Hyun J W, Yi S H, Mackenzie S J, Timmer L W, Kim K S, Kang S K, Kwon H M, Lim H C
Citrus Experiment Station, National Institute of Subtropical Agriculture, R.D.A. Jeju, 697-943, S. Korea.
Phytopathology. 2009 Jun;99(6):721-8. doi: 10.1094/PHYTO-99-6-0721.
Two scab diseases are recognized currently on citrus: citrus scab, caused by Elsinoë fawcettii, and sweet orange scab, caused by E. australis. Because the two species cannot be reliably distinguished by morphological or cultural characteristics, host range and molecular methods must be used to identify isolates. Four pathotypes of E. fawcettii and two of E. australis have been described to date based on host range. The host specificity and genetic relationships among 76 isolates from Argentina, Australia, Brazil, Korea, New Zealand, and the United States were investigated. Based on pathogenicity tests on eight differential hosts, 61 isolates were identified as E. fawcettii and 15 as E. australis. Of 61 isolates of E. fawcettii, 24 isolates were identified as the Florida broad host range (FBHR) pathotype, 7 as the Florida narrow host range (FNHR) pathotype, 10 as the Tryon's pathotype, and 3 as the "Lemon" pathotype. Two new pathotypes, the "Jingeul" and the satsuma, rough lemon, grape-fruit, clementine (SRGC), are described, and four isolates did not fit into any of the known pathotypes of E. fawcettii. Of the 15 isolates of E. australis from Argentina and Brazil, 9 belonged to the sweet orange pathotype and 6 from Korea to the natsudaidai pathotype. E. fawcettii and E. australis were clearly distinguishable among groups by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) assays and the E. fawcettii group was divided into three subgroups, A-1, A-2, and A-3. The A-1 group was composed of the FBHR, FNHR, and SRGC pathotypes; some Lemon pathotypes; and the uncertain isolates. The A-2 subgroup included all of the Tryon's pathotype isolates and one of the three Lemon pathotype isolates and the A-3 group contained the Jingeul pathotype isolates. E. australis was differentiated into two groups: B-1, the natsudaidai pathotype isolates, and B-2, the sweet orange pathotype isolates. Isolates of E. fawcettii and E. australis were clearly distinguishable by sequence analysis of the internal transcribed spacer (ITS) region and the translation elongation factor 1 alpha (TEF) gene. There were also fixed nucleotide differences in the ITS and TEF genes that distinguished subgroups separated by RAPD-PCR within species. We confirmed two species of Elsinoë, two pathotypes of E. australis, and at least six pathotypes of E. fawcettii and described their distribution in the countries included in this study.
由法氏痂圆孢（Elsinoë fawcettii）引起的柑橘痂病，以及由南方痂圆孢（E. australis）引起的甜橙痂病。由于这两个物种无法通过形态或培养特征可靠区分，因此必须使用寄主范围和分子方法来鉴定分离株。迄今为止，基于寄主范围已描述了法氏痂圆孢的4个致病型和南方痂圆孢的2个致病型。对来自阿根廷、澳大利亚、巴西、韩国、新西兰和美国的76个分离株的寄主特异性和遗传关系进行了研究。基于对8个鉴别寄主的致病性测试，61个分离株被鉴定为法氏痂圆孢，15个为南方痂圆孢。在61个法氏痂圆孢分离株中，24个分离株被鉴定为佛罗里达广寄主范围（FBHR）致病型，7个为佛罗里达窄寄主范围（FNHR）致病型，10个为特赖恩致病型，3个为“柠檬”致病型。描述了两个新的致病型，即“金秋”致病型和温州蜜柑、粗柠檬、葡萄柚、克莱门氏小柑橘（SRGC）致病型，还有4个分离株不符合法氏痂圆孢任何已知的致病型。在来自阿根廷和巴西的15个南方痂圆孢分离株中，9个属于甜橙致病型，来自韩国的6个属于夏橙致病型。通过随机扩增多态性DNA - 聚合酶链反应（RAPD - PCR）分析，法氏痂圆孢和南方痂圆孢在组间明显可区分，并且法氏痂圆孢组被分为三个亚组，A - 1、A - 2和A - 3。A - 1组由FBHR、FNHR和SRGC致病型；一些柠檬致病型；以及不确定的分离株组成。A - 2亚组包括所有特赖恩致病型分离株和三个柠檬致病型分离株中的一个，A - 3组包含金秋致病型分离株。南方痂圆孢分为两组：B - 1，夏橙致病型分离株，和B - 2，甜橙致病型分离株。通过对内部转录间隔区（ITS）区域和翻译延伸因子1α（TEF）基因的序列分析，法氏痂圆孢和南方痂圆孢的分离株明显可区分。在ITS和TEF基因中也存在固定的核苷酸差异，这些差异区分了物种内通过RAPD - PCR分离的亚组。我们确认了痂圆孢属的两个物种、南方痂圆孢的两个致病型以及法氏痂圆孢的至少六个致病型，并描述了它们在本研究涵盖国家中的分布。
