Protection against a vine trunk attack by Phaeomoniella chlamydosporais concomitant with root colonization by the oomycete Pythium oligandrum
Abstract: Strains of the biocontrol agent, Pythium oligandrum, have been isolated from variousvineyards of the Bordeaux region and ability of the oomycete to protect vines from attacks byPhaeomoniella chlamydospora (Pch) has been assessed. Pch is a fungus associated with Escadecline of vines and it induces wood lesions in the trunk of plants. In our experiment roots weresampled from vine plants grown in three different soils, i.e. silt-clay, sandy-clay, stony. Whateverthe conditions, P. oligandrum strains were isolated from 11 out of 12 samples. It seems thereforewell ecologically adapted to vineyard soils. Forty strains were isolated and purified.P. oligandrum strains were identified by sequencing of the rDNA repeat unit, i.e. 3’end of the 18srRNA gene, ITS-1, 5.8s rRNA gene, ITS-2, and around 580 bp of the 5’end of the 28S rRNA.P. oligandrum elicitor detections have been carried out by amplification of two genes: oligandrinand POD1. They were detected in most of the strains. Subsequently, some P. oligandrum strainswere used to carry out experiment about vine protection. Cabernet Sauvignon vine cuttings werefirst inoculated at the root level with P. oligandrum strains, then one week later trunk of youngplants were inoculated with Pch. The Pch strain used was chosen because of its aggressivenessand its ability to induce necrosis in wood. Protection of up to 50% was obtained when therhizosphere of vine cuttings was colonized with P. oligandrum. These observations provide thefirst convincing evidence that P. oligandrum has the potential to induce plant resistance in woodof vine and that it should be useful for the biological control of grapevine wood disease.