Keywords

Arbuscular mycorrhizal fungi, Bridge, Plant growth, Symbiosis, Stress tolerance

Introduction

Soil microorganisms are the most important to increasing agriculture crop production through N2 fixation, recycling of nutrients like N, P, S and C, formation and maintenance of soil structure, Pest control and the degradation of agro-chemicals and pollutants [1]. Arbuscular mycorrhizal fungi are one of the most soil microorganism used in agriculture to enhance crop production, which are symbionts associations with almost all habitats [2]. They are root symbionts more than 80% of vascular plants [3, 4]. It can penetrates the cortical cells of the roots a vascular plant by arbuscules [5] which help to transfer nutrients (P, S, N, C and micronutrients) from the soil to plants. They are associate mutually with plant species in the rhizosphere to facilitate uptake of nutrients and pest control [6]. AM fungi also help to improve soil structures, which reduce soil erosion through enhance water holding capacity of soil and facilitate a better plant rooting capacity. It also improves soil nutrient deficient or polluted soil environments [7]. It enhanced suitable agro ecosystems through improving drought stress [8]. AMF also important for improving human diets by transferring unavailable mineral nutrients as Iron (Fe), Zinc (Zn), iodine (I), selenium (Se), calcium (Ca), Mg, and Cu from the soil to plant parts [9]. These mineral nutrients are enhancing productivity and nutritional qualities of plants are closely related to human diets. This review focused on arbuscular mycorrhizal fungi as a bridge between plants, soils humans for enhancing crop production and human nutrition. They are great roles for sustainable environmentfriendship and agricultural production.

Taxonomy and Morphology

Arbuscular mycorrhiza fungus is common symbiotic interaction with the plant root through nutrients transfer and improving stress tolerance. AM fungi has belongs to Kingdom of Fungus, phylum Glomeromycota, class of Glomeromycetes, order  Glomerales, familiyGlomeraceae, genera Glomus and the 214 species [10]. The major morphology structures of AM fungi are Arbuscules, Vesicles, Spores and External Hyphae. Arbuscules are the major junction used for exchange of nutrients among the fungus and host plant whereas Vesicles are rounded intercellular structures which act as storage organs of phosphorus, oil droplets and also function as propagules [11].  External hyphaeare thick and runner type which responsible for nutrient acquisition and spore formation.These hyphae contain two modifications hyphae networks such as Paris-type and Arum-type. Paris-type where hyphae development is completely intracellular, forming coils in host plant cortical cells, increase the growth of hyphae from one cell to the next whereas the Arum-type is forms arbuscules, which are intra-radical hyphae development in  the root cortical cells [12]. It is the sites of exchange for phosphorus, carbon, water, and other nutrients to enhance the growth of hyphae in plant cells [13].  Spores is another AMF structure which is multi-nucleate, heterokaryotic [14], and formed a sexually [15]. The spores are multi-walled and large (40-400 μm). It found in the soil or in the roots [11]. This structure used for survival and dispersal mechanism of AM fungi by wind, water, invertebrates, birds and mammals [16]. The spores also can germinate under favorable conditions of the soil environment [13].

