AMF Inoculation Enhances Growth and Improves the Nutrient Uptake Rates of Transplanted, Salt-Stressed Tomato Seedlings

Astrit Balliu,Glenda Sallaku,Boris Rewald

doi:10.3390/su71215799

Abstract

The study aimed to investigate the effects of commercially available AMF inoculate (Glomus sp. mixture) on the growth and the nutrient acquisition in tomato (Solanumlycopersicum L.) plants directly after transplanting and under different levels of salinity. Inoculated (AMF+) and non-inoculated (AMF−) tomato plants were subjected to three levels of NaCl salinity (0, 50, and 100 mM·NaCl). Seven days after transplanting, plants were analyzed for dry matter and RGR of whole plants and root systems. Leaf tissue was analyzed for mineral concentration before and after transplanting; leaf nutrient content and relative uptake rates (RUR) were calculated. AMF inoculation did not affect plant dry matter or RGR under fresh water-irrigation. The growth rate of AMF−plants did significantly decline under both moderate (77%) and severe (61%) salt stress compared to the fresh water-irrigated controls, while the decline was much less (88% and 75%,respectively)and statistically non-significant in salt-stressed AMF+ plants. Interestingly, root system dry matter of AMF+ plants (0.098 g plant–1) remained significantly greater under severe soil salinity compared to non-inoculated seedlings (0.082 g plant–1). The relative uptake rates of N, P, Mg, Ca, Mn, and Fe were enhanced in inoculated tomato seedlings and remained higher under (moderate) salt stress compared to AMF− plants This study suggests that inoculation with commercial AMF during nursery establishment contributes to alleviation of salt stress by maintaining a favorable nutrient profile. Therefore, nursery inoculation seems to be a viable solution to attenuate the effects of increasing soil salinity levels, especially in greenhouses with low natural abundance of AMF spores.

Highlights

Soil salinity is a common and very severe environmental stressor in agriculture [1,2], affecting almost every aspect of plant physiology and biochemistry [3]
The relative uptake rates of N, P, Mg, Ca, Mn, and Fe were enhanced in inoculated tomato seedlings and remained higher under salt stress compared to AMFplants This study suggests that inoculation with commercial Arbuscular mycorrhizal fungi (AMF) during nursery establishment contributes to alleviation of salt stress by maintaining a favorable nutrient profile
In inoculated (AMF+) plants, RGRPlant was significantly reduced under severe salt stress (100 mM NaCl) only, while in non-inoculated (AMF) plants both moderate (50 mM NaCl) and severe salinity caused a significant reduction of RGRPlant

Summary

Introduction

Soil salinity is a common and very severe environmental stressor in agriculture [1,2], affecting almost every aspect of plant physiology and biochemistry [3]. About 2% of land farmed by dry-land agriculture, and >20% of irrigated land have already been damaged by excess soil salinity [4]. Soil salinization is dramatically exacerbated by irrigation [5], which “imports” large quantities of new ions to the soil and/or relocates them to surface soil layers, i.e., the rooting zone, by evaporation [6]. Soil salinization is predicted to intensify in the decades to come [5], especially under protected cultivation where natural leaching of excess salts by rain water is absent. Na+ can promote dispersion of soil aggregates to break down; the increasing bulk density will make the soil more compact and decrease total porosity, thereby hampering soil aeration and as a result, plants in saline soils suffer from high Na+ levels, but are affected by some degree of hypoxia [5]

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