A new class of carboxin-resistant mutants of Ustilago maydis

  • S. G. Georgopoulos
  • B. N. Ziogas
Resistance to Systemic Fungicides


A small percentage of mutants of Ustilago maydis, selected on medium containing 40 μM carboxin, are distinctly more resistant than the mutants previously described, with an ED50 at least 100 times higher than that of wild type strains. Nine mutants of this category were studied. Crosses involving any one of these mutants gave Mendelian ratios in all cases and no transgressive segregation for level of tolerance was observed. All nine mutants were found to carry a mutation at the locus previously designated as oxr-1. In all cases carboxin resistance in vivo could be related to the resistance of the succinic dehydrogenase system in mitochondrial preparations and no other mechanism of resistance has been recognized. It appears that two allelic mutant genes at the oxr-1 locus code for two altered types of the succinic dehydrogenase complex distinguished by the level of carboxin tolerance.


Succinic Dehydrogenase Benomyl Aspergillus Nidulans Succinic Dehydrogenase Activity Mitochondrial Preparation 
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Copyright information

© Koninklijke Nederlandse Planteziektenkundige Vereniging 1977

Authors and Affiliations

  • S. G. Georgopoulos
    • 1
  • B. N. Ziogas
    • 2
  1. 1.Department of Plant PathologyAgricultural College of AthensAthensGreece
  2. 2.Department of BiologyN.R.C. ‘Demokritos’AthensGreece

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