• DOI:10.1002/PS.399
• Corpus ID: 34130467

Laboratory studies to assess the risk of development of resistance to zoxamide.

@article{Young2001LaboratoryST,
  title={Laboratory studies to assess the risk of development of resistance to zoxamide.},
  author={David H Young and Sebastian Śpiewak and Richard A. Slawecki},
  journal={Pest management science},
  year={2001},
  volume={57 11},
  pages={
          1081-7
        }
}

• D. Young, S. Śpiewak, R. Slawecki
• Published 1 November 2001
• Biology
• Pest management science

Laboratory studies were conducted to evaluate the risk of developing field resistance to zoxamide, a new Oomycete fungicide which acts on microtubules. Zoxamide, metalaxyl and dimethomorph were compared with respect to the ease with which fungicide-resistant mutants could be isolated and their level of resistance. Attempts to generate mutants of Phytophthora capsici and P infestans with resistance to zoxamide by mycelial adaptation on fungicide-amended medium were unsuccessful. Similarly, changes in sensitivity to zoxamide were small (resistance factors < or = 2.2) in mutants of P capsici isolated by chemical mutagenesis of zoospore cysts. In parallel experiments with metalaxyl, highly resistant mutants were obtained using both adaptation (P capsici or P infestans) and chemical mutagenesis (P capsici). For dimethomorph, chemical mutagenesis (P capsici) yielded moderately resistant mutants (maximum resistance factor = 20.9), and adaptation (P capsici or P infestans) did not induce resistance. It is proposed that failure to isolate mutants resistant to zoxamide results from the diploid nature of Oomycete fungi and the likelihood that target-site mutations would produce a recessive phenotype. Our studies suggest that the risk of a highly resistant pathogen population developing rapidly in the field is much lower for zoxamide than for metalaxyl. However, as with any site-specific fungicide, appropriate precautions against resistance development should be taken.