AMF as Bridge between Plants, Soils and Humans

AMF is ability to create a “bridge” among the soil and the plant through exchange of nutrients between them [17]. It can promote plant growth by providing inorganic nutrients from the soil [18].  They also received carbon from the plant [19, 20].  The role of  AM fungi are absorb unavailable mineral nutrient from the soil then transfer to the plant organ and also release carbon element from the host plant in to the soil. In addition, it was connecting the plant root with the surrounding soil microorganisms [21]. This connection is important for promoting plant-growth through improve nutrient and reduce the pest [22] AMF develop symbiosis converting of toxic mineral nutrients such as N, P, K, Ca, Zn, and S return to the plant root cells [9]. AMF have increased and nitrogen, potassium, calcium, and phosphorus contents in plant leaf area, to enhanced plant growth [23]. The AMF is used for flows amino acids concentration between soil, plants and humans. AMF used as Bio-fertilizers to enhance nutrients recycling and improve soil structure which are important for plant growth [24]. Mycorrhizal fungi hyphae also benefit for formation of soil structure, which retain the moisture in the soil [17]. The improved soil structure is increase the ability of root to penetrate the soil and encourage plant development [25-27].  AMF contains Glomalin hydrophobic glycoprotein is involved in soil-crumb aggregation [4]. AMF is released the mucilaginous glue contribution to binding soil matrix [4]. It maintains moisture content in the soils [28] to regulate water between the soils and plants which to balance osmotic potential.  The hyphae released 30-40% C in the glomalin which enhancing the soil moisture [29]. AMF has improved soil health and crop production by reduced the use of inorganic fertilizer especially, phosphorus [30]. AMF is indirectly important to improve human nutrition.  AMF is facilitate the transfer of nutrients (N, P, K, Ca, Zn, and S) from the soil to plant part then to human [9] which, means humans obtain these nutrient from the consumption of plant parts. Crop productivity and nutritional quality of plants are closely related to human nutrition. AMF can improve nutrient deficiency by increasing minerals contents in staple food crops such as rice, wheat, maize, pearl millet, and others [31]. AMF is 28-60% micronutrient content can be increased in wheat [32], which symbiotic association are improvement of macro- and micronutrients in the crop to increase food quality by minimize the  risk of inorganic fertilizers and pesticides in the diet [33].

AMF symbiosis with Plant

AMFisthe most mutualistic symbiosis association with plant root over 80% of all terrestrial plants [11] which interact to exchange of nutrient and tolerance of stress [8, 16].  This mutualistic symbiosis association has signal molecules between AMF and the host plant which, used for communications between them [8, 34]. These communications signal are phytohormones (strigolactones) and Myc factors. Plant roots produce phytohormones/or strigolactones which, able to stimulate fungal metabolism as well as hyphael branching [35 ,36]. The fungal signal molecule is Myc factors which recognized by Plant genes. After, the recognition it modified the physiological functions of the host plant under stress condition [2, 37]. The hyphae structure especially, vesicles can help the host plant by store large molecules such as salt ions (sodium and chloride) under salinity stress and toxic heavy metals in the soils [36]. This can reduce the effects of stress on plant growth [38].  AMF can produce of phytoalexins and antioxidant enzymes in to the plants which inducing defense mechanisms of the pathogens [39, 40]. Therefore, AMF and plants are positive symbiotic effect in rhizosphere [41] but, the symbiosis association is differ with plant species. The mycorrhizal are 27% of symbiosis association with pearl millet roots and 48% with cowpea roots [42]. Hence, the legume residues are increase mycorrhizal colonization than cereal crops which, contain food source for Mycorrhizae [43].

Roles of AMF as Abiotic stress Tolerance

Abiotic stresses are stunted plant growth and reduce its production. These stresses are including drought, salinity, temperature, nutrients, and heavy metals [9].

Phytoremediation heavy metal pollution

These stresses are reducing by the symbiotic association of AMF and hyper concentration plants.  Such stresses are trace elements (nickel, molybdenum, cobalt, iron) and insoluble phosphorus which is not absorbed by plant root. They need to arbuscular mycorrhiza activates which can modify the physiology of the host plants to tolerance heavy metal toxicity [44], which promote the migration and transformation of heavy metals from roots zone to aboveground parts [45, 46] and also influence root microbial composition [46]. This transformation mechanism of heavy metals is direct or indirect effects on the plant growth [46]. The Direct effects of AMF can stronger absorbing ability of metal than plant root [47]. Its adsorption capacity may be related to the structure of the cell wall. Fungi cell wall is composed of polysaccharides and chitin can be used as a barrier of metal ions and other solutes to enter cells, controlling their absorption [48]. Free amino acids in the cell walls and functional groups such as hydroxyl and carboxyl groups can form a negatively charged structure that has the ability to adsorb the majority of the metal ions in the soil [49]. The Indirect effect of AM fungi has secreted organic acids which can activate insoluble phosphate which are easily absorbed and transported by plants under low available of phosphorus in the soil [50]. The use of AMF can help plants to resist environmental stress as well as promote the restoration and reconstruction of heavy metal contaminated soil [51].

