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active compounds responsible; the plants therefore are utilized as raw source
(Arceusz et al. 2010). Direct use of plants as medicines may have deleterious effect
on humans while others like rosemary, thyme, mint, etc. do not have any side effects.
Green seeds of bitter melon (Momordica charantia) are toxic enough to cause
hypoglycemia (Li et al.
2004; Basch et al. 2003). The fruit otherwise is effectively
used to cure fever in malaria.
254 K. Kiran and G. Sharma
Medi
cinal
plant
s a
re
studi
ed mainly on three aspects, first based on their abun-
dance in a geographical area, such as South Africa, where the plants are marketed
(Masondo and Makunga
2019) for the treatment of Alzheimer’s disease (Masondo
et al.
2019), and Ghana, for the treatment of malaria, HIV/AIDS, hypertension,
tuberculosis, or bleeding disorders (Tchuifon et al. 2017). Various other countries
include parts of Cuba (Thomford et al. 2015) and China (Fernández and Armas
2013). The second line of studies lies on a specific species or genus/family, like
focused studies on Artemisia annua, Aloe vera, Panax ginseng, Punica granatum,
Apocynum cannabinum, and Andrographis paniculata, respectively (Zhang et al.
2010; Xu et al. 2018, 2017; Gupta et al. 2018; Al-Qallaf 2017; Ram 2013). And the
third line of studies covers the plants with some kind of medical interest project. For
instance the plants with special antibacterial, antifungal, antioxidant, and anticancer
activities are studied in depth with clear objectives (Gupta et al.
2019; Ortega-
Cuadros and Tofiño-Rivera 2019; Ahmed and Gupta 2013; Basu et al. 2017;
Yeung et al. 2018; Tang 2014; Ahmed et al. 2014).
Medicinal plants are important and potential contributors to humans and their
well-being; also there is a risk of their existence due to increasing global change;
therefore, certain indicative measures to save medicinal plant resources by
subjecting them to alternative plans could help the future societal development.
These indicative measures could encourage further methodological development and
interdisciplinary research on the diverse aspects of medicinal biodiversity. Informa-
tion on species taxonomy and native geographical distributions from public biodi-
versity databases and spatial databases that link species distributions to bioactive
compounds and therapeutic areas shall be beneficial to protect the medicinal plants.
The ecosystem is the best natural indicator of the capacity of medicinal plant
resources or plant species adapted to specific regions. This also suggests that certain
regions may have increased capacity to contribute plant-based medicines for treating
diseases. Further research on the ecological roles of the bioactive compounds in
medicinal plants and their existing genetic variation is essential for the development
of indicators of ecosystem processes to monitor the environmental change, thus
assisting the sustainable management and protection of natural medicinal plant
resources.
Evidence-based knowledge of plant therapeutic properties is the key to continual
and efficient use of medicinal biodiversity for the societal benefits. The total number
of medicinal plants and the number of plants showing a particular therapeutic
property are indicators of the residual value of regression between the two. This
indica
tor shows the availabil
ity or deficit of a species accumulation in its ability to
treat a disease if they are used as herbal medicines.
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15 Regulation of PGPR-Related Genes in Medicinal Plants in Adverse Conditions 255
15.4 Plant Grow th-Promoting Rhizobacteria: Correlation
with Medicinal Plants
The world today comes up with a new ailment after every short span of time, and
thus our requirement of medicines and drugs continues to amplify. Natural
compounds are most preferred over synthetic drugs for curing diseases, and these
natural compounds are variedly obtained from medicinal plants. Medicinal plants
like Matricaria necati,
Aloe vera, Thymus vulgaris, etc. are known to produce
bioactive molecules and induce genetic factors to overcome the ionic toxicity during
drought stress which leads to nutrient deficiency in these plants.
Numerous plant growth-promoting rhizobacteria are well known to exhibit bene-
ficial effects on plenty of medicinal plants. Eleven medicinal plants, namely,
Ocimum basilicum, Marrubium vulgare, Melissa officinalis, Origanum syriacum,
Quisqualis indica, Solidago virgaurea, Melilotus officinalis, Cymbopogon citratus,
Matricaria chamomilla, Thymus vulgaris, and Majorana hortensis, were analyzed
for their microbial densities within the
rhizosphere. M. chamomill a and M. hortensis
rhizospheres contained the lowest populations as compared to others. The strains
identified were found to be effective PGPR inoculants since they contained numer-
ous traits bene ficial for plant growth (Jansson and Hofmockel 2018).
