Abstract
Isolates ofPenicillium italicum with differential levels of resistance to imazalil were obtained via step-wise mass selection of conidia of the fenarimol-resistant isolate E300-3 on imazalilamended PDA. Three out of five selection steps were successful. The resistance level to imazalil of isolates acquired after the two last selection steps was on average 122 and 197. The differential level of resistance was also apparent in decay control on oranges by imazalil inoculated with the various isolates. The isolates showed a similar cross-resistance pattern to other fungicides which inhibit C-14 demethylation of sterols (DMIs), although the level of resistance to these fungicides was significantly higher. All isolates displayed negatively-correlated cross-resistance to tridemorph and dodine. Most isolates had a normal virulence on oranges. In competition experiments with mixed-inocula of the wild-type and a resistant isolate, the proportion of the wild-type increased in successive generations on untreated oranges and the proportion of the resistant isolate increased on imazalil-treated oranges. The lower competitive ability of the resistant isolate on untreated oranges may be due to a decrease in spore production as compared with the wild-type.
Since isolate E300-3 was obtained in two selection steps on fenarimol-amended PDA, the isolates obtained in the last selection steps on imazalil-amended PDA may have at least five different genes for resistance to DMIs. This is consistent with resistance to DMIs being under polygenic control, with the genes involved having an additive interaction, although this is not the only possible explanation of the results.
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Berg, D., Büchel, K.-H. Krämer, W., Plempel, M. & Scheinpflug, H., 1988. Mechanistic studies as a tool for development of new compounds. In: Berg, D. & Plempel, M. (Eds), Sterol Biosynthesis Inhibitors. Pharmaceutical and Agrochemical Aspects. Ellis Horwood Ltd, Chichester, England, p. 168–184.
Berg, D., Born, L., Büchel, K.-H., Holmwood, G. & Kaulen, J., 1987. HWG 1608 — Chemistry and biochemistry of a new azole fungicide. Pflanzenschutz Nachrichten Bayer 40: 111–132.
Eckert, J.W., 1987.Penicillium digitatum biotypes with reduced sensitivity to imazalil. Phytopathology 77: 1728.
Eckert, J.W., 1990. Impact of fungicide resistance on citrus fruit decay control. In: Green, M.B. Le Baron, H.M. & Moberg, W.K. (Eds), Managing Resistance to Agrochemicals. ACS Symposium Serie 421: 286–302.
Georgopoulos, S.G., 1988. Genetics and population genetics. In: Delp, C.J. (Ed.) Fungicide Resistance in North America. APS Press, St Paul, USA, p. 12–13.
Heany, S.P., 1988. Population dynamics of DMI fungicide sensitivity changes in barley powdery mildew. In: Delp, C.J. (Ed.), Fungicide Resistance in North America. APS Press, St Paul, USA, p. 89–92.
Hollomon, D.W., Butters, J. & Clark, J., 1984. Genetic control of triadimenol resistance in barley powdery mildew. Proceedings 1984 Brighton Crop Protection Conference 2: 477–482.
Kalamarakis, A.E., Ziogas, B.N. & Georgopoulos, S.G., 1987. Resistance to ergosterol biosynthesis inhibitors inNectria haematococca var.cucurbitae. Chemical Control Newsletter 8: 18–19.
Köller, W. & Wubben, J.P., 1989. Variable resistance factors of fungicides acting as sterol demethylation inhibitors. Pesticide Science 26: 133–145.
Schepers, H.T.A.M., 1985. Changes during a three-year period in the sensitivity to ergosterol biosynthesis inhibitors ofSphaerotheca fuliginea in the Netherlands. Netherlands Journal of Plant Pathology 91: 105–118.
Tuyl, J.M. van, 1977. Genetics of fungal resistance to systemic fungicides. Mededelingen Landbouwhogeschool, Wageningen, the Netherlands 77–2, p. 1–136.
Waard, M.A. de & Fuchs, A., 1982. Resistance to ergosterol biosynthesis inhibitors. II. Genetic and physiological aspects. In: Dekker, J. & Georgopoulos, S.G. (Eds), Fungicide Resistance in Plant Protection. Pudoc, Wageningen, p. 87–100.
Waard, M.A. de, Groeneweg, H. & Nistelrooy, J.G.M. van 1982a. Laboratory resistance to fungicides which inhibit ergosterol biosynthesis inPenicillium italicum. Netherlands Journal of Plant Pathology 88: 99–112.
Waard, M.A. de & Nistelrooy, J.G.M. van, 1982b. Toxicity of fenpropimorph to fenarimol-resistant isolates ofPenicillium italicum. Netherlands Journal of Plant Pathology 88: 231–236.
Waard, M.A. de & Nistelrooy, J.G.M. van, 1983. Negatively correlated cross-resistance to dodine in fenarimol-resistant isolates of various fungi. Netherlands Journal of Plant Pathology 89: 67–73.
Waard, M.A. de & Nistelrooy, J.G.M. van, 1984. Differential accumulation of fenarimol by a wild-type isolate and fenarimol-resistant isolates ofPenicillium italicum. Netherlands Journal of Plant Pathology 90: 143–153.
Waard, M.A. de & Nistelrooy, J.G.M. van, 1988. Accumulation of SBI fungicides in wild-type and fenarimol resistant isolates ofPenicillium italicum. Pesticide Science 22: 371–382.
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De Waard, M.A., Van Nistelrooy, J.G.M. Stepwise development of laboratory resistance to DMI-fungicides in Penicillium italicum. Netherlands Journal of Plant Pathology 96, 321–329 (1990). https://doi.org/10.1007/BF01998780
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DOI: https://doi.org/10.1007/BF01998780