Baseline sensitivity of Botrytis cinerea isolates from raspberry to a novel fungicide fluopyram

Botrytis cinerea Pers. Fr., the anamorph of Botryotinia fuckeliana, is a pathogen that causes grey mould on a wide variety of plants. It is one of the main factors that affect raspberry production worldwide. Sinde resistant cultivars do not exist, control of the disease is mainly based on fungicide sprays in flowering period. Most of the fungicides that have been recently developed for B. cinerea control (anilinpyrimidines, phenylpiroles and hydroxyanilides) are site specific inhibitors with a high-risk for resistance development. The intensive use of these chemicals led to rapid selection of resistant strains in many pathogens. In these cases, introduction of new fungicides belonging in different chemical groups with no cross-resistance with botryticides already in use, into spray programs is a convenient solution for overcoming limitations in disease control caused by fungicide resistance. Fluopyram belongs in a new chemical class known as pyridinyl ethylbenzamides. The active ingredient was developed to effectively control various plant diseases caused by fungal pathogens. The present study was conducted to evaluate the sensitivity to fluopyram of B. cinerea isolates from wild type population. The initial isolation was done from infected raspberry fruits originating from a field which had never be treated with any pesticides, Twenty six B. cinerea single spore isolates were obtained and identified based on colonial and conidial morphology. Sensitivity of the isolates to fluopyram was determined in radial growth experiment on PDA medium supplemented with a range of fungicide concentrations. Mycelial growth on fungicide-amended media was presented as percentage of the control. The fungicide concentration that inhibited mycelial growth by 50% (EC-50) compared to the control was calculated using probit analysis. The results showed that the sensitivity to fluopyram of B. cinerea isolates from wild type population, based on EC-50 values, ranged from 0.017 mg/l to 6.70 mg/l. These data will serve as a baseline to which any future B. cinerea sensitivity data can be compared to reveal any possible shifts in pathogen population regarding sensitivity to fluopyram.