15.5 PGPR-Induced Phytobeneficial Genes
The interaction of plant and soil microbes is too complicated and has been a
challenge (Ullah et al.
2021). A network of signaling between the plant symbionts
and the microbes persists. A wide range of secondary metabolites and root secretions
which are extremely rich in numerous organic compounds, sugars, and amino acids
regulate this interkingdom signaling mechanism thereby helping in attracting or
repulsing the other beneficial microbes or harmful pathogens (Haas and Défago
2005).
Several indicative PGPR strains have been extensively characterized over the last
two decades, demonstrating the molecular basis of their plant-beneficial effects.
These reports have witnessed many PGPR strains typically harboring multiple
plant-beneficial properties (Almario et al. 2014; Kim and Price 2011
). It was
therefore hypothesized that the selection of genes contributing whether through
direct stimulating or indirectly stimulating a mechanism to develop plant-beneficial
traits is due to the interaction of these bacteria with plants. This also led to the basis
that PGPR might be identified by their distinct array of genes contributing to plants
benefit. Phylogenetic analyses and genome comparative studies would be extre mely
helpful to understand the potential associations of phytobeneficial traits within
PGPR/B (Martiny et al. 2013; Bruto et al.
2014a). They examined the distribution
of 23 genes contributing to eight key plant-beneficial functions. A total of 25 poten-
tial genomes of proteobacterial PGPR (bacteria colonizing root surface and/or
tissues and displaying plant growth-promotion effects) along with phylogenetic
analyses including the possibility of any ancestral gene transfers were considered.
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These genomes were also compared with those of 279 other proteobacteria
representing (α,γ,β) from different taxonomic and ecological groups/status
(symbionts, saprophytes, plant and animal pathogens). A list of such genes can be
found in the study published by (Pörtner et al.
2021).
256 K. Kiran and G. Sharma
15.6 PGPR in Mitigating Abiotic Stress
Climate change has increased the risk of species extinction thereby effected the use
of land; this definitely shall affect the earth’s biodiversity in the coming decades
(Warren et al.
2018). An increase in annual temperature compared with all the
industrial development observed is predicted to vanish plant species approximately
by more than 50% (Allen et al.
2014). These drastic ecosystem disruptions globally
shall also include reduction of different medicinal plants as they too are an integral
part of terrestrial biodiversity (Applequist et al.
2020; Holopainen et al. 2018).
Medicinal plants produce several metabolites, and their production is greatly
affected by extreme temperatures, drought conditions, and the high atmospheric
CO
2
concentration. Such abiotic factors greatly affect the production and release of
compounds like flavonoids, phenolic acids, and plant volatiles (Langthorp 2021).
Therefore, integrative approaches combining diverse scientific fields like climate
science, satellitic observations of earth, and biodiversity genomics can help
immensely to predict the effects of global environmental change both in species
extinction risk (Shah et al.
2021b) and in understanding the changes in genes
involved in biosynthetic pathway and their adaptability effecting the production of
pharmacologically applicable bioactive compounds.
PGPR can decrease the necessity of nitrogen supplementation demanded by the
plants for their growth directly by the process of nitrogen (N) fixation and mobiliza-
tion. They also indirectly act by altering the root anatomy and help the N-fixers
through their secretions (Vacheron et al. 2013b; Jiao et al. 2021; Dos Santos et al.
2020). According to earlier studies, PGPR of various free-living N-fixers from
Bacillus sp. (Calvo et al. 2019) stimulate the expression levels of Arabidop sis nitrate
and ammonium transporters resulting in higher nutrient uptake (Oleńska et al. 2020).
PGPR are also known to increase the root surface area and root morphology thereby
improving the nitrogen bioavailability (Khan et al. 2016).
Plants in due course of time have adapted to various mechanisms to overcome
and tolerate adverse conditions like salinity, drought, and other prevailing constrains
in the environment. The use of PGPR/B has emerged as a potential solution to this
problem to enhance crop growth. For example, ACC deaminase production under
drought stress by PGPR has been known to have an important role in improving
plant growth and drought tolerance (Mohanty et al.
