CHARACTERIZATION OF PLANT GROWTH PROMOTING RHIZOBACTERIA AND EVALUATION OF THEIR BIOCONTROL POTENTIAL AGAINST TOMATO BACTERIAL WILT
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Date
2014
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UHF,NAUNI
Abstract
ABSTRACT
Bacteria that colonize plant roots and promote plant growth are referred to as plant
growth-promoting rhizobacteria (PGPR). PGPR are highly diverse and in this study we focus
on rhizobacteria as biocontrol agents. Their effects can occur via local antagonism to soilborne pathogens or by induction of systemic resistance against pathogens throughout the
entire plant. Several substances produced by antagonistic rhizobacteria have been related to
pathogen control and indirect promotion of growth in many plants, such as siderophores, lytic
enzymes and antibiotics. Induced systemic resistance (ISR) in plants resembles pathogeninduced systemic acquired resistance (SAR) under conditions where the inducing bacteria and
the challenging pathogen remain spatially separated. There is a considerable experimental
support for the idea that PGPR may be used as biocontrol agent and biofertilizers to increase
the yield of tomato crop with concomitant decrease in the chemical fertilizers and pesticides.
Therefore, the aim of this study is to screen the antagonistic plant growth promoting
rhizobacteria for biocontrol of tomato bacterial wilt with multifarious plant growth promoting
traits. The antagonistic bacterial strains were characterized for antagonistic activity along with
multifarious plant growth promoting activities like P solubilisation, IAA production,
siderophore synthesis, lytic enzyme activity, and ability to fix atmospheric nitrogen under in
vitro conditions. Five antagonistic bacterial isolates were tested for biocontrol potential under
net house conditions. Isolate CT7A showed maximum reduction of disease incidence.
Increase in plant biomass was also observed with the isolate. The isolate was identified as
Bacillus subtilis by 16S rDNA sequencing. Therefore, CT7A strain had considerable
biocontrol potential as well as growth promotion ability and therefore it could be used as a
biocontrol agent against bacterial wilt of tomato.
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