Soil Bacterial Diversity In Wheat Rhizosphere Under Straw Returning Conditions

The straw return has been commonly used in agricultural production practices as the most effective way to utilise straw resources.It can significantly change the soil bacterial community and increase the number of soil microorganisms.In this study,we analyzed the soil community structure of wheat inter-rhizosphere collected under different treatments of straw return and fertilizer application based on high-throughput sequencing technology.We used the dilution coating method to isolate bacteria in soil samples and establish a bacterial resource library.A bacterial strain LH-01 with a broad-spectrum inhibition effect was obtained from the straw soil samples,returned to the field by screening,and identified as Pantoea agglomerans.Further study on its disease prevention and growth promotion function,combined with the carrier screening to formulate microbial fertilizer,confirmed the growth promotion effect of microbial fertilizer on wheat seedlings through potting experiments.This project will help reveal the distribution pattern and mechanism of inter-root microorganisms under straw return,promote the utilization of beneficial microorganisms,and lay the foundation for promoting the development and utilization of microbial fertilizer.The related research is divided as follows:1.Diversity analysis of inter-root soil bacteria of wheatUsing high-throughput sequencing technology,the bacterial population structure of wheat rhizosphere soil under straw returning and fertilization treatment was analyzed.After Illumina Miseq sequencing,536,014 CCS sequences were obtained from 24 wheat rhizosphere soil samples.Combined with Alpha and Beta diversity analysis,the bacterial composition of wheat rhizosphere soil was abundant after straw returning,which could provide data for the development and utilization of microbial resources.The species of a dominant phylum of inter-rhizosphere soil bacteria differed among treatments,with the phylum Aspergillus(38.92%),Acidobacteria(26.51%),and Synechococcus(20.51%)as the dominant phylum at the overall phylum level;Bacillariophyta(24.15%),Synechococcus(20.29%),Acidobacteria(25.56%),and α-Aspergillus(14.77%)as the dominant phyla;RB41,Mucilaginibacter and unclassified＿Chitinophagaceae were the dominant genera.Straw return increased the diversity of soil bacteria in the rhizosphere of wheat.The diversity of rhizosphere soil bacterial communities between the groups was most evident in the soil samples under straw return without fertilization,further proving that straw return significantly increased the abundance and diversity of the inter-rhizosphere soil bacterial community of wheat.At the same time,fertilizer application caused the reduction of the original bacterial community and changed the bacterial community structure.2.Identification and plant beneficial function analysis of the biocontrol bacterium LH-01A total of 203 bacterial strains were isolated from wheat inter-root soil samples using the dilution coating culture method.They were screened by the plate standoff method,and 52 beneficial biocontrol strains were obtained.Among them,29 inorganic phosphorus-solving strains,23 organophosphorus-solving strains,40 potassium-solving strains,27nitrogen-fixing strains and 37 iron-loving strains were obtained,and a bacterial germplasm resource bank was initially established.The bacterial germplasm resource library screened strain LH-01 was identified as Pantoea agglomerans by morphological,physiological,biochemical and multilocus sequence analysis.Its beneficial functions for plants were investigated,and it was found that LH-01 has the effects of inorganic phosphorus,organic phosphorus,potassium and nitrogen fixation,no ironophilic effect,and broad-spectrum bacterial inhibition.It has a good growth-promoting effect on wheat seedlings,increasing the height of wheat seedlings by 20.44 %;root length by 18.76 %;fresh weight and dry weight by 17.97 % and 18.92 %,respectively.These results indicated that Panomycetes LH-01 had a variety of beneficial functions on plants and had a good growth-promoting effect on wheat seedlings.3.Determination of the effectiveness of biocontrol strain LH-01 against stem rot of wheatThe efficacy of Fusarium oxysporum LH-01 against stem rot of wheat was determined by the inoculation of Fusarium oxysporum LH-01,which significantly inhibited the growth of mycelium of Fusarium oxysporum,with 55.01 % inhibition rate.The control effect was66.67 %.The above results indicate that the phytoplasma paniculata LH-01 is able to control the stem rot disease of wheat caused by Fusarium graminearum,thus playing an essential role in the prevention and control of stem rot disease of wheat.4.The preparation of microbial fertilizer and the test of the effect of promoting growthThe toxicity test of the carrier,water absorption test,and the effective bacterium release rate and bacterium survival rate were measured,and it was found that the substrate soil was more appropriate for the bacterium’s survival.The microbial fertilizer was obtained by preparing wheat straw: wood chips: substrate soil: bacteria solution = 1:1:2:1.The growth-promoting effect of the fertilizer was measured using wheat seedlings,and it was found that the height of wheat seedlings increased by 30.19 %,root length increased by17.36 %,fresh weight increased by 41.23 % and dry weight increased by 34.62 % after the fertilizer treatment.The microbial fertilizer configured with biocontrol strain LH-01 had a growth-promoting effect on wheat seedlings.