DISTRIBUTION AND FITNESS OF ISOLATES OF BOTRYTIS-CINEREA WITH MULTIPLE FUNGICIDE RESISTANCE IN SPANISH GREENHOUSES

Forty-nine greenhouses of vegetable crops were surveyed in southeast S pain at the beginning of the disease season in December 1992 to estima te frequencies of resistance to benzimidazoles. dicarboximides and N-p henylcarbamates (NPC) in B. cinerea. Out of 261 isolates collected, 28 % were sensitive to both benzimidazoles and dicarboximides, 15% were b enzimidazole-resistant and dicarboximide-sensitive, 8% were benzimidaz ole-sensitive and dicarboximide-resistant and 46% were benzimidazole- and dicarboximide-resistant. Resistance to benzimidazole, dicarboximid e and N-phenylcarbamate was determined by measuring the ability of eac h isolate to,row in the presence of carbendazim, procymidone and dieth ofencarb fungicides respectively. Carbendazim- or procymidone-resistan t isolates were found in all surveyed greenhouses. Three isolates were found with resistance to carbendazim, procymidone and diethofencarb c ollected in two adjacent greenhouses that were sprayed with the carben dazim and diethofencarb mixture. All other isolates were sensitive to the mixture because they were either sensitive to carbendazim and resi stant to diethofencarb or vice versa. Fitness of 31 isolates of B. cin erea was determined in vivo by measuring their sporulation and lesion growth rate on leaf disks. No fitness costs were associated with resis tance to iprodione (dicarboximide) and benomyl (benzimidazole). Isolat es with EC(50) values higher than 101 mg/L for benomyl and 1.6 mg/L fo r iprodione were considered to be field resistant (they caused visible lesions on cucumber leaf disks treated with each fungicide).