Acta Horticulturae Sinica ›› 2022, Vol. 49 ›› Issue (1): 129-140.doi: 10.16420/j.issn.0513-353x.2020-1033

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Identification of Pathogen Causing Allium ascalonicum Anthracnose in Guangdong

YU Lin1,2, SHE Xiaoman1, TANG Yafei1, LAN Guobing1, LI Zhenggang1, HE Zifu1,2,*()   

  1. 1Plant Protection Research Institute,Guangdong Academy of Agricultural Sciences,Guangzhou 510640,China
    2Guangdong Provincial Key Laboratory of High Technology for Plant Protection,Guangzhou 510640,China
  • Received:2021-07-18 Revised:2021-08-19 Online:2022-01-25 Published:2022-01-24
  • Contact: HE Zifu


To clarify the taxonomy of the pathogen causing Allium ascalonicum anthracnose in Guangdong, diseased plant samples of A. ascalonicum showing anthracnose symptoms from Huizhou and Shaoguan in Guangdong were collected as test materials. Strains were isolated and purified by conidial suspension dilution method. The pathogenicity of these strains was determined by the Koch’s postulates with in vivo or in vitro inoculation of conidial suspension on plants of A. ascalonicum. The pathogen was identified based on morphological characteristics,combined with polygene sequence analysis and phylogenetic analysis method using partial sequences of internal ribosome transcribed spacer(ITS),actin (ACT),chitin synthase 1(CHS1),glyceraldehyde-3-phosphate dehydrogenase(GAPDH)and β-tublin (TUB2). Results showed that 23 single-conidium-isolates with similar morphological characteristics were obtained from diseased plant samples of A. ascalonicum showing anthracnose symptoms. Artificial in vivo and in vitro inoculation results showed that the tested isolate could infect A. ascalonicum and cause typical anthracnose symptoms both at 20 ℃ and 25 ℃. Old leaves were more susceptible than young leaves. On PDA medium,the colony was gray,and mycelia of the tested isolate grew evenly and fast at 20 ℃. But it grew abnormally and slowly,the colony showing petal-like shape at 25 ℃ and 28 ℃. Conidiomata in orange color were formed on the surface of the colony. Conidiophores were hyaline with conidia on the top. Conidia were hyaline,single-spore,slightly curved,13.1-19.6 µm × 3.2-3.9 µm. Appressoria were dark brown,irregular shapes,11.7-25.5 µm × 5.0-14.3 µm. Setae were light brown to dark brown,with enlarged base and pointy or rounded tip,44.5 to 106.4 µm in length. These morphological characteristics were similar with Colletotrichum spaethianum. Sequence identities of partial sequences of ITS,ACT,CHS1,GAPDH and TUB2 genes of representative isolates were 99.46% to 100% identical to the ex-holotype strain CBS 167.49. The phylogenetic tree showed that two representative isolates were grouped together with three C. spaethianum strains to form a single clade. This study clarified that the pathogen causing A. ascalonicum anthracnose in Guangdong was determined as C. spaethianum and reported for the first time that C. spaethianum could cause A. ascalonicum anthracnose.

Key words: Allium ascalonicum, anthracnose, Colletotrichum spaethianum, pathogen identification

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