Salinity and Drought Tolerance

These Soil stresses are cause huge losses in crop production and productivity [52-54] . The combination of drought and salinity causes highly injurious to plants [52, 55].

The direct effects of salt & drought on plant growth through reduction in the osmotic potential of the soil solution which, prevent water movement from soil into the plant parts [56, 57]; the  accumulation of excessive Na+ and Cl2 ions towards the cell which toxic effects on the  destruction of structure of enzymes and the damage plasma membrane cause disruption of photosynthesis, respiration and protein synthesis [56, 58]; and  nutrient imbalance also affect the transport of nutrient  in to the shoot which cause deficiencies [52]. These stresses are suppressing the growth of plants by reduce the absorption and photosynthesis rate which reduced crop yields [59, 60].  The applications of AMF are the better option to alleviate this abiotic stress [52]. They  can helping the plant by provide different mechanisms through enhancing nutrient acquisition, water absorption capacity, producing plant growth hormones, improving rhizosphere and soil conditions which improve these stress by the altering the physiological and biochemical properties of the host [52] and also inducing defending against soil-borne diseases.  For example, the symbioses association among wheat and Glomus mosseae can increased crop yield under salinity and drought stress [61, 62].AMF also can increase plant tolerance to under heat or cold stress [63].

Roles of AMF as Biotic Stress Tolerance

Arbuscular mycorrhizal fungi are symbioses with the most of plant species which can give many benefits to the host plant as improved nutrient uptake, resistance to drought and the pests [64]. AMF are supporting plants by resistance to pests which considering as biocontrol. AMF are the reduction of severity soil-borne pathogens such as root rot or wilting caused by fungi (Fusarium, Rhizoctonia, Macrophomina or Verticillium), bacteria (Erwinia carotovora) and oomycetes(Phytophthora, Pythium and Aphanomyces) [65,66].  It also reduced the severity of the plant parasitic nematodes (Pratylenchus and Meloidogyne)  [67,68].  AMF can induce resistance by the production of phytoalexins and the antioxidant enzymes in plants [39,40]. And also another mechanism of mycorrhizal to protection plant from fungal disease by increase the accumulation of non-soluble polysaccharides and lignin in the cell walls of plant roots, which can constitute a physical barrier of fungal disease infections [17,69].  The symbiotic association among AMF and strawberry are produce exudates, which reduction the severity about 64-89% of Phytopthora fragariae, compared with untreated of AMF strawberry [70].  Glomus mossae can reduce about 30-39%, of severity of Phytopthora parasitica disease on root and 30 % reduction in fruit necrosis [71]. The synergistic stimulation of maize and microbial inoculants (Azospirillum, Pseudomonas, and Trichoderma) can increases enzyme activities in the rhizosphere to enhance plant growth [72]. Mycorrhizal fungi can direct or indirect influence of plant defense to herbivory by changes plant nutrition, by altering plant gene expression or generate hormone [73],which helps plant that act to deter herbivore or attraction of enemies considered as ‘defense syndrome’ [74]. Many agricultural plants produce both direct or indirect defenses against herbivory. For example, cotton, tobacco and maize plants produce the direct defenses chemical such as gossypol, nicotine and 2, 4-dihydroxy-7-methoxy-1,4- benzoxazin-3-one, respectively [73,75] and  also it releasing volatile organic compounds upon herbivore attack that attract natural enemies [73].

