STUDIES ON Azospirillum ISOLATES OF ORNAMENTAL PLANTS AND THEIR EFFECT ON Gaillardia pulchella var picta Fouger
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Date
2001-08-08
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
Abstract
Investigations were carried out on the isolation, identification,
genetic diversity, scrcening of Azospirillum for beneficial traits and their
inoculation effect on the growth and flowering of Gaillardia. Attempts were
made to improve tlie nitrogen fixing efficiency of Azospirillum through
mutagensis.
From tlie present investigation, it can be concluded that
Azospihllum is a common inhabitant of roots of ornamental plants. Of the 88
isolations made, 55 per cent of isolate were Azospirillum lipofemm while
Azospirillum bmsilense represented 41.57 per cent. The nitrogen fixation by
Azospirillum isolates in the semi solid medium ranged Irom 1.40 (OAD-36
and OAD-72) to 20.54 (OAD-2) mg g-1 of malate. The ability to fix dinitrogen
was also confiiined by acetylene reduction assay. Although all the
Azospirillum isolates could produce variable quantity of lAA and GA, strain
OAD-57 produced the highest amount of plant growth promoting
substances. The genetic diversity of Azospirillum isolates was analyzed
tlirough iiitiinsic antibiotic resistance, protein and plasmid profile. The
isolates showed wide diversity with respect to intrinsic antibiotic resistance.
However using the protein finger printing two definite groups of Azospirillum
could discerned. All the isolates contained only one plasmid (22 kb).
Based on preliminary screening of all the isolates under pot culture,
seven efficient isolates were selected for further field study. From the field
experiment, it could be concluded that OAD-2 can play an impoiiant role in
tlie N-nutrition of Gaillardia pulchella. Further 25 AziĀ® and EDAR mutants
were obtained through NTG mutagenesis. These mutants had highei*
nitrogenase activity and in vitro N fixation (g-1 malate.) The AziR OAD-904,
and EDAR OAD-209 perfoimed better tlian their respective wild type isolates,
m pot cultures in augmenting plant growth and N-uptake of Gaillardia
puldiella.
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