TABLE 5.
Influence of P. putida strains differing in pyoverdine production on population size of P. putida N1R Pvd− (pvd-inaZ) or P. putida N1R (pvd-inaZ) in the rhizosphere of cucumber grown in sterilized or nonsterilized soil
| Coinoculated straina | Rhizosphere population sizeb (log10 [CFU/root system] ± SEM)
|
|||||||
|---|---|---|---|---|---|---|---|---|
| Sterilized soil
|
Nonsterilized soil
|
|||||||
| N1R Pvd− (pvd-inaZ)
|
N1R (pvd-inaZ)
|
N1R Pvd− (pvd-inaZ)
|
N1R (pvd-inaZ)
|
|||||
| Day 1 | Day 6 | Day 1 | Day 6 | Day 1 | Day 6 | Day 1 | Day 6 | |
| None | 6.54 ± 0.17 | 7.50 ± 0.05 | 6.61 ± 0.15 | 7.43 ± 0.08 | 4.09 ± 0.24 | 4.23 ± 0.16 | 4.26 ± 0.13 | 4.39 ± 0.19 |
| WCS358 | 6.40 ± 0.10 | 7.37 ± 0.08 | 5.85 ± 0.27 | 7.06 ± 0.08 | 3.75 ± 0.25 | 4.35 ± 0.28 | 3.81 ± 0.29 | 3.98 ± 0.18 |
| WCS358 Pvd− | 5.99 ± 0.33 | 7.17 ± 0.04 | 6.30 ± 0.15 | 7.22 ± 0.09 | 4.05 ± 0.19 | 4.40 ± 0.17 | 3.40 ± 0.22 | 4.49 ± 0.09 |
Before planting in sterilized or nonsterilized soil, root systems were dipped in aqueous suspensions of N1R Pvd− (pvd-inaZ) or N1R (pvd-inaZ) alone or in combination with a coinoculated strain (WCS358 or WCS358 Pvd−). Immediately following inoculation, the population size of coinoculated strains on roots was approximately 104 CFU/root system. In sterilized soil, mean population sizes of WCS358 and WCS358 Pvd− on five replicate root systems were 6.0 to 6.5 log10 (CFU/root system) at day 1 and 6.8 to 7.5 log10 (CFU/root system) at day 6. In nonsterilized soil, mean population sizes of these strains were 3.0 to 4.3 log10 (CFU/root system) at day 1 and 3.6 to 4.7 log10 (CFU/root system) at day 6.
Immediately following inoculation, the population sizes of N1R (pvd-inaZ) and N1R Pvd− (pvd-inaZ) were approximately 104 CFU/root system each. Mean rhizosphere population sizes were estimated at 1 or 6 days after root systems were inoculated with bacterial strains.