Roles of AMF Agriculture Sustainability

Arbuscular Mycorrhizal Fungi (AMF) can key role for enhance crop production by improving plant nutrition, soil microbe activity, altering the availability of nutrients and controlling of pests [76]. AMF are the most ample in agricultural soils, which used for crop production among 5-50% of the total soil microbial biomass [77]. They can enhance the plant growth and yield by refining acquisition of nutrients, improved resistance to pests, drought, salinity and increased soil structure [76,78]. AMF are used as prominent of bio-fertilizers to enhance crop production and productivity [79]. Today, microbial-based biofertilizers are important for improve agriculture crop productivity and contribute to sustainable agro-ecosystems [76]. AMF are produce glomalin-related soil protein, which maintain moisture content in soils reduced to different abiotic stresses [28,29]. This regulates water content among soil and plants, automatically prompting plant growth. In addition, application of AMF is enhances moisture uptake from the soil to improving plant tolerance drought and salinity. Therefore, AMF are the most important environment-friendly and a sustainable crop production as a replacement of pesticides and chemical fertilizers [18] , which contribute greatly improves organic farming for yield maximization.

Conclusion

Arbuscular mycorrhizal Fungi are the greatest common symbiotic relationships with almost all plant species. The most important roles of mycorrhizal fungi (AMF) are their ability to create a “bridge” between the plant, soil and humans. Bridge means linking among the soil, plant and the human through exchange of nutrients. The main importance Arbuscular mycorrhiza fungi are enhanced plant performance or crop yield in many ways, including maintains soil condition by improving soil structure; availability of essential and mineral nutrients (Zn, S, Fe, Ca, Mg and NPK), phytoremediation of heavy metals pollution and immobile phosphorus, tolerance of drought and salinity stress and biocontrol of pests. This review focused on the roles of arbuscular mycorrhizal fungi to enhancing crop production and human nutrition. Generally, the application of AM Fungi could be replacement the use of inorganic fertilizers and pesticides through sustainable environment-friendly and agricultural production.

Acknowledgement

I would like to thanks Wakjira Tesfahun and Fenta Assefa for helping in suggestion, comment and advice and also, thanks Raya University to support laptop computer for this studies.

