Effects of MgO and Mg(OH)2 Microparticle Foliar Treatment

on Tomato PR Gene Expression and Leaf Microbiome

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Effects of Magnesium Oxide and Magnesium Hydroxide Microparticle Foliar Treatment

by Aggeliki Andreadelli, Spyros Petrakis, Antiopi Tsoureki, George Tsiolas, Sofia Michailidou, Penelope Baltzopoulou, Robert van Merkestein, Philip Hodgson, Mark Sceats, George Karagiannakis, Antonios M. Makris

Institute of Applied Biosciences, Centre for Research & Technology, Hellas (CERTH), 570 01 Thessaloniki, Greece

Chemical Process & Energy Resources Institute, Centre for Research & Technology, Hellas (CERTH), 570 01 Thessaloniki, Greece

Calix Limited, Pymble, NSW 2073, Australia

Academic Editor: Tim J. Dumonceaux

Microorganisms 20219(6), 1217; https://doi.org/10.3390/microorganisms9061217

Received: 19 April 2021 / Revised: 31 May 2021 / Accepted: 2 June 2021 / Published: 4 June 2021

(This article belongs to the Section Environmental Microbiology)



Recently, metal oxides and magnesium hydroxide nanoparticles (NPs) with high surface-to-volume ratios were shown to possess antibacterial properties with applications in biomedicine and agriculture. To assess recent observations from field trials on tomatoes showing resistance to pathogen attacks, porous micron-scale particles composed of nano-grains of MgO were hydrated and sprayed on the leaves of healthy tomato (Solanum lycopersicum) plants in a 20-day program. The results showed that the spray induced (a) a modest and selective stress gene response that was consistent with the absence of phytotoxicity and the production of salicylic acid as a signalling response to pathogens; (b) a shift of the phylloplane microbiota from near 100% dominance by Gram (−) bacteria, leaving extremophiles and cyanobacteria to cover the void; and (c) a response of the fungal leaf phylloplane that showed that the leaf epiphytome was unchanged but the fungal load was reduced by about 70%. The direct microbiome changes together with the low level priming of the plant’s immune system may explain the previously observed resistance to pathogen assaults in field tomato plants sprayed with the same hydrated porous micron-scale particles.

Keywords: MgO nanoparticles; Mg(OH)2 nanoparticles; porous micron particles (PMP); Mg(OH)2 adhesion; plant signalling; leaf microbiome; antibacterial; crop protection


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