2021). Soil is the foremost base
of plant nutrient uptake; soil contains a lot of elements in the form of micro- and
macronutrients. Plant roots somehow are not able to utilize them due to their
complex structure. The bacteria present in the rhizosphere zone (Rhizobium,
Burkholderia, Azotobacter, Bacillus, Pseudomonas, Erwinia, and Serratia) release
organic acids like gluconic acid and 2-keto-gluconic acid which are able to solubilize
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the inorganic P (Khan et al. 2016). Siderophores produced by some bacteria contrib-
ute to iron accession by produci ng certain low molecular weight compounds in
deficiency of iron (Backer et al. 2018). They also are helpful in inhibiting disease
development in plants since the pathogens are deprived of iron supply (Dimkpa et al.
2014). Likewise, siderophores prevent accumulation of toxic metals in the soil, and
therefore, under excess metal stress, the plants are able to survive (Bruto et al.
2014b)
.
15 Regulation of PGPR-Related Genes in Medicinal Plants in Adverse Conditions 257
15.7 PGPR Genomics and Status of Research
In recent years, the genome characterization of emblematic PGPR model strains has
uncovered the molecular basis of some of their beneficial effects, leading the
identification of genes that are involved in the PGPR-plant cooperation (Liu et al.
2020; Shariati et al. 2017; Leontidou et al. 2020
). Around 85 rhizobacterial strains
from tomato wild species growing naturally under natural conditions along with a
local cultivar growing under stressed conditions wer e isolated and characterized.
Few of the selected strains showed multiple in vitro PGP-associated traits, like
phosphate solubilization, indole-3-acetic acid production, and
1-aminocyclopropane-1-carboxylate deaminase activity. The genome analyses
revealed that some of these belong to the class of Gammaproteobacteria and one
of them to Bacteroidetes. Several genes within the genomes were found to be
involved in plant growth promotion and stress regulation (Boss et al. 2022). A
PGPR strain AEW4 from the genus Sphingobium belonging to the class of
Alphaproteobacteria was isolated from the rhizosphere of the beachgrass Ammophila
breviligulata. Using sequence-based and genome-wide analyses along with the
phenotypic analyses, the authors proposed Sphingobium sp. strain AEW4 to possess
a variety of plant growth-promoting properties that enhance the growth of
beachgrass (Zhang et al.
2022). Strain JD37 from Pseudomonas chlororaphis
subsp. aurantiaca is known to possess important characteristics like plant growth
promotion, rhizosphere colonization, and biocontrol activities. A comparative
genome-wide study of JD37 with other Pseudomonas PGPR strains, viz., PA23,
Pf-5, and M18 from P. chlororaphis, Pseudomonas protegens, and Pseudomonas
aeruginosa, respectively, was also performed to understand the relationship among
themselves. JD37 genome was reported to contain numerous genes involved in plant
growth promotion, biocontrol activities, defense responses, rhizosphere coloniza-
tion, and mobility genes including genes of resistance against metal toxicity, and
genes responsible for secondary metabolite biosynthesis were also identified
(Zouagui et al. 2023). In a most recent study by (Hayat et al.
2010), draft genomes
of four PGPR strains, namely, Rahnella perminowiae (S11P1), Variovorax
sp. (S12S4), and two Pseudomonas sp. strains (S11A4 and S11P7) isolated from
saffron (Crocus sativus L.) rhizosphere, were reported. The genes predicted in their
study were reported to be involved in auxin production, phosphate solubilization,
and various other specialized functions in plant growth and defense (Hayat et al.
2010).
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258 K. Kiran and G. Sharma
15.8 Transcriptional Regulation of Rhizobacterial Genes
The rhizosphere of a plant is rich in microbial species that help in promoting its
growth and development (Ghosh et al. 2021). The rhizobacteria are in a mutually
beneficial associ ation with their host plant. The plant growth-promoting microbiome
derives energy and organic compounds from the plants and provides nutrients,
phytohormones, and protection from various biotic and abiotic stresses to the plant
(Badri et al.
2008). The cross talk between the host plant and rhizobacteria involves
multiple molecular factors and signaling mechanisms that help in the host coloniza-
tion and transcriptional regulation of rhizobacterial genes.
Soil microbiome is modulated by the root exudates secreted by the host plant.
ATP-binding cassette (ABC) transporters play an important role in such activity that
has been demonstrated in model plants such as Arabidopsis, Medicago, and rice
(Zhou et al.
2016; Bakker et al. 2018). Root exudates influence the soil microbiome
by acting as signal molecules and altering the soil’s physicochemical properties and
nutrient availability (Yuan et al.
2018; Olanrewaju et al. 2019). Azospirillum,
Bacillus,and Pseudomonas are some examples of rhizobacteria whose gene expres-
sion is regulated by plant root exudates (Aguirre-Noyola et al.