References

1. Lupwayi NZ, Kennedy AC, Chirwa RM (2011) Grain legume impacts on soil biological processes in sub-Saharan Africa. African Journal of Plant Science 5(1): 1-7.
2. Feddermann N, Finlay R, Boller T, Elfstrand M (2010) Functional diversity in arbuscular mycorrhiza-the role of gene expression, phosphorous nutrition and symbiotic efficiency. Fungal Ecology 3(1):1-8.
3. Wang B, Qui YL (2006) Phylogenetic distribution and evolution of mycorrhizae in land plants. Mycorrhiza 16: 299-363.
4. Willis A, Rodrigues BF, Harris PJ (2013) The ecology of arbuscular mycorrhizal fungi. Critical Reviews in Plant Sciences 32(1): 1-20.
5. Brundrett MC (2002) Coevolution of roots and mycorrhiza of land plants. New phytologist, 154: 275-304. 
6. Rodrigues KM, Rodrigues BF (2014) Arbuscular Mycorrhizal (AM) fungi and plant health. SIES College, Sion, Mumbai.
7. Chen M, Arato M, Borghi L, Nouri E, Reinhardt D (2018) Beneficial Services of Arbuscular Mycorrhizal Fungi-From Ecology to Application. Front. Plant Sci. 9: 1270.
8. Ramasamy K, Joe MM, Kim KY, Lee SM, Shagol C, et al (2011)  Synergistic effects of arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria for sustainable agricultural production. Korean Journal of Soil Science and Fertilizer 44(4): 637-649.
9. Begum N, Qin C, Ahanger MA, Raza S, Khan MI, et al. (2019) Role of Arbuscular Mycorrhizal Fungi in Plant Growth Regulation: Implications in Abiotic Stress Tolerance. Front. Plant Sci. 10: 1068. 
10. Kehri HK, Akhtar O, Zoomi I, Pandey D (2018) Arbuscular mycorrhizal fungi: taxonomy and its systematics. Int. J. Life Sci. Res. 6(4): 58-71.
11. Khanday M, Shamsul H, Rouf A, Bhat  M, Aslam D (2016) Arbuscular Mycorrhizal Fungi Boon for Plant Nutrition and Soil Health. Microbiota and Biofertilizers 2: 317-332
12. Dickson S (2004) The Arum-Paris continuum of mycorrhizal symbioses. New Phytol. 163: 187-200.
13. Wright SF (2005) Management of arbuscular mycorrhizal fungi. Roots and Soil Management: Interactions between Roots and the Soil, USA: American Society of Agronomy. 183-197.
14. Hijri M, Sanders IR (2005) Low gene copy number shows that arbuscular mycorrhizal fungi inherit genetically different nuclei. Nature 433: 160-163.
15. Pawlowska TE (2005) Genetic processes in arbuscular mycorrhizal fungi. FEMS Microbiol. Lett. 251: 185-192.
16. Smith SE, Read DJ (1997) Mycorrhizal Symbiosis Academic Press San Diego. 605.
17. JamioÅ?kowska  A, KsiÄ?żniak A, Hetman B, Kopacki M, SkwaryÅ?o-Bednarz B, et al (2017) Interactions of arbuscular mycorrhizal fungi with plants and soil microflora. Acta Scientiarum Polonorum, Hortorum Cultus 16(5): 89-95.
18. Kim SJ, Eo JK, Lee EH, Park H, Eom AH (2017) Effects of arbuscular mycorrhizal fungi and soil conditions on crop plant growth. Microbiology 45(1): 20-24.  
19. Jiang YN, Wang WX, Xie QJ, Liu N, Liu LX, et al (2017) Plants transfer lipids to sustain colonization by mutualistic mycorrhizal and parasitic fungi. Science 356: 1172-1175. 
20. Luginbuehl LH, Menard GN, Kurup S, Van Erp H, Radhakrishnan GV, et al (2017) Fatty acids in arbuscular mycorrhizal fungi are synthesized by the host plant. Science 356: 1175-1178. 
21. Barea JM, Azcón R, Azcón-Aguilar C (2005) Interactions between mycorrhizal fungi and bacteria to improve plant nutrient cycling and soil structure. In Microorganisms in soils: roles in genesis and functions. Springer, 195-212. 
22. Karthikeyan B, Abitha B, Henry AJ, Sa T, Joe MM (2016) Interaction of rhizobacteria with Arbuscular Mycorrhizal Fungi (AMF) and their role in stress abetment in agriculture. In Recent Advances on Mycorrhizal Fungi. Springer, Cham: 117-142.
