Abstract
AIMS: Plant growth promoting rhizobacteria (PGPR) are commonly used as inoculants for improving the growth and yield of agricultural crops, however screening for the selection of effective PGPR strains is very critical. This study focuses on the screening of effective PGPR strains on the basis of their potential for in vitro auxin production and plant growth promoting activity under gnotobiotic conditions. METHODS AND RESULTS: A large number of bacteria were isolated from the rhizosphere soil of wheat plants grown at different sites. Thirty isolates showing prolific growth on agar medium were selected and evaluated for their potential to produce auxins in vitro. Colorimetric analysis showed variable amount of auxins (ranging from 1.1 to 12.1 mg l-1) produced by the rhizobacteria in vitro and amendment of the culture media with l-tryptophan (l-TRP), further stimulated auxin biosynthesis (ranging from 1.8 to 24.8 mg l-1). HPLC analysis confirmed the presence of indole acetic acid (IAA) and indole acetamide (IAM) as the major auxins in the culture filtrates of these rhizobacteria. A series of laboratory experiments conducted on two cv. of wheat under gnotobiotic (axenic) conditions demonstrated increases in root elongation (up to 17.3%), root dry weight (up to 13.5%), shoot elongation (up to 37.7%) and shoot dry weight (up to 36.3%) of inoculated wheat seedlings. Linear positive correlation (r = 0.99) between in vitro auxin production and increase in growth parameters of inoculated seeds was found. Based upon auxin biosynthesis and growth-promoting activity, four isolates were selected and designated as plant growth-promoting rhizobacteria (PGPR). Auxin biosynthesis in sterilized vs nonsterilized soil inoculated with selected PGPR was also monitored that revealed superiority of the selected PGPR over indigenous microflora. Peat-based seed inoculation with selected PGPR isolates exhibited stimulatory effects on grain yields of tested wheat cv. in pot (up to 14.7% increase over control) and field experiments (up to 27.5% increase over control); however, the response varied with cv. and PGPR strains. CONCLUSIONS: It was concluded that the strain, which produced the highest amount of auxins in nonsterilized soil, also caused maximum increase in growth and yield of both the wheat cv. SIGNIFICANCE AND IMPACT OF STUDY: This study suggested that potential for auxin biosynthesis by rhizobacteria could be used as a tool for the screening of effective PGPR strains.
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Claims 12
Claim · model-written summary
Rhizobacteria produced variable amounts of auxins in vitro.
- Taxon
- wheat
Triticum aestivumt0 - Interactor
- rhizobacteriaHyphomicrobialese0
- Outcome
- auxinse0
- Direction
- variablee0
- Value
- 1.1 to 12.1 mg l-1e0
Not reportedTreatmentComparatorSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“variable amount of auxins (ranging from 1.1 to 12.1 mg l-1) produced by the rhizobacteria in vitro”
Claim · model-written summary
Adding l-tryptophan stimulated bacterial auxin biosynthesis.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- amendment of the culture media with l-tryptophane0
- Outcome
- auxin biosynthesise0
- Direction
- stimulatede0
- Value
- 1.8 to 24.8 mg l-1e0
Not reportedInteractorComparatorSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“amendment of the culture media with l-tryptophan (l-TRP), further stimulated auxin biosynthesis (ranging from 1.8 to 24.8 mg l-1)”
Claim · model-written summary
IAA and IAM were major auxins in rhizobacterial culture filtrates.
