Phytophthora citrophthora, a new pathogen causing decline on horse chestnut in Turkey

Dieback symptoms were observed on horse chestnut trees planted approximately 40 years ago in Ankara, Turkey. Lesions at the stem bases of the affected trees were similar to those of ink disease on sweet chestnut. A Phytophthora sp. was isolated from the fine roots and soil samples collected around the stem bases by baiting using chestnut leaves. The pathogen was identified as Phytophthora citrophthora based on several morphological features and DNA sequences of the ITS region. Pathogenicity of P.similar to citrophthora was tested by stem inoculation on 3-year-old horse chestnut saplings. P.similar to citrophthora produced large cankers in 20 days and killed 40% of the saplings. This is the first report of P.similar to citrophthora causing dieback on horse chestnut.