STUDIES ON INTERACTION BETWEEN PLANT GROWTH PROMOTING RHIZOBACTERIA (PGPR) AND SOIL BORNE PATHOGEN (Pythium spp.) OF TOMATO
Abstract
ABSTRACT
Free living plant growth promoting Rhizobacteria (PGPR) can be used in a variety of
ways when plant growth enhancements are required. Interest in biological control of plant
pathogen have been stimulated in recent years by trends in agriculture towards greater
sustainability and public concern about the use of hazardous pesticides. There is now
unequivocal evidence that antibiotics play a key role in the suppression of various soil borne
plant pathogens by antagonistc microorganisms. In the present study, bacterial isolates were
tested for plant growth promoting traits viz., phosphate solubilization, siderophore production
and antagonism against Pythium aphanidermatum and Alternaria solani, the disease causing
pathogens of tomato ( Solanum lycopesicum L.). Fourteen isolates were selected as
representatives by modified replica plating technique from the rhizosphere soil and roots of
the tomato seedlings in nursery at different sites of Palampur H.P. These fourteen isolates
were selected for screening of the above mentioned traits. An isolate THS II showed
multifarious plant growth promoting activities along with phosphate solubilization and
siderophore production. Isolate THS II was selected for further studies on production of
antifungal antibiotic activity with culture filtrate. The production reached its peak in 72 h and
optimum pH was 6.5 respectively. Effect of bacterial antagonists on rhizosphere and
endophytic bacterial population densities, plant growth response and nutrient status of plant
was also investigated. Endophytic and rhizosphere bacterial population was recorded
maximum when seeds were treated with inoculants as compare to untreated control. Among
four bacterial strains, germination parameters, shoot and root length, shoot and root dry
weight, N, P, and K content of soil and whole shoot system was found more in THS II
bacterial isolate. Therefore, THS II strain had considerable colonization and competitive ability
and it could be used as a biofertillizers or biocontrol agent.