Response Of Fungal Community Structure Associated With Blueberry Hair Roots To Nitrogen And Phosphorus Addition

Ericaceous plants family is widely distributed across continental ecosystems.They are well known to be able to resist and survive in a tough environment with the assistance of a symbiotic relationship with the ericoid mycorrhizal fungi（ERMF）.Anthropogenic nitrogen（N）and phosphorus（P）deposition has increased dramatically in recent years and thus affected global ecosystems,as well as fungal communities associated with plant hair roots.However,their impact on these fungal communities remains largely misunderstood.We implemented greenhouse experiments on 3-year-old highbush blueberry plants in pots by adding different nutrients such as N（NH₄Cl）,N（NH₄Cl）with P（Na H₂PO₄）,and P（Na H₂PO₄）with various concentration gradients levels.After 4（spring season）and 8（summer season）months of treatment,the samples were collected.The determination of the fungal communities associated with the host hair roots under the addition of nutrients was carried with high-throughput sequencing technology,as well as the physicochemical parameters in soil and the rate of mycorrhizal infection in hair roots.The result revealed that 259 OTUs and 549 OTUs were discovered during the spring and summer seasons.The main dominant orders were Archaeorhizomycetales belonged to Ascomycota,and Sebacinales（putative ERMF）were appertained to Basidiomycota.Besides,the nutrient addition induced multiple variations in the fungal communities compared to the control which was clearly illustrated in the ordination plots.N with P addition treatment group had the highest richness and diversity of fungal communities compared to the control and other treatment groups.Also,N with P treatment addition enhanced the growth of ERMF relative abundance during both seasons and was more stable compared to other treatment groups.However,in N addition and P addition treatment groups,the ERMF abundance varied by concentration gradient level and season.Withal,ERMF were most abundant during the summer season and were not significantly correlated to any edaphic parameters.Furthermore,special order with unknown function（Branch06 and GS34）and some pathogenic fungi order（Olpidiales）were found in this study and were both strongly correlated to edaphic factors.The results of sequencing showed that the relative abundance of Helotiales of Ascomycetes,which was putative ERMF order,was very low.Compared with the control,the mycorrhizal infection rate of the host with N and P addition was decreased to some extent.These results may help to better understand the responses of the fungal community structure associated with ericaceous hair roots under the addition of the nutrients.Nevertheless,further studies on the identification of these unknown fungi,the continued stress of nutrients on the ERMF associated with hair roots of blueberry by different cultivated varieties could be done in the greenhouse and the garden.