Department of Plant Protection, College of Agriculture, Shiraz University, Shiraz, Iran.
Laboratorio de Microbiología Molecular y Biotecnología Ambiental, Chemistry Department and Centro de Biotecnología Daniel Alkalay Lowitt, Universidad Técnica Federico Santa María, Valparaíso, Chile.
Appl Environ Microbiol. 2019 Nov 27;85(24). doi: 10.1128/AEM.02098-19. Print 2019 Dec 15.
Tomato bacterial canker caused by subsp. is one of the most important seed-borne tomato diseases around the globe. The disease was initially reported in 1993 in Iran, and it became a rising threat for the multibillion dollar tomato industry of the country during the last decade. In this study, using phylogeographic analyses, we determined genetic diversity and geographic distribution of subsp in Iran. Our field surveys showed that the pathogen is expanding into the southern and eastern areas of the country. Furthermore, multilocus sequence analysis and typing (MLSA/MLST) using the sequences of five housekeeping genes (, , , , and ) revealed that 37 subsp strains isolated in Iran had high genetic diversity and placed in 15 sequence types (STs), while all the available 184 worldwide subsp sequences were placed in 43 STs. MLSA divided the worldwide subsp strains into two phylogroups (I and II). Among the 37 strains isolated in Iran, 30 strains clustered in phylogroup I, while 7 strains clustered in phylogroup II. Phylogeographic data inferred from the allelic profile of the five housekeeping genes suggested multiple introductions of subsp inoculum into Iran, while the geographic origin of the Iranian subsp strains remains undetermined. Further analyses using higher numbers of strains are warranted to decipher the evolutionary history of subsp in Iran. Additionally, stricter seed/transplant inspections are recommended to reduce the risk of pathogen expansion to areas with no history of the disease. subsp. , the causal agent of tomato bacterial canker disease, is one of the economically important pathogens of solanaceous crops (e.g., eggplant, pepper, and tomato) around the world. The disease occurs in many countries, with a particular importance in regions characterized by high precipitation and humid environmental conditions. As a seed-borne pathogen, subsp is included in the A2 (high risk) list of quarantine pathogens by the European and Mediterranean Plant Protection Organization (EPPO). Bacterial canker disease was reported for the first time in 1993 in Iran, while the geographic distribution, genetic diversity, and phylogenetic position of the causal agent remain undetermined. In this study, using the multilocus sequence analysis and typing (MLSA/MLST) approach, we provided a phylogeographic scheme for the subsp strains isolated in Iran. Furthermore, global-scale phylogenetic analyses led to determination of phylogenetic position of Iranian subsp strains among worldwide population of the pathogen. Based on diversity parameters and population structure, we suggest relatively higher genetic diversity of the bacterial canker pathogen in Iran than has so far been observed in the other areas of the world. Results obtained in this study provide a novel insight into the genetic diversity and population structure of the bacterial canker pathogen on a global scale.
番茄细菌性溃疡病由丁香假单胞菌番茄亚种引起，是全球最重要的种传番茄病害之一。该病害于 1993 年首次在伊朗报道，在过去十年间，它对该国数十亿美元的番茄产业构成了日益严重的威胁。在本研究中，我们利用系统地理学分析，确定了伊朗丁香假单胞菌番茄亚种的遗传多样性和地理分布。我们的田间调查显示，该病原菌正在向该国南部和东部地区扩散。此外，使用五个管家基因（、、、、和）的序列进行多位点序列分析和分型（MLSA/MLST）表明，在伊朗分离的 37 株丁香假单胞菌番茄亚种具有高度遗传多样性，可分为 15 个序列型（ST），而全球范围内可获得的 184 株丁香假单胞菌番茄亚种序列可分为 43 个 ST。MLSA 将全球范围内的丁香假单胞菌番茄亚种菌株分为两个系统发育群（I 和 II）。在伊朗分离的 37 株菌株中，30 株聚集在系统发育群 I 中，而 7 株聚集在系统发育群 II 中。基于五个管家基因等位基因谱推断的系统地理学数据表明，丁香假单胞菌番茄亚种接种体多次传入伊朗，而伊朗丁香假单胞菌番茄亚种菌株的地理起源仍不确定。使用更多数量的菌株进行进一步分析，有助于解析伊朗丁香假单胞菌番茄亚种的进化历史。此外，建议加强种子/移植检查，以降低病原菌向无该病历史地区扩散的风险。丁香假单胞菌番茄亚种是茄科作物（如茄子、辣椒和番茄）的一种重要经济病原菌。该病害发生在许多国家，特别是在降水多、湿度大的地区尤为重要。作为一种种传病原菌，丁香假单胞菌番茄亚种被欧洲和地中海植物保护组织（EPPO）列入检疫性病原菌 A2（高风险）名单。1993 年，伊朗首次报告发生番茄细菌性溃疡病，但病原菌的地理分布、遗传多样性和系统发育地位仍不确定。在本研究中，我们使用多位点序列分析和分型（MLSA/MLST）方法，为伊朗分离的丁香假单胞菌番茄亚种菌株提供了系统地理学图谱。此外，全球范围内的系统发育分析确定了伊朗丁香假单胞菌番茄亚种菌株在病原菌全球种群中的系统发育地位。基于多样性参数和种群结构，我们认为伊朗的细菌性溃疡病原菌具有相对较高的遗传多样性，高于目前在世界其他地区观察到的水平。本研究结果为全球范围内细菌性溃疡病原菌的遗传多样性和种群结构提供了新的认识。
