Isolation,Identification And Characterization Of Phosphorus Soluble Bacteria In Rhizosphere Soil Of Apple Orchard

In order to alleviate the serious shortage of soil available phosphorus in apple orchards on the Loess Plateau safely,scientifically and effectively.Attempts were made to increase the effective phosphorus content of the soil available for plants by digging efficient phosphorussolubilizing bacteria resources in the plant rhizosphere.In this study,Pikovskaya(PVK)agar medium was used to screen isolates of rhizosphere soil samples of apple orchard(Trifolium repens L.)on the Loess Plateau.16 S r RNA gene and genome sequencing technology were used to clarify the taxonomic status of the strains,and the amount of phosphorus dissolved in the liquid medium with different phosphorus sources were measured.The strains YJ101 and YJILJH with strong phosphorus-solubilizing ability were screened comprehensively,and the ability of the two strains to produce indoleacetic acid and the relative expression levels of the indoleacetic acid-related genes(ipd C,trp D,trp A)in the liquid medium of different phosphorus sources were determined,the growth promotion mechanism of YJ101 and YJILJH were preliminarily explored.In the pot experiments,the water content,fresh weight,available phosphorus and total phosphorus in the soil of white clover were measured after inoculation with YJ101 and YJILJH.In the field experiment,strain YJ101 was inoculated into the soil in which white clover was planted between rows of apple orchards,and the total phosphorus and available phosphorus content of the soil were analyzed.Furthermore,the differences of microbial communities in the rhizosphere of white clover in apple orchard rows inoculated with YJ101 were analyzed by high-throughput sequencing.The main results were as follows:(1)Seven strains of phosphate soluble bacteria were screened,which were YJ101,YJH,YJILJH,YJK,YJM,YJP and YJQ,respectively.YJ101 and YJILJH were Staphylococcus sp.,YJH and YJQ were Cedecea sp.,YJK and YJP were Buttiauxella sp.,YJM was Pantoea sp.(2)The SI values of 7 strains ranged from 3.42 to 4.39.YJ101 has the strongest ability to dissolve lecithin and tricalcium phosphate,which were 387.324 mg / L and 711.35 mg / L respectively;YJP was the weakest,72.13 mg / L and 291.15 mg / L,respectively.(3)The sequencing results of the 16 s r RNA genes and draft genome of YJ101 and YJILJH were submitted to the NCBI Gen Bank database,and the Gen Bank accession number for 16 S r RNA gene sequence and whole genome sequence were MK691488,MK101025 and WJUN00000000,WJUO00000000,respectively.Comprehensive analysis determined that YJ101 was Staphylococcus epidermidis and YJILJH was Staphylococcus hominis.(4)The pot experiments showed that YJ101 and YJILJH could promote the growth of white clover,and increase the soil available phosphorus content(P<0.05).The available phosphorus content of the strains YJ101 and YJILJH were 33.05 mg/kg and 41.92 mg/kg,respectively.(5)The indoleacetic acid produced by YJ101 in inorganic phosphorus and organic phosphorus medium were 54.33 pmol/L and 40.82 pmol/L,YJILJH's were 45.34 pmol/L and 55.95 pmol/L,respectively.The pathways for the synthesis of indoleacetic acid by YJILJH and YJ101 may be related to the tryptophan side chain pathway and the indole-3-pyruvate pathway;When inorganic phosphorus was present in the medium,the biosynthesis pathway of indoleacetic acid of two strains may only be related to the tryptophan side chain pathway.(6)Field experiments showed that the available phosphorus content in the soil could be increased by 40.06% after inoculation of YJ101,the number of microbial communities in the soil changed.At the level of phylum,the number of Acidobacteria,Gemmatimonadetes and Cyanobacteria were reduced,and the number of Bacteroidetes and Proteobacteria increased;at the family level,the number of Chitinophagaceae was increased,the number of Pyrinomonadaceae and Gemmatimonadaceae decreased;at the genus level,the number of Staphylococcus in the inoculated soil increased.