Alternaria steviae に起因するステビアの黒斑病

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A new disease of Stevia rebaudiana Bertoni caused by a hitherto undescribed species of the genus Alternaria was found in Kagawa Prefecture in the late August of 1978 and was named as the black spot disease of stevia. Symptom on leaves appeared as small spots at an early stage of the infection, similar to that of the leaf spot caused by Septoria steviae. The spots expanded to irregular shape in black color and were surrounded with a chlorotic zone. The spots also occurred on stems, petiols and involucral scales. Among several Alternaria species isolated from the diseased stevia leaves, the fungus showed pathogenicity on stevia leaves by an artificial inoculation. The fungus was also pathogenic on the injured leaves of taxonomically related plants : Eupatorium chinense and E. fortunei, but not on the leaves of Chrysanthemum frutescens, C. morifolium, Erigeron annuus and Tagetes patula. Maximum mycelial growth of the causal fungus Alternaria sp. (Kagawa-a=IFO 31182) on PSA medium was at 25 C and in a range of pH 6.0 to 6.5. Based on the morphological characteristics and specific pathogenicity on stevia plants, the present fungus was considered as a new species of the genus Alternaria and Alternaria steviae, sp. nov. was proposed. The occurrence of black spot disease in fields was diversed depending on stevia strains and this was highly correlated with the susceptibility of leaves to the fungus as tested by the artificial inoculation. The culture filtrate of the pathogen growing in Richard's liquid medium induced a necrotic lesion on the leaves of susceptible strains at a concentration of 1:8. On the leaves of resistant strains, however, necrosis appeared only when undiluted culture filtrate was applied. The use of culture filtrate was suggested as effective for selection of the stevia strains resistant to the black spot of stevia caused by Alternaria steviae.
日本植物病理学会の論文
1982-01-25

Alternaria steviae に起因するステビアの黒斑病

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