- Taxon
- wheatTriticum aestivumt0
- Interactor
- rhizobacteriaHyphomicrobialese0
- Outcome
- indole acetic acid (IAA) and indole acetamide (IAM)e0
Not reportedTreatmentComparatorSettingDirectionValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“presence of indole acetic acid (IAA) and indole acetamide (IAM) as the major auxins in the culture filtrates of these rhizobacteria”
Claim · model-written summary
Inoculation increased wheat seedling root elongation by up to 17.3%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- inoculatede0
- Outcome
- root elongatione0
- Direction
- increasese0
- Value
- 17.3%e0
Not reportedInteractorComparatorSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“increases in root elongation (up to 17.3%), root dry weight (up to 13.5%), shoot elongation (up to 37.7%) and shoot dry weight (up to 36.3%) of inoculated wheat seedlings”
Claim · model-written summary
Inoculation increased wheat seedling root dry weight by up to 13.5%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- inoculatede0
- Outcome
- root dry weighte0
- Direction
- increasese0
- Value
- 13.5%e0
Not reportedInteractorComparatorSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“increases in root elongation (up to 17.3%), root dry weight (up to 13.5%), shoot elongation (up to 37.7%) and shoot dry weight (up to 36.3%) of inoculated wheat seedlings”
Claim · model-written summary
Inoculation increased wheat seedling shoot elongation by up to 37.7%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- inoculatede0
- Outcome
- shoot elongatione0
- Direction
- increasese0
- Value
- 37.7%e0
Not reportedInteractorComparatorSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“increases in root elongation (up to 17.3%), root dry weight (up to 13.5%), shoot elongation (up to 37.7%) and shoot dry weight (up to 36.3%) of inoculated wheat seedlings”
Claim · model-written summary
Inoculation increased wheat seedling shoot dry weight by up to 36.3%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- inoculatede0
- Outcome
- shoot dry weighte0
- Direction
- increasese0
- Value
- 36.3%e0
Not reportedInteractorComparatorSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“increases in root elongation (up to 17.3%), root dry weight (up to 13.5%), shoot elongation (up to 37.7%) and shoot dry weight (up to 36.3%) of inoculated wheat seedlings”
Claim · model-written summary
In vitro auxin production correlated positively with growth increases of inoculated wheat.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- in vitro auxin productione0
- Outcome
- growth parameterse0
- Direction
- increasee0
- Value
- r = 0.99e0
Not reportedInteractorComparatorSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“Linear positive correlation (r = 0.99) between in vitro auxin production and increase in growth parameters of inoculated seeds”
Claim · model-written summary
Selected PGPR produced more auxin in sterilized than nonsterilized soil.
- Taxon
- wheatTriticum aestivumt0
- Interactor
- PGPRe0
- Outcome
- Auxin biosynthesise0
- Direction
- superioritye0
- Comparator
- indigenous microflorae0
Not reportedTreatmentSettingValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“Auxin biosynthesis in sterilized vs nonsterilized soil inoculated with selected PGPR was also monitored that revealed superiority of the selected PGPR over indigenous microflora”
Claim · model-written summary
Selected PGPR seed inoculation raised wheat grain yield by up to 14.7% in pot experiments.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Peat-based seed inoculation with selected PGPR isolatese0
- Interactor
- PGPRe0
- Outcome
- grain yieldse0
- Direction
- increasee0
- Value
- 14.7%e0
- Comparator
- controle0
- Setting
- pote0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“Peat-based seed inoculation with selected PGPR isolates exhibited stimulatory effects on grain yields of tested wheat cv. in pot (up to 14.7% increase over control) and field experiments (up to 27.5% increase over control)”
Claim · model-written summary
Selected PGPR seed inoculation raised wheat grain yield by up to 27.5% in field experiments.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Peat-based seed inoculation with selected PGPR isolatese0
- Interactor
- PGPRe0
- Outcome
- grain yieldse0
- Direction
- increasee0
- Value
- 27.5%e0
- Comparator
- controle0
- Setting
- fielde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“Peat-based seed inoculation with selected PGPR isolates exhibited stimulatory effects on grain yields of tested wheat cv. in pot (up to 14.7% increase over control) and field experiments (up to 27.5% increase over control)”
Claim · model-written summary
The strain with highest auxin production in nonsterilized soil produced the maximum growth and yield increase in wheat.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- highest amount of auxins in nonsterilized soile0
- Outcome
- growth and yielde0
- Direction
- maximum increasee0
Not reportedInteractorComparatorSettingValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“the strain, which produced the highest amount of auxins in nonsterilized soil, also caused maximum increase in growth and yield of both the wheat cv.”
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Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.