In July 2018, a sample of lavender var. Grosso (Lavandula × intermedia 'Grosso') from Miami County, OH was received by The Ohio State University Vegetable Pathology Laboratory in Wooster. Lavender plants were field-grown in sandy clay soil with plastic mulch under drip irrigation. Disease incidence ranged from 0 to 32% depending on variety. Leaves and stems showed dark necrotic lesions that varied from roughly circular (ca. 0.3 to 0.5 mm diameter) to large coalesced necrotic areas surrounded by a water-soaked halo. Bacterial streaming from lesions was observed microscopically. Leaf tissue pieces (~0.5 cm2) were surface sterilized in 70% ethanol for 30 seconds and rinsed in sterile deionized water. The tissue was sliced aseptically into smaller sections in 100 μl sterile water and the bacterial suspension was streaked on yeast dextrose calcium carbonate agar medium. Ten yellow Xanthomonas-like colonies were selected after 72 hours of incubation at 28ºC in the dark. Strains were gram negative, oxidase negative and caused hypersensitive reactions on Nicotiana benthamiana (L.). All strains were genotyped after whole-cell DNA extraction by BOX-PCR (Louws et al. 1999) and had the same banding profile. Four 8-wk-old lavender plants (Lavandula dentata and Lavandula × ginginsii 'Goodwin Creek Gray') were spray-inoculated with a 106 CFU/ml suspension of strain SM175-2018 in sterile water. Control plants were sprayed with sterile water. Plants were kept in plastic bags for the first 48 h at 28°C with a 14-h photoperiod. Water-soaked necrotic lesions appeared 14 days after inoculation with SM175-2018, whereas mock-inoculated plants did not show symptoms. Bacterial isolation from symptomatic leaf tissue was carried out as described above. The BOX-PCR profile of the re-isolated strain was identical to that of SM175-2018. Multilocus sequence analysis of the housekeeping genes fuyA, gyrB, and rpoD was performed (Accession numbers: MT764834 - MT764836). The resulting concatenated data set was used to perform a phylogenetic analysis using maximum likelihood criteria to evaluate relationships with closely related Xanthomonas spp. using published reference sequences (Young et al. 2008). SM175-2018 was assigned to the X. hortorum clade (Moriniere et al. 2020) with strong bootstrap support. The strain was subjected to whole genome analysis. Genomic DNA was extracted using a QIAGEN Genomic DNA buffer set with genomic-tip 100/G following manufacturer's protocol and sequenced using the iSeq-100 Illumina platform with the Nextera DNA Flex Library Prep protocol kit and Nextera DNA CD indexes. Average nucleotide identity (ANI) analysis was performed with the ANI-Matrix software Enveomics tool (Rodriguez-R and Konstantinidis 2016) using the sequenced genome (NCBI GenBank Biosample no. SAMN11831455) and those of other X. hortorum (Vauterin et al. 1995) bacteria (pvs. hederae, carotae, vitians). SM175-2018 shared a 96% ANI with other X. hortorum strains. X. hortorum is associated with bacterial leaf spot of carrot (Scott and Dung, 2020) and also reported on ornamental plants (Mirik et al. 2010, Oliver et al. 2012, Roberts and Parkinson 2014, Klass et al. 2019), however additional research is needed to establish the host specificity of lavender strains. To our knowledge this is the first report of X. hortorum causing bacterial leaf spot of lavender in Ohio. The disease may negatively impact the yield and quality of flowers used in production of lavender oils and essences.

中文翻译：

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Xhorhomonas hortorum首次报道在俄亥俄州造成薰衣草细菌叶斑（Lavandula×intermedia）。

2018年7月，薰衣草变种样本。来自俄亥俄州迈阿密县的格罗索（Lavandula×intermedia'Grosso'）被俄亥俄州立大学伍斯特市的蔬菜病理学实验室接收。薰衣草植株在滴灌条件下在塑料覆盖的沙质粘土田间生长。疾病的发生率在0％到32％之间，具体取决于品种。叶子和茎部显示出深色坏死性病变，从大致圆形（直径约0.3到0.5毫米）到大的合并坏死区域（周围被水浸透的光环）变化。显微镜下观察到病灶中的细菌流出。将叶片组织片（〜0.5 cm2）在70％乙醇中表面灭菌30秒，然后在无菌去离子水中冲洗。将组织在100μl无菌水中无菌切片，然后在酵母葡萄糖碳酸钙琼脂培养基上划线。在黑暗中于28ºC温育72小时后，选择了十个黄色的Xanthomonas样菌落。菌株为革兰氏阴性，氧化酶阴性，并引起本氏烟草（L.）的过敏反应。通过BOX-PCR提取全细胞DNA后，对所有菌株进行基因分型（Louws等，1999），并具有相同的条带分布。用106 CFU / ml菌株SM175-2018的悬浮液喷雾接种4株8周龄的薰衣草植物（Lavandula dentata和Lavandula×ginginsii'Goodwin Creek Gray'）。对照植物用无菌水喷雾。将植物在塑料袋中于28°C的前48小时内保持14小时的光周期。接种SM175-2018后14天出现了水浸泡的坏死病斑，而模拟接种的植物没有出现症状。如上所述，从有症状的叶组织分离细菌。重新分离的菌株的BOX-PCR谱与SM175-2018相同。对管家基因fuyA，gyrB和rpoD进行了多基因座序列分析（登录号：MT764834-MT764836）。使用最大似然标准，使用所得的级联数据集执行系统发育分析，以评估与紧密相关的黄单胞菌属的关系。使用公开的参考序列（Young等，2008）。SM175-2018被分配给具有强大自举支持的hortorum X. horadeum进化枝（Moriniere et al。2020）。对该菌株进行全基因组分析。使用QIAGEN基因组DNA缓冲液组（按照制造商的操作规程，使用基因组尖端100 / G提取基因组DNA），并使用iSeq-100 Illumina平台，Nextera DNA Flex Library Prep方案试剂盒和Nextera DNA CD索引对基因组DNA进行测序。使用测序的基因组（NCBI GenBank生物样品编号SAMN11831455）和其他荷尔蒙X.hortorum（Vauterin et al.1995）的基因组，使用ANI-Matrix软件Enveomics工具（Rodriguez-R和Konstantinidis 2016）进行平均核苷酸同一性（ANI）分析。 ）细菌（对伞形科植物，胡萝卜，胡萝卜属）。SM175-2018与其他hortorum菌株共享96％ANI。hortorum（X.hortorum）与胡萝卜的细菌性叶斑病有关（Scott和Dung，2020），并且在观赏植物上也有报道（Mirik et al.2010，Oliver et al.2012，Roberts and Parkinson 2014，Klass et al.2019），然而，还需要进一步的研究来确定薰衣草菌株的宿主特异性。据我们所知，这是俄亥俄州的X. hortorum引起薰衣草细菌性叶斑的首次报道。该疾病可能会对薰衣草油和香精生产中使用的花朵的产量和质量产生负面影响。