Irrigation of radish (Raphanus sativus L.) with microcystin-enriched water holds low risk for plants and their associated rhizopheric and epiphytic microbiome

M Petrou; P A Karas; S Vasileiadis; I Zafiriadis; T Papadimitriou; E Levizou; K Kormas; D G Karpouzas

doi:10.1016/j.envpol.2020.115208

Irrigation of radish (Raphanus sativus L.) with microcystin-enriched water holds low risk for plants and their associated rhizopheric and epiphytic microbiome

Environ Pollut. 2020 Nov;266(Pt 1):115208. doi: 10.1016/j.envpol.2020.115208. Epub 2020 Jul 13.

Authors

M Petrou¹, P A Karas¹, S Vasileiadis¹, I Zafiriadis², T Papadimitriou³, E Levizou², K Kormas³, D G Karpouzas⁴

Affiliations

¹ University of Thessaly, Department of Biochemistry and Biotechnology, Laboratory of Plant and Environmental Biotechnology, Viopolis, 41500, Larissa, Greece.
² University of Thessaly, Department of Agriculture, Crop Production and Agricultural Environment, Fytokou, 38446, Nea Ionia, Volos, Greece.
³ University of Thessaly, Department of Agriculture, Ichthyology & Aquatic Environment, Fytokou, 38446, Nea Ionia, Volos, Greece.
⁴ University of Thessaly, Department of Biochemistry and Biotechnology, Laboratory of Plant and Environmental Biotechnology, Viopolis, 41500, Larissa, Greece. Electronic address: dkarpouzas@bio.uth.gr.

PMID: 32683235
DOI: 10.1016/j.envpol.2020.115208

Abstract

Microcystins (MCs) are toxins produced during cyanobacterial blooms. They reach soil and translocated to plants through irrigation of agricultural land with water from MC-impacted freshwater systems. To date we have good understanding of MC effects on plants, but not for their effects on plant-associated microbiota. We tested the hypothesis that MC-LR, either alone or with other stressors present in the water of the Karla reservoir (a low ecological quality and MC-impacted freshwater system), would affect radish plants and their rhizospheric and phyllospheric microbiome. In this context a pot experiment was employed where radish plants were irrigated with tap water without MC-LR (control) or with 2 or 12 μg L^-1 of pure MC-LR (MC2 and MC12), or water from the Karla reservoir amended (12 μg L^-1) or not with MC-LR. We measured MC levels in plants and rhizospheric soil and we determined effects on (i) plant growth and physiology (ii) the nitrifying microorganisms via q-PCR, (ii) the diversity of bacterial and fungal rhizospheric and epiphytic communities via amplicon sequencing. MC-LR and/or Karla water treatments resulted in the accumulation of MC in taproot at levels (480-700 ng g^-1) entailing possible health risks. MC did not affect plant growth or physiology and it did not impose a consistent inhibitory effect on soil nitrifiers. Karla water rather than MC-LR was the stronger determinant of the rhizospheric and epiphytic microbial communities, suggesting the presence of biotic or abiotic stressors, other than MC-LR, in the water of the Karla reservoir which affect microorganisms with a potential role (i.e. pathogens inhibition, methylotrophy) in the homeostasis of the plant-soil system. Overall, our findings suggest that MC-LR, when applied at environmentally relevant concentrations, is not expected to adversely affect the radish-microbiota system but might still pose risk for consumers' health.

Keywords: Karla reservoir; MC-LR; Microbiome; Microcystins; Phyllosphere; Rhizosphere.

MeSH terms

Cyanobacteria*
Microbiota*
Microcystins
Raphanus*
Water

Substances

Microcystins
Water