Evidently, PGP traits along with chromium detoxifying property
showed that PGPB have great potential to improve plantgrowth
and concurrently, phytoremediation of chromiumstressed
soils. Since, performance of specific PGPB varies significantly
according to the soil type and environmental conditions;
an intensive research is needed to enhance the
rhizosphere colonization and chromium phytoavailability by
PGPB in chromium-stressed soils. Using consortia (more than
one ecologically distinct PGPB) instead of mono-inoculant is a
better strategy in order that plant-beneficial bacterial activities
are expressed continuously in soils. Moreover, unravelling the
exact mechanisms of PGPB in facilitating chromium uptake
and evasion by plants would further consolidate the PGPB-assisted
phytoremediation of chromium in diverse niches.
In addition, efficiency of phytoextraction/phytostabilization
is measured by translocation factor (TF) and bio-concentration
factor (BF). Therefore, compatibility of chromium
remediating plants with the appropriate PGPB is required in
a specific soil type so that the maximum efficiency can be
achieved in terms of TF and BF.
Further, most of the studies of PGPB-assisted phytoextraction/
phytostabilization have been conducted in chromiumspiked
soils under controlled environment (pots/greenhouse/
gnotobiotic conditions); field trials would reveal the actual
practicability of chromium-reducing PGPB in accelerating
the pace of remediation vis-a` -vis plant-growth amelioration
because field environment is exposed to several constraints
including biotic (biological antagonism by indigenous
microflora and phytopathogens) and abiotic (acidity, salinity,
drought, temperature, and radiation etc.) factors.
Recently, new biotechnological and genetic engineering
tools have revolutionized the bioscience as new traits can be
produced in the recipient organism by inserting/modifying
specific genetic sequence of desired traits from host organisms.
By this approach, PGPB can be genetically modified in order
to increase the phytoextraction or mobilization of chromium.
But releasing such PGPB strains in natural environment would
encounter legal and ethical problems which must be addressed
prior to their application.
Considering the above scenario, plant-growth promotion
with chromium-stress evasion and simultaneously expediting
phytoremediation through PGPB can be realized with full
potential.