First laboratory confirmation of Xylophilus ampelinus in Slovenia*

Abstract

Bacterial blight of grapevine is caused by a slow‐growing bacterium Xylophilus ampelinus. It has been suspected to occur in Slovenia on the basis of visual observation of characteristic symptoms in the 1960s. In the present study, symptoms were recorded in an infected vineyard during three consecutive years (2002/2004). Samples from this vineyard were tested by nested‐PCR and isolation of bacteria on media was attempted. In the first year, angular lesions on leaves were highly expressed and an isolate morphologically similar to X. ampelinus was obtained from one sample. It was purified and identified as X. ampelinus using biochemical and nutritional tests, fatty acid analysis, immuno‐fluorescence, nested PCR and partial sequencing of the 16S rRNA gene. The 16S rDNA sequence showed 99–100% homology to known sequences of X. ampelinus strains, including the type strain. Pathogenicity of the isolate was confirmed in tissue‐cultured and potted grapevine plants. In the following two years, symptoms of bacterial blight were only faintly expressed. Using isolation on media and nested‐PCR, 23 and 17 extracts prepared from 10 and 8 grapevines, respectively, were analysed. In 2003, no positive sample was found, but X. ampelinus was again isolated and identified by colony morphology and nested‐PCR in 2004.