Table 1.

An overview of endophytes mediating drought and salt tolerance and their physiological attributes in host plants

Abiotic stress	Site	Host plant	Isolated plant parts	Endophytes	Physiological responses in plants	References
Drought	Field trial; Experimental Farm of Institute of Soil and Environmental Sciences, University of Agriculture (UAF), Faisalabad	Triticum aestivum L. (Poaceae)	Roots	Burkholderia phytofirmans PsJN	Inoculation of B. phytofirmans PsJN improved the photosynthetic rate, water use efficiency and chlorophyll content	[164]
	Lab study; Zhejiang University, Huajiachi Campus, China	Brassica rapa L. (= B. campestris subsp. chinensis (L.) Makino) (Brassicaceae)	Root	Piriformospora indica	Inoculation of P. indica increased level of peroxidases, catalases, and superoxide dismutases, thus, inhibiting drought-induced degradation of chlorophyll and thylakoids proteins	[223]
	Pot experiment; G. B. Pant University of Agriculture and Technology, India	Oryza sativa L. (Poaceae)	Root	Trichoderma harzianum TH-56	Inoculation with increasing dose of T. harzianum strain Th-56 caused upregulation of aquaporin, dehydrin, and malondialdehyde genes	[181]
	Agriculture and Agri-Food Canada Research Centre, Canada	Brachypodium distachyon (L.) P. Beauv. (Poaceae)	Leaves	Bacillus subtilis B26	Endophyte-mediated up-regulation of DREB2B-like, DHN3-like and LEA-14-A-like and modulation of DNA methylation genes, MET1B-like, CMT3-like and DRM2-like genes that induce biochemical changes to overcome stress condition	[71]
	Agriculture and Agri-Food Canada Research Centre, Canada	Phleum pratense L. (Poaceae)	Leaves	B. subtilis B26	B. subtilis B26 modified osmolyte accumulation in roots and shoots	[70]
	Esmeraldas Province, Ecuador	Theobroma cacao L. (Malvaceae)	Pod	Trichoderma hamatum DIS 219b	Bacterial colonization caused drought-induced changes in stomatal conductance, net photosynthesis, and green fluorescence emissions	[21]
	Lab experiment; Institute of Biological Process Research, Japan	Kalmia latifolia L. (Ericaceae)	NM	Streptomyces padanus	Inoculation of S. padanus induced accumulation and lignification in cell walls in sieve cells conferred tolerance to drought in Kalmia latifolia	[88]
	Greenhouse experiment; Campus of Laboratório de Biologia Molecular de Plantas, Brazil	Saccharum officinarum cv. SP70-1143	NM	Gluconacetobacter diazotrophicus	Sugar plants colonized with G. diazotrophicus cause gene expression in shoots, contributing to drought resistance	[237]
	Lab experiment conducted in Crop Stress Biology for Arid Areas and College of Life Sciences	Arabidopsis sp. (Brassicaceae) and wheat (Triticum sp., Poaceae)	Leaves	Pantoea alhagi LTYR-11ZT	Strain LTYR-11ZT increased the contents of soluble sugars, but decreased proline, MDA and chlorophyll contents	[36]
	Gansu Province, northwest China	Ammopiptanthus mongolicus (Fabaceae)	Roots of Gymnocarpos przewalskii Bunge ex Maxim. (Caryophyllaceae)	Dark septate endophyte (DSE)	DSE enhanced root biomass and branch growth that might allow desert species to adapt in arid condition	[124]
	Field trial experiment at Sumter County and Stimpson Wildlife Sanctuary of southern Clarke County, USA Greenhouse experiment; Malayer University, Iran	Solanum lycopersicum L. (Solanaceae) Solanum lycopersicum L	Upper root and lower stem of Pyrrhopappus carolinianus (Walter) DC. (Asteraceae) Upper root and lower stem of Pyrrhopappus carolinianus (Walter) DC. (Asteraceae)	Ampelomyces sp. Ampelomyces sp.	Ampelomyces sp. enhanced strong root and shoot system under drought conditions. The overall study speculated that the improved health of the plant is due to the synergistic effects Symbiotic association between plant and fungal colonization increase the drought tolerance through morphological changes and molecular expression	[19, 160]
