Taiwan Agricultural Research Institute, Council of Agriculture, Executive Yuan--Publication-Journal of Taiwan Agricultural Research

Journal of Taiwan Agricultural Research

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Circular Spot of Sweet Potato Caused by Sclerotium rolfsii in Taiwan

Huang, C. W., H. R. Yang, C. Y. Lin, S. L. Hsu, S. Y. Lai, W. C. Ko, and H. F. Ni. 2017. Circular spot of sweet potato caused by Sclerotium rolfsi in Taiwan. J. Taiwan Agric. Res. 66(2):158–166.

Circular Spot of Sweet Potato Caused by Sclerotium rolfsii in Taiwan

Chiao-Wen Huang1, Hong-Ren Yang2, Ching-Yi Lin3, Sui-Li Hsu4, Su-Yu Lai4, Wen-Chi Ko4, and Hui-Fang Ni5,*

Abstract

    In 2015, a severe disease outbreak on sweet potato storage root with the symptoms of circular yellowish brown to brown lesions occurred in Chunghua, Yunlin, and Pingtung areas. The pathogen isolated from the diseased tissue had white mycelium, clamp connection, and it produced brown sclerotia, which was identified as Sclerotium rolfsii Sacc. based on these morphological characters and ITS sequence. The growth temperature of pathogen isolates ranged from 15 to 35℃, and the optimum growth temperature was 30 ℃. The pathogen isolate, SCL-003, showed pathogenic ability on sweet potato storage roots and seedlings. Nine fungicides were selected for evaluating the inhibition effect on mycelial growth of two pathogen isolates (SCL-001 and SCL-003). The results showed that the effective fungicides with more than 89% inhibition rate were 50% flutolanil, 75.0% mepronil, 7.5% epoxiconazole, 23.0% hexaconazole, and 25.0% pencycuron + tebuconazole with 10 mg a.i. L-1 dilution concentration. This is the first report of circular spot disease on sweet potato caused by Sclerotium rolfsii in Taiwan.

Key words: Sweet potato (Ipomoea batatas), Circular spot diseases, Fungicide screening.


* Corresponding author, e-mail: hfni@dns.caes.gov.tw
1 Assistant Research Fellow, Plant Pathology Division, Taiwan Agricultural Research Institute, Taichung, Taiwan, ROC.
2 Research Fellow and Director, Chiayi Agricultural Experiment Branch, Taiwan Agricultural Research Institute, Chiayi, Taiwan, ROC.
3 Assistant Research Fellow, Department of Plant Protection, Chiayi Agricultural Experiment Branch, Taiwan Agricultural Research Institute, Chiayi, Taiwan, ROC.
4 Research Assistants, Department of Plant Protection, Chiayi Agricultural Experiment Branch, Taiwan Agricultural Research Institute, Chiayi, Taiwan, ROC.
5 Associate Research Fellow and Head, Department of Plant Protection, Chiayi Agricultural Experiment Branch, Taiwan Agricultural Research Institute, Chiayi, Taiwan, ROC.

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