Progress in understanding molecular mechanisms and evolution of resistance to succinate dehydrogenase inhibiting (SDHI) fungicides in phytopathogenic fungi

Effectiveness of isofetamid, a new succinate dehydrogenase inhibitor fungicide, in the control of grapevine gray mold

“…It belongs to the phenyl-oxoethyl thiophene amide chemical group (FRAC, 2013) and has a single-site mode of action that inhibits fungal respiration by blocking electron transport, which is achieved by reducing the activity of the succinate dehydrogenase at complex II in the electron chain in the inner mitochondria membrane (FRAC, 2013). This new fungicide and the more commonly known fungicide boscalid are succinate dehydrogenase inhibitors (SDHIs) (Avenot and Michailides, 2010;FRAC, 2013). The objectives of this study were i. to determine baseline sensitivity of B. cinerea to isofetamid and ii.…”

Detection of Fungicide Resistance

“…The amplified fragments from S and R contain two and three RE recognition sites, respectively, which is sufficient discrimination in the case of fungi, which are mostly haploid. (Sierotzki et al 2000;Avenot and Michailides, 2010). This can also result in the identification of heteroplasmy in resistance (as seen in Fontaine et al, 2009) with restriction patterns that resemble those found in heterozygous diploids, or even incomplete digestions.…”

“…Field and laboratory mutants resistant to carboxin and boscalid have been reported in a variety of fungi and cropping systems (For a recent review see Avenot and Michailides 2010). Carboxin and other SDHI fungicide resistances are described as monogenic, and have been identified in both field and laboratory.…”

“…This class of compounds targets and binds to the ubiquinone-binding site (Q-site) of the mitochondrial complex II, specifically the succinate dehydrogenase (SDH) complex in the respiratory chain also referred to as complex II or succinate:ubiquinone oxidoreductase (SQR), inhibiting fungal respiration by blocking electron transport [Kuhn, 1984; reviewed by Avenot and Michailides (2010), including a recent list of resistant organisms and corresponding mutations]. There is no evidence of cross-resistance with other similarly acting chemical classes such as QoI fungicides (which also affect energy production and electron transport) due to their unique mode of action and target site.…”

Structure-activity relationships of positional isomers in aromatic heterocyclic carboxamide fungicides

“…Because of their specific mode of action, they generally show no cross-resistance with other chemical classes (strobilurins, benzimidazoles, and dicarboximides). 3,4) Furthermore, they show high activity against various diseases. Therefore, they are excellent candidates for resistance management of fungicides and were first used in agriculture in the late 1960s.…”