Molecular characterisation and detection of resistance to succinate dehydrogenase inhibitor fungicides in Botryotinia fuckeliana (Botrytis cinerea)

Abstract

Fluopyram-resistant mutants are currently rarely detected in the field sprayed with boscalid, but this may change with intensive exposure of the fungal population to fluopyram. PCR assays/methods developed in the study provide tools for fast monitoring of field populations and observing possible changes in population composition following fluopyram introduction, useful for the setting-up of appropriate preventive measures.

Baseline sensitivity and efficacy of fluopyram against Botrytis cinerea from table grape in Italy

“…Different single-point mutations in sdh gene are involved in resistance mechanisms of B. cinerea for these compounds (Veloukas et al, 2011(Veloukas et al, , 2013Yin et al, 2011;Veloukas & Karaoglanidis, 2012;Amiri et al, 2014). Our data are in agreement with recent reports (Veloukas et al, 2013;Amiri et al, 2014) as boscalid-resistant isolates used in this study possessed H272R mutation in the SdhB subunit that display a differential sensitivity to the SDHIs (Lalève et al, 2013;De Miccolis Angelini et al, 2014a). Control efficacy of SDHI fungicides confirmed data obtained in vitro.…”

“…The discrepancies of cross-resistance patterns within SDHIs group, with particular reference to boscalid and fluopyram, were recently detected in vitro and by molecular analysis in target fungi from different hosts (Avenot & Michailides, 2010;Avenot et al, 2012;Amiri et al, 2014;De Miccolis Angelini et al, 2014a). These findings suggested slight differences in the binding sites in complex II of SDH and additional mechanisms of resistance for these molecules (Avenot et al, 2014).…”

“…The SDHIs have a single mode of action and inhibit the fungal respiration process by binding to the ubiquinone reduction site of complex II of the respiratory chain, known as succinate dehydrogenase (Horsefield et al, 2006;Stammler et al, 2008;Avenot & Michailides, 2010). Recently, boscalid has been re-classified by FRAC as a fungicide with a medium-high level of resistance (http://www.frac.info) as several cases of field and laboratory resistance were claimed in Europe and other continents (Bertetti et al, 2008;Bardas et al, 2010;Mercier et al, 2010;Leroch et al, 2011;Veloukas et al, 2011;Weber, 2011;Yin et al, 2011;Fernández-Ortuño et al, 2012;Latorre & Torres, 2012;De Miccolis Angelini et al, 2014a).…”

Detection of sdhB Gene Mutations in SDHI-Resistant Isolates of Botrytis cinerea Using High Resolution Melting (HRM) Analysis

“…The availability of different molecules belonging in the same fungicide class along with the observed variability in sdh B mutations associated with resistance to SDHIs makes necessary the development of a rapid method enabling the simultaneous detection of the several sdh B mutations. This is particularly important taking into account that the several sdh B mutations confer differential levels of resistance to the different SDHI molecules (Veloukas et al, 2013; Amiri et al, 2014; De Miccolis Angelini et al, 2014a). For instance, H272Y mutation confers moderate levels of resistance to boscalid or low levels of resistance to isopyrazam but it is associated with hypersensitivity to fluopyram.…”

“…Sequence analysis of the four sdh subunits in SDHI-resistant strains revealed that resistance was associated with nine target site mutations located in the sdh B subunit and one mutation in the sdh D subunit. In the sdh B subunit mutations associated with resistance to SDHIs have been detected at codons 225, 230, and 272 (Leroux et al, 2010; Veloukas et al, 2011; De Miccolis Angelini et al, 2014a; Esterio et al, 2015). At codon 225 the proline can be substituted by phenylalanine (P225F), leucine (P225L), threonine (P225T), or histidine (P225H).…”