The Relationship Between Endophyte Community And Soil Microfood Web Of Citrus Greening Disease In Guangxi

Citrus Huanglongbing is a devastating disease caused by Candidatus Liberibacter asiaticus,which poses a serious threat to the citrus industry.In this study,the diversity and community structure of the endophytic flora of citrus trees with fine roots,stems and leaves,soil(inter-and marginal soils)microbiota and soil nematode communities were systematically analysed using high-throughput sequencing and microscopic enumeration of healthy and differently affected sassafras in Linchuan County,Guilin City.The aim of this study was to clarify the effects of disease differences on plant endophytes,soil microorganisms and nematodes,to reveal the relationship between citrus yellow dragon disease endophyte communities and soil microfood webs under different disease differences,to find endophyte strains and nematode species that are antagonistic or companion to yellow dragon disease pathogens,and to lay the foundation for research on the preparation of yellow dragon disease control drugs and the sustainable development of the citrus industry.The main findings of the study are as follows:(1)Ascomycota and Basidiomycota are the dominant endophytic fungi in citrus rhizomes and leaves.The abundance of Ascomycota increased with the severity of the disease,while the abundance of Basidiomycota decreased.Actinobacteria and Proteobacteria were the dominant groups of endophytic bacteria in citrus rhizomes and leaves.The abundance of Actinobacteria decreased and Proteobacteria increased with the severity of the disease.The fungal richness index was significantly reduced in citrus soils with more severe disease.(2)The disease reduced the abundance and diversity of soil nematodes,and hindered the construction of complex community of soil nematodes.Compared with healthy citrus samples,disease had negative effects on soil microbial food webs.The disease may damage the structure of soil biome to a certain extent,resulting in low activity of organisms in the co-occurrence network,reduced synergy and antagonism between organisms,decreased complexity of food web,and decreased stability of food web.(3)PERMANOVA association analysis between the rhizosphere core microbiota and Xanthobacter spp.confirmed the co-occurrence relationship between Xanthobacter spp.and members of Comamonadaceae,Sphingomonadaceae and Rhizobiaceae.There was a significant positive correlation between Clas spp.and Micromonospora,Cupriavidus,Anaeromyxobacter and Microbacterium members in the bacterial community.There was a significant negative correlation with the rare bacteria genus Amycolatopsis.There was a significant positive correlation between Xanthobacter and the nematode genera Diphtherophora,Paratylenchus,Psilenchus and Tripyla.In conclusion,the invasion of Xanthobacter changed the community structure and diversity of plant endophytes and soil microfood webs,and there were significant differences in the diversity and abundance of plant endophytes,soil microorganisms and nematodes between the healthy and diseased groups.Focusing on the effects of different disease differences on the endophytic flora,soil microorganisms and nematodes of citrus in Guangxi will not only provide new ideas for the control of citrus greening disease,but also provide scientific basis for the sustainable production of citrus.