The role of arbuscular mycorrhizal fungi in alleviating salt stress in Medicago sativa L. var. icon

Abstract

Medicago sativa L. is the most important forage crop in arid and semi-arid areas, where increased salinity is a major factor limiting plant growth and crop productivity. The role of arbuscular mycorrhizal (AM) fungus Glomus viscosum H.T. Nicolson strain A6 in protecting alfalfa plants from salt stress, induced by sodium chloride (NaCl), was studied in two ways. Firstly, the root systems of 3-month old M. sativa plants, both mycorrhizal (AM+) and nonmycorrhizal (non-AM) (M. sativa L. var. icon), were placed in solutions of increasing salt concentrations (0, 50, 100, 150, 200 mM NaCl) to study the wilting response. G. viscosum improved the tolerance to salinity stress and the benefit was expressed in terms of the time required to reach the T4 stage in the wilting experiment. Secondly, to evaluate the ability of the Glomus-alfalfa symbiosis to tolerate salt, a pot experiment was set up in a glasshouse in which 3-month old alfalfa plants (M. sativa var. icon) were grown in a peat substratum at three salinity levels (0, 100, 150 mM NaCl). The AM symbiosis stimulated plant height, leaf area, root density, fresh and dry plant weight under saline conditions. Furthermore, proline accumulation was higher in mycorrhizal M. sativa plants than in non-mycorrhizal plants under conditions of salt stress. These and other results indicated that the micropropagated selected clone of M. sativa var. icon, when in symbiosis with G. viscosum H.T. Nicolson strain A6, exhibited better growth and physiological activities under saline conditions than non-AM plants. The AM+ plants also had lower sodium and chloride concentrations in tissues than non-AM plants

Alleviation of Salt Stress in Upland Rice (Oryza sativa L. ssp. indica cv. Leum Pua) Using Arbuscular Mycorrhizal Fungi Inoculation

“…It was confirmed that the P5CS plays a major role in proline biosynthesis under salt stress in both salt tolerant PBG-5 and salt sensitive CSG-9505 genotypes of chickpea (Jahromi et al, 2008;Garg and Baher, 2013). Free proline and total soluble sugars are the major osmolytes in AMF-inoculated plants under salt stress that control the osmotic potential at the cellular level, leading to enhanced salt tolerant ability (Campanelli et al, 2013;Yang et al, 2014;Evelin et al, 2019). Free proline enrichment in the salt stressed plants with AMF inoculation plays a key role as osmotic adjustment (Chun et al, 2018), which confirmed the function as osmolytes by mitigation of NaCl stress in mustard plant (Sarwat et al, 2016).…”

“…NaCl (mM) alfalfa cv. icon, low levels of Na + in AMF inoculated plants were demonstrated when compared with the control (Campanelli et al, 2013). In citrus (red tangerine) seedlings, Na + enrichment is generally antagonist with K + when subjected to 100 mM NaCl for 60 days and also, Na + in AMF inoculated plants (GM and Paraglomus occultum) was significantly lower than in uninoculated plants (Wu et al, 2010).…”

“…collected from rhizosphere of maize plants was inoculated in wheat plants, and subsequently exposed to salt stress, a decline in AM-fungal colonization, especially at high salinity levels (4.7 and 9.4 dS m −1 ) was observed (Talaat and Shawky, 2014). Similarly, in alfalfa, colonization percentage of AMF (Glomus viscosum) was sharply declined, in relation to the degree of salt treatments (100-150 mM NaCl) (Campanelli et al, 2013). Colonization percentage of R. intraradices, Massilia sp.…”

“…For example, ion homeostasis (influx/efflux), compartmentalization (vacuolar storage), and Na + translocation from root to shoot via apoplastic and/or symplastic routes have been regulated by AMFinoculation (Evelin et al, 2009;Porcel et al, 2012;He and Huang, 2013;Porcel et al, 2016;Yadav et al, 2017;Evelin et al, 2019). Better defense responses in terms of the higher production of free proline, glycine betaine, and soluble sugars in AMF inoculated plants against salt stress have also been reported (Campanelli et al, 2013;Evelin et al, 2013;Garg and Baher, 2013;Talaat and Shawky, 2014). The regulation of proline biosynthesis [pyrroline-5-carboxylate synthetase (P5CS)] and inhibition of proline degradation [proline dehydrogenase (PDH)] are evidently observed when AMF-inoculated plants are exposed to salt stress (Jahromi et al, 2008;Garg and Baher, 2013).…”

Influence of arbuscular mycorrhiza on photosynthesis and water status of Populus cathayana Rehder males and females under salt stress

“…Given the factors of environmental deterioration, unsuitable irrigation management, increasing human population, soil salinization is becoming more and more prominent . Salt stress adversely affects biological and physiological processes of plants via inducing water deficiency, osmotic stress, nutritional imbalance and ionic toxicity (Campanelli et al 2013), eventually resulting in the structural damage of plant cell, photosynthesis inhibition, growth limitation, or even death Munns and Tester 2008).…”