Exogenous application of L-homoserine induced <i>Oidium neolycopersici</i> resistance and necrosis in tomato.

<p>(<b>A</b>), Quantification of fungal growth, 8 days post inoculations of Moneymaker (MM) plants sprayed with different amino-acid solutions prior to pathogen inoculations. Spray application of L-homoserine reduces fungal growth significantly compared to spray application of H₂O or isoleucine, leucine, threonine or valine. Data indicate the mean of 3 or more biological replicates with error bars representing the standard error. Number of asterisks indicate degree of significance (***p<0.001). (<b>B–C</b>), Spray application of L-homoserine induces cell death in MM plants whereas the H₂O control does not.</p

Tomato <i>SlDMR1</i> is a S-gene for the tomato powdery mildew <i>Oidium neolycopersici</i>.

<p>(<b>A</b>), relative transcript abundance of <i>SlDMR1</i> in multiple independent cuttings of untransformed Moneymaker (MM) plants or T1 transformants harbouring an RNAi::<i>SlDMR1</i> construct (Line2, 3 and 5). (<b>B</b>), Quantification of fungal growth at 8 days post inoculation (dpi). <i>SlDMR1</i> silenced plants support significantly less fungal growth compared to untransformed plants. (<b>C</b>), Leaves of an untransformed MM and <i>SlDMR1</i> silenced plant at 8 dpi. Silencing of <i>SlDMR1</i> results in reduced leaf size and yellowish colour. For <b>A</b> and <b>B</b>. Data indicate the mean of 3 or more biological replicates with error bars representing the standard error. Number of asterisks indicate degree of significance (***p<0.001).</p

Impairment of <i>PMR4</i> in Arabidopsis results in resistance to tomato powdery mildew <i>Oidium neolycopersici</i>.

<p>(<b>A and B</b>), Col-0 and <i>pmr4</i> mutant plants photographed 14 days post inoculation with <i>Oidium neolycopersici</i>. Fungal sporulation is visible as whitish powder on multiple leaves of Col-0 but not on <i>pmr4</i> mutants, showing that Arabidopsis <i>PMR4</i> is a susceptibility (<i>S</i>) gene for <i>O. neolycopersici</i>. (<b>C</b>), Phylogenetic tree of Arabidopsis PMR4 family members plus tomato PMR4 family orthologs. The protein SlPMR4_h1 encoded by the tomato gene <i>Solyc07g053980</i> is considered to be the tomato ortholog of AtPMR4.</p

Arabidopsis <i>DMR1</i> is a S-gene for the tomato powdery mildew <i>Oidium neolycopersici</i>.

<p>(<b>A–F</b>), Photograph of L<i>er eds1-2</i> (A), <i>dmr1-3</i> (B), <i>dmr1-6</i> (C), <i>dmr1-1</i> (D), <i>dmr1-2</i> (E) and <i>dmr1-5</i> (F) at 14 days post inoculations (dpi) with <i>O. neolycopersici</i>. (<b>G</b>), Quantification of <i>O. neolycopersici</i> growth at 14 dpi by Disease Index (DI) score (see M&M). (<b>H</b>), Fresh weight of 5 weeks old L<i>er eds1-2</i> and <i>dmr1</i> mutant plants. Fresh weights are given as percentage of the parental line L<i>er eds1-2</i>. For <b>G</b> and <b>H</b>. Data indicate the mean of 3 or more biological replicates with error bars representing the standard error. Number of asterisks indicate degree of significance (***p<0.001).</p

Powdery mildew resistance by impairment of <i>PMR4</i> is conserved between Arabidopsis and tomato.

<p>(<b>A and B</b>), Leaf of T2 plant 4–5 (A) carrying a <i>RNAi::SlPMR4</i> silencing construct (+) and of T2 plant 4–4 (B) without silencing construct (−) at the age of 5 weeks and 8 days post <i>O. neolycopersici</i> inoculation. (<b>C</b>), Relative <i>SlPMR4</i> transcript levels in untransformed Moneymaker (MM) plants and progeny of 3 independent T1 plants transformed with a silencing construct specifically targeting <i>SlPMR4</i> (family 2, 3 and 4). T2 progenies harbouring a silencing construct (RNAi::<i>SlPMR4</i> (+)) showed significantly lower transcript levels compared to untransformed Moneymaker plants and progenies not harbouring a silencing construct (−) as indicated by asterisks. (<b>D</b>), Quantification of fungal growth of lines mentioned in (C). <i>SlPMR4</i> silenced plants show significantly less fungal growth compared to non-silenced plants as indicated by asterisks, demonstrating that <i>SlPMR4</i> is a functional ortholog of <i>PMR4</i>. (<b>E and F</b>), Relative plant height and stem diameter of 12 week old plants respectively. A slight reduction (although significant as indicated by asterisks) in plant height was observed for progenies carrying a <i>RNAi::SlPMR4</i> construct of families 2 and 3, but not 4. Stem diameters were somewhat lower among T1 progenies of all 3 families, but differences were not statistically significant. For <b>C</b>, <b>D</b>, <b>E</b> and <b>F</b>, data indicate the mean of 3 or more biological replicates with error bars representing the standard error. Number of asterisks indicate degree of significance (**p<0.01; ***p<0.001).</p