23. Balliu A, Sallaku G, Rewald B (2015) AMF Inoculation enhances growth and improves the nutrient uptake rates of transplanted, salt-stressed tomato seedlings. Sustainability7: 15967-15981. 
24. Sadhana B (2014) Arbuscular Mycorrhizal Fungi (AMF) as a biofertilizers-A review. Int. J. Curr. Microbiol. App. Sci. 3(4): 384-400.
25. Navarro JM, Perez-Tornero O, Morte A (2014) Alleviation of salt stress in citrus seedlings inoculated with arbuscular mycorrhizal fungi depends on the root stock salt tolerance. J Plant Physiol. 171 (1): 76-85. 
26. Alqarawi AA, Abd-Allah EF, Hashem A (2014) Alleviation of salt-induced adverse impact via mycorrhizal fungi in Ephedra aphylla Forssk. J. Plant. Interact. 9: 802-810.
27. Alqarawi AA, Hashem A, Abd Allah EF, Alshahrani TS, Huqail AA (2014) Effect of salinity on moisture content, pigment system, and lipid composition in Ephedra alata Decne. Acta Biol. Hung.65: 61-71.
28. Wu Z, McGrouther K, Huang J, Wu P, Wu W, et al (2014) Decomposition and the contribution of Glomalin Related Soil Protein (GRSP) in heavy metal sequestration: Field experiment. Soil Biol. Biochem. 68: 283-290.
29. Sharma S, Prasad R, Varma A, Sharma AK (2017) Glycoprotein associated with Funneliformis coronatum, Gigaspora margarita and Acaulospora scrobiculata suppress the plant pathogens in vitro. Asian J Plant Pathol. 11: 199-202.
30. Ortas I (2012) The effect of mycorrhizal fungal inoculation on plant yield, nutrient uptake and inoculation effectiveness under long-term field conditions. Field crops research 125: 35-48.
31. Prasanna R, Nain L, Rana A, Shivay YS (2016) Biofortification with microorganisms: present status and future challenges. In: Singh U, Praharaj SC, Singh SS, Singh PN (eds) Biofortification of food crops. Springer, India: 249-262.
32. Rana A, Saharan B, Nain L, Prasanna R, Shivay YS (2012) Enhancing micronutrient uptake and yield of wheat through bacterial PGPR consortia. Soil Sci. Plant Nutr. 58: 573-582.
33. Rana A, Kabi SR, Verma S, Adak A, Pal  M, et al (2015) Prospecting plant growth promoting bacteria and cyanobacteria as options for enrichment of macro-and micronutrients in grains in rice-wheat cropping sequence. Cog. Food Agric. 1: 1037379.
34. Matusova R, Rani K, Verstappen FWA, Franssen MCR, Beale MH, et al (2005) The strigolactone germination stimu-lants of the plant-parasitic striga and Orobanche spp. are derived from the carotenoid pathway. Plant Physiol. 139: 920-934.
35. Akiyama K, Matsuzaki K, Hayashi H (2005) Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi. Nature 435: 824-827
36. Miransari M (2011) Interactions between arbuscular mycorrhizal fungi and soil bacteria. Applied Microbiology and Biotechnology 89(4): 917-930.
37. Parniske M (2000) Intracellular accommodation of microbes by plants: A common developmental program for symbiosis and disease. Current opinion in plant biology 3(4): 320-328.
38. Smith SE, Read D (2008) Mycorrhizal Symbiosis 3rd end Academic Introduction. Mycorrhizal Symbiosis. 787: 1-9.
39. Morandi D (1996) Occurrence of phytoalexins and phenolic compounds in endomycorrhizal interactions, and their potential role in biological control. Plant Soil 185(2): 241-251.
40. Yang Y, Han X, Liang Y, Ghosh A, Chen J, et al (2015) The combined effects of Arbuscular Mycorrhizal Fungi (AMF) and lead (Pb) stress on Pb accumulation, plant growth parameters, photosynthesis, and antioxidant enzymes in Robinia pseudoacacia L. PloS one, 10: 1-24.
41. Zarea MJ, Karimi N, Goltapeh EM, Ghalavand A (2011) Effect of cropping systems and arbuscular mycorrhizal fungi on soil microbial activity and root nodule nitrogenase. Journal of the Saudi Society of Agricultural Sciences 10(2): 109-120.
