Analysis Of Elements And Microbial Communities In Rhizosphere Soil Of Weak And Healthy Chinese Bayberry

Chinese bayberry(Myrica rubar Sieb.et Zucc.)is a characteristic fruit tree in China.It is mainly distributed in Zhejiang,Fujian,Hunan,Guangxi and other southern regions of China.It likes acid soil and often grows in hillside or valley forests.In recent years,with the continuous expansion of planting scale,the weakening of trees is becoming more and more serious.Previous studies have found that the adverse growth state of fruit trees was strongly correlated with soil elements and soil microbial community.In order to find out the different rhizosphere flora between weak and healthy trees,to explore the reasons for the weakness of bayberry,and to provide effective bacteria for green prevention and control of the weakness of bayberry.In this study,the physiological indexes of fruits,leaves and branches of weak trees were measured and analyzed,and the element content in rhizosphere soil,rhizosphere microbial community structure and their correlation between healthy and weak bayberry were deeply analyzed,and the rhizosphere strains with growth promoting function were screened.The main results are as follows:Firstly,the growth and fruit quality of weak trees were worse than that of healthy trees,while the rhizosphere microbial community was lower ?-Diversity index(Shannon,Simpson,Chao1,ACE)had no significant correlation with tree health status;The results showed that the relative abundance of Burkholderiaceae,Streptomycetaceae,and Beijerinckiaceae in the rhizosphere of healthy trees were higher than that of weak trees,while the relative abundance of Pleotrichocladium,Fusarium,and Mortierella in the rhizosphere of weak trees were higher than that of healthy soil samples.It was speculated that the decline of bayberry might be related to the decrease of Burkholderiaceae and the increase of Fusarium.Secondly,the element content of Rhizosphere Soil in all experimental groups could meet the needs of normal growth and development of trees.The contents of soil available K,P,Mg,Mn,Mo,Cu,Zn,Ni,Pb,Cr in group W were higher than those in Group E(extensive management of healthy tree samples)and group F(fine management of healthy tree samples),indicating that the absorption capacity of most soil elements by weak trees was weaker than that of healthy trees.Thirdly,in terms of bacteria,among the 10 phylum and 10 genus with the highest relative abundance,the relative abundance of 2 phylum(unidentified bacteria and actinobacteriata)and 3 genus(RB41,Sphingomonas and Bradyrhizobium)in group W were higher than those in groups E and F,while the relative abundance of bacteroidota and granulicella in group W were lower than those in groups E and F.In terms of fungi,among the 10 phylum and 10 genus with the highest relative abundance,the relative abundance of 5phylum(Ascomycota,mucoromycota,monolpharomycota,Glomeromycota,basidiobolomycota)and 3 genus(Knufia,Humicola,Fusarium)in group W were higher than those in groups E and F,while the relative abundance of 1 phylum(Chytridiomycota)and 3genus(Penicillium,Saitozyma and unidentified sordariomycetes sp.)were lower than that of E and f groups.Statistical analysis showed that there were significant differences in the relative abundance of Tremellomycetes between group W and groups E and F.the weakness of bayberry may be related to the decrease of beneficial rhizosphere microorganism such as Tremellomycetes.It was found that the relative abundance of Fusarium in the rhizosphere of all samples in the experimental area was higher than that of healthy samples in the same area;Further analysis showed that the relative abundance of Fusarium solani and Fusarium sp.in rhizosphere soil increased,which was one of the important reasons for the weakness of bayberry.Fourthly,Bradyrhizobium and Sphingomonas were positively correlated with Mg,Cu and Pb in rhizosphere,and Knufia was positively correlated with available P in rhizosphere.Among the top 35 bacterial genera,9 bacterial genera were significantly correlated with Mg,Cr and Cu,indicating that the bacterial genera in the rhizosphere of bayberry mainly affected the cycling of Mg,Cr and Cu;The results showed that there was a significant correlation between the content of available phosphorus and 11 fungi,which indicated that the harmful fungi in rhizosphere might affect the absorption of available phosphorus by plants,resulting in the decline of fruit quality and growth index.Fifthly,58 strains of nitrogen fixing and 28 strains of phosphorus dissolving functional strains were screened from rhizosphere soil of weak trees and healthy trees,and the ability of IAA secretion of strains was further tested.It was identified that strain TTH1-13 had the functions of IAA secretion,nitrogen fixation and phosphorus dissolving at the same time,which would provide important candidate strains for the development of microbial fertilizer for bayberry in the future.