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 strainaRhizosphere population sizeb (log10 [CFU/root system] ± SEM)
Sterilized soilNonsterilized soil
N1R Pvd(pvd-inaZ)N1R (pvd-inaZ)N1R Pvd(pvd-inaZ)N1R (pvd-inaZ)
Day 1Day 6Day 1Day 6Day 1Day 6Day 1Day 6
None6.54 ± 0.177.50 ± 0.056.61 ± 0.157.43 ± 0.084.09 ± 0.244.23 ± 0.164.26 ± 0.134.39 ± 0.19
WCS3586.40 ± 0.107.37 ± 0.085.85 ± 0.277.06 ± 0.083.75 ± 0.254.35 ± 0.283.81 ± 0.293.98 ± 0.18
WCS358 Pvd 5.99 ± 0.337.17 ± 0.046.30 ± 0.157.22 ± 0.094.05 ± 0.194.40 ± 0.173.40 ± 0.224.49 ± 0.09
  • a 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.

  • b 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.