding fungal pathogens occurring in stored grain in Australia. When combined with next generation sequencing and measurement of volatile organic compounds the presence of fungi in storage facilities may be determined at an early stage of development, allowing mitigation strategies to be implemented to reduce postharvest loss and ensure the supply of quality grain in Australia.