抗病和感病香蕉品种根系内生细菌群落结构与多样性

Community structure and diversity of endophytic bacteria in root of resistant and susceptible banana varieties

  • 摘要: 【目的】分析抗病和感病香蕉品种根系内生细菌群落结构与多样性,探究香蕉抗枯萎病能力与香蕉根系微生物组的关联,为发掘利用香蕉枯萎病土著生防微生物组提供理论依据。【方法】以香蕉枯萎病感病品种威廉斯B6和抗病品种中蕉9号为材料,在枯萎病发病初期(营养生长旺盛期)和发病严重期(孕蕾期)采集香蕉根系,采样前均调查香蕉发病情况;分别提取抗病和感病香蕉植株根系DNA,利用高通量测序技术对香蕉根系内生细菌16S rRNA基因V3~V4区进行测序分析,通过Fastp和Flash软件对原始测序序列进行质控、拼接,利用RDP classifier和Silva数据库对序列进行比对、注释,采用Excel 2010对数据进行整理统计,运用DPS 7.0进行差异显著性分析。【结果】随着香蕉的生长发育和枯萎病的越发严重,抗病品种中蕉9号在生长过程中相对感病品种威廉斯B6表现出极显著(P<0.01)的抗病能力。测序获得的2568个OTUs分属于32门89纲220目369科673属1139种。Alpha多样性和物种组成分析结果表明,抗病品种中蕉9号根系细菌多样性高于感病品种威廉斯B6,但差异不显著(P>0.05)。2个品种根系细菌群落在发病初期和严重期的优势菌门无差异,但相对丰度随着香蕉的生长发生显著变化(P<0.05,下同)。在发病初期,感病和抗病香蕉植株根系细菌群落中主要优势菌属较单一;发病严重期细菌群落组成较丰富,其中抗病品种中有益微生物链霉菌属(Streptomyces)、拟无枝菌酸菌属(Amycolatopsis)和短杆菌属(Brevibacterium)的相对丰度显著增加,分析发现短杆菌属只在抗病品种香蕉根系中特异富集。NMDS和PCoA分析表明,感病与抗病香蕉植株根系细菌群落结构在发病初期大致相同,到发病严重期时2个品种间内生细菌群落结构具有显著差异。【结论】感病与抗病香蕉植株根系内生细菌群落结构随着生长发育和发病进程而变化,优势菌门和菌属群落组成变化较大且差异显著,尤其是抗病品种中有益微生的相对丰度显著增加。感病与抗病香蕉植株根系微生物结构组成变化对香蕉枯萎病的发生有较大影响,特异微生物的富集对香蕉抗枯萎病产生直接或间接的影响。

     

    Abstract: 【Objective】To analyze the community structure and diversity of endophytic bacteria in banana roots of resistant and susceptible banana varieties and explore the association between resistance to fusarium wilt and the root microbiome of banana,which would provide theoretical basis for exploiting and utilizing indigenous biocontrol microbiome of banana fusarium wilt. 【Method】The banana fusarium wilt susceptible variety Williams B6 and resistant variety Zhongjiao 9 were used as materials. The banana root system was collected at the initial stage of fusarium wilt(the period of vigorous vegetative growth)and the severe stage(the period of gestational bud stage),the incidence of banana was investigated before two sampling;the root DNAof susceptible and disease-resistant banana plants was extracted respectively. The V3-V4 region of 16S rRNAgene of endophytic bacteria in banana roots was sequenced by high-throughput sequencing technology. Raw sequencing files were quality-filtered by Fastp and merged by Flash. The taxonomy of each 16S rRNA gene sequence was compared and annotated by RDP classifier algorithm against the Silva 16S rRNA database. Excel 2010 was used to analyze the data,and DPS 7.0 software was used for significant difference analysis.【Result】With the growth and development of banana,the fusarium wilt became more and more serious,and the resistant variety Zhongjiao 9 showed extremely significant(P<0.01)disease resistance compared with the susceptible variety Williams B6 during the growth process. A total of 2568 OTUs were obtained by high-throughput sequencing,which belonged to 1139 species, 673 genera,369 families,220 orders,89 classes,and 32 phyla. The results of Alpha diversity and species composition analysis showed that the root bacteria diversity of resistant variety Zhongjiao 9 was higher than that of susceptible variety Williams B6,but the differences was not significant(P>0.05). There was no difference in the dominant bacterial phyla of root bacterial community between the two varieties at the initial stage and the severe stage,however,the relative abundances changed significantly with the growth of bananas(P<0.05,the same below). At the initial stage,the main dominant bacterial genus in the root system of susceptible and disease-resistant bananas was relatively single,while the bacterial community composition in the severe stage was more abundant,the relative adundance of beneficial microorganism Streptomyces,Bacteroides and Brevibacterium increased significantly in the resistant banana variety,genus Brevibacterium was found and enriched only in the roots of resistant variety. NMDS and PCoA analysis showed that the community structure of endophytic bacteria in the disease initial stage was basiclly the same,and the community structure of endophytic bacteria of disease-resistant variety in the severe disease stage was significantly different from the other treatment group.【Conclusion】The community structure of endophytic bacteria in the root of susceptible and disease-resistant banana changes with the progression of the disease process. The community composition of dominant phyla and genera vary significantly,especially the relative abundance of beneficial microorganism increas significantly in resistant variety. The variation of root microbial structure of susceptible and resistant banana have great effect on the occurrence of fusarium wilt,and the accumulation of specific microorganisms has direct or indirect effect on fusarium wilt resistance of banana.

     

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