Efficiency of two arbuscular mycorrhizal fungal inocula to improve saline stress tolerance in lettuce plants by changes of antioxidant defense mechanisms

Abstract

BACKGROUND: Arbuscular mycorrhizal (AM) fungi establish symbioses with most agricultural plants and improves growthunder soil stress conditions. The present study aimed to evaluate the functional contribution of 2 AM fungal inocula (a native consortium isolated from saline soils of the Atacama Desert, 'HMC', and a reference inoculum Claroideoglomus claroideum, 'Cc') on the growth and antioxidant compounds of two cultivars of lettuce (Lactuca sativa cvs. 'Grand Rapids' and 'Lollo Bionda') at increasing salt stress conditions (0, 40, and 80 mmol L -1 NaCl). At 60 days of plant growth, the symbiotic development, biomass production, lipid peroxidation, proline content, antioxidant enzymes, phenolic compound profiles and antioxidant activity were evaluated. RESULTS: The 2 AM inocula differentially colonized the roots of Grand Rapids and Lollo Bionda lettuce plants. The AM symbioses increased proline synthesis and superoxide dismutase, catalase and ascorbate peroxidase activities and diminished phenolic compound synthesis and oxidative damage in lettuce, which was related positively to a higher growth of inoculated plants under salt exposure. The higher concentration of phenolic compounds induced by salinity in non-inoculated plants was associated with high oxidative stress and low fresh biomass production.CONCLUSION: Modulation of salinity stress in lettuce by AM root colonization is a result of changes of antioxidant enzymatic systems that reduce oxidative damage and sustain growth. The application of AM fungi to improve crop production by means of directed inoculation with efficient AM fungal strains may enhance lettuce production on soils plagued with salinity worldwide.

Rhizobium laguerreae Improves Productivity and Phenolic Compound Content of Lettuce (Lactuca sativa L.) under Saline Stress Conditions

“…Both inoculums employed in this study lead to lower levels of phenolic compounds in lettuce when they were grown under saline conditions. They proposed that the microorganism can be useful for reducing the negative effect of salinity on the lettuce growth, which would be achieved by affecting the glycoside synthesis pathways, thus explaining the lower levels of phenolic compounds [16]. These results are in accordance with those reported in the present study so, it seems that HUTR05 inoculum can favor the growth of lettuce under saline conditions although the alleviation of saline stress may negatively affect the phenolic compound levels.…”

“…These authors also reported significant phenolic content variety effects depending on the inoculum [3], highlighting again that the efficiency of inoculation can change according to the lettuce variety. Similarly, Santander and co-workers [16] have reported that the concentration of phenolic compounds in lettuce leaves was significantly affected not only by the cultivar and the inoculation with arbuscular mycorrhizal but also by the salinity level in growth conditions [16]. Both inoculums employed in this study lead to lower levels of phenolic compounds in lettuce when they were grown under saline conditions.…”

“…According to the literature, a soil is considered saline when it has an electrical conductivity of the saturation extract higher than 4 dS/m (40 mM NaCl, approximately) [15]. Many horticultural crops stand out for their sensitivity to salinity, including lettuce, whose tolerance threshold for this type of abiotic stress is 1.3 dS/m [16].…”

Reactive Oxygen Species and Antioxidant Defense in Plants under Abiotic Stress: Revisiting the Crucial Role of a Universal Defense Regulator

“…Similar transcriptional regulation of antioxidant enzyme transcript levels (cAPX, CAT, GR, and MnSOD) decreased 0.4-fold H 2 O 2 and 3.9-fold NO in hydrogen sulfide (H 2 S)-primed strawberry plants under NaCl stress in a hydroponic setup [184]. Santander et al [185] reported that arbuscular mycorrhizae-induced increased SOD, CAT, and APX activities in 40 and 80 mM NaCl-stressed cucumber. Moreover, Moringa oleifera leaf extract (6%) or Glycyrrhiza glabra root extract mitigates salt stress by upregulating antioxidants in wheat and bean (P. vulgaris) [186,187].…”

Antioxidant Responses of Phenolic Compounds and Immobilization of Copper in Imperata cylindrica, a Plant with Potential Use for Bioremediation of Cu Contaminated Environments

“…All the extracts were dried in a rotary evaporator and re-suspended in 1 mL of the mobile phase (water:acetonitrile:formic acid; 92:3:5; v / v / v ). Quantification of phenolic compounds was carried out in a Shimadzu HPLC system (Tokyo, Japan) equipped with a quaternary LC-20AT pump with a DGU-20A5R degassing unit, a CTO-20A oven, a SIL-20a autosampler and an UV-vis diode array spectrophotometer (SPD-M20A), according to the described by Santander et al [ 50 ]. HPLC-DAD system coupled to a mass spectrometer (QTrap LC/MS/MS 3200 Applied Biosystem MDS Sciex system (Foster City, CA, USA)) was used to obtain the identity assignments [ 51 ].…”