Quambalaria cyanescens, a new fungal trunk pathogen associated with grapevine decline in Iran

Abstract

During surveys on grapevines trunk diseases in vineyards at different localities in East and WestAzerbaijan and Ardabil provinces, Iran, wood samples (two, three year-old cordons) were collected from grapevine showing decline symptoms, including leaf yellowing and necrosis, stunted growth, internal wood necrosis, black vascular discolouration. Nine fungal isolates with similar morphology were recovered from grapevines with decline symptoms in five different areas, which one-third of the isolates were recovered as the sole fungal agents. The identity of fungal isolates was determined as Quambalaria cyanescens based on the combination of cultural and morphological characteristics and DNA phylogeny. Pathogenicity trials based on excised shoot assay and potted grapevine under greenhouse conditions confirmed Q. cyanescens being pathogenic on grapevines; the isolates induced symptoms similar to those observed in naturally infected grapevines. Our findings confirm Q. cyanescens as a new fungal trunk pathogen of grapevine. Members of the genus Quambalaria are known to cause leaf spot, shoot blight and canker disease on Eucalyptus and its relative Corymbia. The current study is the first regarding pathogenicity of the Q. cyanescens on woody hosts; in previous studies Q. cyanescens has proven to be non-pathogenic to Corymbia spp. The host range, extent of geographical distribution and economic significance of this new pathogen on grapevine remains to be studied.