Resistance to Thiabendazole and Benomyl of Penicillium digitatum and P. italicum Isolated from Citrus Fruit from Several Countries1

Abstract

Abstract Strains of Penicillium digitatum (Sacc.) and P. italicum (Wehmer) resistant to thiabendazole and benomyl were isolated from decaying citrus fruits obtained from the Rotterdam, Netherlands, terminal market and originating from 18 countries. Significantly more Penicillium sp isolates with resistance to thiabendazole and benomyl were collected from grapefruit and lemons than from oranges. Significantly more isolates of P. digitatum than P. italicum grew on agar plates with 4, 10, or 40 ppm thiabendazole. A greater percentage of P. digitatum than P. italicum isolates grew on 4 and 10 ppm benomyl-agar plates, but a greater percentage of P. italicum than P. digitatum isolates grew on 40 and 80 ppm benomyl-agar plates. Both species were more resistant to thiabendazole than to benomyl, and often showed cross-resistance to the fungicides. Resistant Penicillium sp isolates produced larger colonies on 4 and 10 ppm thiabendazole and 40 and 80 ppm benomyl.