50
A. Dahiya et al.
3.6.2 Phytohormone
Mehta et al. (2014) obtained endophytic P-solubilizing rhizobacteria from 20 healthy
apple roots and found that endophyte B. methylotrophicus CKAM obtained from
root endosphere showed the higher phosphate solubilization (on PVK agar plates
in vitro). B. methylotrophicus also showed nitrogenase activity, IAA, siderophore,
and antifungal activity against F. oxysporum, Phytophthora sp., D. necatrix, S. rolfsii,
and P. aphanidermatum. Pirhadi et al. (2018) isolated bacterial endophytes from
roots, stems, and leaves of sugarcane grown in saline and non-saline soil. The
authors observed a prevalence of Bacillaceae, with Bacillus sp. being the most
frequently isolated bacterium and salinity affected the bacterial community structure and higher diversity of root entophytic P-solubilizing bacteria. Earlier, Kruasuwan and Thamchaipenet (2016) reported that bacterial endophytes isolated from
sugarcane rhizosphere exhibited plant growth-promoting traits especially indole-3acetic acid, nitrogen fixation, ACC deaminase, phosphate solubilization, siderophore
production, etc. Shabanamol et al. (2018) observed that three diazotrophic isolates
inhibited the growth of rice sheath blight pathogen Rhizoctonia solani, also produced
indole-3-acetic acid, gibberellic acid, and cytokinins. Ribeiro et al. (2018) reported
that Bacillus strains produced high levels of IAA in the presence of tryptophan. Sun
et al. (2019) observed that the production of indole acetic acid significantly enhanced
root biomass and root–shoot ratio on medicinal plant Astragalus mongholicus.
3.6.3 Endophytic Microbes as a Biocontrol Agent
A few endopytic microorganisms also act as potential biocontrol agents. An endophytic bacteria Pantoea vagans C9-1 was commercialized as a bacterial biocontrol agent for fire blight (Smits et al. 2011). Aravind et al. (2009) reported for
suppression of phyto-parasitic burrowing nematode (Radopholus similis Thorne) by
endophytic bacteria Bacillus megaterium BP17 and Curtobacterium luteum TC10.
Similar to B. thuringiensis, endophytic bacteria active against plant pests have also
been demonstrated, where genetically modified endophytic P. fluorescens expressing
Bacillus thuringiensis toxin and Serratia marcescens chitinase effectively targeted
Eldana saccharina (sugarcane borer) larvae (Downing et al. 2000). Niu et al. (2011)
showed that B. cereus AR156 triggered both the SA and JA/ET signaling pathways in
Arabidopsis to induce ISR, which led to an additive effect of plant protection. Earlier,
similar to the above studies, Conn et al. (2008) indicated that A. thaliana plants inoculated with endophytic actinobacteria showed upregulation of both defense pathways,
thereby protecting against subsequent infection by phytopathogenic bacteria E. carotovora and fungus F. oxysporum. However, the primed defense pathways differed for
the two pathogen types. The resistance to E. carotovora involved JA/ET pathway,
while resistance toward F. oxysporum was mainly followed the SA pathway. It is
A. Dahiya et al.
3.6.2 Phytohormone
Mehta et al. (2014) obtained endophytic P-solubilizing rhizobacteria from 20 healthy
apple roots and found that endophyte B. methylotrophicus CKAM obtained from
root endosphere showed the higher phosphate solubilization (on PVK agar plates
in vitro). B. methylotrophicus also showed nitrogenase activity, IAA, siderophore,
and antifungal activity against F. oxysporum, Phytophthora sp., D. necatrix, S. rolfsii,
and P. aphanidermatum. Pirhadi et al. (2018) isolated bacterial endophytes from
roots, stems, and leaves of sugarcane grown in saline and non-saline soil. The
authors observed a prevalence of Bacillaceae, with Bacillus sp. being the most
frequently isolated bacterium and salinity affected the bacterial community structure and higher diversity of root entophytic P-solubilizing bacteria. Earlier, Kruasuwan and Thamchaipenet (2016) reported that bacterial endophytes isolated from
sugarcane rhizosphere exhibited plant growth-promoting traits especially indole-3acetic acid, nitrogen fixation, ACC deaminase, phosphate solubilization, siderophore
production, etc. Shabanamol et al. (2018) observed that three diazotrophic isolates
inhibited the growth of rice sheath blight pathogen Rhizoctonia solani, also produced
indole-3-acetic acid, gibberellic acid, and cytokinins. Ribeiro et al. (2018) reported
that Bacillus strains produced high levels of IAA in the presence of tryptophan. Sun
et al. (2019) observed that the production of indole acetic acid significantly enhanced
root biomass and root–shoot ratio on medicinal plant Astragalus mongholicus.
3.6.3 Endophytic Microbes as a Biocontrol Agent
A few endopytic microorganisms also act as potential biocontrol agents. An endophytic bacteria Pantoea vagans C9-1 was commercialized as a bacterial biocontrol agent for fire blight (Smits et al. 2011). Aravind et al. (2009) reported for
suppression of phyto-parasitic burrowing nematode (Radopholus similis Thorne) by
endophytic bacteria Bacillus megaterium BP17 and Curtobacterium luteum TC10.
Similar to B. thuringiensis, endophytic bacteria active against plant pests have also
been demonstrated, where genetically modified endophytic P. fluorescens expressing
Bacillus thuringiensis toxin and Serratia marcescens chitinase effectively targeted
Eldana saccharina (sugarcane borer) larvae (Downing et al. 2000). Niu et al. (2011)
showed that B. cereus AR156 triggered both the SA and JA/ET signaling pathways in
Arabidopsis to induce ISR, which led to an additive effect of plant protection. Earlier,
similar to the above studies, Conn et al. (2008) indicated that A. thaliana plants inoculated with endophytic actinobacteria showed upregulation of both defense pathways,
thereby protecting against subsequent infection by phytopathogenic bacteria E. carotovora and fungus F. oxysporum. However, the primed defense pathways differed for
the two pathogen types. The resistance to E. carotovora involved JA/ET pathway,
while resistance toward F. oxysporum was mainly followed the SA pathway. It is