Knockdown of MLO genes reduces susceptibility to powdery mildew in grapevine

Abstract

Erysiphe necator is the causal agent of powdery mildew (PM), one of the most destructive diseases of grapevine. PM is controlled by sulfur-based and synthetic fungicides, which every year are dispersed into the environment. This is why PM-resistant varieties should become a priority for sustainable grapevine and wine production. PM resistance can be achieved in other crops by knocking out susceptibility S-genes, such as those residing at genetic loci known as MLO (Mildew Locus O). All MLO S-genes of dicots belong to the phylogenetic clade V, including grapevine genes VvMLO7, 11 and 13, which are upregulated during PM infection, and VvMLO6, which is not upregulated. Before adopting a gene-editing approach to knockout candidate S-genes, the evidence that loss of function of MLO genes can reduce PM susceptibility is necessary. This paper reports the knockdown through RNA interference of VvMLO6, 7, 11 and 13. The knockdown of VvMLO6, 11 and 13 did not decrease PM severity, whereas the knockdown of VvMLO7 in combination with VvMLO6 and VvMLO11 reduced PM severity up to 77%. The knockdown of VvMLO7 and VvMLO6 seemed to be important for PM resistance, whereas a role for VvMLO11 does not seem likely. Cell wall appositions (papillae) were present in both resistant and susceptible lines in response to PM attack. Thirteen genes involved in defense were less upregulated in infected mlo plants, highlighting the early mlo-dependent disruption of PM invasion.

DNA-Free Genetically Edited Grapevine and Apple Protoplast Using CRISPR/Cas9 Ribonucleoproteins

“…Here, we demonstrate adoption of next-generation CRISPR/Cas9 RNPs technology for these fruit species to establish an efficient DNA-free method for the site-directed mutagenesis system. In the grapevine, PM (Gadoury et al, 2012; Pessina et al, 2016) is caused by the destructive fungal pathogen Erysiphe necator , an obligate biotroph infecting all green tissues and berries, resulting in drastic losses in yield and berry quality. Currently PM can be effectively controlled by frequent applications of fungicides in the field.…”

A critical review of plant protection tools for reducing pesticide use on grapevine and new perspectives for the implementation of IPM in viticulture

“…The high level of synteny between the wild North American species Muscadinia rotundifolia and the European cultivated grapevine at the MrRUN1/MrRPV1 locus also opens up the possibility of obtaining resistant phenotypes from elite varieties using targeted genome engineering. Alternative approaches to R-genes may be based on susceptibility genes (Sgenes), in which loss of function results in recessively inherited resistance (Pessina et al, 2016). In any event, with the increase in the acreage of partially resistant varieties grown, the evolution of pathogen populations responding to new host plant selective pressure will require further monitoring (Delmotte et al, 2014).…”

Identification and Expression Analysis of Fragaria Vesca MLO Genes Involved in Interaction with Powdery Mildew (Podosphaera Aphanis)

“…In another study, the knock-down of grapevine MLO genes (VvMLO7 in combination with VvMLO6 and VvMLO11) decreased powdery mildew severity up to 77 % [25].…”