Table I. Differences in virulence of GFP-tagged F. graminearum strains to wheat due to the application of FFAs and 2-DDG.
Wheat spikelets were inoculated with 400 conidia of F. graminearum wt-GFP-1 and Δfgl1-GFP-1. Four microliters of ethanol-dissolved FFAs and 2-DDG (concentration, 3.2 mm) and ethanol as a control was added at 3 dpi to each of the previously inoculated spikelets. FFAs were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2), and α-linolenic acid (18:3).
| Treatmenta | Percentage of Infectionb |
Percentage of Rachis Colonizationc | Rating of Rachis Colonization Severityd |
||
|---|---|---|---|---|---|
| Mean | se | Mean | se | ||
| Ethanol control | 0.0 | – | – | – | – |
| 16:0 control | 0.0 | – | – | – | – |
| 18:0 control | 0.0 | – | – | – | – |
| 18:1 control | 0.0 | – | – | – | – |
| 18:2 control | 0.0 | – | – | – | – |
| 18:3 control | 0.0 | – | – | – | – |
| 2-DDG control | 0.0 | – | – | – | – |
| wt-GFP-1 | 80.5 | 8.7e | 100 | 2.7 | 0.2e |
| wt-GFP-1 + ethanol | 88.2 | 5.4e | 100 | 2.9 | 0.1e |
| wt-GFP-1 + 16:0 | 84.4 | 7.6e | 100 | 2.5 | 0.3e |
| wt-GFP-1 + 18:0 | 86.5 | 4.6e | 100 | 2.8 | 0.1e |
| wt-GFP-1 + 18:1 | 84.9 | 4.8e | 100 | 2.8 | 0.1e |
| wt-GFP-1 + 18:2 | 82.8 | 4.9e | 100 | 2.9 | 0.1e |
| wt-GFP-1 + 18:3 | 81.5 | 4.9e | 100 | 2.9 | 0.1e |
| wt-GFP-1 + 2-DDG | 84.5 | 6.1e | 100 | 2.6 | 0.2e |
| Δfgl1-GFP-1 | 22.1 | 5.3f | 45.0 | 0.7 | 0.2f |
| Δfgl1-GFP-1 + ethanol | 20.5 | 4.2f | 39.1 | 0.5 | 0.2f |
| Δfgl1-GFP-1 + 16:0 | 18.7 | 2.7f | 25.0 | 0.3 | 0.1f |
| Δfgl1-GFP-1 + 18:0 | 31.2 | 5.2f | 60.0 | 1.1 | 0.3g |
| Δfgl1-GFP-1 + 18:1 | 51.2 | 6.3h | 73.7 | 1.6 | 0.3h |
| Δfgl1-GFP-1 + 18:2 | 51.8 | 5.9h | 90.0 | 2.0 | 0.2h |
| Δfgl1-GFP-1 + 18:3 | 49.6 | 6.8h | 85.0 | 1.9 | 0.2h |
| Δfgl1-GFP-1 + 2-DDG | 70.8 | 8.0h | 80.0 | 1.9 | 0.2h |
Repeat experiments gave similar results. bInfection referred to partially or completely bleached spikelets observed at 21 dpi. Spikelets with minor symptoms (tiny yellow or brown spots) were not counted. Results are averages of 10 (control and wt-GFP-1) and 20 (Δfgl1-GFP-1) wheat spikes (16–24 spikelets per spike). cPercentage of all inoculations with GFP-tagged F. graminearum mycelium detectable in rachis tissue located between two inoculated spikelets. dColonization severity by rating the green fluorescence of GFP-tagged F. graminearum mycelium in rachis tissue located between two inoculated spikelets at 21 dpi (Supplemental Fig. S3). Results are averages of 10 (wt-GFP-1) and 20 (Δfgl1-GFP-1) inoculated wheat spikes. eStatistically different from Δfgl1-GFP-1 strains with or without the addition of FFAs or 2-DDG, with no statistical differences among approaches (P < 0.05). fStatistically different from Δfgl1-GFP-1 strains with the addition of unsaturated FFAs and 2-DDG, with no statistical differences among approaches (P < 0.05). gRachis colonization severity was not statistically different from that of Δfgl1-GFP-1 strains with the addition of other FFAs or without the addition of FFAs (P < 0.05). hNo statistical differences among approaches (P < 0.05).