280
B. N. Aloo et al.
field conditions are extremely scarce (Liu et al. 2017). Several endophytic rhizobacteria have been identified in laboratory studies but generally fail to give consistent results under field conditions and there is need to understand the complex
dynamics that control plant-endophyte associations probably by identifying genes
that govern these relationships at the molecular level. Although some studies have
been conducted in this area, they remain limited and genomic analyses can decipher into the capabilities of endophytes and their roles in plant mineral acquisition.
Our knowledge about the plant-microbe interactions can greatly be enhanced using
metabolomic, genomic, and transcriptomic methods (Dubey et al. 2020). At the
moment, only a limited number of genes that contribute to endophytic invasion and
colonization have been identified. Perhaps whole-genome sequencing of these organisms will facilitate the identification of novel isolates and their successful exploitation
for plant mineral nutrients acquisition. Further analysis of the sequenced genomes and
characterization of the involved genes can also help to improve our understanding of
their interaction with plants (Compant et al. 2010) for full exploitation. These efforts
can also lead to the identification of some new genes required for endophytic lifestyle
but there would be a need to separate the common genes for rhizosphere colonization
from those involved in the endophytic lifestyle. Additionally, a more comprehensive
understanding of whether these organisms are likely to establish themselves in plants
if applied as biofertilizers is needed (Compant et al. 2010).
Numerous reports have revealed a range of beneficial features of the endophytic
rhizobacteria for plant mineral nutrients acquisition. Nevertheless, there is still a
great scope of further exploration and identification of more novel functions. For
instance, research on N 2 fixation and P solubilization abilities by endophytic plant
rhizobacteria continues to expand, but very little strides have been made regarding
K solubilization yet K is the third major essential macronutrient for plant growth.
Similarly, limited work has been carried out on S-oxidation (Dhiman et al. 2019). A
combination of both traditional and modern biotechnological methods will help in
advancements toward improved plant mineral nutrients acquisition and sustainable
agriculture (Waghunde et al. 2017). Although a broad range of endophytes with traits
for enhancing mineral nutrient acquisition in different plants have been described,
only a few of these have conclusively been studied to demonstrate their significance
in plants (Chhabra and Dowling 2017). Furthermore, the impact of endophytic colonization and enhanced nutrient uptake in plants can be varied depending on plant
host species/cultivars, endophyte strains, and environmental conditions (Shi et al.
2014).
The successful manipulation of the plant microbiome can substantially contribute
to sustainable agricultural production (Bakker et al. 2012; Tkacz et al. 2015), by
reducing the need for chemical inputs (Adesemoye et al. 2009; Kandel et al. 2017)
and GHG emissions (Singh et al. 2010). This chapter provides a comprehensive
review of the putatie functions and ecological significance of endophytic PGPR
for mineral nutrient acquisition in plants. Taking into consideration the intimate
relationships they form with their plant hosts, these rhizobacteria present special
tools for improving plant mineral nutrients acquisition and could be better plant
growth promoters than their external counterparts (Lata et al. 2019). Endophytes are
B. N. Aloo et al.
field conditions are extremely scarce (Liu et al. 2017). Several endophytic rhizobacteria have been identified in laboratory studies but generally fail to give consistent results under field conditions and there is need to understand the complex
dynamics that control plant-endophyte associations probably by identifying genes
that govern these relationships at the molecular level. Although some studies have
been conducted in this area, they remain limited and genomic analyses can decipher into the capabilities of endophytes and their roles in plant mineral acquisition.
Our knowledge about the plant-microbe interactions can greatly be enhanced using
metabolomic, genomic, and transcriptomic methods (Dubey et al. 2020). At the
moment, only a limited number of genes that contribute to endophytic invasion and
colonization have been identified. Perhaps whole-genome sequencing of these organisms will facilitate the identification of novel isolates and their successful exploitation
for plant mineral nutrients acquisition. Further analysis of the sequenced genomes and
characterization of the involved genes can also help to improve our understanding of
their interaction with plants (Compant et al. 2010) for full exploitation. These efforts
can also lead to the identification of some new genes required for endophytic lifestyle
but there would be a need to separate the common genes for rhizosphere colonization
from those involved in the endophytic lifestyle. Additionally, a more comprehensive
understanding of whether these organisms are likely to establish themselves in plants
if applied as biofertilizers is needed (Compant et al. 2010).
Numerous reports have revealed a range of beneficial features of the endophytic
rhizobacteria for plant mineral nutrients acquisition. Nevertheless, there is still a
great scope of further exploration and identification of more novel functions. For
instance, research on N 2 fixation and P solubilization abilities by endophytic plant
rhizobacteria continues to expand, but very little strides have been made regarding
K solubilization yet K is the third major essential macronutrient for plant growth.
Similarly, limited work has been carried out on S-oxidation (Dhiman et al. 2019). A
combination of both traditional and modern biotechnological methods will help in
advancements toward improved plant mineral nutrients acquisition and sustainable
agriculture (Waghunde et al. 2017). Although a broad range of endophytes with traits
for enhancing mineral nutrient acquisition in different plants have been described,
only a few of these have conclusively been studied to demonstrate their significance
in plants (Chhabra and Dowling 2017). Furthermore, the impact of endophytic colonization and enhanced nutrient uptake in plants can be varied depending on plant
host species/cultivars, endophyte strains, and environmental conditions (Shi et al.
2014).
The successful manipulation of the plant microbiome can substantially contribute
to sustainable agricultural production (Bakker et al. 2012; Tkacz et al. 2015), by
reducing the need for chemical inputs (Adesemoye et al. 2009; Kandel et al. 2017)
and GHG emissions (Singh et al. 2010). This chapter provides a comprehensive
review of the putatie functions and ecological significance of endophytic PGPR
for mineral nutrient acquisition in plants. Taking into consideration the intimate
relationships they form with their plant hosts, these rhizobacteria present special
tools for improving plant mineral nutrients acquisition and could be better plant
growth promoters than their external counterparts (Lata et al. 2019). Endophytes are