Bacterial and Fungal Communities Are Differentially Modified by Melatonin in Agricultural Soils Under Abiotic Stress.

Andrew P Madigan,Ashley E Franks,Frank Bedon,Kim M Plummer,Eleonora Egidi

doi:10.3389/fmicb.2019.02616

Andrew P Madigan, Ashley E Franks + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2019.02616

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Abstract

An extensive body of evidence from the last decade has indicated that melatonin enhances plant resistance to a range of biotic and abiotic stressors. This has led to an interest in the application of melatonin in agriculture to reduce negative physiological effects from environmental stresses that affect yield and crop quality. However, there are no reports regarding the effects of melatonin on soil microbial communities under abiotic stress, despite the importance of microbes for plant root health and function. Three agricultural soils associated with different land usage histories (pasture, canola or wheat) were placed under abiotic stress by cadmium (100 or 280 mg kg−1 soil) or salt (4 or 7 g kg−1 soil) and treated with melatonin (0.2 and 4 mg kg−1 soil). Automated Ribosomal Intergenic Spacer Analysis (ARISA) was used to generate Operational Taxonomic Units (OTU) for microbial community analysis in each soil. Significant differences in richness (α diversity) and community structures (β diversity) were observed between bacterial and fungal assemblages across all three soils, demonstrating the effect of melatonin on soil microbial communities under abiotic stress. The analysis also indicated that the microbial response to melatonin is governed by the type of soil and history. The effects of melatonin on soil microbes need to be regarded in potential future agricultural applications.

Highlights

Soil microbial communities have an essential role in maintaining ecosystem health
Three agricultural soils differing in land use practices, physiochemical characteristics, and microbial content were used to assess the modulatory effect of melatonin on soil community
This study has demonstrated that exogenous melatonin altered the structures of soil bacterial and, to a lesser extent, fungal assemblages under unstressed and abiotic stressed conditions

Summary

Introduction

Soil microbial communities have an essential role in maintaining ecosystem health. Microbes can exchange nutrients and minerals directly with the plant root systems as well as indirectly benefit plant growth through nutrient cycling of organic matter in soils (Wall and Virginia, 1999; Yao et al, 2000; Kirk et al, 2004; Wahid et al, 2016). The diversity and structure of microbial communities in soils can be altered by various abiotic stresses. Melatonin Alters Soil Microbiomes threat to many terrestrial systems, increasing levels of salinity and contaminants due to anthropogenic activities have a prominent role (Badri and Vivanco, 2009; Wood et al, 2016a,b; Geisseler et al, 2017). Contaminated irrigation water is a common source of cadmium or salt into agricultural soils (Khairy et al, 2014; Qadir et al, 2014; Roberts, 2014; Bencherif et al, 2015; Franzaring et al, 2019). Salt stress can impact ion homeostasis, photosynthetic capacity, and root and shoot dry weight in plants (Zhan et al, 2019)

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