Abstract
Nitrogen (N) is one of the limiting factors for plant growth, and it is mainly supplied exogenously by fertilizer application. It is well documented that diazotrophic rhizobacteria improve plant growth by fixing atmospheric N in the soil. The present study investigates the nitrogen-fixing potential of two Azospirillum spp. strains using the 15 N isotope-dilution method. The two diazotrophic strains (TN03 and TN09) native to the rhizosphere of potato belong to the genus Azospirillum (16S rRNA gene accession numbers LN833443 and LN833448 , respectively). Both strains were able to grow on an N-free medium with N-fixation potential (138–143 nmol mg −1 protein h −1 ) and contained the nifH gene. Strain TN03 showed highest indole acetic acid (IAA) production (30.43 μg/mL), while TN09 showed highest phosphate solubilization activity (249.38 μg/mL) while both diazotrophs showed the production of organic acids. A 15 N dilution experiment was conducted with different fertilizer inputs to evaluate the N-fixing potential of both diazotrophs in pots. The results showed that plant growth parameters and N contents increased significantly by the inoculations. Moreover, reduced 15 N enrichment was found compared to uninoculated controls that received similar N fertilizer levels. This validates the occurrence of N-fixation through isotopic dilution. Strain TN09 showed higher N-fixing potential than TN03 and the uninoculated controls. Inoculation with either strain also showed a remarkable increase in plant growth under field conditions. Thus, there were remarkable increases in N use efficiency, N uptake and N utilization levels. Confocal laser scanning and transmission electron microscopy showed that TN03 is an ectophyte, i.e., present outside root cells or within the grooves of root hairs, while TN09 is an endophyte, i.e., present within root cells, forming a strong association withroot it. This study confirms that diazotrophic Azospirillum spp. added to potato systems can improve plant growth and N use efficiency, opening avenues for improvement of potato crop growth with reduced input of N fertilizer.
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Claims 11
Claim · model-written summary
Strains TN03 and TN09 have N-fixation potential of 138–143 nmol mg −1 protein h −1 in N-free medium.
- Taxon
- potato
Solanum tuberosumt0 - Material
- TN03 and TN09e0
- Interactor
- Azospirillum
Azospirillume0symbiont - Outcome
- N-fixation potentiale1
- Value
- 138–143 nmol mg −1 protein h −1e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e0“The two diazotrophic strains (TN03 and TN09) native to the rhizosphere of potato belong to the genus Azospirillum”
e1“Both strains were able to grow on an N-free medium with N-fixation potential (138–143 nmol mg −1 protein h −1 ) and contained the nifH gene”
Claim · model-written summary
Strain TN03 showed the highest indole acetic acid production, 30.43 μg/mL.
- Taxon
- potatoSolanum tuberosumt0
- Material
- TN03e2
- Interactor
- AzospirillumAzospirillume0symbiont
- Outcome
- indole acetic acid (IAA) productione2
- Value
- 30.43 μg/mLe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e0“The two diazotrophic strains (TN03 and TN09) native to the rhizosphere of potato belong to the genus Azospirillum”
e2“Strain TN03 showed highest indole acetic acid (IAA) production (30.43 μg/mL)”
Claim · model-written summary
Strain TN09 showed the highest phosphate solubilization activity, 249.38 μg/mL.
- Taxon
- potatoSolanum tuberosumt0
- Material
- TN09e3
- Interactor
- AzospirillumAzospirillume0symbiont
- Outcome
- phosphate solubilization activitye3
- Value
- 249.38 μg/mLe3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e0“The two diazotrophic strains (TN03 and TN09) native to the rhizosphere of potato belong to the genus Azospirillum”
e3“TN09 showed highest phosphate solubilization activity (249.38 μg/mL)”
Claim · model-written summary
Both diazotrophs produced organic acids.
- Taxon
- potatoSolanum tuberosumt0
- Material
- both diazotrophse4
- Interactor
- AzospirillumAzospirillume0symbiont
- Outcome
- the production of organic acidse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e0“The two diazotrophic strains (TN03 and TN09) native to the rhizosphere of potato belong to the genus Azospirillum”
e4“both diazotrophs showed the production of organic acids”
Claim · model-written summary
Azospirillum inoculation significantly increased potato growth parameters and N contents.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- inoculationse5
- Interactor
- AzospirillumAzospirillume0symbiont
- Outcome
- plant growth parameters and N contentse5
- Direction
- increasede5
- Comparator
- uninoculated controlse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e0“The two diazotrophic strains (TN03 and TN09) native to the rhizosphere of potato belong to the genus Azospirillum”
e5“The results showed that plant growth parameters and N contents increased significantly by the inoculations”
e6“reduced 15 N enrichment was found compared to uninoculated controls that received similar N fertilizer levels”
Claim · model-written summary
Inoculated potato showed reduced 15N enrichment compared with uninoculated controls, validating N fixation by isotope dilution.
- Taxon
- potatoSolanum tuberosumt0
- Outcome
- 15 N enrichmente6
- Direction
- reducede6
- Comparator
- uninoculated controlse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e6“reduced 15 N enrichment was found compared to uninoculated controls that received similar N fertilizer levels”
Claim · model-written summary
Strain TN09 had higher N-fixing potential than TN03 and the uninoculated controls.
- Taxon
- potatoSolanum tuberosumt0
- Material
- TN09e7
- Outcome
- N-fixing potentiale7
- Direction
- highere7
- Comparator
- TN03e7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e7“Strain TN09 showed higher N-fixing potential than TN03 and the uninoculated controls”
Claim · model-written summary
Inoculation with either strain remarkably increased potato growth under field conditions.
- Taxon
- potatoSolanum tuberosumt0
- Treatment
- Inoculation with either straine1
- Outcome
- plant growthe1
- Direction
- increasee1
- Setting
- field conditionse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e1“Inoculation with either strain also showed a remarkable increase in plant growth under field conditions”
Claim · model-written summary
Azospirillum strains remarkably increased N use efficiency, N uptake and N utilization in potato.
- Taxon
- potatoSolanum tuberosumt0
- Outcome
- N use efficiency, N uptake and N utilizatione1
- Direction
- increasese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e1“there were remarkable increases in N use efficiency, N uptake and N utilization levels”
Claim · model-written summary
Strain TN03 is an ectophyte, present outside root cells or within the grooves of root hairs.
- Taxon
- potatoSolanum tuberosumt0
- Material
- TN03e1
- Organ / stage
- root hairse1
- Outcome
- presente1
- Qualifier
- ectophytee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e1“TN03 is an ectophyte, i.e., present outside root cells or within the grooves of root hairs”
Claim · model-written summary
Strain TN09 is an endophyte, present within root cells.
- Taxon
- potatoSolanum tuberosumt0
- Material
- TN09e1
- Organ / stage
- root cellse1
- Outcome
- presente1
- Qualifier
- endophytee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nitrogen Use Efficiency of Potato”
e1“TN09 is an endophyte, i.e., present within root cells”
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