2021; Sun et al. 2021;
Mondal et al. 2023; Redondo-N ieto et al. 2012).
Pseudomonas fluorescens strain F113 is extensively studied for its biocontrol
property against fungal pathogens (Fusarium oxysporum) and nematodes
(Globodera rostochiensis, Heterodera glycines, Meloidogyne incognita, and
Pratylenchus scribneri). It is considered as a model for rhizosphere establishment
(Glick et al.
2007). Its genome is sequenced and contains several genes encoding
proteins involved in plant growth promotion, such as 1-aminocyclopropane-1-car-
boxylate (ACC) deaminase, secreted protease, and biosynthesis of secondary
metabolites, such as 2,4-diacetylphloroglucinol (DAPG) and hydrogen cyanide
(HCN) (Glick et al. 2007). ACC deaminase enzyme account s for the dissociation
of ACC into ammonia and α-ketobutyrate, thereby limiting the production of
ethylene (Singh et al.
2022; González et al. 2013). Within the genus Pseudomonas,
PsoR proteins that are a subfamily of LuxR proteins regulate the production of
2,4-diacetylphloroglucinol, a natural phenol involved in the antimicrobial and bio-
control property (Chaudhry et al. 2017).
15.9 Modern Approaches Followed to Understand
the Regulation of PGPR Genes
The increasing popularity of cost-effective next-generation sequencing technology
has made it possible to investigate multidimensional factors involved in plant-
microbe interactions. Next-generation sequencing is a useful tool that can predict
the PGPR-related genes in the soil microbiome. Multiomic approaches include the
use of metagenomics, transcriptomics, genomics, proteomics, and metabolomics
(Krishna et al. 2019; Moradi et al. 2021; Xia et al.
2020). Stable isotope probing is
another emerging tool in the field of microbial ecology (Hu et al.
2021a; Msimbira
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et al. 2022). LC/MS of proteome profiles of Bacillus subtilis (EB2004S) and
Lactobacillus helveticus (EL2006H) cell-free supern atant revealed the effect of
soil pH conditions on plant growth promotion (Kandaswamy et al. 2019). Compara-
tive transcriptome analysis can be utilized to reveal differentially regulated genes
between PGPR-treated and contr ol plants (Shariati et al.
2017; Caradonia et al. 2022;
Gao et al. 2022; Prabhukarthikeyan et al.
2020). Similarly, proteome analysis of
PGPR can also reveal stress-induced variations in protein expression (Zhou et al.
2022; Mashabela et al. 2022; Priya et al. 2022; Kuramae et al. 2020).
15 Regulation of PGPR-Related Genes in Medicinal Plants in Adverse Conditions 259
Genomic and metagenomic
analysis of PGPR of sorghum revealed that
Paraburkholderia tropica strain IAC/BECa 135 helps in the nutrient uptake and
Herbaspirillum frisingense strain IAC/BECa 152 influences signaling of
phytohormones to boost growth (Aloo et al.
2020). Whole-genome sequencing of
Burkholderia sp. Nafp2/4-1b revealed the presence of genes involved in
siderophores biosynthesis (PvdF), ACC deaminase (acdS), tryptophan synthase
(TSA1, TSB1), and phosphate solubilization (pqqABCDE operon) (Hassen et al.
2021). In another study, the whole-genome sequence of Klebsiella sp. strain
MPUS7, Serratia sp. strain NGAS9, and Citrobacter sp. strain LUTT5 revealed
genes associated with nitrogen, phosphorus, potassium, and iron metabolism that are
vital for plant growth promotion (Nisrina et al.
2021). Metagenome sequencing is
useful to characterize the microbial community. Whole shotgun metagenomic
sequence was analyzed for soil conducive and suppressive for Panama disease
pathogen Fusarium oxysporum f. sp. cubense that revealed a difference in microbial
richness between the two samples. PGPR species including Pseudomonas and
Burkholderia species were abundant in suppressive soil, while Bacillus and Strepto-
myces species were abundant in conducive soil, suggesting the role of PGPR
community toward biocontrol or co-occurrence in rhizosphere (Rai 2019).
15.10 Biological Control of PGPR on Medicinal Plants
Rhizobacteria play a significant role in the protection of their host plants against
biotic stress. Biomolecules such as antibiotics, lytic enzymes, and siderophores are
produced by the rhizobacteria that assist in the biocontrol activity against various
plant pests and pathogens. In addition to this, certain phytohormones or their analogs
are produced by the rhizobacteria that facilitate the induction of various defense
responses. The plant growth-promoting microbes also restrict the plant pathogens by
creating competition for nutrient acquisition and biosphere.
