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

Abstract:

[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 Microbacteriumthan 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,andRhodococcus,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.

Key words:wild watermelon varieties;high-throughput sequencing;endophytic microorganisms;root