Agriculture Reference
In-Depth Information
bacteria enhance plant growth and tolerance to pesti-
cide stress. The effects of different concentrations of
fipronil and pyriproxyfen on lentil plants were studied
by Ahemad and Khan (2011e).
Rhizobium
sp. strain
MRL3, which was tolerant to pyriproxyfen and fipronil,
could produce biomolecules responsible for plant
growth promotion in sufficient amounts, both in the
presence and absence of insecticide. Insecticides at the
recommended and higher doses reduced the symbiotic
properties, plant dry biomass, seed yield and nutrient
uptake of lentil plants. The application of
Rhizobium
sp.
strain MRL3 enhanced the measured parameters signif-
icantly in comparison to the plants grown in soils having
the same concentrations of both insecticides and no
inoculant (Ahemad & Khan, 2011e).
Bradyrhizobium
strain MRM6, tolerant to quizalofop-
p
-ethyl and
clodinafop, produced sufficient amounts of plant
growth-promoting substances both in the presence and
absence of quizalofop-
p
-ethyl and clodinafop (Ahemad
& Khan, 2011f). Similar plant growth-promoting
substances are produced by
Mesorhizobium ciceri
(Wani
et al.,
2008). The rhizobacteria isolated from the
chickpea, pea, green gram and lentil nodule and mustard
rhizosphere showed tolerance to herbicides (quizalofop-
p
-ethyl, clodinafop, metribuzin and glyphosate),
insecticides (fipronil, pyriproxyfen, imidacloprid and
thiamethoxam) and fungicides (tebuconazole, hexacon-
azole, metalaxyl and kitazin) ranging from 400 to
3200 μg/mL (Ahemad & Khan, 2011g). The genetic
make-up and physiology in microbes are implicated in
making plant-microbe systems resistant to pesticides by
forming new bypass metabolic mechanisms that are not
inhibited by pesticides (Bellinaso
et al.,
2003).
growth and yield of these plants, which are negatively
affected due to the adverse effects of pesticides on the
bacteria. Bacterial tolerance to pesticides increases the
growth and performance of legume plants under pesti-
cide stress.
references
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Ahemad M, Khan MS (2011a) Ecotoxicological assessment of
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Ahemad M, Khan MS (2011b) Pesticide interactions with soil
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Agricultural and Environmental Applications
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Ahemad M, Khan MS (2011c) Comparative study of the growth
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Ahemad M, Khan MS (2011d) Effect of tebuconazole-tolerant
and plant growth promoting
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Rhizobium
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6.5 Conclusion
Pesticides taken up by plants from the environment
move to the various plant parts either through xylem or
phloem. By metabolic conversions pesticides are ulti-
mately changed into soluble conjugates by phase II
reactions or to bound residues by phase III reactions.
Pesticides can persist in plants for a long time due to
their long half-lives. Their application adversely affects
the activity, efficiency and survival of symbiotic bacteria
of legumes. Nitrogen fixed by these bacteria and the
other compounds produced by them, like HCN, sidero-
phores and phytohormones, are very important for the
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