Knockdown of MLO genes reduces susceptibility to powdery mildew in grapevine.

Michele Perazzolli,Riccardo Velasco,Luisa Lenzi,Stefano Pessina,Mickael Malnoy,Francesco Salamini,Simona Urso,Lorenza Dalla Costa,Manuela Campa,Giampiero Valè

doi:10.1038/hortres.2016.16

Michele Perazzolli, Riccardo Velasco + Show 8 more

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https://doi.org/10.1038/hortres.2016.16

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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.

Highlights

Vineyards are treated with an impressive amount of chemical compounds, fungicides, to prevent yield losses due to fungal pathogens
This paper reports the knockdown through RNA interference of VvMLO6, 7, 11 and 13 and its effect on powdery mildew (PM) infection in grapevine
Because in dicots not all Clade V MLO susceptibility genes (S-genes) are implicated in PM susceptibility,21,22,29,30 the aim of this work was to identify which of the clade V MLO genes of grapevine have a role in PM susceptibility and can be inactivated to develop resistant genotypes

Summary

Introduction

Vineyards are treated with an impressive amount of chemical compounds, fungicides, to prevent yield losses due to fungal pathogens. In France, Italy, Spain and Germany, between. 1992 and 2003, 73% of the fungicides were used for grapevine protection, a crop that covers only 8% of the agricultural land in those countries.. Grapevine powdery mildew (PM), caused by the fungus Erysiphe necator, is a destructive disease.. Uncinula necator (Schw.) Burr.) is an obligate biotroph infecting all green tissues of grapevine and results in significant losses in yield and berry quality. Symptoms are a white or gray powder covering both leaf surfaces, and, after infection, the fruits show shriveling or cracking.. The quality of the fruit is severely damaged, due to increased acidity and decreased anthocyanin and sugar content. Symptoms are a white or gray powder covering both leaf surfaces, and, after infection, the fruits show shriveling or cracking. The quality of the fruit is severely damaged, due to increased acidity and decreased anthocyanin and sugar content.

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