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Aflatoxin production by entomopathogenic isolates of Aspergillus parasiticus and Aspergillus flavus
1Department of Entomology, University of Adelaide, Glen Osmond, Australia.
Abstract:
Fourteen isolates of Aspergillus parasiticus and 2 isolates of Aspergillus flavus isolated from the mealybug Saccharicoccus sacchari were analyzed for production of aflatoxins B1, B2, G1, and G2 in liquid culture over a 20-day period. Twelve Aspergillus isolates including 11 A. parasiticus and 1 A. flavus produced aflatoxins which were extracted from both the mycelium and culture filtrate. Aflatoxin production was detected at day 3 and was detected continually for up to day 20. Aflatoxin B1 production was greatest between 7 and 10 days and significantly higher quantities were produced by A. flavus compared to A. parasiticus. Aflatoxin production was not a stable trait in 1 A. parasiticus isolate passaged 50 times on agar. In addition to loss of aflatoxin production, an associated loss in sporulation ability was also observed in this passaged isolate, although it did maintain pathogenicity against S. sacchari. An aflatoxin B1 concentration of 0.16 micrograms/mealybug (14.2 micrograms/g wet wt) was detected within the tissues of infected mealybugs 7 days after inoculation. In conclusion, the ability of Aspergillus isolates to produce aflatoxins was not essential to the entomopathogenic activity of this fungus against its host S. sacchari.
Insights
Aspergillus fungi isolated from mealybugs can produce aflatoxins, with production varying between species and over time. Aflatoxin production is not essential for the fungus
Area of Science:
- Mycology
- Plant Pathology
- Entomology
Background:
- Mealybugs, such as Saccharicoccus sacchari, can host various microorganisms.
- Certain Aspergillus species are known producers of aflatoxins, which are toxic secondary metabolites.
Purpose of the Study:
- To analyze aflatoxin production by Aspergillus parasiticus and Aspergillus flavus isolates from S. sacchari.
- To determine the stability of aflatoxin production and its relation to pathogenicity.
Main Methods:
- Isolation of Aspergillus species from S. sacchari.
- Culturing isolates in liquid media for 20 days to assess aflatoxin B1, B2, G1, and G2 production.
- Extraction and quantification of aflatoxins from mycelium and culture filtrate.
- Passaging one isolate to evaluate stability of aflatoxin production and pathogenicity.
Main Results:
- Twelve of the 16 Aspergillus isolates produced aflatoxins, with production detected from day 3 to day 20.
- Aflatoxin B1 production peaked between 7 and 10 days, with higher yields from A. flavus compared to A. parasiticus.
- One A. parasiticus isolate lost aflatoxin production and sporulation ability after repeated passaging but retained pathogenicity.
Conclusions:
- Aspergillus isolates from S. sacchari are capable of producing aflatoxins.
- Aflatoxin production is not a stable trait in all isolates and is not essential for entomopathogenicity against S. sacchari.