Table 3.
Molecular approaches used to monitor plant growth‒promoting bacteria and root interaction.
| Strains | Experimental conditions | Method | Plant substrate | Results | Reference |
|---|---|---|---|---|---|
| Gluconacetobacter diazotrophicus | Field experiment on sugarcane | qPCR | Soil (pH 5.3, P 6.1, 6.8 mg/dm3, K 44 mg/dm3, organic matter 1.3%) | Quantification of bacterial cells in plant tissues using species-specific primers | Sorte et al., 2014 |
|
Azospirillum brasilense UAP-154 Azospirillum brasilense CFN-535 |
Pots in greenhouse on maize (18-h/6-h light/dark, 18–22°C, 10 days) | qPCR | Sieved non sterile soil from La Côte St André adjusted to 20% (w/w) water content | Quantification of bacterial cells in the rhizosphere using primers designed on strain-specific SCAR markers | Couillerot et al., 2010 |
| Azospirillum brasilense FP2 | Wheat plants germinated under sterile conditions, incubated in a greenhouse (14-h light/10-h dark, 23°C, humidity above 50%) | qPCR | Hoagland solution and quartz beads in glass tubes | Quantification of A. brasilense FP2 in the rhizosphere under sterile conditions | Stets et al., 2015 |
| Azospirillum brasilense FP2 alone or co-inoculated with Azospirillum brasilense NH, Herbaspirillum seropedicae Z67, Gluconacetobacter diazotrophicus DSM 5601, Azospirillum lipoferum DSM 1691 | Wheat plants germinated under nonsterile conditions, incubated in a greenhouse (14-h light/10-h dark, 23°C, humidity above 50%) | qPCR | Quartz beads in glass tubes | Quantification of A. brasilense FP2 in the rhizosphere even under nonsterile conditions and when coinoculated with other rhizobacteria using strain-specific primers | Stets et al., 2015 |
|
Burkholderia sp. J62 Pseudomonas thivervalensis Y-1-3-9 |
Pot with rape plants (30.4 ± 4.6°C/18.3 ± 3.2°C day/night, relative humidity 67.5 ± 12.9%) | PCR-DGGE | Contaminated soils (0.50 mg/kg of Cd and 100 mg/kg of CdSO4) | Inoculated bacteria were detected in the root interiors and rhizosphere soils | Chen et al., 2013 |
| Azospirillum brasilense Cd | Shade house with sorghum (temperature ~29°C, light intensity of ~1,000 μmol photons m2/s, 20 days; three crop cycles) | PCR-DGGE | Highly degraded alluvial desert soil | Persistence of the inoculant within the bacterial community of the rhizosphere of sorghum plants by purification and sequencing od DGGE bands | Lopez et al., 2013 |
| Dyadobacter sp. | Pot trial in a net house (sampling at 30, 45, 60, and 90 days) | PCR-DGGE - qPCR | Soil (pH 7.5, oxidazable organic carbon 0.3–0.5%; phosphorus pentoxide <22 kg/ha, ammonia 15 kg/ha, nitrate 4 kg/ha) | Quantification of diazotrophic abundance by qPCR and persistence of inoculant in the soil by detection of a specific DGGE band. | Kumar et al., 2018 |
| Streptomyces sp. AH-B | Containers with dry natural soil sprayed with quinclorac solution | NGS | - | Streptomyces sp. AH-B became the dominant species following inoculation in quinclorac-contaminated soil | Lang et al., 2018 |
| Bacillus amyloliquefaciens FZB42 | Field trial on lettuce rhizosphere | WGS - metagenomic study |
Soil (alluvial loam, total N 112 mg/100 g, P 32.3 mg/100 g, K 17.4 mg/100 g, Mg 9.1 mg/100 g, pH 6.5 | Presence of the strain in the rhizosphere over 5 weeks in field. Marginal changes in the bacterial community after inoculant application. | Kröber et al., 2014 |
SCAR, sequence characterized amplified region; qPCR, quantitative real-time PCR; DGGE, denaturing gradient gel electrophoresis; NGS, next-generation sequencing; WGS, whole-genome sequencing.