Genetic effects of phthalimide fungicides on diploid Aspergillus nidulans

Abstract

A few specimens of ‘Ridomil 25 WP’, a commercial formulation of metalaxyl, showed high genetic activity on a heterozygous diploid strain of Aspergillus nidulans. This activity was due to an impurity which was identified by mass and n.m.r. spectroscopy as captafol. This and the related fungicides captan, dichlofluanid, and tolyfluanid greatly increased the yield of euploid colour segregants from the diploid strain. At low captafol concentrations, most of the induced segregants resulted from mitotic crossing over but chromosome non‐disjunction or loss was also caused at high concentrations. Mitotic crossing over could be induced also by vapour‐phase action of captafol and captan. The mechanism by which these phthalimides may exert their genetic effects is discussed.

Phenylpyrrole Fungicides: Mitotic Instability in Aspergillus nidulans and Resistance in Botrytis cinerea

“…of Aspergillus nidulans used in this work, was obtained from the collection of the Plant Pathology Laboratory of the Agricultural University of Athens. The genotype and the characteristics of this heterozygous diploid strain have been described by Ziogas and Georgopoulos (1987). To maintain the diploid heterozygotic condition this strain was kept on minimal medium (MM) containing only glucose and salts.…”

The effects of captafol on mitosis of Aspergillus nidulans through light and electron microscopic investigations

“…Previous reports suggested that captan and folpet, two fungicides relative to captafol, increased sectoring in a heterozygous diploid strain of A. nidulans (Richmond and Somers, 1966;Ziogas and Georgopoulos, 1987). Furthermore, captan has been reported to have mutagenic effects on some bacteria (Davidse, 1973;De Waard and Van Nistelrooy, 1984b).…”

“…Captafol was tested in concentrations 0.075 and 0.15 μg/ml. The above two concentrations were selected because of the observation made by Ziogas and Georgopoulos (1987) on the different mechanism of genetic activity on diploid strain of A. nidulans. At low captafol concentration (0.075 μg/ml) most of the induced segregants resulted from mitotic crossing-over but chromosome non-disjunction or loss was also caused at high concentration of the fungicide (0.15 μg/ml).…”

“…Furthermore, it has already been reported that pthalimides increase the frequency of mitotic segregation, leading to the production of color in diploid strains of Aspergillus nidulans. It has been also shown by Ziogas and Georgopoulos (1987) that most of the induced segregants resulted from mitotic crossing-over observed at low fungicide concentrations, while high concentrations also showed some effects. In addition, Couch and Siegel (1977) suggested that phthalimides exert deleterious effects on the genetic material.…”

The lipid compositions of two isolates of Cladosporium cucumerinum do not explain their differences in sensitivity to fungicides which inhibit sterol biosynthesis

“…Isolate 49628 had slightly less than 840905, which is in accord with their relative sensitivities to the polyene antibiotic pimaricin (V), for this polyene is known to bind preferentially to ergosterol. 15 The lack of methylated sterols in both treated and untreated mycelia eliminates the possibility that the resistance mechanism of isolate 49628 to DMIs is based on a capacity to utilise abnormal sterols in the absence of ergosterol. This is not surprising, as there appear to be no reported instances of mutants of filamentous fungi growing adequately with C-14a-methyl sterols as membrane components, although viable C-14a-methyl sterol-containing mutants of budding fungi are known.…”