First report of Cryphonectria parasitica on chestnut (Castanea sativa) in Azerbaijan

Abstract

Since 2003, there have been reports of sweet chestnut mortality from the Great Caucasus region of Azerbaijan. Upon field inspection in 2004, symptoms on the dead and dying trees included crown dieback and cankers on the main stem with yellow to orange, sometimes reddish, fungal stromata. Cankers were collected from the Gabala forestry section in October 2004, and from the Ismailli, Oghuz, and Zagatala forestry sections in 2006. Cankers had orange to red stromata with embedded pycnidia; cultures from cankers formed pycnidia with conidia that were 2·5–4 × 1·0–1·2 µm. Sequences of the internal transcribed spacer regions and the 5·8S gene of rDNA were determined (White et al., 1990) for 15 isolates from Azerbaijan, and two representative sequences were deposited as Acc. Nos. EF545114 and EF545115. These sequences closely matched sequences of Chinese and Japanese isolates of Cryphonectria parasitica (e.g. Acc. Nos. AY141862, AY141863, AY697928, and AY67929). Pathogenicity of isolates A475 and A480 (deposited at Iowa State University; dried specimens = MAH2821 and MAH2822, deposited in the Central Herbarium at the Institute of Botany, Baku, Azerbaijan) from Gabala was tested on 3-year-old chestnut seedlings in a greenhouse. Wounds (5 mm diameter) to the cambium were made on the stems. Discs (5 mm diameter) from cultures on malt extract agar were then placed, mycelium surface down, into the wounds of 10 seedlings each. After 2·5 months, cankers with stromata and pycnidia formed on the 20 inoculated seedlings, and all seedlings died. Ten control plants similarly treated with sterile MEA discs did not display symptoms. The Asian fungus C. parasitica is well-known on sweet chestnut in Europe (Heiniger & Rigling, 1994). This is the first report of chestnut blight in Azerbaijan and is apparently the easternmost location of the disease on the European continent. We appreciate the financial support of the Science & Technology Center in Ukraine and the UNESCO/Keizo Obuchi Research Fellowship Program.