42. Bagayoko M, Buerkert A, Lung G, Bationo A, Romheld V. (2000) Cereal/legume rotation effects on cereal growth in Sudano-Sahelian West Africa: Soil mineral nitrogen, mycorrhizae and nematodes. Plant Soil 218: 103-116.
43. Borie F, Redel Y, Rubio R, Rouanet J, Barea J (2002) Interactions between crop residues application and mycorrhizal developments and some soil-root interface properties and mineral acquisition by plants in an acidic soil. Biology and Fertility of Soils36(2): 151-160.
44. Wang L, Wang F (2012) Remediation of cadmium-polluted soils with Arbuscular Mycorrhiza. J. Guangdong Agricultural Sciences 39(2): 51-53.
45. Li Y, Peng J, Shi P, Zhao B (2009) The effect of Cd on mycorrhizal development and enzyme activity of Glomus mosseae and Glomus intraradices in Astragalus sinicus L. Chemosphere 75(7): 894-899.
46. Gong X, Tian DQ (2019) Study on the effect mechanism of Arbuscular Mycorrhiza on the absorption of heavy metal elements in soil by plants. In IOP Conference Series: Earth and Environmental Science 267(5): 052-064.
47. Chen B (2002) Role of arbuscular mycorrhizae in alleviation of zinc and cadmium phytotoxicity. China Agricultural University, Beijing 6: 1-129.
48. Liu YG, Feng BY, Fan T, Pan C, Peng LJ (2008) Study on the Biosorption of Heavy Metals by Fungi. Journal of Hunan University (Natural Sciences) 35(1): 71-74.
49. Meier S, Borie F, Bolan N, Cornejo P (2012) Phytoremediation of metal-polluted soils by arbuscular mycorrhizal fungi. Critical Reviews in Environmental Science and Technology 42(7): 741-775.
50. Zhang Y, Feng G, Li X (2003) The effect of arbuscular mycorrhizal fungion the components and concentrations of organic acids in the exudates of mycorrhizeal red clover. Acta Ecologica Sinica 23: 30-37.
51. Hong-xin W (2010) Application of arbuscular mycorrhizae in phytoremediation of heavy metal contamination soils. Soil and Fertilizer Sciences in China 5: 1-5.
52. Evelin H, Rupam K, Bhoopander G (2009) Arbuscular mycorrhizal fungi in alleviation of salt stress: A review. Annals of Botany 104:1263-1280.
53. Giri B, Kapoor R, Mukerji KG (2003) Influence of arbuscular mycorrhizal fungi and salinity on growth, biomass and mineral nutrition of Acacia auriculiformis. Biology and Fertility of Soils 38: 170-175.
54. Mathur N, Singh J, Bohra S, Vyas A (2007) Arbuscular mycorrhizal status of medicinal halophytes in saline areas of Indian Thar Desert. International Journal of Soil Science 2(2): 119-127.
55. Bauddh K, Singh RP (2012) Growth, tolerance efficiency and phytoremediation potential of Ricinus communis (L.) and Brassica juncea (L.) in salinity and drought affected cadmium contaminated soil. Ecotoxicology and Environmental safety85: 13-22.
56. Feng G, Zhang FS, Li Xl, Tian CY, Tang C, et al (2002) Improved tolerance of maize plants to salt stress by arbuscular mycorrhiza is related to higher accumulation of soluble sugars in roots. Mycorrhiza 12: 185-190.
57. Jahromi F, Aroca R, Porcel R, Ruiz-Lozano JM (2008) Influence of salinity on the in vitro development of Glomus intraradices and on the in vivo physiological and molecular responses of mycorrhizal lettuce plants. Microbial Ecology 55: 45-53.
58. Juniper S, Abbott LK (1993) Vesicular-arbuscular mycorrhizas and soil salinity. Mycorrhiza 4: 45-57.
59. Hasanuzzaman M, Gill SS, Fujita M (2013) “Physiological role of nitric oxide in plants grown under adverse environmental conditions,” in Plant acclimation to environmental stress. Springer, 269-322.
