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Tolerance of Botrytis cinerea to 2,6-Dichloro-4-nitroaniline. R. K. Webster, Department of Plant Pathology, University of California, Davis 95616; J. M. Ogawa(2), and Elaine Bose(3). (2)(3)Department of Plant Pathology, University of California, Davis 95616. Phytopathology 60:1489-1492. Accepted for publication 5 May 1970. DOI: 10.1094/Phyto-60-1489.

Isolates of Botrytis cinerea grown on media containing 2,6-dichloro-4-nitroaniline (DCNA) gave rise to DCNA-tolerant variants. The growth of tolerant strains on the chemical was normal and usually equal to that on check plates. Subsequent hyphal-tip and single-spore cultures revealed that tolerant isolates may be heterocaryotic for tolerance and capable of growing on 7,000 ppm DCNA. Most isolates maintained tolerance even after growing for extensive periods in the absence of DCNA. Tolerant and susceptible isolates did not differ significantly in ability to rot peach and cherry fruits except, of course, on DCNA-treated fruits. Some DCNA-tolerant isolates showed tolerance also to other fungicides. Spores did not differ from mycelium in tolerance.