EFFECT OF PHTHALIMIDE FUNGICIDES ON SOMATIC SEGREGATION IN DIPLOID ASPERGILLUS NIDULANS

摘要

The fungicide metalaxyl did not increase the frequency of mitotic segregation (recombination) in a heterozygous diploid strain of Aspergillus nidulans. Some specimens of its formulated product Ridomil 25 WP, however, exhibited high recombinogenic activity. It was shown that this activity was due to an impurity which was separated by column and thin layer chromatography and bioassays of the various fractions, using A. nidulans and Pythium ultimum. The fractions which were not toxic to the former organism were genetically inactive, while those toxic only to the latter contained mainly metalaxyl. The genetically active compound was obtained as a colorless crystalline material whose mass and NMR spectra were identical to those of captafol. This and the related phthalimide fungicides captan, dichlofluanid, and tolylfluanid were subsequently found to greatly increase the yield of euploid segregants from the heterozygous diploid strain of A. nidulans.