In planta screening of various bacterial strains from vineyards for their antagonistic potential against Neofusicoccum parvum, a major grapevine trunk fungal pathogen

Abstract: Nowadays, no efficient fungicide treatment is available against Esca, the most frequent Grapevine Trunk Disease (GTD). Therefore, detection and development of antagonistic microorganisms to achieve biological control would be an important future alternative practice in viticulture. However, very few studies deal with in planta screening of bacteria against major GTD fungi. Our objective was to carry out a screening of 26 bacterial strains for antagonism against Neofusicoccum parvum. All bacterial strains were originated from grapevine of the Bordeaux region (either from grape berry surface or wood tissues). Under greenhouse conditions, the woody stems of 672 rooted cuttings (Cabernet sauvignon and Ugni blanc) were wounded and co-inoculated with each bacterial strain and the same pathogenic strain (control cuttings were inoculated by the pathogen only). After an approximately three-month incubation period, disease severity was measured visually considering i) the frequency or incidence of external cankers and ii) total internal necrotic lesion length in absolute (mm) and relative (%) values. The strains efficacy in decreasing the internal necrotic lesion length reached 33.1%. Two bacterial strains belonging to Pantoea sp. decreased significantly (P = 0.05) the internal lesion length compared with control. As further studies, these strains of interest will be better investigated to better understand the bacteria-fungi relationships in planta with the ultimate goal of an effective biocontrol strategy against Esca disease in vineyards.