Quinoxyfen perturbs signal transduction in barley powdery mildew (Blumeria graminis f.sp. hordei)

Abstract

SUMMARY Quinoxyfen is a protectant fungicide which controls powdery mildew diseases by interfering with germination and/or appressorium formation. Mutants of barley powdery mildew, Blumeria graminis f.sp. hordei, which are resistant to quinoxyfen produce fewer conidia, which germinate and form appressoria more promiscuously than do the prolific numbers of wild‐type spores. This suggests that resistance bypasses host recognition signals. RT‐PCR profiles of signal transduction genes, recorded during wild‐type germling morphogenesis, reveals that quinoxyfen alters the accumulation of Protein Kinase C (pkc), pkc‐like and catalytic subunit of Protein Kinase A (cpka) transcripts. Differential display‐reverse transcription PCR identified a gene transcript in wild‐type conidia that was absent, or much less abundant, in conidia from quinoxyfen‐resistant mutants. This mRNA was not detectable 24 h after wild‐type conidia were inoculated on to barley. It encodes a GTPase activating protein (GAP), which may interact with a small molecular weight Ras‐type GTP binding protein. In the presence of quinoxyfen, the gap mRNA remains throughout germling morphogenesis. The involvement of GAP in resistance suggests that quinoxyfen inhibits mildew infection by disrupting early cell signalling events.

Phenolic compounds and antioxidant activity of red wine made from grapes treated with different fungicides

“…Nowadays, several fungicides are used to control diseases in grapes: famoxadone, oxazolidinone known for its effective, wideranging prevention of various foliar fungal diseases (Bartlett et al, 2002;Jernberg, 2003); fenhexamid, hydroxyanilide used in the control of Botrytis cinerea in grapes (Duben, Rosslenbroich, & Jenner, 2002); fluquinconazole, thiazole used in the control of Uncinula necator (Metcalfe, Shaw, & Russell, 2000); kresoximmethyl, oxymino acetate (strobilurin) used to control U. necator in grapes (Grossmann & Retzlaff, 1999); quinoxyfen, a quinoline used in grapes to control powdery mildew (U. necator) (Wheeler et al, 2003); and trifloxystrobin, an active strobilurin to combat powdery mildew in grapes (De Melo, Correia, Herbet, Santos, & Alves, 2005).…”

Effect of null mutations in the AbNIK1 gene on saprophytic and parasitic fitness of Alternaria brassicicola isolates highly resistant to dicarboximide fungicides

“…Similarly, over the last decade, several studies have strongly suggested that some fungicides may also interfere with fungal intracellular signal transduction pathways. Quinoxyfen, a phenoxyquinoline introduced for control of powdery mildew diseases, has been shown to inhibit mildew infection by disrupting G‐protein production and early cell signalling events (Wheeler et al ., 2003). Dicarboximide fungicides (DCF), which are highly active broad‐spectrum compounds, and phenylpyrolles, which have mainly been used to control Botrytis cinerea , are both believed to exert their toxic effects on fungi through activation of the osmoregulation pathway (Kojima et al ., 2004; Ma & Michailides, 2005).…”

Sensitivity of Uncinula necator to quinoxyfen: evaluation of isolates selected using a discriminatory dose screen

“…Although the exact site of action of quinoxyfen has not yet been determined, its effects have been linked to disruption of early cell signalling events in Blumeria graminis Speer f. sp. hordei Marchal (Bgh) 5. Because it acts on early stages of development, it has been demonstrated that quinoxyfen is only successful in preventing infection and eventual colony development if it is present within the first 4–6 h after Bgh contacts a host plant (Dow AgroSciences, unpublished).…”