Application of Pseudomonas fluorescens strains isolated from rhizospheric soils
in Nepal on medicinal plants such as mint (Mentha sp.) and marigold (Tagetes sp.)
displayed improved height, number of branches, fresh and dry weight, and protec-
tion from phytopathogens such as Alternaria spp., Rhizoctonia solani, and Sclero-
tium rolfsii (Oloyede et al. 2021). Two non-native rhizobacteria (Acinetobacter
sp. and Alcaligenes faecalis) that were isolated from the rhizosphere of medicinal
plants inhibited the growth of bacterial canker pathogen Clavibacter michiganensis
subsp. michiganensis on tomato (Solanum lycopersicum) plants in the antibacterial
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assay as well as greenhouse trials. Furthermore, the reported rhizobacteria promoted
the growth of tomato plants in the greenhouse trials (Hu et al. 2021b). Pseudomonas
aeruginosa strain YY322 isolated from the rhizosphere soil of saffron (Crocus
sativus L.) exhibited antagonistic activity against common fungal pathogens of
saffron such as Fusarium oxysporum, F. solani, Penicillium citreosulfuratum, Peni-
cillium citrinum, and Stromatinia gladioli, by releasing volatile organic compounds
and producing lytic enzymes such as protease and glucanase (Ahmed et al.
2019)
.
260 K. Kiran and G. Sharma
15.11 Growth and Yield of Medicinal Plants Induced by PGPR
The role of PGPR in combating biotic (various plant pests and pathogens) and
abiotic stresses (drought and salinity) has been detailed in previous sections.
Rhizobacteria also have a positive impact on plant growth and development. Such
interactions are regulated by various direct and indirect mechanisms. In a study by
Ahmed et al. (
2014) conducted in Egypt, Bacillus thuringiensis strain C110, Pseu-
domonas fluorescens strain Th98, and Pseudomonas poae strain Th75 were the most
potent strains associated with the rhizosphere of 11 medicinal plants. Further
biochemical analysis confirmed the presence of traits useful for plant growth such
as production of IAA and HCN, chitinase activity, and solubilization of phosphate
and potassium. Pseudomonas aeruginosa strain YY322 isolated from the rhizo-
sphere soil of saffron (Crocus sativus L.) helped its host plant in nutrient acquisition
via nitrogen fixation, production of amm onia, and phosphate solubilization
(Msimbira et al. 2022). A salt-tolerant PGPR strain Priestia endophytica SK1 was
reported to boost the growth of fenugreek plant (Trigonella foenum-graecum) under
salt stress conditions by inducing nitrogen fixation and alkaloid (trigonelline) bio-
synthesis of trigonelline content (Rizvi et al.
2022).
15.12 Impact of PGPR Within a Diverse Range of Medicinal Plants
Medicinal plants are used as a traditional medicine in many countries of South East
Asia, including China, India, Pakistan, Sri Lanka, and Thailand. The usage of
chemical fertilizers and pesticides poses a hazard to the environment as well as the
yield of therapeutically important metabolites of medicinal plants such as flavonoids
and polyphenols. PGPR provide a sustainable solution toward the growth and
productivity of medicinal plants (Dehghani Bidgoli et al. 2019). Positive effects of
PGPR on the antioxidant activity, production of essential oil, total phenolic content,
and nutrient uptake have also been recorded for sweet basil (Ocimum basilicum)
(Ahmed et al. 2014; Ordookhani et al. 2011), rosemary (Rosmarinus officinalis)
(Ordookhani et al.
2011; Kasmaei et al. 2019; Sharma et al. 2021), and hyssop
(Hyssopus officinalis) (Sharifi 2017).
In Withania somnifera (Ashwagandha), treatment of microbial consortium
including Azospirillum, Azotobacter, Bacillus, and Pseudomonas species resulted
in improved growth and alkaloid content (Rajasekar and Elango
2011). Treatment of
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native phosphate solubilizer Bacillus megaterium and diazotrophic bacteria,
Azospirillum amazonense, and Azotobacter sp. on turmeric (Curcuma longa) rhi-
zome resulted in increased secondary metabolite production, including flavonoids,
curcumin, and phenols (Dutta and Neog
2016). Application of Pseudomonas
plecoglossicida strain Pp20, Bacillus sp. strain Bt04, Rhizobium sp. strain Konm6,
and Agrobacterium rhizogenes strain A4 resulted in substantial enhancement in the
amino acid and bioactive tropane alkaloids content, as well as C/N ratio in Datura
plant (Rahmoune et al.
