Yeasts as a model for assessing the toxicity of the fungicides Penconazol, Cymoxanil and Dichlo¯uanid I.C. Ribeiro a , I. Ver  õssimo a , L. Moniz a , H. Cardoso a , M.J. Sousa a , A.M.V.M. Soares b , C. Le~ ao a, * a Departamento de Biologia, Centro de Ci^ encias do Ambiente, Universidade do Minho, Campus de Gualtar, 4700 Braga Codex, Portugal b Instituto do Ambiente e Vida e Departamento de Zoologia, Universidade de Coimbra, Coimbra, Portugal Received 8 April 1999; accepted 18 January 2000 Abstract In the present work the sensitivity of yeast strains of Kluyveromyces marxianus, Pichia anomala, Candida utilis, Schizosaccharomyces pombe and Saccharomyces cerevisiae, to the fungicides cymoxanil, penconazol, and dichlo¯ua- nid, was evaluated. Dichlo¯uanid induced the most negative eects, whereas penconazol in general was not very toxic. Overall, our results show that the parameters IC 50 for speci®c respiration rates of C. utilis and S. cerevisiae and C D for cell viability of S. cerevisiae can be applied to quantify the toxicity level of the above compounds in yeast. Hence, could be explored as an alternative or at least as a complementary test in toxicity studies and, therefore, its potential for inclusion in a tier testing toxicity test battery merits further research. Ó 2000 Elsevier Science Ltd. All rights reserved. 1. Introduction The ecotoxicity of chemical compounds or natural toxins can be assessed with vertebrate bioassays, in vitro bioassays or bioassays with invertebrates, bacteria or algae. Fungicides are widely used in agriculture, being released to the environment in large amounts. Studies on the evaluation of the toxicity of these compounds still depend extensively on the utilization of animals, but in the last years several publications have dealt with the development and appropriateness of several alternative methods for assessing toxicity, that either do not depend on animal utilization or explore the use of rapid and cost-eective alternatives (Guilhermino et al., 1994, 1996, 1999; da Silva et al., 1998). Yeast, as euchariotics, are potentially good model systems particularly for the evaluation of citotoxicity. Furthermore, they are widely spread in nature playing important roles in many eco- systems. From a practical point of view they also present advantages, since they are easy to maintain and cultivate under controlled conditions, avoiding the problems of variability found with more complex organisms (for a review see Soares and Calow, 1993). Although Koch et al. (1993) has already proposed yeast as alternative organism for testing acute toxicity of drugs and environ- mental chemicals, the use of yeast as alternative toxicity test organisms or as tools for a preliminary toxicity screening or for inclusion in a tier testing battery has received little attention. In this work, strains of ®ve dierent yeast species were selected for testing toxicity of the fungicides pen- conazol, cymoxanil and dichlo¯uanid, evaluating their eects on the speci®c growth rate, the biomass produc- tion, the speci®c respiration rate and the yeast viability. The results will be compared with those reported for other organisms, and evidence is presented suggesting yeast as a model for assessing the toxicity of the fungi- cides tested. Chemosphere 41 (2000) 1637±1642 * Corresponding author. Tel.: +351-253-604310; fax: +351- 253-678980. E-mail address: cleao@bio.uminho.pt (C. Le~ ao). 0045-6535/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 5 - 6 5 3 5 ( 0 0 ) 0 0 0 3 9 - 4