Geographic distribution and genetic diversity of Waitea circinata var. circinata isolated from annual bluegrass in the U.S.

 

論文發表人: 陳其敏 (加州大學河濱分校植物病理所博士班)

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在美國高爾夫球場草坪樣本中分離出Waitea circinata var. circinata (Wcc)◦ Wcc是Rhizoctonia的有性世代之一, Rhizoctonia spp能感染禾本科葉部或根部造成植株死亡◦ 早熟禾屬的annual bluegrass (Poa annua)草種在美國被廣泛的用於草坪植被例如高爾夫球場◦ 實驗用菌株包括從加州, 康乃迪克州, 伊利諾州, 緬因州, 內華達州, 紐約州, 奧勒岡州, 羅德島以及華盛頓州分離而得◦ 經過形態鑑定以及rDNA ITS分子鑑定(RFLP, Restriction fragment length polymorphism)確定引起病害的真菌是Wcc◦ 然而rDNA ITS經過酵素(Hap II)脢切後少數菌株在電泳圖上顯示三個DNA片段, 有異於前人研究的兩個片段◦ 研究顯示未被酵素脢切的第三個片段之尺寸約為rDNA ITS全長◦ 經過序列解析以及基因選殖, 發現在酵素作用位置上此真菌發生突變或是經由遺傳導致同一株菌系中同一個核酸位置擁有兩種不同的核酸導致酵素無法辨識進行脢切◦此研究顯示此真菌的ITS雖然有約2%的多樣性,但是仍足夠用以分辨此真菌與其他同樣是Rhizoctonia spp且能在禾本科上引起病害的不同種類◦ 同時,此研究也彰顯出此真菌在美國是廣泛分布,而不僅僅如同前人研究所指只分布於美國西岸◦

Waitea circinata var. circinata (Wcc), is the causal agent of brown ring patch of Poa annua that was recently discovered in the U.S and it is also a pathogen on Agrostis stolonifera in Japan. 42 isolates were identified as Wcc based on colony morphology and RFLP method using HapII. Some of the isolates produced two bands whereas others produced three bands. Sequencing the ITS rDNA confirmed that few isolates have heterozygous at the HapII restriction site. The sequencing reactions failed which was due to two indels at poly T positions. Intra-species variability in the ITS was low but phylogenetic analysis clearly separates Wcc from other varieties. It indicates that Wcc is wide spread across the U.S. as a pathogen of Poa annua.