2019). In Aloe vera (Aloe barbadensis), treatment of
phosphorus-solubilizing bacteria Pseudomonas putida strain P13 and Pantoea
agglomerans strain P5 lead to improved growth in terms of the offset number,
water productivity, and root colonization (Khajeeyan et al.
2022).
15 Regulation of PGPR-Related Genes in Medicinal Plants in Adverse Conditions 261
15.13 Therapeutic Benefits of Medicinal Plants in Association
with Rhizobacteria
Plant-derived health and wellness natural products are gaining popularity as most of
the urban population is becoming health centric. Organically grown medicinal plants
and their natural products are popular and thus economically important. Thus,
utilizing the PGPR for enhancing the therapeutic properties of medicinal plants is
another great area to explore further. PGPR have been associated with a positive
influence on the production of various therapeutically important phytocompounds
such as flavonoids, organic acids, phenols, tannins, and vitamins. Application of
Pseudomonas fluorescens strain p-69 on roselle (Hibiscus sabdariffa L.) resulted in
an increase in chlorophyll a and b and carotenoid content along with improved
growth (Sanayei et al. 2021). Treatment of roots of Sweet basil (Ocimum basilicum
L.) with Azospirillum baldaniorum strain Sp245 resulted in increased water potential
and photosynthetic performance due to improvement in leaf pigments (chlorophylls,
carotenoids, anthocyanins). This further facilitated the plant to alleviate the drought
stress (Mariotti et al. 2021). Similar effects were observed upon the application of
Pseudomonas and Azotobacter spp. on lemongrass (Cymbopogon citratus) (Mirzaei
et al. 2020) and Bacillus amyloliquefaciens strain QST713 on alfalfa varieties (Han
et al. 2022) under drought conditions.
15.14 Challenges Faced by Plants to Withstand the Harsh
Conditions: PGPR Perspective
Rhizosphere is an intricate plant-microbe interaction. Modern agricultural practices
rely on the indiscriminate use of fertilizers and chemical fertilizers to achieve better
productivity and protection from pets. Such measures are not environmentally
sustainable and adversely affect soil fertility. The beneficial microorganisms from
the soil microbiome could provide an environment-friendly solution for the promo-
tion of plant growth and development. The biocontrol properties of PGPR can
provide a solution for pest control. The positive effects of PGPR on inducing the
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synthesis of growth-promoting phytohormones and secondary metabolites are
another important property that will benefit agriculture. Thus, in times of global
warming and challenges of global food security, PGPR provide hope for sustainable
agriculture and clean environment (Shah et al.
2021a; Backer et al. 2018; Prasad
et al. 2019; Chandran et al. 2021).
262 K. Kiran and G. Sharma
15.15 Conclusions and Future Prospects
This chapter highlighted the areas of PGPR-associated information in relation to
medicinal plants published in literature and research articles. Various aspects of
different stress conditions prevailing that initiate the mechanism of regulation of the
PGPR genes within the rhizosphere zone were discussed. Further research from the
agronomic and medicine perspective regarding domestication, production, or genetic
or biotechnological research on breeding and development of medicinal plants
should be promoted.
Commercialization of PGPR shall require proper molecular analysis to stabilize
their effect on disease or growth control mechanisms and the risk involved. Specific
organism with all technical improvements for effective application of the microbe
for crop protection and disease control in coming years shall become a demand.
Therefore, it is essential to identify individual strains of a microbial pool possessing
multiple plant-protecting parameters to enhance plant growth and benefit the
farmers. Naturally though, PGPR through several mechanisms promote plant
growth. But then, for improved commercialization of PGPR, monitored and con-
trolled field trials of crop plants inoculated with PGPR are a prime requisite.
The research of medicinal plants in India is quite developed as compared to other
Asian countries and the other outer world countries. Scientific literature studies have
also shown significant output in the last two decades within the area of plant-based
active compounds used for medicine. Further advanced bioinformatics-based
analyses on genome-wide studies to identify novel strains in the rhizosphere of
plants with medicinal properties that can withstand the current stress conditions are a
prime requisite and are a more most demanded in the benefit of the ecosystem.
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