The Diversity And Composition Of Microbial Community In The Camellia Oleifera Rhizosphere And The Activity Of Phosphate-Dissolving Rhizobacteria

Camellia oleifera is a unique woody oil crop in China.In recent years,planting Camellia oleifera has been encouraged in China and there are increasing studies on its growth and development.The root system absorb the moisture and nutrients from the soil,which laid a foundation for rejuvenation of theover-ground part of the plants.The root system of Camellia oleifera has different growth cycles and showing different character of hydrotaxi and fertiliertaxis as different growth period.Rhizospheric microorganism plays an important role in promoting the growth and absorption of nutriets of the plant.Demonstrating the nutrient change of rhizosphere soil and characters of the microbial community structure as different growth period of the root system,which can provide theoretical guidance for reasonable water and fertilizer management of Camellia oleifera.The Camellia oleifera planting area is mostly located in the red soil region of the south in China.The problem of phosphorus deficiency and accumulation is serious and the effective utilization rate of phosphorus is low.The normal growth of Camellia oleifera and the guarantee of yield are inseparable from the role of rhizosphere microorganisms,especially phosphate-dissolving bacteria.In this study,soil nutrient changes and rhizosphere bacterial community structure were analyzed by collecting rhizosphere soil samples from different growth cycles of Camellia oleifera roots system.A number of high-efficiency rhizosphere phosphate-dissolving bacteria were isolated,screened and identified from Camellia oleifera rhizosphere soil.The effects of the addition of high-efficiency phosphate-dissolving bacteria on plant biomass,plant nutrient content and soil phosphorus forms were verified.The major conclusions as follows.?1?The nutrient contents of TN,TP and TK and the activities of various enzyme in the Camellia oleifera rhizosphere soil were always higher in the rhizosphere active stage than in the dormancy stage.There are outstanding differences of the rhizospheric microbial community structure and its indicator microorganism as different growth period of the root system.According to the redundancy analysis,soil available NO₃-N and AK exerted significant influence on rhizosphere microbial community structure.A co-occurring network analysis found that the interaction between rhizosphere bacteria was the strongest in the active growth of roots and was significantly weakened at the dormant period of roots,indicating that the nutrients,enzyme activities,microbial community structure and interactions between species in the rhizosphere soil were largely affected by the host root system activity.The change trend of microbial community structure and activities was consistent.Therefore,ensuring the healthy growth of above-ground Camellia oleifera is also an important basis for maintaining the stability and activity of the underground soil microbial system.?2?A total of 94 strains of phosphorus solubilizing bacteria were isolated and screened from the rhizosphere soil of Camellia oleifera.The phosphate-dissolving ability of inorganic phosphorus and organic phosphorus was determined by qualitative and quantitative methods.The results showed that the strains had higher solubility for inorganic phosphorus than organic phosphorus.Among which CK2 has the highest ability to solubiliting inorganic phosphorus,reaching 74.8 mg/L.Twelve strains with good comprehensive performance of inorganic phosphorus and organic phosphorus solubiliting ability were selected for phylogenetic identification.Among which 11strains?CK2,CK20,CK25,CK30,CK32,CK34,DG7,DG9,FM13,DF9,DF17?were Burkholderia sp.and 1 strain?FM21?was Paraburkholderia sp.?3?According to the pot experiment,when insoluble phosphorus was added into the corn planting,the inoculation treatment could better promote the biomass of corn planting.Among which mixed bacteria have a more significant effect on plant growth.From the perspective of corn biomass,the treatment of T2?CK2+CK32+FM21?,T3?CK2+FM13+FM21?and F1?CK2+CK32+FM13+FM21?was the best;from the perspective of plant nutrient absorption,the treatment of T1?CK2+CK32+FM13?,T2 and F1 increased the nutrient content of plants;from the soil phosphorus forms,the treatment of T2 and F1 has the best effect on improving soil available phosphorus.The three parts are integrated,in which T2 and F1 are the optimal combination.Therefore,This indicates that the mixed phosphate-dissolving bacteria group is better than the single bacteria in promoting plant growth and phosphorus dissolving.