イチゴ品種「エッチエス-138」における黒斑病の発生とその病原菌の形態

抄録

A leaf spot disease of strawberry plants（cv. ‘HS-138’）has been observed in southwest Hokkaido, Japan since 2003. An Alternaria species was isolated from diseased leaves. We studied the pathogenicity and morphology of the Alternaria isolate. Typical symptoms were reproduced in cv. ‘HS-138’ and ‘Morioka-16’but not in the other three cultivars by inoculation. Conidia formed on PCA in chains of 4－9, and lateral branches were absent or uncommon. They were brown to olive brown, ovoid to ellipsoidal or obclavate, 12-65.5 × 5.5-15.5μm with 0–9 transverse and 0–6 longitudinal septa. False beaks were short in 1-2 cells. The conidiophores were 20-82.5 × 3-4.5μm. The morphology and restrictive pathogenicity of the causal fungus were identical to those of the strawberry black leaf spot pathogen. However the causal fungus was clearly different from A. alternata sensu Simmons 1999 in having large conidia and short unbranched chains. This is the first report on the occurrence of black leaf spot in a strawberry cultivar other than cv. ‘Morioka-16’ in Japan.