Influence of constitutive phenolic compounds on the response of grapevine (Vitis vinifera L.) leaves to infection by Plasmopara viticola

Abstract

Flavonols and hydroxycinnamic acids are known to contribute to plant resistance against pathogens, but there are few reports on the implication of flavonols in the resistance of grapevine against Plasmopara viticola, and none on the involvement of hydroxycinnamic acids. In order to analyze the effect of flavonols on P. viticola infection, variable amounts of flavonols were induced by different light conditions in otherwise phenologically identical leaves. Differences in content of leaf hydroxycinnamic acids were induced at the same time. A non-invasive monitoring of flavonols and hydroxycinnamic acids was performed with Dualex leaf-clip optical sensors. Whatever the light condition, there were no significant changes in flavonol or in hydroxycinnamic acid contents for control and inoculated leaves during the development of P. viticola until 6 days after inoculation. The violet-blue autofluorescence of stilbenes, the main phytoalexins of grapevine that accumulate in inoculated leaves, was used as an indicator of infection by P. viticola. The implication of leaf constitutive flavonols and hydroxycinnamic acids in the defence of Vitis vinifera against P. viticola could be investigated in vivo thanks to this indicator. The increase in stilbene violet-blue autofluorescence started earlier for leaves with low flavonol content than for leaves with higher content, suggesting that constitutive flavonols are able to slow down the infection by P. viticola. On the contrary, constitutive hydroxycinnamic acids did not seem to play a role in defence against P. viticola. The non-destructive nature of the methods used alleviates the major problem of destructive experiments: the large variability in leaf phenolic contents.

Grapevine Grafting: Scion Transcript Profiling and Defense-Related Metabolites Induced by Rootstocks

“…Besides the role of viniferin, a negative correlation between the amount of trans -resveratrol and trans -piceid and the disease index of all samples was observed (Figure 7B), suggesting that graft combinations with a high level of trans -resveratrol and its storage form trans -piceid could be more prepared to respond to pathogen attack. While an inverse relationship between preformed flavonoids and the susceptibility of grapevines to downy mildew has been demonstrated (Agati et al, 2008; Latouche et al, 2013), in this work, we suggest a similar role for the preformed non-oxidized form of stilbenes. Resveratrol and its glycosylated form trans -piceid are produced in susceptible grapevines as response to infection of downy mildew (Pezet et al, 2004; Houillé et al, 2015), with limited antifungal activity when the infection is in progress.…”

Rediscovering leaf optical properties: New insights into plant acclimation to solar UV radiation

“…While the mechanistic underpinnings of these responses are clear in certain cases (e.g., the adjustments of mature shade leaves to abrupt increases in UV exposure) the basis of other responses (e.g., diurnal changes in UV shielding) are less understood. Additional studies are needed to evaluate the adaptive significance of rapid modulation in UV shielding in plants and the potential implications of a dynamic UV protection system for other abiotic (drought, nutrient limitation and temperature extremes; [e.g., (Bilger et al, 2007;Petridis et al, 2012;Meyer et al, 2006)]) and biotic factors (herbivore and pathogen protection; (Ballar e, 2014; Latouche et al, 2013)) that are cross-linked to this UV acclimation response.…”

First detection of the presence of naturally occurring grapevine downy mildew in the field by a fluorescence-based method

“…Curtis) Berl & de Toni. 5 This autofluorescent property of the stilbenoid phytoalexins, which is absent from healthy leaves, 5 was exploited to detect the presence of downy mildew in greenhouse-grown plants, [4][5][6] in outdoor-grown plants 5,6 and in the field. One of the reactions of plants to both downy and powdery mildew is the synthesis of a variety of stilbenoid compounds.…”