First report of Fusarium culmorum causing marigold root rot in China
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First report of Fusarium culmorum causing marigold root rot in China Manlin Xu 1 & Jing Yu 1 & Yongliang Li 2 & Shifei Zhang 3 & Chaoqun Zhang 4 & Xia Zhang 1 & Zhiqing Guo 1 & Juxiang Wu 1 & Yucheng Chi 1 & Jinguang Yang 5 Received: 19 June 2019 / Accepted: 7 May 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020
Keywords Marigold . Fusarium culmorum . Root rot
In 2018, marigold (Tagetes erecta L.) root rot caused significant crop losses in Tengchong City, Yunnan Province, China. About one month after seedling emergence, the basement of the marigold stem became water-soaked, and as time passed, the stem basement became brown and black, sometimes with some burgundy and yellow discoloration. The plants became stunted and wilted. Disease incidence was about 3% in the area we investigated. The symptomatic specimens were placed on potato dextrose agar (PDA). Pure cultures were subsequently established from single spores. The fungal colonies produced abundant, dense, white, aerial mycelium. The underside of PDA plate ranged from carmine red, burgundy to light yellowish brown. The macroconidia, which were 4.3–7.5 × 28.5–58.1 μm in size, had 3–5 five septa and some were moderately curved, like spindles. The
Manlin Xu and Jing Yu contributed equally to this work. * Yucheng Chi [email protected] * Jinguang Yang [email protected] 1
Shandong peanut research institute, Qingdao, Shandong, China
2
Baoshan Branch of Yunnan tobacco company, Baoshan, Yunnan, China
3
Hongyunhonghe Tobacco (Group) Co., Ltd, Kunming, Yunnan, China
4
Jiangxi Tobacco Research Institute, Nanchang, Jiangxi, China
5
Tobacco Research Institute of CAAS, Qingdao, Shandong, China
microconidia were absent. The chlamydospores were oval or elliptical, with smooth intercalary or terminal hyphae. The EasyPure Genomic DNA Kit (TransGen, Beijing, China) was used to extract the total genomic DNA from the mycelia. We used the universal fungal PCR primers ITS1 and ITS4 (White et al. 1990) to amplify the 5.8S rDNA internal transcribed spacer (ITS) region, EF1 and EF2 (O’Donnell et al. 1998) to amplify the translation elongation factor 1-alpha (TEF) gene. The consensus sequences of ITS (MK215779) and EF1 (MN044434) showed 100% identity with the sequence of Fusarium culmorum isolates (MH681156.1 for ITS and for KP065682.1 for EF1) use NCBI BLASTn. The culture characteristics and molecular identification confirmed that the fungus isolated from the infected marigold samples was F. culmorum. Koch’s postulates were tested under greenhouse conditions. Twenty 2-week-old marigold seedlings (cv. Inner Mongolia hybrid F1) grown in 20 cm pots of autoclaved soil were inoculated with 5 ml of conidial (macroconidial) suspension (106 macroconidia ml −1 ). Twenty untreated marigold plants were used as the controls. All the marigold plants were arranged in a randomized complete block design, and grown at 25 °C with a 12 h photoperiod. After about 2 weeks, symptoms similar to those observed in the field appeared on the marigold treated with conidial
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