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Management of Monilinia fructicola resistance to tebuconazole in the field

Louise Larissa May De Mio: Federal University of Parana

<div>Brown rot is the main peach disease in the world and the main control is based in fungicides. The tebuconazole has been the most used one in the last decade in Brazil. Several resistant individuals are present in the population and still exist a lack in information how to manage the resistance in the field. The frequency of resistance in <em>M. fructicola</em> population from orchards with different managements of tebuconazole was monitored during 3 seasons (2012/13, 2013/14 and 2014/15) in the states of Paraná (PR) and São Paulo (SP). The number of sprayings with demethylation inhibitors (DMI) fungicides varied from 0 to 2 (PR) and 6 to 16 (SP) until the 2011/12 season. The application of DMI was reduced to 0 to 1 in subsequent seasons and isolates growth at discriminatory concentration of 0.3 µg/ml of tebuconazole. Changes in density curves and sensitivity distributions revealed that SP and PR populations differed (<em>p</em> value<0.05). PR population has remained sensitive during the seasons. The population from SP had high, intermediate and low frequency of the resistance isolates in the season 2012/13, 2013/14 and 2014/15, respectively. The absence of tebuconazole fungicide applications associated with fitness penalty of resistant isolates could restore sensitivity of the population in the field. To confirm resistant phenotypes a sample of isolates was analyzed and the G461S mutation in the MfCYP51 gene was detected in 88 % of the isolates.</div>