Toxicity assessment of metabolites of fungal biocontrol agents using two different (Artemia salina and Daphnia magna) invertebrate bioassays

Fungal biocontrol agents (BCAs) have been marketed for control of crop pests, weeds, and diseases. However, BCAs may produce toxic metabolites, whose presence in the formulated products, in the crops and in the environment should be considered along with the associated risk. Two invertebrate models, viz. Artemia salina and Daphnia magna were used to assess the acute toxicity of seven BCA metabolites, characterized by different chemical nature and mode of action, namely alamethicin (ALA), paracelsin (PCS), antiamoebin (AAM), gliotoxin (GTX), destruxin A (DA), oosporein (OOS), and elsinochrome A (EA). The two invertebrates were very sensitive to all the metabolites examined, except OOS. The LC50s after 24 and 36 h exposures showed the following toxicity ranks: A. salina, DA > ALA > EA > GTX > AAM > PCS (LC50s ranging from 9.78 to 40.84 μg/ml at 24 h and from 2.92 to 18.56 μg/ml at 36 h); D. magna, DA > GTX = EA > ALA > PCS > AAM (LC50s ranging from 0.20 to 24.41 μg/ml at 24 h and from 0.16 to 11.98 μg/ml at 36 h). LC50 of OOS to D. magna increased dramatically in 36 h exposure, compared to 24 h exposures (5.84 and 68.40 μg/ml, respectively). A. salina and D. magna proved to be suitable models for rapid and inexpensive screening of toxicity of BCAs at an early stage of product development.