Caucasian alder (Alnus subcordata) is among the major constituents of the Hyrcanian forests extending all along the southern coast of the Caspian Sea in northern Iran. An angular leaf spot with a yellowish chlorotic halo has attained a widespread occurrence throughout the forest and suburban areas of the northern provinces including Guilan, Mazandaran and Golestan. Strains of a Xanthomonas sp. were consistently isolated from the symptomatic leaves of A. subcordata. Colonies of the isolates were yellow circular, convex and mucoid on nutrient agar containing glucose or sucrose. In multilocus sequence analysis using the genes gyrB, rpoD, dnaK, gltA, fyuA and gapA, the representative isolates occupied a clade shared by the known pathovars of Xanthomonas arboricola. The isolates were relatively heterogeneous phenotypically, but more so in their rep-PCR fingerprints. Pathogenicity of several isolates was confirmed on seedlings of A. subcordata and Alnus rhombifolia, whereas Alnus cordata, Alnus glutinosa and Alnus crispa appeared not to be susceptible. Based on these characteristics, the isolates causing angular leaf spots of Caucasian alder appear to represent a novel pathovar of X. arboricola.

中文翻译：

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由木木黄单胞菌引起的高加索桤木角斑病

高加索桤木（Alnus subcordata）是沿着伊朗北部里海南部海岸延伸的希尔卡尼亚森林的主要组成部分之一。带有黄色褪绿晕的角状叶斑病在吉兰、马赞德兰和古勒斯坦等北部省份的森林和郊区广泛发生。黄单胞菌菌株。始终从A. subcordata的症状叶子中分离出来。分离物的菌落在含有葡萄糖或蔗糖的营养琼脂上呈黄色圆形、凸状和粘液状。在使用基因gyrB、rpoD、dnaK、gltA、fyuA和gapA进行的多位点序列分析中，代表性分离株与已知的木纹黄单胞菌致病变种共享一个进化枝。这些分离株在表型上相对异质，但其rep-PCR 指纹更是如此。几个分离株的致病性在A的幼苗上得到了证实。subcordata和Alnus rhombifolia，而Alnus cordata、Alnus glutinosa和Alnus Cripa似乎不受影响。基于这些特征，引起高加索桤木角叶斑的分离株似乎代表了一种新的木树病原菌。