Welcome to Chinese Agricultural Science Bulletin,

Chinese Agricultural Science Bulletin ›› 2026, Vol. 42 ›› Issue (14): 147-157.doi: 10.11924/j.issn.1000-6850.casb2025-0441

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Pathogen of Sweet Potato Southern Blight: Biological Characteristics, Infection Process and Fungicide Screening

WANG Chenfei1,2(), ZHANG Jingxin1, PU Xiaoming1, SHEN Huifang1, LIU Pingping1, YANG Qiyun1, WANG Wenyi2, SUN Dayuan1()   

  1. 1 Institute of Plant Protection, Guangdong Academy of Agricultural Sciences/Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China, Ministry of Agriculture and Rural Affairs/Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Guangzhou 510640
    2 South China Agricultural University, Guangzhou 510000
  • Received:2025-05-21 Revised:2025-10-11 Online:2026-07-25 Published:2026-07-24

Abstract:

Southern blight has become an important root and stem disease of sweet potato from seedling stage to adult stage in South China. The pathogen species, infection rules, suitable conditions and efficient control agents are still unclear. To identify the pathogen causing stem base rot of sweet potato at the seedling stage in Guangzhou, and to study its biological characteristics, infection process, and effective chemical control, the pathogen was identified based on molecular and morphological characteristics. The effects of temperature, pH, carbon sources, and nitrogen sources on its biological traits were investigated. The infection process was observed microscopically using tissue staining, and the toxicity of 13 fungicides was tested in vitro using the mycelial growth rate method. The results showed that the pathogen of sweet potato southern blight was identified as Agroathelia rolfsii. The optimal temperature for mycelial growth was 28-32℃, with the best growth at 32℃. The suitable pH range was 5.4-7.5, with an optimum at pH 6.0. D-galactose, D-sorbitol, and D-mannitol were favorable carbon sources, while ammonium dihydrogen phosphate and ammonium chloride were suitable nitrogen sources. Microscopic observation revealed that hyphae began to infect within 12h, infection cushions formed at 24h, and the number of infection cushions peaked at 72 h. Hyphae were also able to infect through stomata. Among the tested fungicides, thifluzamide, pyraclostrobin, tebuconazole, and azoxystrobin showed the strongest inhibitory effects, with EC50 values of 0.01, 0.14, 0.20, and 0.96 mg/L, respectively. The result of this study provides a theoretical basis for the accurate diagnosis and control of sweet potato southern blight.

Key words: sweet potato southern blight, Agroathelia rolfsii, biological characteristics, fungicide screening, infection process, fungicide

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