Pessina Stefano, Angeli Dario, Martens Stefan, Visser Richard G F, Bai Yuling, Salamini Francesco, Velasco Riccardo, Schouten Henk J, Malnoy Mickael
Research and Innovation Center, Fondazione Edmund Mach, San Michele all'Adige, Italy.
Wageningen UR Plant Breeding, Wageningen University and Research Centre, Wageningen, The Netherlands.
Plant Biotechnol J. 2016 Oct;14(10):2033-44. doi: 10.1111/pbi.12562. Epub 2016 May 11.
Varieties resistant to powdery mildew (PM; caused by Podosphaera leucotricha) are a major component of sustainable apple production. Resistance can be achieved by knocking-out susceptibility S-genes to be singled out among members of the MLO (Mildew Locus O) gene family. Candidates are MLO S-genes of phylogenetic clade V up-regulated upon PM inoculation, such as MdMLO11 and 19 (clade V) and MdMLO18 (clade VII). We report the knock-down through RNA interference of MdMLO11 and 19, as well as the complementation of resistance with MdMLO18 in the Arabidopsis thaliana triple mlo mutant Atmlo2/6/12. The knock-down of MdMLO19 reduced PM disease severity by 75%, whereas the knock-down of MdMLO11, alone or in combination with MdMLO19, did not result in any reduction or additional reduction of susceptibility compared with MdMLO19 alone. The test in A. thaliana excluded a role for MdMLO18 in PM susceptibility. Cell wall appositions (papillae) were present in both PM-resistant and PM-susceptible plants, but were larger in resistant lines. No obvious negative phenotype was observed in plants with mlo genes knocked down. Apparently, MdMLO19 plays the pivotal role in apple PM susceptibility and its knock-down induces a very significant level of resistance.
抗白粉病（由白叉丝单囊壳引起）的苹果品种是可持续苹果生产的主要组成部分。可以通过敲除在MLO（白粉病位点O）基因家族成员中筛选出的感病S基因来实现抗性。候选基因是在接种白粉病后上调的系统发育分支V的MLO S基因，如MdMLO11和19（分支V）以及MdMLO18（分支VII）。我们报道了通过RNA干扰敲低MdMLO11和19，以及在拟南芥三重mlo突变体Atmlo2/6/12中用MdMLO18互补抗性。敲低MdMLO19使白粉病病情严重程度降低了75%，而单独敲低MdMLO11或与MdMLO19联合敲低，与单独敲低MdMLO19相比，并未导致感病性有任何降低或额外降低。在拟南芥中的试验排除了MdMLO18在白粉病感病性中的作用。细胞壁沉积物（乳突）在抗白粉病和感白粉病的植物中均有存在，但在抗性品系中更大。在敲除mlo基因的植物中未观察到明显的负面表型。显然，MdMLO19在苹果白粉病感病性中起关键作用，其敲低可诱导非常显著水平的抗性。
