カナムグラ褐斑病の病原学的研究 (I) : 病徴,病原性,分生子の発芽条件および病原菌の所属

概要

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Brown leaf spot of Humulus scandens was observed in Tsukuba, Ibaraki Prefecture in 1995-1996 as angular brown spots about 1-3 mm in size delimited by fine veins on the leaf surface. Diseased leaves gradually turned yellow and defoliated. On the leaf spots, numerous grayish green powdery masses of cnidia and conidiohores were formed. Pathogenicity of this fungus was confirmed through inoculation tests with conidial and mycelial suspensions. The causal fungus was identified as Pseudocercospora humuli (Hori) Guo et Liu Based on comparison its morphological characteristics to Cercopora humuli Hori. Conidia began to germinate after 2 hr and reached 93% germination within 24 hr. Conidia could germinate from 5 to 35℃ with an optimum temperature at 25℃ and from pH 3 to pH 9 with an optimum between pH 4 and pH 9. Conidia germinated at humidities between 97.5% and 100% with the most favorable germination in a saturated atmosphere, but not at 89% and below. Conidia remained viable for about 2 months at room temperature.
1999-10-25