부산대학교 도서관

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 Md MLO11 and 19 (clade V) and Md MLO18 (clade VII). We report the knock-down through RNA interference of Md MLO11 and 19, as well as the complementation of resistance with Md MLO18 in the Arabidopsis thaliana triple mlo mutant Atmlo2/6/12. The knock-down of Md MLO19 reduced PM disease severity by 75%, whereas the knock-down of Md MLO11, alone or in combination with Md MLO19, did not result in any reduction or additional reduction of susceptibility compared with Md MLO19 alone. The test in A. thaliana excluded a role for Md MLO18 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, Md MLO19 plays the pivotal role in apple PM susceptibility and its knock-down induces a very significant level of resistance. [ABSTRACT FROM AUTHOR]