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Resistance to benzimidazole fungicides in the gummy stem blight pathogen Didymelta bryoniae on cucurbits
Author(s) -
MALATHRAKIS N. E.,
VAKALOUNAKIS D. J.
Publication year - 1983
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/j.1365-3059.1983.tb02853.x
Subject(s) - benomyl , biology , fungicide , carbendazim , horticulture , inoculation , spore , mycelium , spore germination , pathogen , germination , botany , microbiology and biotechnology
Benzimidazoles were used successfully against gummy stem blight of cucurbits for only one growing season (1980). It was soon noticed in experiments in vivo that they were not effective against some isolates of the pathogen. In a survey during the 1981 crop season, 76 out of 102 isolates collected from 20 plastic greenhouses all over the main cucurbit‐growing areas of Crete were resistant to benomyl. The average benomyl concentrations that reduced mycelial growth rates of seven resistant and seven sensitive isolates by 50% were 716 ± 49 and 1.2 ± 0.34μg/ml respectively. The average growth rate of resistant isolates was lower than that of sensitive isolates but there were no differences in spore production and spore germination. The pathogenicity of resistant isolates on young cucumber plants was lower than that of sensitive isolates. The application of benomyl, carbendazim, cypendazole and thiophanate methyl to young cucumber plants at the rate of 300μg a.i./ml 1 day before inoculation with 500 000 spores/ml of the resistant isolates did not affect the infection rate of the disease after 4 days. Sensitive isolates caused no onslight symptoms on similarly treated plants.