The Fungus Aspergillus aculeatus Enhances Salt-Stress Tolerance, Metabolite Accumulation, and Improves Forage Quality in Perennial Ryegrass

Abstract

Perennial ryegrass (Lolium perenne) is an important forage grass with high yield and superior quality in temperate regions which is widely used in parks, sport field, and other places. However, perennial ryegrass is moderately tolerant to salinity stress compared to other commercial cultivars and salt stress reduces their growth and productivity. Aspergillus aculeatus has been documented to participate in alleviating damage induced by salinity. Therefore, the objective of this study was to investigate the mechanisms underlying A. aculeatus-mediated salt tolerance, and forage quality of perennial ryegrass exposed to 0, 200, and 400 mM NaCl concentrations. Physiological markers and forage quality of perennial ryegrass to salt stress were evaluated based on the growth rate, photosynthesis, antioxidant enzymes activity, lipid peroxidation, ionic homeostasis, the nutritional value of forage, and metabolites. Plants inoculated with A. aculeatus exhibited higher relative growth rate (RGR), turf and forage quality under salt stress than un-inoculated plants. Moreover, in inoculated plants, the fungus remarkably improved plant photosynthetic efficiency, reduced the antioxidant enzymes activity (POD and CAT), and attenuated lipid peroxidation (decreased H2O2 and MDA accumulation) induced by salinity, compared to un-inoculated plants. Furthermore, the fungus also acts as an important role in maintaining the lower Na/K ratio and metabolites and lower the amino acids (Alanine, Proline, GABA, and Asparagine), and soluble sugars (Glucose and Fructose) for inoculated plants than un-inoculated ones. Our results suggest that A. aculeatus may be involved in modulating perennial ryegrass tolerance to salinity in various ways.

Investigation of biochemical changes in barley inoculated with Trichoderma harzianum T-22 under salt stress

“…Here we can speculate that the fungus may enhance the capacity of Gairdner to withstand salt stress through coordinating with amino acids exerting a protective mechanism or a significant reduction in amino acid levels could indicate their contribution to growth in Gairdner (inoculated) under saline conditions. This is also in alignment with past research where Li et al (2017) found that Aspergillus aculeatus inoculated roots of ryegrass showed decreased amino acid concentrations following salt stress.…”

Exogenous Calcium Enhances the Photosystem II Photochemistry Response in Salt Stressed Tall Fescue

“…The K + and Ca 2+ content of the mineral extract were determined by atomic absorption spectroscopy (PerkinElmer, Optima 8000DV, America) with standard sample (National Institute of Metrology, Beijing, China). The concentration of Ca 2+ , K + was defined as the Ca 2+ , K + content (mg) per unit tissues (g) (Li et al, 2017 ).…”

Mechanisms of Environmental Stress Tolerance in Turfgrass

“…A further investigation of PSII with the JIP-test method in perennial ryegrass and seashore paspalum (Paspalum vaginatum Swartz cv. 'SeaSpray') revealed that quantum yields, efficiencies and energy fluxes were compromised after salt stress treatment [28,29]. Sodium ion toxicity is a typical effect produced by salt stress, especially NaCl stress.…”

“…Moreover, signal molecules such as Ca 2+ and nitric oxide are reportedly involved in improving salt stress tolerance of turfgrasses including tall fescue, bermudagrass, and sheep fescue (Festuca ovina L) during the early growth stage [44,45]. Recently, the fungus Aspergillus aculeatus is reported to play a protective role on perennial ryegrass and bermudagrass under salinity condition [29,46]. Turfgrass species can be C 3 and C 4 according to their photosynthetic pathways.…”