野生和栽培种西瓜根系内生微生物群落结构比较

Comparison of endophytic microbial community structure in roots between wild and cultivated watermelon varieties

【目的】以野生西瓜品种为研究对象,比较分析野生和栽培种西瓜根系内生微生物群落组成,旨在阐明野生西瓜的驯化特征和抗性机制,为构建新型西瓜育种评价体系以及开发利用有益微生物功能提供理论依据和技术支撑。【方法】基于高通量测序技术分析野生和栽培种西瓜根系内生微生物(细菌及真菌)的群落结构特征。【结果】野生西瓜根系内生细菌和真菌群落的门和属与栽培种西瓜相比均具有显著差异。野生西瓜根系中,类诺卡氏菌属(Nocardioides)和微杆菌属(Microbacterium)的细菌相对丰度显著高于栽培种西瓜根系的相应类群;游动放线菌属(Actinoplanes)、分枝杆菌属(Mycobacterium)、列契瓦尼尔氏菌属(Lechevalieria)、拟无枝酸菌属(Amycolatopsis)、慢生根瘤菌属(Bradyrhizobium)、红球菌属(Rhodococcus)是野生西瓜根系特有的优势内生细菌;刺盾炱目未分类菌属(unclassified_o__Chaetothyriales)真菌丰度占比在野生西瓜根系中显著高于相应的栽培种西瓜,并且刺盾炱目未分类菌属、光黑壳属(Preussia)、小囊菌科未分类菌属(unclassified_f__Microascaceae)是野生西瓜根系中特有的优势内生真菌。【结论】野生西瓜驯化成栽培种后,类诺卡氏菌属、微杆菌属、红球菌属等具有固氮、溶磷、产铁载体、生物活性物质、抗生素功能的有益细菌,以及产生生长激素的光黑壳属真菌缺失。由此推断野生西瓜品种驯化过程中,部分内生微生物的缺失是栽培种西瓜应对环境胁迫抗性弱于野生西瓜品种的重要原因之一。此外,类诺卡氏菌属、微杆菌属、红球菌属细菌,以及光黑壳属真菌有望作为提高西瓜抗性的备选微生物资源。

[Objective]To clarify the domestication characteristics and resistant mechanism of wild watermelon plants and provide a theoretical basis and technical support for building a new evaluation system for watermelon breeding and developing beneficial microorganisms,we compared the endophytic microbial community structure in roots between wild and cultivated watermelon varieties.[Methods]High-throughput sequencing was employed to reveal the community structures of endophytic microorganisms(bacteria and fungi)in the roots of wild and cultivated watermelon varieties.[Results]The phyla and genera of endophytic bacteria and fungi in the roots were significantly different between wild and cultivated watermelon varieties.The roots of wild watermelon varieties had significantly higher relative abundance of Nocardioides and Microbacterium than those of cultivated watermelon varieties.Actinoplanes,Mycobacterium,Lechevalieria,Amycolatopsis,Bradyrhizobium,and Rhodococcus were the special dominant endophytic bacterial genera in the roots of wild watermelon varieties.The relative abundance of unclassified_o__Chaetothyriale in the roots of wild watermelon varieties was significantly higher than that in cultivated watermelon varieties.unclassified__o_Chaetothyriales,Preussia,and unclassified_f__Microascaceae were the dominant endophytic fungi specific to wild watermelon varieties.[Conclusion]The beneficial bacteria,such as Nocardioides,Microbacterium,and Rhodococcus,which were capable of fixing nitrogen,solubilizing phosphorus,secreting siderophores,and producing bioactive substances and antibiotics,and the growth hormone-producing fungi,such as Preussia,were lost in the roots of cultivated watermelon varieties after the domestication of wild watermelon.Therefore,it can be concluded that parts of endophytic microorganisms in the roots disappear during the domestication process of watermelon varieties,which is a major reason for the weak resistance of cultivated watermelon varieties to stresses.In addition,the bacterial genera such as Nocardioides,Microbacterium,and Rhodococcus and the fungal genus Preussia can be taken as the candidate microbial resources for enhancing watermelon resistance.