Stice Shaun P, Shin Gi Yoon, De Armas Stefanie, Koirala Santosh, Galván Guillermo A, Siri María Inés, Severns Paul M, Coutinho Teresa, Dutta Bhabesh, Kvitko Brian H
Department of Plant Pathology, University of Georgia College of Agricultural and Environmental Sciences, Athens, GA, United States.
Centre for Microbial Ecology and Genomics, Forestry and Agriculture Biotechnology Institute, Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa.
Front Plant Sci. 2021 Mar 10;12:643787. doi: 10.3389/fpls.2021.643787. eCollection 2021.
is a gram-negative bacterium and the primary causal agent of center rot of onions in Georgia. Previous genomic studies identified two virulence gene clusters, HiVir and , associated with center rot. The HiVir gene cluster is required to induce necrosis on onion tissues via synthesis of pantaphos, (2-hydroxy[phosphono-methyl)maleate), a phosphonate phytotoxin. The gene cluster aids in tolerance to thiosulfinates generated during onion tissue damage. Whole genome sequencing of other species suggests that these gene clusters are present outside of . To assess the distribution of these gene clusters, two PCR primer sets were designed to detect the presence of HiVir and . Two hundred fifty-two strains of spp. were phenotyped using the red onion scale necrosis (RSN) assay and were genotyped using PCR for the presence of these virulence genes. A diverse panel of strains from three distinct culture collections comprised of 24 species, 41 isolation sources, and 23 countries, collected from 1946-2019, was tested. There is a significant association between the PCR assay and strains recovered from symptomatic onion ( < 0.001). There is also a significant association of a positive HiVir PCR and RSN assay among strains but not among spp., congeners. This may indicate a divergent HiVir cluster or different pathogenicity and virulence mechanisms. Last, we describe natural positive [RSN/HiVir/ ] strains, which cause extensive bulb necrosis in a neck-to-bulb infection assay compared to negative [RSN/HiVir/ ] strains. A combination of assays that include PCR of virulence genes [HiVir and ] and an RSN assay can potentially aid in identification of onion-bulb-rotting pathogenic strains.
是一种革兰氏阴性细菌，是佐治亚州洋葱中心腐烂的主要致病因子。先前的基因组研究确定了两个与中心腐烂相关的毒力基因簇，HiVir和 。HiVir基因簇通过合成泛磷菌素（(2-羟基[膦酰基甲基]马来酸），一种膦酸盐植物毒素，来诱导洋葱组织坏死。 基因簇有助于耐受洋葱组织损伤期间产生的硫代亚磺酸盐。其他 物种的全基因组测序表明，这些基因簇存在于 之外。为了评估这些基因簇的分布，设计了两组PCR引物来检测HiVir和 的存在。使用红洋葱鳞片坏死（RSN）试验对252株 菌株进行表型分析，并使用PCR对这些毒力基因的存在进行基因分型。测试了来自三个不同培养物保藏中心的一组多样的菌株，这些菌株由1946年至2019年收集的24个 物种、41个分离源和23个国家组成。从有症状的洋葱中回收的 菌株的PCR检测与 之间存在显著关联（<0.001）。在 菌株中，HiVir PCR阳性与RSN检测之间也存在显著关联，但在 属同属物种中不存在。这可能表明HiVir簇存在差异或致病和毒力机制不同。最后，我们描述了天然的 阳性[RSN/HiVir/ ] 菌株，与 阴性[RSN/HiVir/ ] 菌株相比，在颈部到鳞茎感染试验中，它们会导致广泛的鳞茎坏死。包括毒力基因[HiVir和 ]的PCR和RSN检测在内的一组检测方法可能有助于识别导致洋葱鳞茎腐烂的致病 菌株。
