Study on fungicide sensitivity and resistance in a population of botryotinia fuckeliana collected from table grapes in Sicily (Southern Italy)

Abstract

Grey mould, caused by Botrytis cinerea, is one of the major disease in grapevine. Chemical control represents the main way to reduce the incidence of grey mould in grapevine. However, the intensive use of fungicides has led to a rapid selection of resistance strains both in Italy and in many other countries worldwide. This occurrence has been becoming a severe problem for disease control on table grapevine crop. During 2009-2012, a total of 146 B. cinerea isolates was collected from several commercial vineyards located in Catania and Ragusa provinces. They were tested in vitro for fungicide sensitivity to boscalid, carbendazim, fenhexamid, fludioxonil, iprodione, pyrimethanil and fluopyram. Measurement of sensitivity to fungicides was based on inhibition of mycelial growth and by determining of EC50 (Effective concentration that is able to reduced by 50% the mycelial growth and sporulation). A few isolates were resistant to boscalid, carbendazim and iprodione. No resistance to fenhexamid and fludioxonil was detected. Fungicide sensitivity phenotypes determined by mycelium growth was verified in vivo on leaves of bean seedlings and grape leaves. The second objective of this study was to verify the efficacy of the fungicides in controlling gray mould on detached grape berries and to determine whether their effectiveness was compromised by fungicide-resistant isolates of B. cinerea. The efficacy of pyrimethanil was determined also on apple fruits cv. Golden Delicious.