Search

Unlabelled: The objective of this work was to study the sensitivity to mandipropamid of 33 Plasmopara viticola populations utilizing both molecular and biological techniques. The PCR-RFLP technique was developed in order to detect the single point mutation, G1105S, occurring on the PvCesA3 gene. The sensitivity was also studied using the leaf-disc bioassay. Thirty-three downy mildew-infected leaf samples, collected from 2010 to 2013 from Italian vineyards, were used in the study. PCR-RFLP revealed the presence of 7 resistant, 12 sensitive, 14 mixed (sensitive and resistant) mutation profiles. Effective concentration for 50% inhibition rate (EC50 ) calculated from the bioassays showed an EC50  < 1 mg l(-1) for samples that showed sensitive profiles, while for those samples that had a mixed profile, EC50 ranged from <1 to >300 mg l(-1) , and values for resistant profiles ranged from 200·28 to >300 mg l(-1) . The results suggest that P. viticola populations infecting Italian vineyards are under a selection pressure due to CAA-based fungicide applications., Significance and Impact of the Study: We characterized Plasmopara viticola populations utilizing PCR-RFLP technique to detect a point mutation known to cause resistance to carboxylic acid amides (CAA) fungicides. Sensitivity of these samples to the mandipropamid fungicide was assayed by a leaf-disc method. In this work, we provide the first evidence about the presence of mandipropamid-resistant populations of P. viticola from commercial vineyards in Italy. Improving the knowledge about development of resistant populations could enhance the current grapevine downy mildew management strategies and minimize the risk of the spread of mandipropamid and other CAA-resistant populations., (© 2016 The Society for Applied Microbiology.) more...

Background: Plasmopara viticola is controlled by fungicides with different modes of action, including carboxylic acid amides (CAAs). The aim of this study was to evaluate differences in the response of CAA-resistant P. viticola strains towards CAAs., Results: The G1105S mutation affects all four CAAs, but with different impacts. While this confirms that they have the same mode of action, it shows that differences between CAAs can occur., Conclusion: Further molecular modelling and docking studies are needed to gain a better understanding of the different behaviours reported here. © 2015 Society of Chemical Industry., (© 2015 Society of Chemical Industry.) more...

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.) more...