BcLTF1 is required for full virulence.

<p>(<b>A</b>) Overexpression of <i>bcltf1</i> affects the formation of infection structures. Onion epidermal strips were inoculated with conidial suspensions (on the left) or non-sporulating mycelia (on the right), and incubated for 24 h in DD. Conidia and hyphae on the surface were stained with lactophenol blue whereas invasively growing hyphae remain colorless. Scale bars, 50 µm. (<b>B</b>) Deletion of <i>bcltf1</i> impairs the capability to colonize primary leaves of <i>P. vulgaris</i>. Leaves of living plants were inoculated with conidial suspensions and incubated in LD. White scale bars, 1 cm; black scale bars, 2 mm. (<b>C</b>) Spreading lesions provoked by Δ<i>bcltf1</i> mutants are characterized by increased H<sub>2</sub>O<sub>2</sub> accumulation. Primary leaves were inoculated with conidial suspensions, detached 1 to 4 dpi, and incubated for 2 h in DAB solution. Plant tissues were decolorized prior to microscopy. (<b>D</b>) Addition of ascorbic acid restores virulence of Δ<i>bcltf1</i> mutants. Conidia were suspended in GB5 (gray) or in GB5 supplemented with 5 g/l ascorbic acid (black). Mean values and standard deviations of lesion diameters were calculated from eight lesions per strain and condition at 3 dpi. Asterisks indicate significant differences compared to WT:B05.10 in each condition (p<0.001). Pictures of lesions derived from ascorbic acid-supplemented conidial suspensions were taken 3 dpi.</p>