STUDIES ON Azospirillum ISOLATES OF ORNAMENTAL PLANTS AND THEIR EFFECT ON Gaillardia pulchella var picta Fouger
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Date
1999
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University of Agricultural Sciences, Dharwad
Abstract
Investigations were carried out on the isolation, identification, genetic diversity, screening of Azospirillum and their inoculation effect on the
growth and flowering of Gaillardia. Attempts were made to improve the nitrogen-fixing efficiency of Azospirillum through mutagenesis.
From the present investigation, it can be concluded that Azospirillum is common inhabitant of roots of ornamental plants. From the
88 isolations made, 55 percent of isolate were Azospirillum lipoferum while Azospirillum brasilense represented 41.57 percent. The nitrogen fixation by
Azospirillum isolates in the semi-solid medium ranged from 1.40 (OAD-36 and OAD-72) to 20.54 (OAD-2) mg gi of malate. Further, ability- to fix
dinitrogen was also confirmed by acetylene reduction assay. Although all the Azospirillum isolates could produce variable quantity of IAA and GA,
Strain OAD-57 produced the highest plant growth-promoting substances. Genetic diversity of Azospirillum isolates was analyzed through intrinsic
antibiotic resistance, protein and plasmid profile. The isolates showed wide diversity with respect to intrinsic antibiotic resistance. However, using the
protein finger printing the two definite groups of Azospirillum could discerned. All the isolates contained only one plasmid (22 kb).
Seven efficient isolates were selected for further field study, based on preliminary screening of all the isolates under pot culture. From
the field experiment, it can be concluded that OAD-2 can play an important role in the N-nutrition of Gaillardia pulchella. Further 25 AziR and EDAR
mutants were obtained through NTG mutagenesis. TShese mutants had higher nitrogenase activity and in vitro N fixed g-1 malate. The AziR
OAD-904 and EDAR OAD-209 performed better than their respective wild type, in pot cultures in augmenting plant growth and N-uptake of
Gaillardia pulchella.
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No . of references 264