健康与感染黑胫病烟株根际土壤与茎秆细菌群落结构与多样性

  背景和目的  黑胫病为烟草常见土传病害，当环境条件适宜时，土壤中的病原菌便会侵染烟株导致发病。  目的  研究感染黑胫病前后烟株根际土壤、发病茎秆以及病健交界茎秆细菌群落结构与多样性。  方法  以健康与感染黑胫病烟株根际土壤和茎秆为研究对象，通过PCR技术扩增样本中细菌16S rRNA基因的V3-V4可变区域，采用Illumina Miseq高通量测序技术对扩增片段进行测序，分析健康与感染黑胫病烟株不同部位细菌群落结构与多样性。  结果  感染黑胫病烟株根际土壤细菌群落较健康烟株丰富度增加，但多样性略有降低；发病烟株茎秆发病部位和病健交界部位的细菌群落丰富度和多样性较健康烟株均有增加，发病茎秆病健交界部位增幅显著。门水平上，变形菌门（Proteobacteria）、酸杆菌门（Acidobacteria）以及放线菌门（Actinobacteria）等为根际土壤优势菌门，且在健康与感染黑胫病烟株中各优势菌门相对丰度无显著性差异。茎秆样品中变形菌门与蓝细菌门为优势菌门，病健交界茎秆中2者的相对丰度与健康茎秆和发病茎秆存在显著性差异。属水平上，健康与感染黑胫病烟株根际土壤中主要菌属为Candidatus_solibacter、芽单胞菌属（Gemmatimonas）和鞘脂单胞菌属（Sphingomonas）等。所有茎秆样品中优势菌属为蓝细菌（norank_c_Cyanobacteria）和劳尔氏菌属（Ralstonia），病健交界茎秆中蓝细菌相对丰度与健康茎秆和发病茎秆差异显著。  结论  感染黑胫病后烟株各部位细菌群落结构发生改变，细菌群落多样性增加；所有样品中均检测到青枯病病原菌茄科劳尔氏菌，表明烟草黑胫病与青枯病存在混合发生的情况。因此在对烟草黑胫病防治的同时也需加强青枯病的防治。 

Bacterial community structure and diversity in rhizospheric soil and in stalk of healthy and black shank disease-infected tobacco plants

Black shank is a common soil-borne disease in tobacco.When environmental conditions are appropriate,the pathogens present in soil will penetrate into tobacco plant,and eventually lead to disease of tobacco plant.To understand the changes of bacterial community structure and diversity in rhizosphere soil,diseased stem tissue and symptomatic-asymptomatic junction stem tissue of black shank infected tobacco plants,the hypervariable V3-V4 region of 16S rRNA gene was amplified by PCR,and the amplified fragments were sequenced using Illumina Miseq high-throughput sequencing technology.Bacterial communities structure and diversity in different parts of healthy and black shank infected tobacco plants were analyzed.The richness of bacterial community in rhizosphere soil of black shank infected tobacco plants were higher than that of healthy tobacco plants,while the bacterial diversity was slightly lower than that of healthy tobacco plants.The richness and diversity of diseased stem and symptomatic-asymptomatic junction stem were higher than that of healthy stem,and the increase of symptomatic-asymptomatic junction stem was significant.At phylum level,Proteobacteria,Acidobacteria and Actinobacteria were the dominant phyla in rhizosphere soil.There was no significant difference in relative abundance of dominant phyla between healthy and diseased groups.Proteobacteria and Cyanobacteria were dominant bacteria in stem samples.The relative abundance of Proteobacteria and Cyanobacteria in the symptomatic-asymptomatic junction stem was significantly different from that of healthy stem and diseased stem.At genus level,the main bacteria in rhizosphere soil were Candidatus_solibacter,Gemmatimonas and Sphingomonas,norank_c_Cyanobacteria and Ralstonia were the dominant bacteria in all stem samples.The relative abundance of norank_c_Cyanobacteria in symptomatic-asymptomatic junction stem was significantly different from that in healthy stem and diseased stem.After infected with black shank,the bacterial community structure changed and the diversity of bacterial community increased.The pathogen of bacterial wilt,Ralstonia solanacearum,was detected in all samples,which indicated that there was a possibility of mixed occurrence of tobacco black shank and bacterial wilt.It is therefore necessary to strengthen control of tobacco bacterial wilt while controlling tobacco black shank disease.