Effect of sterol biosynthesis inhibitors and azole-type inducers on growth and development of Plasmopara viticola on grapevine
Keywords:downy mildew, finasteride, fungicides, peronosporomycetes, Vitis vinifera
AbstractThe effect of various azole fungicides (demethylation inhibitors, DMIs), mainly triazoles, that interfere with sterol metabolism in higher fungi, triazole-type inducers and an inhibitor of plant brassinosteroid biosynthesis on growth and spore production of the downy mildew pathogen of grapevine (Plasmopara viticola) was tested in a leaf disc-based system. Application of DMIs and azole-type inducers two days before inoculation resulted in a delayed mycelial growth during the first three days pot inoculation, which was not observed at day 5 or 7 post inoculation, and in a weakly reduced sporulation of the pathogen. These effects were not observed when compounds were applied during or post inoculation. Thus, azole treatments do not interfere with infections and epidemics caused by the downy mildew pathogen as observed in the field. However, alteration of brassinosteroid metabolism of the plant induced by the inhibition of a 5α-reductase with finasteride resulted in a markedly reduced sporulation. This indicates that plant derived sterols or those processes modulated by sterols interfere with the reproduction of the pathogen.
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