PRELIMINARY RESULTS OF STROBILURIN SENSITIVITY OF ZYMOSEPTORIA TRITICI ITALIAN STRAINS

Mycosphaerella graminicola (anamorph: Zymoseptoria tritici) is the causal agent of leaf blotch, the most important foliar disease of wheat in Northern and Central Europe. In Italy only during the last few years, the incidence of the disease has been increased. The most common strategies for the control of the disease is the use of fungicides in particular QoIs, DMIs, and more recently were introduced the SDHIs. The resistance to QoIs and DMIs was already common in the main wheat cultivated areas in the world (Cools and Fraaije, 2008; Estep et al., 2015; Fraaije et al., 2005; Gisi et al., 2005; Leroux et al., 2005; Stammler and Semar, 2011; Stewart et al., 2014) while in Italy no results coming from wide and specific sensitivity monitoring are available. The aim of this study was to test the sensitivity of Z. tritici strains to QoI in order to obtain the first data about the Italian scenario. Leaves of bread and durum wheat were collected during 2015 from 10 fields with different use of fungicides (wild type, experimental centers and commercial ones) located in the North of Italy. The sensitivity of 60 isolates to azoxystrobin at different concentrations (0-0.001-0.01-0.1-1-2-10-20 mg/L of active ingredient) have been determined in vitro by microtiter assay (Stammler and Semar, 2011). The EC50 values of the wild types ranged from 0.02 to 0.12 mg/L of azoxystrobin, while the first analyzed isolates collected from experimental plots and commercial fields showed EC50s variable from 1.92 to 5.1 mg/L. Only one isolate pointed out an EC50 of 20.6 mg/L of active ingredient. On the base of these first results, we can suppose the presence of a slight decrease of sensitivity of Z. tritici isolates collected from Italian fields (according to Gisi et al., 2005). Molecular analysis on the presence of G143A substitution will be carried out.