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Fungicide resistance of Botrytis cinerea in tomato greenhouses in the Canary Islands and effectiveness of non-chemical treatments against gray mold

Rodríguez, A., Acosta, A., Rodríguez, C.
World journal of microbiology & biotechnology 2014 v.30 no.9 pp. 2397-2406
Botrytis cinerea, Candida, biological control agents, boscalid, carbendazim, diethofencarb, elicitors, fenhexamid, fruits, fungicide resistance, greenhouses, iprodione, petioles, phenotype, pyraclostrobin, pyrimethanil, tomatoes, yeasts, Canary Islands, Spain
Tomato greenhouses in the Canary Islands, Spain, were surveyed to estimate frequencies of resistance to benzimidazoles, dicarboximides, anilinopyrimidines and N-phenylcarbamates in Botrytis cinerea. Resistance to carbendazim, iprodione, pyrimethanil and diethofencarb was found in 74.2, 86.4, 28.8 and 31.8 % of isolates, respectively. Benzimidazole- and anilinopyrimide-resistant isolates were highly resistant, showing EC₅₀values above 500 µg/ml carbendazim and a mean EC₅₀value of 28.42 µg/ml pyrimethanil, respectively. By contrast, a low level of resistance was observed among dicarboximide-resistant isolates (mean EC₅₀value of 1.81 µg/ml iprodione). Phenotypes with double resistance to carbendazim and iprodione, and triple resistance to carbendazim, iprodione and pyrimethanil were the most common, occurring in 36.4 and 28.8 % of isolates. The surveyed greenhouses had never been treated with fenhexamid and Signum™ (pre-packed mixture of boscalid and pyraclostrobin), and baseline sensitivities of B. cinerea isolates to these fungicides were determined. The EC₅₀values were within the range of 0.009–0.795 µg/ml fenhexamid and of 0.014–0.48 µg/ml Signum. In addition, available formulations based on elicitors of plant defense response and biocontrol agents were evaluated against B. cinerea in tomato plants under semi-controlled greenhouse conditions, the yeast Candida sake CPA-1 being able to reduce gray mold significantly when it was applied on petiole wounds and the plants were inoculated 24 h later. Likewise, C. sake was effective against B. cinerea in harvested tomato fruits, yeast-treated tomatoes showed a 70.66 and 30.31 % reduction in the diameters of decay lesions compared with controls after 10 days of storage at 20 and 9 °C, respectively.