Determination of sensitivity levels of gray mold disease pathogen (Botrytis cinerea Pers. Ex. Fr.) in lettuce agai̇nst some fungits in the eastern marmara region

One of the important diseases that causes a problem in lettuce production is gray mold disease caused by Botrytis cinerea. This pathogen is one of the microorganisms that gain the fastest resistance to fungicides. This thesis study was carried out to determine the susceptibility levels of Botrytis cinerea, which causes gray mold in lettuce, to some fungicides. Isolates were obtained from the samples taken from greenhouse lettuce production area in Söğüt district of Bilecik province. The isolates were evaluated according to colony morphology based on mycelial growth, sporulation and sclerotia production. The decreases in susceptibility of the isolates toward fungicides containing the active substances 125 g/L fluopyram+375 g/L pyrimethanil, 26.7% boscalid+6.7% pyraclostrobin and 75 g/L fluxapyroxad+50 g/L difenoconazole are determined in vitro condition. As a result of the studies, 20 isolates were obtained from samples. According to the colony morphology, 4 isolates were grouped in the mycelial group, while 16 isolates were grouped in the sclerotia group. As a result of in vitro studies, the highest EC50 value determined in isolate of M2 against fungicides containing Fluopyram+pyrimethanil and boscalid+pyraclostrobin active substances. The EC50 values calculated for M2 isolate was determined as 37.657 µg/ml and 51.025 µg/ml, respectively. Against the fungicide containing fluxapyroxad+difenoconazole active substances, the highest EC50 value was determined in isolate of M8 with 11.154 µg/ml. In detached leaf test, 2 isolates with the highest EC50 value and 1 isolate with the lowest EC50 value were chosen and tested against each fungicide. As a result of the experiments, isolates with high EC50 values formed lesions on lettuce leaves. Fungicides have failed to inhibit these isolates. On the other hand, isolate with low EC50 value could not form lesions on lettuce leaves. This situation reveals that the isolate is sensitive to fungicides. It has been determined that some Botrytis cinerea isolates have low susceptibility toward used fungicides, both in vitro conditions and in detached leaf test.