Screening of <Emphasis Type="Italic">Botrytis cinerea</Emphasis> isolates from vineyards in Israel for resistance to fungicides

Plots in two vineyards in the Golan Heights, Israel were treated with six botryticides during three growing seasons with 3 applications per season. Applications of fenhexamid, pyrimethanil and cyprodinil + fludioxonil were effective, resulting in 52–65% and 53–63% mean reduction in grey mould incidence and severity, respectively. Carbendazim, fluazinam and iprodione were ineffective or slightly effective. Five hundred and sixteen B. cinerea isolates were collected from infected berries or trapped from the air in the vineyards, and profiles of sensitivity to benomyl, fenhexamid, fluazinam, fludioxonil, iprodione and pyrimethanil were established for each of the isolates based on a mycelial growth test. Seventy-four percent of the isolates were sensitive to the six tested fungicides, and the other 26% of the isolates were classified into 10 phenotypes characterized by resistance to one or more fungicides. Resistant isolates showed fitness parameters similar or reduced in comparison to sensitive isolates. Resistance to benzimidazoles and to dicarboximides was the most frequent (up to 25%) and apparently pre-existed in the populations tested. Increased frequency of benzimidazole resistance, but not dicarboximide resistance, was observed following the 3 years of applications of the fungicides. High level resistance to pyrimethanil was present at a frequency of about 2% in both vineyards in the first 2 years of the sampling survey and reached 10% in the third year at Site 2. A few isolates were resistant to fenhexamid or fludioxonil (0.8 or 0.2%, respectively). No strong resistance to fluazinam was detected, although numerous, less sensitive isolates, presumably possessing multi-drug resistance traits, were recovered at higher frequency from the plots treated with fluazinam than from the untreated plots.     

Resistance to polyoxin AL and other fungicides in Botrytis cinerea collected from sweet basil crops in Israel

A total of 568 B. cinerea isolates were collected from diseased sweet basil plants and the air in 10 sweet basil greenhouses. Mycelial growth tests were used to evaluate the sensitivity of these isolates to benomyl, fenhexamid, iprodione, polyoxin AL and pyrimethanil. EC₅₀ values for polyoxin, the main botryticide on sweet basil in Israel, ranged from 0.4 to 6.5 μg ml^?1 and had a bimodal distribution; the EC₅₀ values for sensitive isolates ranged from 0.4 to 1.5 μg ml^?1 and the EC₅₀ values for low-level resistant isolates ranged from 4 to 6.5 μg ml^?1. Among populations that had not been exposed to polyoxin treatments, 20 to 35 % of the collected isolates were low-level resistant for polyoxin. Polyoxin treatments in an experimental greenhouse shifted the equilibrium in favour of low-level resistant isolates, and the change occurred rapidly: from a frequency of 20 % low-level resistant isolates in the population that had never been treated with polyoxin to a frequency of 72 % after a few treatments over two seasons. Prolonged use of polyoxin in Israeli basil crops (in some sites for more than 10 years) does not appear to have led to the development of high-level resistance, but low-level resistant isolates were found in commercial greenhouses with the frequency of up to 73 %. High-level resistance to benzimidazoles was common (60 to 80 % of isolates) in greenhouses with a history of benzimidazole treatments; whereas 15–25 % of the isolates from greenhouses in which fungicides were not used were resistant. Low-level resistance to dicarboximides was fairly widespread (frequency of 30 to 80 % depending on the greenhouse) and a few cases of moderate resistance to dicarboximides were also noted (frequency of 0 to 9 %). Neither high- nor low-level resistance to anilinopyrimidines was common in sweet basil commercial greenhouses (0 to 7 %). However, 34 % of the isolates were strongly resistant in the experimental greenhouse, following a few treatments with anilinopyrimidine fungicides during the previous season. Before those treatments, the proportion of anilinopyrimidines resistant isolates had been 1 %. About 3 % of the isolates exhibited low-level resistance to fenhexamid and no isolates were found to be strongly resistant to fenhexamid. Low-level resistance to one fungicide was often associated with low-level resistances to other fungicides. Thirty-two phenotypes exhibiting resistance to one or more of the tested fungicides were noted among B. cinerea isolates. Resistant isolates showed similar or reduced fitness parameters in comparison to wild-type isolates.