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Background: The oomycete Plasmopara viticola (Berk. and Curt.) Berl. and de Toni causes downy mildew in grapevine (Vitis vinifera L.). This pathogen is strictly biotrophic, thus completely dependent on living host cells for its survival. The molecular basis of compatibility and disease development in this system is poorly understood. We have carried out a large-scale cDNA-AFLP analysis to identify grapevine and P. viticola genes associated with the infection process.

HighlightWe show that the ancestor of cultivated grapevine harbours genetic factors that increase the inducibility of stilbenes correlated with increased resistance to the important pathogen grapevine downy mildew.

Grapevine (Vitis vinifera ssp. vinifera) is one of the most important fruit species; however, it is highly susceptible to various pathogens, which can cause severe crop losses in viticulture. It has been shown that several WRKY class transcription factors (TFs) are part of the signal transduction cascade, which leads to the activation of plant defense reactions against various pathogens. In the present investigation, a full-length cDNA was isolated from V. vinifera leaf tissue encoding a predicted protein, designated VvWRKY33, which shows the characteristics of group I WRKY protein family. VvWRKY33 induction correlates with the expression of VvPR10.1 (pathogenesis-related 10.1) gene in the leaves of the resistant cultivar 'Regent' after infection with Plasmopara viticola, whereas in the susceptible cultivar 'Lemberger' VvWRKY33 and VvPR10.1 are not induced. Corresponding expression of the TF and VvPR10.1 was even obtained in uninfected ripening berries. In planta, analysis of VvWRKY33 has been performed by ectopic expression of VvWRKY33 in grapevine leaves of greenhouse plants mediated via Agrobacterium tumefaciens transformation. In consequence, VvWRKY33 strongly increases resistance to P. viticola in the susceptible cultivar 'Shiraz' and reduces pathogen sporulation of about 50-70%, indicating a functional role for resistance in grapevine. Complementation of the resistance-deficient Arabidopsis thaliana Columbia-0 (Col-0) mutant line wrky33-1 by constitutive expression of VvWRKY33 restores resistance against Botrytis cinerea to wild-type level and in some complemented mutant lines even exceeds the resistance level of the parental line Col-0. Our results support the involvement of VvWRKY33 in the defense reaction of grapevine against different pathogens.

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Background European grapevine cultivars ( Vitis vinifera spp.) are highly susceptible to the downy mildew pathogen Plasmopara viticola . Breeding of resistant V. vinifera cultivars is a promising strategy to reduce the impact of disease management. Most cultivars that have been bred for resistance to downy mildew, rely on resistance mediated by the Rpv3 ( R esistance to P . v iticola ) locus. However, despite the extensive use of this locus, little is known about the mechanism of Rpv3 -mediated resistance. Results In this study, Rpv3 -mediated defense responses were investigated in Rpv3 + and Rpv3ˉ grapevine cultivars following inoculation with two distinct P. viticola isolates avrRpv3 + and avrRpv3ˉ , with the latter being able to overcome Rpv3 resistance. Based on comparative microscopic, metabolomic and transcriptomic analyses, our results show that the Rpv3–1 -mediated resistance is associated with a defense mechanism that triggers synthesis of fungi-toxic stilbenes and programmed cell death (PCD), resulting in reduced but not suppressed pathogen growth and development. Functional annotation of the encoded protein sequence of genes significantly upregulated during the Rpv3–1 -mediated defense response revealed putative roles in pathogen recognition, signal transduction and defense responses. Conclusion This study used histochemical, transcriptomic and metabolomic analyses of Rpv3 + and susceptible cultivars inoculated with avirulent and virulent P. viticola isolates to investigate mechanism underlying the Rpv3–1 -mediated resistance response. We demonstrated a strong correlation between the expressions of stilbene biosynthesis related genes, the accumulation of fungi-toxic stilbenes, pathogen growth inhibition and PCD. Electronic supplementary material The online version of this article (10.1186/s12870-019-1935-3) contains supplementary material, which is available to authorized users.

The in~uence of hairs during the interaction of Plas! mopara viticola with leaves of four Vitis species was stud! ied both under natural conditions and upon treatment with the detergent Tween 19[ The hydrophobic felt con! sisting of hairs on the adaxial leaf sides repels water from the leaf surface preventing a successful penetration of the host via fungal germ tubes[ Treatment with a detergent solution led to an enhanced attachment of water droplets[ As a consequence of the detergent treatment\ infection structures of P[ viticola were formed on the _eld!resistant hosts Vitis doaniana and Vitis davidii as in the susceptible Vitis vinifera hosts[ It can be concluded that covering the leaf surface with hydrophobic hairs represents a major defence strategy and that the infection process is depen! dent on wetness[ Although in Vitis cinerea and Vitis lab! rusca primary infection structures can be monitored after detergent treatment\ the growth of the fungus was found to be restricted in these species indicating the action of additional or di}erent defence strategies[ ZusammenfassungBlatthaare als grundlegende Schu Ãtzende Barriere gegen den Falschen Mehltau der Weinrebe U[ S[ Copyright Clearance Center Code Statement] 9820Ð0674:88:3697Ð9342 , 03[99:9 Resistenzfaktor in diesen Arten darstellt\ und da) ein erfolgreicher Infektionsprozess von der Benetzbarkeit der Blattunterseite abha Ãngt[ Obwohl in Vitis cinerea und Vitis labrusca ebenfalls zuna Ãchst prima Ãre Infektionsstrukturen nach einer Detergens!Behandlung gebildet wurden\ kam es zu keinem weiteren Pilzwachstum\ was auf das Vorhan! densein weiterer wichtiger Resistenzmechanismen bei die! sen beiden Arten schlie)en la Ã)t[

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