TABLE 3.
Endophytes inducing abiotic stress tolerance in host plants.
| Stress tolerance | Host | Endophytes | Mechanism of action | References |
| Drought | Arabidopsis thaliana | Azospirillum brasilense | Enhancement of ABA | Cohen et al., 2015 |
| Populus deltoids | Rhodotorula graminis, Burkholderia vietnamiensis, and Rhizobium tropici | Host plant damage reduced by ROS scavenging machinery | Khan A. et al., 2016 | |
| Oryza sativa | Piriformospora indica | Regulation of miR159/miR396 that target MYB and GRF transcription factors involved in regulation of growth and hyposensitivity response | Fard et al., 2017 | |
| Zea mays L. | Piriformospora indica | Enhanced antioxidant enzyme activity, proline accumulation, and expression of drought-related genes and lowered membrane damage | Xu et al., 2017 | |
| Elymus dahuricus and Triticum aestivum | Alternaria alternata LQ1230 | IAA secretion contributes to the growth and upregulation of antioxidant enzymes activities and osmoregulatory substances | Qiang et al., 2019 | |
| Hordeum vulgare | Piriformospora indica | Resources in host redistributed to reduce negative impact of stress and presence of aquaporin water channels sustained | Ghaffari et al., 2019 | |
| Salinity | Lycopersicon esculentum | Pseudomonas fluorescens and Pseudomonas migulae | ACC deaminase activity | Ali et al., 2014 |
| Chlorophytum borivilianum | Brachybacterium paraconglomeratum strain SMR20 | Potential deamination of ACC in the host roots leading to decreased production of stress ethylene, delayed chlorosis and senescence that resulted in improved yield of plants | Barnawal et al., 2016 | |
| Triticum aestivum | Dietzia natronolimnaea | Enhanced expression of TaST, a salt stress-induced gene | Bharti et al., 2016 | |
| Oryza sativa | Bacillus pumilus | Effective salt tolerance, survivability, root colonization and multifarious PGP trait, significant reduction in antioxidant enzyme activities and MDA content | Khan Z. et al., 2016 | |
| Zea mays | Pseudomonas fluorescens 002 | Release of IAA and protection of plants against the inhibitory effects of NaCl | Zerrouk et al., 2016 | |
| Triticum aestivum | Arthrobacter protophormiae SA3, Dietzia natronolimnaea STR1, and Bacillus subtilis LDR2 | IAA content of wheat increased under salt and drought stress conditions. SA3 and LDR2 inoculation counteracted increase of ABA and ACC | Barnawal et al., 2017 | |
| Triticum aestivum | Chryseobacterium gleum sp. SUK | Improved root-shoot length, fresh-dry weight, chlorophyll, proteins, amino acids, phenolics, flavonoids content and decreased level of proline, Na+ uptake, increase in K+ uptake | Bhise et al., 2017 | |
| Cicer arietinum | Mesorhizobium ciceri and Bacillus subtilis | Decreased H2O2 concentration and improved proline contents. | Egamberdieva et al., 2017 | |
| Avena sativa | Klebsiella sp. | Biochemical parameters such as proline content, electrolyte leakage, MDA content and antioxidant enzyme activities analyzed and found to be notably lesser in IG3 inoculated plants | Sapre et al., 2018 | |
| Oryza sativa | Burkholderia strain P50 | ACC deaminase activity and united PGP traits of P50 successfully alleviate salt stress in rice seedlings by improving morphological and biochemical parameters and decreasing ROS scavenging antioxidant enzymes, osmolytes and stress ethylene | Sarkar et al., 2018 | |
| Capsicum annuum L. | Bacillus sp. | Induced high levels of proline production and antioxidant enzyme activities | Wang et al., 2018 | |
| Oryza sativa | Curtobacterium albidum strain SRV4 | SRV4 expressed positive attribute for nitrogen fixation, EPS, HCN, IAA, and ACCD activity leading to improvement in plant growth parameters, photosynthetic efficiency, membrane stabilization index and proline content, antioxidative enzymatic activities and K+ uptake | Vimal et al., 2019 | |
| Heat | Lycopersicon esculentum Mill | Paraburkholderia phytofirmans | Accumulation of sugars, total amino acids, proline, and malate, promotion of gas exchange | Issa et al., 2018 |
| Glycine max | Bacillus cereus SA1 | Induction in the endogenous levels of several phytohormones (ABA and SA), essential amino acids | Khan M. A. et al., 2020 | |
| Cold | Arabidopsis thaliana | Burkholderia phytofirmans strain PsJN | Significant changes in PS-II activity, differential accumulation of pigments | Su et al., 2015 |
| Solanum lycopersicum Mill. | Pseudomonas vancouverensis and P. frederiksbergensis | Improved reactive oxygen species levels and reduced membrane damage and high expression of cold acclimation genes LeCBF1 and LeCBF3 | Subramanian et al., 2015 | |
| Lycopersicon esculentum | Bacillus cereus; Bacillus subtilis; Serratia sp. | Promoting soluble sugar, proline, and osmotin accumulation, enhancing antioxidant defense system | Wang et al., 2016 | |
| Heavy metal | Miscanthus sinensis | Pseudomonas koreensis AGB-1 | High tolerance to Zn, Cd, As, and Pb by extracellular sequestration, increased CAT and SOD activities | Babu et al., 2015 |
| Solanum nigrum | Pseudomonas aeruginosa | Enhanced Cd stress tolerance | Shi et al., 2016 | |
| Panicum virgatum L. | Pseudomonas putida Bj05, Pseudomonas fluorescens Ps14, Enterobacter spp. Le14, So02, and Bo03 | Plants protected from inhibitory effects of Cd, plant growth improved and Cd concentration decreased | Afzal S. et al., 2017 | |
| Zea mays L. | Gaeumannomyces cylindrosporus | Height, basal diameter, root length, and biomass of maize seedlings increased significantly under Pb stress | Ban et al., 2017 | |
| Glycine max L. | Sphingomonas sp. | Reduced Cr translocation to roots, shoot, and leaves and oxidative stress was significantly reduced regulating reduced GSH and enzymatic antioxidant CAT | Bilal et al., 2018 | |
| Oryza sativa | Enterobacter ludwigii SAK5, Exiguobacterium indicum SA22 | Protection against heavy metal Cd and Ni hyperaccumulation by enhanced detoxification mechanisms | Jan et al., 2019 | |
| Brassica juncea | Serratia sp., Enterobacter sp. | Phytohormone production, phosphate solubilization, and antioxidative support responsible for Cd resistance | Ullah et al., 2019 | |
| Saccharum officinarum | Pseudomonas fluorescens, Kosakonia radicincitans, Paraburkholderia tropica, and Herbaspirillum frisingense | Alleviating Al stress | Labanca et al., 2020 | |
| Brassica napus L. | Serratia sp. IU01 | Minimized the magnitude of the oxidative damage and advantages in terms of growth promotion and alleviating Cd toxicity | Shah et al., 2020 |
ABA, abscisic acid; MYB, myeloblastosis family; GRF, growth-regulating factors; ACCD, 1-aminocyclopropane-1-carboxylic acid deaminase; MDA, malondialdehyde; HCN, hydrogen cyanide; SA, salicylic acid; CAT, catalase; SOD, superoxide dismutase; GSH, glutathione.