Sensitivity to strobilurin fungicides of Italian Venturia inaequalis populations with different origin and scab control.

BACKGROUND

Venturia inaequalis (Cooke) Winter with reduced sensitivity to strobilurins has been reported in several countries, including Italy. This study aimed to characterise the sensitivity to strobilurins of three different types of V. inaequalis population: (a) wild types; (b) from commercial orchards satisfactorily managed with strobilurins; (c) from an experimental orchard with control failures by trifloxystrobin and kresoxim-methyl. In vitro sensitivity tests included antigerminative activity on population conidia and mycelial growth inhibition on monoconidial isolates. Cleaved amplified polymorphic sequence (CAPS) analysis was used for the detection of G143A substitution.

RESULTS

Wild-type populations showed EC(50) values lower than 0.031 mg L(-1), while those of orchards with good performance by strobilurins presented EC(50) values never higher than 0.063 mg L(-1). Samples with scab control failures showed a strongly reduced population sensitivity. Similar differences were confirmed in monoconidial isolates. The G143A substitution was always detected in low-sensitivity populations, only sometimes in well-controlled populations and generally not in wild types.

CONCLUSIONS

In vitro sensitivity assays were able to discriminate the three population types with different scab management, while the qualitative PCR analysis (CAPS) was only partially reliable. High sensitivity differences among V. inaequalis populations with good and poor field control by strobilurins were observed.

Copyright © 2011 Society of Chemical Industry.