Toxicology Letters 161 (2006) 43–52 Evaluation of different biological test systems to assess the toxicity of metabolites from fungal biocontrol agents Anke Skrobek a , D´ esir´ ee Boss b , Genevi` eve D´ efago b , Tariq M. Butt a , Monika Maurhofer b,∗ a School of Biological Sciences, University of Wales Swansea, Singleton Park, Swansea SA2 8PP, UK b Institute of Plant Sciences/Phytopathology Group, Swiss Federal Institute of Technology, Universit¨ atsstrasse 2, 8092 Z¨ urich, Switzerland Received 25 April 2005; received in revised form 28 July 2005; accepted 29 July 2005 Available online 1 September 2005 Abstract The development of fungal biocontrol agents (BCAs) as alternatives to chemical pesticides is of increasing public interest. Tools to assess the toxicity of the secondary metabolites that these BCAs produce are often not available or existing methods have not yet been evaluated for these compounds. This study compares five different test systems, which include a representative bacterium, protozoan, arthropod and insect and human cell lines, as regards their sensitivity. It also compares the cost in time and resources for conducting the tests. Pure metabolites and crude extracts from two fungal BCAs as well as two chemical pesticides (hoestar and chlorpyrifos) and the mycotoxin patulin were employed as test compounds. All tests systems proved to be suitable for toxicity studies of metabolites from fungal BCAs and showed different grades of sensitivity to the different substances. The possibility of employing an array of test systems to determine ecotoxicological properties is discussed. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Fungal metabolites; Metarhizium anisopliae; Stagonospora convolvuli; Destruxins; Elsinochrome A; Biological test systems; Risk assessment 1. Introduction The development of safe alternatives to chemical pesticides like fungal biocontrol agents (BCAs) is of increasing public interest but registration poses a major hurdle in the commercialization of fungal BCAs. It is a lengthy, costly process, largely following rules and guidelines developed for synthetic pesticides (Butt et al., 2001). Risk assessment is a prerequisite component of ∗ Corresponding author. Tel.: +41 1 632 38 68; fax: +41 1 632 15 72. E-mail address: monika.maurhofer@ipw.agrl.ethz.ch (M. Maurhofer). registration and of particular concern are the fungal sec- ondary metabolites. At present, no tools or simulation models exist to determine if fungal BCA metabolites enter the food chain and pose a risk to human and animal health. The majority of test systems employed for assessing the toxicity of chemical pesticides have not been evaluated for secondary metabolites from fun- gal BCAs. Although fungal BCAs produce an array of metabolites these are usually secreted in tiny quantities and their production may vary between species, strains and culture conditions (Amiri-Besheli et al., 2000; Kershaw et al., 1999; Quesada-Moraga and Vey, 2003; Strasser et al., 2000; Vey et al., 2001; Wang et al., 2004). The high cost in obtaining enough material to perform common mammal toxicity tests with each individual 0378-4274/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.toxlet.2005.07.014