Abstract
The profound negative effect of inorganic chemical fertilizer application on rhizobacterial diversity has been well documented using 16S rRNA gene amplicon sequencing and predictive metagenomics. We aimed to measure the function and relative abundance of readily culturable putative plant growth-promoting rhizobacterial (PGPR) isolates from wheat root soil samples under contrasting inorganic fertilization regimes. We hypothesized that putative PGPR abundance will be reduced in fertilized relative to unfertilized samples. Triticum aestivum cv. Cadenza seeds were sown in a nutrient depleted agricultural soil in pots treated with and without Osmocote ® fertilizer containing nitrogen-phosphorous-potassium (NPK). Rhizosphere and rhizoplane samples were collected at flowering stage (10 weeks) and analyzed by culture-independent (CI) amplicon sequence variant (ASV) analysis of rhizobacterial DNA as well as culture-dependent (CD) techniques. Rhizosphere and rhizoplane derived microbiota culture collections were tested for plant growth-promoting traits using functional bioassays. In general, fertilizer addition decreased the proportion of nutrient-solubilizing bacteria (nitrate, phosphate, potassium, iron, and zinc) isolated from rhizocompartments in wheat whereas salt tolerant bacteria were not affected. A “PGPR” database was created from isolate 16S rRNA gene sequences against which total amplified 16S rRNA soil DNA was searched, identifying 1.52% of total community ASVs as culturable PGPR isolates. Bioassays identified a higher proportion of PGPR in non-fertilized samples [rhizosphere (49%) and rhizoplane (91%)] compared to fertilized samples [rhizosphere (21%) and rhizoplane (19%)] which constituted approximately 1.95 and 1.25% in non-fertilized and fertilized total community DNA, respectively. The analyses of 16S rRNA genes and deduced functional profiles provide an in-depth understanding of the responses of bacterial communities to fertilizer; our study suggests that rhizobacteria that potentially benefit plants by mobilizing insoluble nutrients in soil are reduced by chemical fertilizer addition. This knowledge will benefit the development of more targeted biofertilization strategies.
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Claims 6
Claim · model-written summary
Fertilizer decreased the proportion of nutrient-solubilizing bacteria isolated from wheat rhizocompartments.
- Taxon
- wheat
Triticum aestivume0 - Treatment
- fertilizer additione0
- Interactor
- nutrient-solubilizing bacteriae0symbiont
- Outcome
- proportion of nutrient-solubilizing bacteriae0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“fertilizer addition decreased the proportion of nutrient-solubilizing bacteria (nitrate, phosphate, potassium, iron, and zinc) isolated from rhizocompartments in wheat”
Claim · model-written summary
Salt tolerant bacteria were unaffected by fertilizer addition.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- Inorganic Chemical Fertilizer Applicationt0
- Interactor
- salt tolerant bacteriae0symbiont
- Outcome
- salt tolerant bacteriae0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“whereas salt tolerant bacteria were not affected”
t0“Inorganic Chemical Fertilizer Application to Wheat”
Claim · model-written summary
The PGPR database identified 1.52% of community ASVs as culturable PGPR isolates.
- Taxon
- WheatTriticum aestivumt0
- Interactor
- culturable PGPR isolatese0symbiont
- Outcome
- total community ASVse0
- Value
- 1.52%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“identifying 1.52% of total community ASVs as culturable PGPR isolates”
t0“Inorganic Chemical Fertilizer Application to Wheat”
Claim · model-written summary
Non-fertilized rhizosphere samples had 49% PGPR versus 21% in fertilized samples.
- Taxon
- WheatTriticum aestivumt0
- Organ / stage
- rhizospheree0
- Treatment
- fertilized samplese0
- Interactor
- PGPRe1symbiont
- Outcome
- proportion of PGPRe1
- Value
- 21%e0
- Qualifier
- 49%e0
- Comparator
- non-fertilized samplese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“non-fertilized samples [rhizosphere (49%) and rhizoplane (91%)] compared to fertilized samples [rhizosphere (21%) and rhizoplane (19%)]”
e1“Bioassays identified a higher proportion of PGPR”
t0“Inorganic Chemical Fertilizer Application to Wheat”
Claim · model-written summary
Non-fertilized rhizoplane samples had 91% PGPR versus 19% in fertilized samples.
- Taxon
- WheatTriticum aestivumt0
- Organ / stage
- rhizoplanee0
- Treatment
- fertilized samplese0
- Interactor
- PGPRe1symbiont
- Outcome
- proportion of PGPRe1
- Value
- 19%e0
- Qualifier
- 91%e0
- Comparator
- non-fertilized samplese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“non-fertilized samples [rhizosphere (49%) and rhizoplane (91%)] compared to fertilized samples [rhizosphere (21%) and rhizoplane (19%)]”
e1“Bioassays identified a higher proportion of PGPR”
t0“Inorganic Chemical Fertilizer Application to Wheat”
Claim · model-written summary
PGPR constituted about 1.95% of non-fertilized community DNA and 1.25% of fertilized community DNA.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- fertilizede0
- Interactor
- PGPRe1symbiont
- Outcome
- total community DNAe0
- Value
- 1.25%e0
- Qualifier
- 1.95e0
- Comparator
- non-fertilizede0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“approximately 1.95 and 1.25% in non-fertilized and fertilized total community DNA, respectively”
e1“Bioassays identified a higher proportion of PGPR”
t0“Inorganic Chemical Fertilizer Application to Wheat”
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