ISOLATION AND CHARACTERIZATION OF CULTURABLE BACTERIAL ENDOPHYTES FROM ROOT TISSUES OF Rosemarinus officinalis AND DETERMINATION OF THEIR BIOACTIVITIES
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Date
2019-11
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UHF,NAUNI
Abstract
ABSTRACT
Medicinal plants are known to harbor distinctive and specific subset of bacterial endophytes that might
be due to production of divergent bioactive compounds. There are many reports regarding production of
bioactive compounds by these endophytic microorganisms but limited work has been done about plant growth
promotion potential of endophytes associated with medicinal plants. Therefore, the present study was aimed to
explore the diversity of plant growth promoting root endophytic bacterial communities associated with
medicinal plant Rosemarinus officinalis and their characterization for plant growth promoting traits followed by
their inoculation efficiency for plant growth promotion of rosemary. A total of ninety eight endorhizospheric
bacteria were isolated fromroot samples ofRosemarinus officinaliscollected from two different sites ofKangra,
Kullu, Solan and Sirmour valleys of Himachal Pradesh and were subjected to one step screening for phosphate
solubilization, siderophore production and ability to fix nitrogen. After preliminary screening, a total of seventy
nine isolates were selected for quantitative estimation of P-solubilzation, siderophore production and additional
plant growth promoting traits viz. IAA, lytic enzymes production, production of secondary metabolites and
antifungal activity. Forty two isolates exhibiting maximum PGP traits were subjected to study genetic diversity
among them using 16S rDNA sequencing. In silico analysis grouped these isolates into nine major genera i.e.
Bacillus, Pseudomonas being predominant while other were Pseudoxanthomonas, Lysobacter, Kosakonia,
Ensifer, Beijerinckia, Oxynema and Serratia, respectively. Sole application of most efficient eleven isolates
belonged to different genera (KA7, KU5, KA10, SI12, KU13, KU2, KU14, KA14, KA11, KA2 and KU21)
resulted in significant increase in plant parameters of rosemary and soil physico-chemical properties under net
house conditions. Isolates Bacillus subtilis strain KU21, Pseudomonas aeruginosa strain SI12, Cedecea lapagei
strain KU14 produced most significant results under net house conditions and were further evaluated under field
conditions. Field studies revealed that conjoint application of Bacillus subtilis strain KU21 and Pseudomonas
aeruginosa strain SI12 increased plant physical, physiological parameters as well as soil physico-chemical
properties over uninoculated control. Direct and indirect plant growth promotion by Bacillus subtilis strain
KU21 and Pseudomonas aeruginosa strain SI12 was further confirmed by molecular and chromatographic
analysis. Attempts have been made to understand the genetic basis of mineral phosphate solubilization in
Bacillus subtilis strain KU21. Cloning and sequencing of gdh gene has paved the way for understanding
molecular mechanisms involved in nutrient mobilization of essential nutrient (phosphorus) and its subsequent
enhanced uptake by plants, as mediated by endophytes. Phytohormone production by Bacillus subtilis strain
KU21 was also evaluated by TLC and HPLC analysis. Indirect plant growth promotion via biocontrol activities
against tested fungal pathogens was best for Pseudomaonas aeruginosa SI12 hence characterized for extraction
and identification of pyocyanin using HPLC. Overall, present study conclude that, exploring large pool of
endophytic communities of medicinal plants appears to be a good strategy for selection of promising strains as
PGPR and the potential application of these endophytes in agricultural traits could results in ameliorate plant
production and health and in another way may lead to improve soil quality and fertility.
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