Table 4.
Root colonization ability and V. dahliae biocontrol performance of P. fluorescens PICF7 and their mutant derivatives in Col-0 A. thaliana plants.
| Experiment1 | Treatment2 | Disease assessment3 |
Bacterial population (log10 cfu g-1 of fresh root)4 | ||
|---|---|---|---|---|---|
| SAUDPC | DII | Final DI (%) | |||
| 1 | Control | 0.37ab | 0.61 | 73.08 | nd |
| P. fluorescens | |||||
| PICF7 | 0.25b | 0.41 | 60.00 | 5.7 ± 0.2 | |
| ME419 (gltA) | 0.33ab | 0.60 | 79.17 | 5.5 ± 0.3 | |
| ME424 (fliI) | 0.35ab | 0.63 | 79.17 | 5.6 ± 0.1 | |
| ME589 (pvdI) | 0.35ab | 0.50 | 65.38 | 5.7 ± 0.3 | |
| ME1508 (Cys Aux) | 0.45a | 0.65 | 84.00 | 5.3 ± 0.2 | |
| 2 | Control | 0.18ab | 0.27 | 58.82 | nd |
| P. fluorescens | |||||
| PICF7 | 0.15b | 0.27 | 72.22 | 7.2 ± 0.4 | |
| ME419 (gltA) | 0.36a | 0.55 | 84.00 | 6.6 ± 0.3 | |
| ME424 (fliI) | 0.25ab | 0.44 | 66.67 | 7.2 ± 0.2 | |
| ME589 (pvdI) | 0.28ab | 0.44 | 68.00 | 7.0 ± 0.4 | |
| ME1508 (Cys Aux) | 0.33ab | 0.50 | 65.22 | 6.4 ± 0.2 | |
| 3 | Control | 0.13a | 0.22 | 47.37 | nd |
| P. fluorescens | |||||
| PICF7 | 0.12a | 0.19 | 23.81 | 7.5 ± 0.4 | |
| ME419 (gltA) | 0.11a | 0.20 | 36.36 | 6.5 ± 0.2∗ | |
| ME424 (fliI) | 0.22a | 0.31 | 40.00 | 6.4 ± 0.1∗ | |
| ME589 (pvdI) | 0.22a | 0.43 | 56.00 | 6.8 ± 0.4∗ | |
| ME1508 (Cys Aux) | 0.14a | 0.24 | 36.00 | 6.0 ± 0.4∗ | |
1Three independent experiments were performed. Experiments 1 and 2 spanned 36 days and Experiment 2 spanned 39 days.
2 The root system of 2-week-old Arabidopsis seedlings were transplanted into PICF7 or TcR-mutant derivatives bacterized soil (1.0–2.8⋅108 cfu/g soil) previously autoclaved for colonization experiment. For biocontrol assays, 1 week after bacterization plants were uprooted and their roots dipped in a V. dahliae isolate V937I (D pathotype) conidia suspension (3.9⋅105–1.7⋅106 conidia/ml) or distilled sterile water (control treatment) for 15 min. Plants were grown in a growth chamber under controlled conditions. See Section “Materials and Methods” for details.
3Standardized area under the disease progress curve of DII plotted over time. Final DI (percentage of affected plants at the end of the experiment). Means in a column followed by different letters are significantly different in accordance to Fisher’s protected LSD test (P < 0.05).
4Pseudomonas cell counts were conducted on modified King’s medium B agar. Data are means of three root samples (1 g each). Means followed by an asterisk are significantly different in accordance to Two-sided Dunnett’s Multiple Comparisons with a Control (PICF7) at α = 0.05. nd, not applicable.