60. Ahanger MA, Tittal  M, Mir RA, Agarwal RM (2017) Alleviation of water and osmotic stress-induced changes in nitrogen metabolizing enzymes in Triticum aestivum L. cultivars by potassium. Protoplasma254: 1953-1963
61. Daei G, Ardakani M, Rejali F, Teimuri S, Miransari M (2009) Alleviation of salinity stress on wheat yield, yield components, and nutrient uptake using arbuscular mycorrhizal fungi under field conditions. J. Plant Physiol. 166: 617-625
62. Sun Z, Song J, Xin X, Xie X,  Zhao B (2018) Arbuscular mycorrhizal fungal proteins 14-3-3- are involved in arbuscule formation and responses to abiotic stresses during AM symbiosis. Front. Microbiol. 5: 9-19.
63. Liu LZ, Gong ZQ, Zhang YL, Li PJ (2014) Growth, cadmium uptake and accumulation of maize Zea mays L. under the effects of arbuscular mycorrhizal fungi. Ecotoxicology 23: 1979-1986.
64. Hage�Ahmed K, Rosner K, Steinkellner S (2019) Arbuscular mycorrhizal fungi and their response to pesticides. Pest management science 75(3): 583-590.
65. Whipps JM (2004) Prospects and limitations for mycorrhizas in biocontrol of root pathogens. Can. J. Bot 82: 1198-1227
66. Pozo MJ, Sabine C, Jung JA, López-Ráez CA (2010) Impact of Arbuscular Mycorrhizal Symbiosis on Plant Response to Biotic Stress: The Role of Plant Defense Mechanisms. A. Mycorrhiza physiology and function 2nd edition springer.
67. Pinochet J, Calvet C, Camprubi A, Fernandez C (1996) Interactions between migratory endoparasitic nematodes and arbuscular mycorrhizal fungi in perennial crops: A review. Plant Soil 185:183-190
68. Li HY, Yang GD, Shu HR, Yang YT, Ye BX, et al (2006) Colonization by the arbuscular mycorrhizal fungus Glomus versiforme induces a defense response against the root-knot nematode Meloidogyne incognita in the grapevine (Vitis amurensis Rupr.), which includes transcriptional activation of the class III chitinase gene VCH3. Plant and cell physiology 47(1): 154-163.
69. Amer MA, Abou-ES, 2008. Mycorrhizal fungi and Trichoderma harzianum as biocontrol agents for suppression of Rhizoctonia solani damping-off disease of tomato. Commun. Agric. Appl. Biol. Sci.73(2): 217-232.
70. Norman JR, Hooker JE (2000) Sporulation of Phytophthora fragariae shows greater stimulation by exudates of non-mycorrhizal than by mycorrhizal strawberry roots. Mycological Research 104(9): 1069-1073.
71. Vigo C, Norman JR, Hooker JE (2000) Biocontrol of the pathogen Phytophthora parasitica by arbuscular mycorrhizal fungi is a consequence of effects on infection loci. Plant pathology 49(4): 509-514.
72. Vázquez MM, César S, Azcón R, Barea JM (2000) Interactions between arbuscular mycorrhizal fungi and other microbial inoculants (Azospirillum, Pseudomonas, Trichoderma) and their effects on microbial population and enzyme activities in the rhizosphere of maize plants. Applied Soil Ecology 15(3): 261-272.
73. Vannette RL, Hunter MD (2009) Mycorrhizal fungi as mediators of defence against insect pests in agricultural systems. 11: 351-358.
74. Agrawal AA, Fishbein M (2006) Plant defense syndromes. Ecology87: S132-S149.
75. Speight MR, Hunter MD, Watt AD (2008) Ecology of Insects: Concepts and Applications, 2nd edn. Wiley-Blackwell, Hoboken, New Jersey.
76. Ingraffia R, Amato G, Frenda AS, Giambalvo D (2019) Impacts of arbuscular mycorrhizal fungi on nutrient uptake, N2 fixation, N transfer, and growth in a wheat/faba bean intercropping system. PloS one 14(3): e0213672.
77. Hodge A, Gosling P, Goodlass G, Bending G (2003) Arbuscular Mycorrhizal Fungi (AMF) in Organic Farming.
78. Rillig MC, Mummey DL (2006) Mycorrhizas and soil structure. New Phytologist 171(1): 41-53.
79. Barrow CJ (2012) Biochar potential for countering land degradation and for improving agriculture. App. Geogr. 34: 21-28.