Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...

228j 11 Rhamnolipid-Producing PGPR and Their Role
11.6
Conclusions and Future Directions
Since rhamnolipids are involved in zoospore lysis of soilborne pathogens such as
Pythium, Phytophthora and Plasmopara spp., application of such rhamnolipid-producing
rhizobacterial strains should facilitate control of damping-off especially at
vegetable cultivation nursery sites. The PGP rhizobacterial isolates are significantly
effective in protecting plants against soilborne pathogens by enhancing peroxidase
and PAL activities in plant tissues [146]. For vegetable nurseries, strain such as
Pseudomonas sp. GRP3 should now be tested for developing an effective management
strategy to control damping-off diseases affecting vegetable nurseries. Using
rhamnolipid-producing plant growth promoting rhizobacteria would open a new
way to combat damping-off disease in vegetables during nursery stage. Furthermore,
other plant growth promoting properties such as siderophore production,
phosphate solubilization and IAA production would be beneficial for plant health
and growth. It would be advantageous to isolate and characterize indigenous rhamnolipid-producing
PGPR to maximize climate and natural adaptation. Such bacterial
strains can also be exploited in hydroponics and recirculating water systems. This
strategy could play an immensely important role in protecting vegetable nursery
crops against attacks by damping-off disease, by using native rhizobacteria having
plant growth promoting activity and rhamnolipid-producing capabilities in such
highly humid geographical regions as the Central Himalayas.
Although current efforts are directed toward laboratory-based assays of molecules
involved in QS systems, their in situ operation in the rhizosphere appears imminent.
Such information will permit not only the delivery of more appropriate and effective
bioinoculants for plant and soil health but also the cell density-dependent control of
in situ biological equilibrium, a feature of consequence in minimizing competition
with indigenous microorganisms for the limited resources available in this unique
ecosystem.
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