Effects of Seawater Nutrients on Plant-Microbe Interactions

Abstract

Globally, there is an urgent need to develop more effective and sustainable practices to maximise crop yields while also minimising industrial-scale agricultural impacts. Seawater irrigation offers an attractive way to replace and/or reduce the use of agrochemicals and other supplements (e.g., fungicides), by reducing trace nutrient deficiencies in crops. There are numerous reports of increased yield and nutritive content of vegetable crops exposed to seawater, as well as greater tolerance to abiotic and biotic stressors, but it is unclear whether the impacts of seawater additions are direct (plants taking up nutrients) or indirect (mediated by shifts in soil-plant-associated microbial communities). A greenhouse experiment was conducted, irrigating Beta vulgaris L., Fragaria x ananassa Duch. and Pisum sativum L. with different concentrations of seawater (0, 10, 20, 30, 50, 70, 100%) to analyse the effects on the nutrient content in the growing medium and edible plant tissues and shifts in fungal root endophyte communities. Endophytes were isolated using culturing methods and identified by ITS gene sequencing. Seawater significantllayincreased the electrical conductivity, pH and moisture content of the growing medium, with >50% seawater having a negative impact on plant growth and soil properties. Typically, the plant -microbiome benefited from 10% seawater, showing increases in either plant biomass or yield, with nutrient uptake and total dissolved solids increasing in edible plant tissues. Significant increases in fungal community richness and diversity were also observed, suggesting that the nutrient niches of seawater could have indirect benefits on plant growth by stimulating the microbial community. Results of this study suggest that when applied at low concentrations, seawater could have a positive effect on plant-microbe-nutrient interactions, having a potential role in sustainable and resource efficient agriculture.