Ozone treatment: a solution to improve sanitary and physiological quality of vine plant

Abstract

Context and purpose of the study – The vineyard world is faced to a lot of fungal diseases. Grapevine Trunk Diseases (GTD) are some of the major. After exhibiting chronical foliar symptoms, grapevines can die by apoplexy within only few days. A range species of fungi was described to be associated with the apparition of early symptoms of GTD. It is well known that ozone dissolved into water is a powerful disinfectant with no remanence. The main goal of this study was to test the efficiency of this process on different fungal species associated with GTD in vitro and in planta conditions.

Material and methods – In vitro sanitary tests: Eighteen strains of two different species associated with GTD were selected (Phaeomoniella chlamydospora and Phaeoacremonium minimum). Ozone dissolved into water (4.5 g.m-3 according the Henry’s law) or autoclaved demineralized water (control) were applied on spore suspensions from strains. Suspensions were then plated on agar medium. Germinating spores were observed after five days. In vivo sanitary tests:Cuttings of Vitis vinifera Cabernet-Sauvignon clone 15 were drilled until the vascular channels. In each injury, plants received 20 µL of spore suspension (105 spores.mL-1) of P. minimum. Immediately after inoculation, infected wounded damages were treated with 20 µL of ozone dissolved into water (4.5 g.m-3 according the Henry’s law). The fungal development was evaluated 4, 6 and 9 weeks after inoculation by q-PCR.

Results – In vitro sanitary tests: Solution of ozone dissolved into water presented a complete sporicide effect. Indeed, no spore germinated in ozonated treatments whereas water treated controls normally developed. In vivo sanitary tests:The anti-fungal abilities of ozone treatment were secondly assessed by quantification of P. minimum DNA in woody tissues (via qPCR). Four and six weeks after inoculation, ozone treatment strongly reduced the source of inoculum present in the injury, resulting in more of 50% decrease of the number of P. minimum copies per ng of total. After nine weeks, the quantity of DNA is more important in ozone modality than in control modality. These results suggest that ozone treatment slowed down the fungal colonization via its primary sporicide effect in cutting-wounding conditions. Finally, consequences on the physiological aspect of the plant after ozone treatment should be discussed during the congress thanks to some news results.