Abstract
The impact of inoculated plant growth-promoting rhizobacteria (PGPR) on its host physiology and nutrition depends on inoculum level. Whether the impact of the inoculated PGPR on the indigenous rhizosphere microbiota also varies with the PGPR inoculum level is unclear. Here, we tested this issue using the PGPR Azospirillum lipoferum CRT1—maize model system, where the initial seed inoculation is known to enhance maize growth and germination, and impacts the maize rhizomicrobiota, including microbial functional groups modulating plant growth. A. lipoferum CRT1 was added to the seeds at standard (105–6 cells.seed−1) or reduced (104–5 cells.seed−1) inoculation levels, in three fields. The effect of the two PGPR formulations was assessed on maize growth and on the nifH (nitrogen fixation), acdS (ACC deaminase activity) and phlD (2,4-diacetylphloroglucinol production) microbial functional groups. The size of the three functional groups was monitored by qPCR at the six-leaf stage and the flowering stage, and the diversity of the nifH and acdS functional groups (as well as the bacterial community) were estimated by MiSeq metabarcoding at the six-leaf stage. The results showed that the benefits of the reduced inoculant formulation were significant in two out of three fields, but different (often lower) than those of the standard formulation. The effects of formulations on the size of the three functional groups differed, and depended on field site and functional group. The reduced formulation had an impact on the diversity of nifH and acdS groups at one site, whereas the standard formulation had an impact at the two other sites. Inoculation significantly impacted the total bacterial community in the three fields, but only with the reduced formulation. In conclusion, the reduced inoculant formulation impacted the indigenous rhizosphere microbiota differently, but not less efficiently, than the standard formulation.
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Claims 6
Claim · model-written summary
The benefits of the reduced inoculant formulation were significant in two out of three fields but lower than those of the standard formulation.
- Taxon
- Field Maizet0
- Treatment
- reduced inoculant formulatione0
- Interactor
- Azospirillum lipoferum CRT1Azospirillum lipoferumt0symbiont
- Outcome
- benefitse0
- Comparator
- standard formulatione0
- Setting
- two out of three fieldse0
Not reportedDirection
Verbatim
t0“Effect of Inoculation Level on the Impact of the PGPR Azospirillum lipoferum CRT1 on Selected Microbial Functional Groups in the Rhizosphere of Field Maize”
e0“The results showed that the benefits of the reduced inoculant formulation were significant in two out of three fields, but different (often lower) than those of the standard formulation”
Claim · model-written summary
The effects of the two formulations on the size of the three microbial functional groups differed and depended on field site and functional group.
- Taxon
- Field Maizet0
- Treatment
- formulationse1
- Outcome
- size of the three functional groupse1
- Qualifier
- depended on field site and functional groupe1
Not reportedComparatorDirection
Verbatim
t0“Effect of Inoculation Level on the Impact of the PGPR Azospirillum lipoferum CRT1 on Selected Microbial Functional Groups in the Rhizosphere of Field Maize”
e1“The effects of formulations on the size of the three functional groups differed, and depended on field site and functional group”
Claim · model-written summary
The reduced formulation had an impact on the diversity of nifH and acdS groups at one site.
- Taxon
- Field Maizet0
- Treatment
- reduced formulatione2
- Outcome
- diversity of nifH and acdS groupse2
- Qualifier
- at one sitee2
Not reportedComparatorDirection
Verbatim
t0“Effect of Inoculation Level on the Impact of the PGPR Azospirillum lipoferum CRT1 on Selected Microbial Functional Groups in the Rhizosphere of Field Maize”
e2“The reduced formulation had an impact on the diversity of nifH and acdS groups at one site, whereas the standard formulation had an impact at the two other sites”
Claim · model-written summary
The standard formulation had an impact on the diversity of nifH and acdS groups at the two other sites.
- Taxon
- Field Maizet0
- Treatment
- standard formulatione2
- Outcome
- diversity of nifH and acdS groupse2
- Qualifier
- at the two other sitese2
Not reportedComparatorDirection
Verbatim
t0“Effect of Inoculation Level on the Impact of the PGPR Azospirillum lipoferum CRT1 on Selected Microbial Functional Groups in the Rhizosphere of Field Maize”
e2“The reduced formulation had an impact on the diversity of nifH and acdS groups at one site, whereas the standard formulation had an impact at the two other sites”
Claim · model-written summary
Inoculation significantly impacted the total bacterial community in the three fields, but only with the reduced formulation.
- Taxon
- Field Maizet0
- Treatment
- reduced formulatione3
- Outcome
- total bacterial communitye3
- Setting
- in the three fieldse3
Not reportedComparatorDirection
Verbatim
t0“Effect of Inoculation Level on the Impact of the PGPR Azospirillum lipoferum CRT1 on Selected Microbial Functional Groups in the Rhizosphere of Field Maize”
e3“Inoculation significantly impacted the total bacterial community in the three fields, but only with the reduced formulation”
Claim · model-written summary
The reduced inoculant formulation impacted the indigenous rhizosphere microbiota differently from, but not less efficiently than, the standard formulation.
- Taxon
- Field Maizet0
- Treatment
- reduced inoculant formulatione4
- Outcome
- indigenous rhizosphere microbiotae4
- Qualifier
- differently, but not less efficientlye4
- Comparator
- standard formulatione4
Not reportedDirection
Verbatim
t0“Effect of Inoculation Level on the Impact of the PGPR Azospirillum lipoferum CRT1 on Selected Microbial Functional Groups in the Rhizosphere of Field Maize”
e4“In conclusion, the reduced inoculant formulation impacted the indigenous rhizosphere microbiota differently, but not less efficiently, than the standard formulation”
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