12 Endophytic Rhizobacteria for Mineral Nutrients …
279
2012). For instance, a study on plant colonization and the establishment of symbionts
by Hardoim et al. (2015) showed the presence of significant putative properties in
endophytes compared to other types of bacteria interacting with plants.
There is an increasing interest in harnessing the potential of endophytic microbes
to develop sustainable crop production systems. Although endophytic rhizobacteria
are considered a subset of the rhizospheric microflora, their endophytic lifestyle
offers them a myriad of advantages over rhizospheric growth (Compant et al. 2010).
For instance, they establish themselves in sheltered micro-environments within the
plant root tissues (Castanheira et al. 2017), which are protective ecological niches
that provide them with safe, consistent, and undisturbed environments as opposed
to external rhizobacteria (Senthilkumar et al. 2011). Literature advances that endophytic microbes are relatively protected from external biotic and biotic environmental
stresses, unlike their external counterparts whose survivability and colonizability are
largely dependent on extrinsic soil factors (Rajkumar et al. 2009; Suman et al. 2016;
Waghunde et al. 2017; Lata et al. 2019; Dubey et al. 2020).
Living endophytically allows these bacteria to maintain close contact with plant
root tissues for the direct and constant supply of nutrients and their beneficial effects
can be exerted onto the host plants more directly (Lata et al. 2019). The plant endosphere niche presents a unique habitat, and bacterial endophytes possibly have differential functions, specializations, adaptations, and competence (Compant et al. 2010).
The diversity of endophytic communities also varies depending on host plant species
and genotypes, location, developmental stages, and local environmental conditions
(Shi et al. 2014). Nevertheless, the direct and intimate interactions that endophytic
rhizobacteria form with plant root tissues makes them highly valuable tools and suitable candidates for improving mineral nutrient acquisition in plants more directly
and efficiently (Sreejith et al. 2019).
12.4 Conclusions and Future Prospects
The need for eco-friendly crop fertilization alternatives is increasingly becoming
urgent. However, endophytic rhizobacteria have not been fully understood and the
prospects of finding unique and interesting bacteria are great. Identifying endophytic
rhizobacterial strains with multiple PGP functions for specific plants can definitely
pave way for more benefits in terms of plant mineral nutrients acquisition. As such,
present and future research work should focus on the largely unexplored rhizobacterial endophytes and their potential uses for mineral nutrients acquisition in plants
(Turner et al. 2013). Most plant-endophyte interactions have involved rhizobia and
legumes and future research should explore fresh alternatives on their application for
other agronomically important crops (Suman et al. 2016).
Although there is a wealth of information on culture-dependent and independent
characterization of endophytic rhizobacterial diversity and their associated in vitro
PGP mechanisms, reports on their practical applications as plant inoculants under
279
2012). For instance, a study on plant colonization and the establishment of symbionts
by Hardoim et al. (2015) showed the presence of significant putative properties in
endophytes compared to other types of bacteria interacting with plants.
There is an increasing interest in harnessing the potential of endophytic microbes
to develop sustainable crop production systems. Although endophytic rhizobacteria
are considered a subset of the rhizospheric microflora, their endophytic lifestyle
offers them a myriad of advantages over rhizospheric growth (Compant et al. 2010).
For instance, they establish themselves in sheltered micro-environments within the
plant root tissues (Castanheira et al. 2017), which are protective ecological niches
that provide them with safe, consistent, and undisturbed environments as opposed
to external rhizobacteria (Senthilkumar et al. 2011). Literature advances that endophytic microbes are relatively protected from external biotic and biotic environmental
stresses, unlike their external counterparts whose survivability and colonizability are
largely dependent on extrinsic soil factors (Rajkumar et al. 2009; Suman et al. 2016;
Waghunde et al. 2017; Lata et al. 2019; Dubey et al. 2020).
Living endophytically allows these bacteria to maintain close contact with plant
root tissues for the direct and constant supply of nutrients and their beneficial effects
can be exerted onto the host plants more directly (Lata et al. 2019). The plant endosphere niche presents a unique habitat, and bacterial endophytes possibly have differential functions, specializations, adaptations, and competence (Compant et al. 2010).
The diversity of endophytic communities also varies depending on host plant species
and genotypes, location, developmental stages, and local environmental conditions
(Shi et al. 2014). Nevertheless, the direct and intimate interactions that endophytic
rhizobacteria form with plant root tissues makes them highly valuable tools and suitable candidates for improving mineral nutrient acquisition in plants more directly
and efficiently (Sreejith et al. 2019).
12.4 Conclusions and Future Prospects
The need for eco-friendly crop fertilization alternatives is increasingly becoming
urgent. However, endophytic rhizobacteria have not been fully understood and the
prospects of finding unique and interesting bacteria are great. Identifying endophytic
rhizobacterial strains with multiple PGP functions for specific plants can definitely
pave way for more benefits in terms of plant mineral nutrients acquisition. As such,
present and future research work should focus on the largely unexplored rhizobacterial endophytes and their potential uses for mineral nutrients acquisition in plants
(Turner et al. 2013). Most plant-endophyte interactions have involved rhizobia and
legumes and future research should explore fresh alternatives on their application for
other agronomically important crops (Suman et al. 2016).
Although there is a wealth of information on culture-dependent and independent
characterization of endophytic rhizobacterial diversity and their associated in vitro
PGP mechanisms, reports on their practical applications as plant inoculants under