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Abstract ▼ AI-Helper

Recently, a symptom similiar to black spot caused by Alternaria kikuchiana on the pear leaves is prevailing in Naju, Chonnam Province. This experiment was conducted in order to clarify causal agent and to survey present status on it. Disease lesions on the leaves were brown or black brown in color, ...

Recently, a symptom similiar to black spot caused by Alternaria kikuchiana on the pear leaves is prevailing in Naju, Chonnam Province. This experiment was conducted in order to clarify causal agent and to survey present status on it. Disease lesions on the leaves were brown or black brown in color, circle or irregular circle in shape, $2\~6mm$ in diameter, and faintly zonal. Central part of lesions was gradually changed to greyish-white. The causal fungus was identified as Alternaria kikuchiana Tanaka causing black spot of pear reported previously on variety I-sib-se-gi (Nijisseki) of pear. However, this disease differed from that of typical black spot reported already in some aspects; It occurred more highly on matured leaves than on young ones. And it occurred severely in varieties Shin-heung, Shin-ko, Man-sam-gil(Okusankichi) etc. which have been reported as resistant varieties, while slightly in varieties Cho-ok(Hayadama), Park-da-cheung (Hakadahare) etc. which have been known as susceptible ones. From the results described above, it is considered that this disease is due to the differentiation in pathogenicity of Alternaria kikuchiana Tanaka in that area.