Submitted to: Extension Reports
Publication Type: Other
Publication Acceptance Date: 12/1/2003
Publication Date: 3/1/2004
Citation: Hua, S.T. 2004. Reduction of aflatoxin in pistachio through biological control of aspergillus flavus. Extension Reports. California Pistachio Commision Production Research Reports. p. 212-220. Interpretive Summary: The experiments demonstrated that the yeast, P. anomala can modulate spore production of fungi including A. flavus on the pistachio nut-fruits. Field spraying of these effective yeasts to pistachio trees may decrease the population of A. flavus in the orchards and thus lower the number of nuts infected by this fungus. The outcome may be a reduction of aflatoxin contamination in the edible nuts. Monitoring A. flavus and A. parasiticus on pistachio buds may provide the growers a way to evaluate the population of the aflatoxin-producing fungi in orchards and help them make decision on control strategy. The use of chemical pesticides has caused the development of pest resistance and resurgence as well as environmental pollution and risks to human health. There is a growing interest in the food industry, including retail supermarkets, grower cooperatives and large food companies to consider 'biocontrol' as a means to minimize risk.
Technical Abstract: Field evaluation of the efficacy of the biocontrol agent, P. anomala strain WRL-076 was carried out. Twenty trees were randomly selected for field trial. Nut-fruits without yeast-spray were used as controls. Pistachio nut-fruits on the trees were sprayed with aqueous suspension of yeasts in mid-August. A second spray of yeasts was applied to the trees one week later. Nut-fruits were collected for analysis 4 weeks after the second spray. Statistical analysis indicated the fungal counts on pistachio nut-fruits were significantly reduced on trees sprayed with the yeast P. anomala WRL-076. Fungal strains of Aspergillus flavus and Aspergillus parasiticus were isolated from pistachio buds. A large number of isolated strains produced aflatoxin in this sampling. One strain of A. parasiticus produced the highest amount of aflatoxin B1 and G1.