Salinity	Pot experiment; Chinese Academy of Forestry, Beijing, China	Populus × tomentosa Carrière (Salicaceae)	Roots of Suaeda maritima subsp. salsa (L.) Soó (= S. salsa (L.) Pall.) (Amaranthaceae)	Curvularia sp.	The endophytic fungi induced the elevated synthesis of the antioxidant enzymes SOD and APX. The inoculated plant expressed a high level of chlorophyll and proline content	[180]
	Pot experiment; CIMAP, Lucknow, India	Chlorophytum borivilianum Santapau & RR Fern (Asparagaceae)	Root	Brachybacterium paraconglomeratum	Bacterial ACC deaminase leads to ethylene reduction and its negative impact on plant growth	[23]
	Pot experiment; Fayoum University, Fayoum, Egypt	Carthamus tinctorius L. (Asteraceae)	Root, stem, and leaf	Bacillus cereus and B. aerius	Production of ACC deaminase causes ethylene reduction, thus lowering the negative impact on plant growth	[193]
	Pot experiment	Oryza sativa L. cv. KDML105 (Poaceae)	Roots of Rotheca serrata (L.) Steane & Mabb. (= Clerodendrum serratum (L.) Moon (Lamiaceae)	Streptomyces sp. GMKU 336	Endophyte enhanced the growth of rice by ethylene reduction via ACC deaminase and further assists plants in scavenging ROS, balancing the ion content and osmotic pressure	[98]
	Experimental farms in Ibaraki Prefecture, Tsukuba, Japan	Solanum lycopersicum L	Interior tissues of organic carrot and turnip crops, respectively	Pseudomonas sp. OFT2 and OFT5	ACC expressing endophyte alleviated salinity stress by reducing stress ethylene	[254]
	Pot experiment; King Abdullah University of Science and Technology Campus, Saudi Arabia	Arabidopsis thaliana (L.) Heynh. (Brassicaceae)	Root	P. pseudoalcaligenes	P. pseudoalcaligenes modulates Na+ and K+ ions under salt expression thus balance ion homeostasis	[4]
	Greenhouse experiment; Shanghai Jiao Tong University, China	Brassica rapa L. (= B. campestris subsp. chinensis (L.) Makino)	Roots	Piriformospora indica	Inoculated plants expressed higher activities of antioxidant enzymes, higher expression of genes conferring salt tolerance	[107]
	Field trial; desert region of Jizan, Saudi Arabia	Tribulus terrestris L. (Zygophyllaceae), Tetraena simplex (L.) Beier & Thulin (= Zygophyllum simplex L., Zygophyllaceae), Panicum turgidum Forssk. (Poaceae) and Euphorbia granulata Forssk. (Euphorbiaceae)	Roots	Endophyte isolate	Inoculation of endophytes conferred salinity tolerance in A. thaliana due to altered transporter transcripts, could be caused by the downfall of Na+/K+ shoot ratios	[50]
	Pot experiment; J.N.U, New Delhi, India	Oryza sativa L	Root	Piriformospora indica	Down-regulation of PiHOG1 confer salinity tolerance	[100]
	Greenhouse experiment; College of Food and Agricultural Sciences, Saudi Arabia	Cicer arietinum L. (Fabaceae)	Roots of Acacia gerrardii Benth. (Fabaceae)	Bacillus subtilis (BERA 71)	Enhancement in plant biomass, photosynthetic pigments, enzymatic and non-enzymatic antioxidant activity coupled with reduced ROS production and lipid peroxidation	[2]
	Field trial experiment at Sumter County and Stimpson Wildlife Sanctuary of southern Clarke County, USA Lab experiment at Root and Soil Biology Laboratory of the Botany Department, Bharathiar University, India Lab experiment; Zhengzhou University; China	Solanum lycopersicum L A. thaliana Arabidopsis thaliana	Acer negundo L. (Sapindaceae) Roots of Chrysanthemum indicum Isolated from salt-tolerant Kosteletzkya sp.	Penicillium chrysogenum Fusarium haematococcum Bacillus cereus KP120	Inoculation with P. chrysogenum showed increased salt tolerance at 300 mM of concentration Inoculation of endophytic F. haematococcum could induce salinity tolerance through production of extracellular enzymes under abiotic stress Up-regulation of key genes involved in IAA synthase and ethylene signaling were observed in B. cereus KP120 inoculated A. thaliana under salt-stressed condition	[160, 192] [266]