which favors those plants even to survive and multiply. The natural environments
tend to pose a given set of stress in particular environment, whereas the plants grown
in conventional agricultural systems have to face stress which is specific to agricultural practices and availability of the natural resources in a continuous cropping
system.
The list of stresses associated with growing plants is increasing day by day. To
overcome these stresses understanding genetics and applying different breeding
techniques were widely exploited to obtain stress tolerant varieties. In addition,
recent advances in biotechnological and genome sequencing applications are
providing a wider platform to develop genetically modified organisms in general
and plants in particular. There is a hue and cry on the use of genetically modified
plants in several parts of the world especially India and even methods employed
questions its suitability and stability in nature. Hence microorganisms being ubiquitous and potentially being gifted with an array of genes which are under simple
regulatory systems seem to be one of the best options to induce resistance to these
stresses naturally in association with the genes which are inherently associated with
stress in plants (Sirari et al. 2016).
Environmental stress and adapting to these changes are not new to plants. They
are naturally gifted with a multitude of stress related genes. These genes in response
to abiotic or biotic stresses, at the molecular level alter gene expression leading to the
synthesis of various proteins or enzymes required to overcome the specific stress
(Bagati et al. 2018). Thermal stress is considered to be a major challenge these days
with the change in environmental conditions due to global warming which directly
relates to the availability of water and increase in heat stress (Godfray et al. 2010;
Ferguson 2019). It is reported to directly hamper the productivity of several valuable
crops and even its ecological fitness. Along with this high salt concentration is
known to hamper several processes of plants at different stages of its growth and
recent studies also indicate that plastic pollution is also playing a vital role in
agricultural production. To overcome all these problems and to facilitate plant
adaptation along with its inherent capacity, microbial inoculants are also reported
to support the plants to alleviate the effects of these stresses significantly (Orhan
2016).
Arthrobacter, Achromobacter, Azospirillum, Azotobacter, Burkholderia, Bacillus, Enterobacter, Paenibacillus, Klebsiella, Pantoea, Microbacterium, Streptomyces, Pseudomonas and Serratia are the common candidate microorganisms of plant
growth promoting rhizobacteria isolated from rhizosphere. The use of these bacteria
as biofertilizers, biopesticides, and biostimulants is already proven valuable in the
agriculture sector. Numana et al. (2018) are of the opinion that these PGPR can also
be exploited as cheap and easily available sources to mitigate the stress associated
with plants. It is involved in stress alleviation directly or indirectly by triggering the
production of additional growth hormones, supporting through the acquisition of the
limiting factors by producing special proteins such as siderophores, providing
protection from free radicals through the activation of antioxidant enzymes, and
improving plant system through overall nutrition balance (Kumar and Verma 2017).
7 Microbe-Mediated Mitigation of Abiotic Stress in Plants
229
tend to pose a given set of stress in particular environment, whereas the plants grown
in conventional agricultural systems have to face stress which is specific to agricultural practices and availability of the natural resources in a continuous cropping
system.
The list of stresses associated with growing plants is increasing day by day. To
overcome these stresses understanding genetics and applying different breeding
techniques were widely exploited to obtain stress tolerant varieties. In addition,
recent advances in biotechnological and genome sequencing applications are
providing a wider platform to develop genetically modified organisms in general
and plants in particular. There is a hue and cry on the use of genetically modified
plants in several parts of the world especially India and even methods employed
questions its suitability and stability in nature. Hence microorganisms being ubiquitous and potentially being gifted with an array of genes which are under simple
regulatory systems seem to be one of the best options to induce resistance to these
stresses naturally in association with the genes which are inherently associated with
stress in plants (Sirari et al. 2016).
Environmental stress and adapting to these changes are not new to plants. They
are naturally gifted with a multitude of stress related genes. These genes in response
to abiotic or biotic stresses, at the molecular level alter gene expression leading to the
synthesis of various proteins or enzymes required to overcome the specific stress
(Bagati et al. 2018). Thermal stress is considered to be a major challenge these days
with the change in environmental conditions due to global warming which directly
relates to the availability of water and increase in heat stress (Godfray et al. 2010;
Ferguson 2019). It is reported to directly hamper the productivity of several valuable
crops and even its ecological fitness. Along with this high salt concentration is
known to hamper several processes of plants at different stages of its growth and
recent studies also indicate that plastic pollution is also playing a vital role in
agricultural production. To overcome all these problems and to facilitate plant
adaptation along with its inherent capacity, microbial inoculants are also reported
to support the plants to alleviate the effects of these stresses significantly (Orhan
2016).
Arthrobacter, Achromobacter, Azospirillum, Azotobacter, Burkholderia, Bacillus, Enterobacter, Paenibacillus, Klebsiella, Pantoea, Microbacterium, Streptomyces, Pseudomonas and Serratia are the common candidate microorganisms of plant
growth promoting rhizobacteria isolated from rhizosphere. The use of these bacteria
as biofertilizers, biopesticides, and biostimulants is already proven valuable in the
agriculture sector. Numana et al. (2018) are of the opinion that these PGPR can also
be exploited as cheap and easily available sources to mitigate the stress associated
with plants. It is involved in stress alleviation directly or indirectly by triggering the
production of additional growth hormones, supporting through the acquisition of the
limiting factors by producing special proteins such as siderophores, providing
protection from free radicals through the activation of antioxidant enzymes, and
improving plant system through overall nutrition balance (Kumar and Verma 2017).
7 Microbe-Mediated Mitigation of Abiotic Stress in Plants
229