Browsing by Author "MINAKSHI"
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ThesisItem Open Access ISOLATION AND CHARACTERIZATION OF CULTURABLE BACTERIAL ENDOPHYTES FROM ROOT TISSUES OF Rosemarinus officinalis AND DETERMINATION OF THEIR BIOACTIVITIES(UHF,NAUNI, 2019-11) MINAKSHI; CHAUHAN, ANJALIABSTRACT 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.ThesisItem Open Access STUDIES ON DIVERSE PLANT GROWTH PROMOTING RHIZOBACTERIA ASSOCIATED WITH RHIZOSPHERE OF Aconitum heterophyllum(2015) MINAKSHI; SRIKOT, C.K.Abstract It has been long recognized that many naturally occurring rhizospheric bacteria are plant growth promoting and may offer a viable substitute for chemicals. One of the important trait of PGPR is to convert insoluble forms of phosphorus to an accessible form for increasing plant growth. Little is known about the composition of phosphate solubilizing bacterial diversity associated with rhizosphere of medicinal plant. Therefore, the present study was aimed to explore the diversity of P-solubilizing bacterial communities colonizing the rhizosphere soil and endosphere of medicinal plant Aconitum heterophyllum grown in natural conditions of trans Himalayan region of Himachal Pradesh. A total of one hundred and seventy one rhizospheric and endorhizospheric bacteria were isolated from soil and root samples of Aconitum heterophyllum collected from two different sites of Kangra and Lahaul valley and were screened for phosphate solubilization, siderophore production and nitrogen fixation. A total of one hundred and ten P-solubilizing bacterial isolates were selected for quantitative estimation of Psolubilzation, and twenty highest P-solubilizing bacterial isolates were selected and further screened for multifarious plant growth promoting traits. Out of twenty P-solubilizing bacterial isolates ten isolates were selected on the basis of high PGP traits for growth promotion of tomato seedlings under net house conditions for sixty days. Treatment with isolate Ka(1)5r showed maximum per cent increase in various growth parameters of tomato seedlings and therefore, was found to be most efficient plant growth promoting rhizobacteria which was further selected for optimization of P-solubilization and IAA production. Optimized cultural conditions resulted in maximum P-solubilization (197 μg/ml) after 96 h of incubation at 35°C in PVK broth (having concentration of TCP 1%) of pH 6.0 with 1% inoculum size of culture. In case of optimized cultural conditions for IAA production, the maximum IAA production (42 μg/ml) was observed after 96h of incubation at 35°C in LB broth (with 1.0% of tryptophan concentration) of pH 8.0 ammended with an inoculum size of 2%. The most efficient bacterial isolate Ka(1)5r was identified as Bacillus subtilis by 16S rRNA sequencing. Thus, the ability of performing multifarious plant growth promoting activities in tandem suggest PSB isolates for plant growth promotion and has significance to develop a cost-effective ecofriendly multifunctional biofertilizer.