Studies on endorhizosphere bacteria of Nothapodytes nimmoniana Grahm and their influence on plant growth and camptothecin content
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Date
2009
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UAS Dharwad
Abstract
Microbiological explorations were made to isolate endorhizosphere bacteria from the
roots of Nothapodytes nimmoniana a medicinal herb distributed in Central Western Ghats of
India. A total of 92 isolates were obtained on six culture media from 23 root samples. All
isolates were characterized based on their biochemical properties and tentatively 70 isolates
could be identified (17 Azotobacter , 18 Pseudomonas, 10 Azomonas, 13 Bacillus , 5
Beijerinckia, 4 Acetobacter and 3 Acidomonas). The functional and molecular diversity was
studied. Sixteen isolates produced about moderate to high quantities of IAA.. Two isolates
produced significantly higher quantity of GA. Twelve isolates with low levels of IAA
production however produced moderate to high levels of GA. Twenty isolates showed ability
to solubilize TCP. Twenty two isolates fixed atmospheric nitrogen among which 20 excreted
ammonia into medium. Sixteen isolates showed antagonistic activity against one or more of
the five plant pathogens tested. The isolates were also examined for MEP pathway and only
26 isolates contained dxs and dxr genes of this pathway. In 18 of these isolates the pathway
was operational. Two isolates also produced tryptamine an important intermediate of
camptothecin biosynthesis. One isolate (SRS-15) produced CPT like compound in Czepak
Dox (CD) medium amended with the two intermediates of CPT biosynthesis. An attempt was
made to bioprospect CPT production from SRS-15 using CD medium amended with 300
μg ml-1 each with IPP, DMAPP. Growth and CPT content of N. nimmoniana in response to
inoculation with selected endorhizosphere bacteria and proven biofertilizers at nursery stage
was studied involving three independent experiments. Biomass and CPT content of plants
increased due to inoculation with either endorhizosphere bacteria (SRS-6) or biofertilizers
(Azotobacter and P. striata). It was found that inoculation of SRS-35 in sterile, SRS-6 and
Azotobacter + P. striata in un-sterile growth medium enhanced growth and CPT content of
N. nimmoniana seedlings.