Abstract
Silicon (Si) efficiently controls Podosphaera xanthii in melon by affecting epidemic components related to the infection and colonization processes. Root amendments of Si prime melon defences, but its mode of action when sprayed on the leaves is unknown. The effects of potassium silicate (PS) on the development of the pathogen were observed by scanning electron microscopy. Both forms of PS application reduced conidial germination and delayed colony development. At 120 h after inoculation (hai), differentiation of the conidiophores was inhibited only by the root treatment and at 144 hai visual differences between PS treatments accentuated. Comparison of foliar PS with compounds of contrasting pH and ionic strength (KOH, KCl and PEG) showed that only PS and PEG inhibited conidial germination ruling out these variables as inhibitory factors. Alteration of the leaf surface tension was also excluded since it was affected by all compounds. The results indicate that foliar-applied PS affects P. xanthii conidial germination of and colony development by modifying the osmotic potential of the leaf surface.
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Acknowledgements
L. J. Dallagnol (Process 308149-2018-1) and L. E. A. Camargo (Process 301787/2017-4) are supported by fellowships from CNPq and Deivid A. Magano is supported by CAPES (PDSE process 99999.010628/2014-02). We thank Prof. G. H. Korndörfer for Si analyses, Prof. Mauricio Hunsche and Knut Wichterich from the University of Bonn (Germany) for ESEM analysis, surface tension and glasshouse studies, and the Núcleo de Apoio à Pesquisa em Microscopia Eletrônica Aplicada à Agricultura of ESALQ for the technical assistance with the SEM analyses.
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Dallagnol, L.J., Magano, D.A. & Camargo, L.E.A. Microscopic analysis reveals potential mode of action of foliar-applied potassium silicate against powdery mildew development. Eur J Plant Pathol 157, 815–823 (2020). https://doi.org/10.1007/s10658-020-02041-6
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DOI: https://doi.org/10.1007/s10658-020-02041-6