Ozone treatments to induce systemic-acquired resistance in leaves of potted vines: molecular responses and NIR evaluation for identifying effective dose and exposition duration

Abstract

The European Community has recently imposed considerable restrictions on the use of pesticides, with the establishment of a regulatory framework for the sustainable use of agro-chemicals. However, in the viticulture sector, the intensive use of chemical pesticides, as well as sulfur and copper, is often required. Recently, ozone has been proposed as a possible environmentally friendly tool for controlling the development of pests on vines. However, little is known about the parameters linked to the practical application of ozone for controlling grapevine pests and how it triggers plant defence mechanisms. The main aim of this preliminary study was to determine the concentration of ozone and exposure duration in a treatment for stimulating the expression of systemic acquired resistance (SAR)-related genes, without inducing toxic effects and affecting vine health. In the first trial, three different combinations of ozone concentration and duration of treatment were tested on potted grapevines: i) gaseous ozone at 300 ppb for 12 hours, ii) gaseous ozone at 100 ppb for 6 hours, and iii) gaseous ozone at 100 ppb for 3 hours. Based on the results of the first trial, the potted vines were treated with just 100 ppb for 3 hours in a second trial. Leaves at different developmental stages were sampled. The expression level of systemic acquired resistance-related genes was analysed 12 hours and 7 days after each treatment. Furthermore, physiological parameters and NIR spectra were analysed. Ozone induced a transient up-regulation (limited to 12 hours after the treatments) of chitinases, β-1,3-glucanase and glutathione-S-transferase. On the other hand, pathogen-related (PR) genes showed a more persistent over-expression. The ozone treatment selectively affected the stomatal conductance depending on the different ozone concentrations. Detected NIR spectra revealed significant structural changes in ozone-treated plants, especially in leaves exposed to higher concentrations of ozone. These results suggest that ozone is able to transiently stimulate the expression of some resistance-related genes even at low and non-toxic doses for the vine leaves.

Effects of fungicide application on physiological and molecular responses of grapevine (Vitis vinifera L.): a comparison between copper and sulfur fungicides applied alone and in combination with novel fungicides

“…S9(F) in Appendix S1). PR genes are involved in the SAR signaling pathway, which is commonly triggered in plants affected by pathogens, including grapevine infected by P. viticola 52 and E. necator 53 and following the application of ozone as resistance inducer 54 . Nonetheless, in our conditions the expression of these genes was greatly affected by genotype‐mediated responses, as both VvBgluc and VvPR1 were induced in ‘Nebbiolo’ and downregulated in ‘Arneis’ upon antifungal compounds.…”

Ozone-Induced Biochemical and Molecular Changes in Vitis vinifera Leaves and Responses to Botrytis cinerea Infections

“…In Bc − /O 3 + leaves, the genes involved in the cell wall degradation of fungi showed a transient over-expression (at 6 and 24 h FET in the case of Chi IV and CHIT B) or down-regulation throughout the whole period of the experiment (e.g., β-1,3 glucanase). Conversely, the genes involved in the detoxification of foreign compounds (e.g., GST) and in the recognition of virulence products (e.g., PR1 and PR6) showed more persistent over-expression (except in the case of PR6 at 24 h FET, PR6 and GST at 48 h FET) confirming that O 3 is able to activate at least two distinct signaling pathways, one of which overlaps with the HR and SAR activation pathways [18,47]. The examined genes categories seem to have reacted in different ways in leaves subjected to sequential double-treatments.…”

“…The PCR conditions were set according to the manufacturer's protocol. Gene-specific primers and dilutions were the same used by [18]. Sample analyses was performed using the SYBR Green PCR Master Mix (Life Technologies™, Milan, Italy), with a final reaction volume of 10 μL, running on the CFX Connect RT-qPCR System (BioRad Laboratories, Inc., Hercules, CA, USA).…”

“…Damage caused by O 3 on grapevine leaves includes anatomical modifications at the mesophyll level and structural changes in the cuticle [25]. Moreover, in our previous study, we demonstrated that a single pulse of O 3 (100 ppb for 3 h) is effective in stimulating the expression of the systemic acquired resistance (SAR)-related genes without affecting grapevine physiological status [18], by confirming that O 3 mimics molecular events induced by pathogens [26]. Considering the above-mentioned issues, one of the main aims of the present study was that of characterizing at functional and molecular level the "indirect" protective mechanism(s) induced by O 3 treatment (at the same dose used in the previous study) through the induction of defense responses in V. vinifera plants artificially inoculated with B. cinerea (Bc).…”

“…Ozone is usually approached as a crucial environmental stressor [16], but some investigations have also highlighted its potential role as "eustressor" [17]. Short-term exposures of plants to adequate and controlled dosages of O 3 have been proposed as a tool to increase nutraceutical quality, since they commonly trigger antioxidants levels without compromising plant performance [8,17,18]. Plant response to O 3 resembles the biotic defense reactions mimicking biochemical and molecular events and includes two steps: The first is a biphasic oxidative burst with a rapid, massive and transient increase in apoplastic reactive oxygen species (ROS) production; the second is the induction of pathogen-like responses, such as local programmed cell death (PCD) and hypersensitive response (HR; [19,20]).…”