Screening Of High Efficiency Biocontrol Bacteria And Their Preliminary Application

A total of 39 bacterial strains were isolated from soil collected from Guangyuan,Chongzhou in Sichuan Province,and Emin County in Xiangjiang Autonomous Region,and their genetic diversity was analyzed by Eric-PCR analysis.The results showed that all strains were gathered one group at the level of 62%similarity,and 10 groups were formed at 75%similarity level,which showed that the genetic diversity was very abundant among these bacterial strains.Then,high effective antagonistic strains were screened,and eight strains with effective antagonistic ability were obtained.16S r DNA analysis determined their taxonomic position,and they were Bacillus firmus WJB 3,Bacillus wiedmannii WJB5,Bacillus weihenstephanensis WJB 6 and WJB 39,Bacillus pseudomycoides WJB 8 and WJB 10,Bacillus pseudomycoides WJB 9,Serratia marcescens WJB 10,and Bacillus vallismortis WJB 17.Of those,strain WJB 17 had broad-spectrum resietance,and could inhibit Staphylococcus aureus,Ralstonia solanacearum,Proteus species,and Escherichia coli.Especicially,WJB 17 could inhibit Alternaria alternate and Colletotrichum gloeosporioides.Furthermore,the inhibition ratio of sterile fermentation broth of WJB 17reached up to 80.22%.The drug sensitivity test showed that they could express the same size of inhibition zone,which was about 11.33 mm.And the inhibition zone of them was similar to the drug sensitive slips of Clindamycin.Using Serratia marcescens WJB 10 and Bacillus vallismortis WJB 17 as tested bacteria,the biofertilizer was performed.The field experiment was carried out in peach tree plantation of Shuanglin village,Jiajia town in Jianyang County.The results showed that the content of soil organic matter,available phosphorus,available potassium and exchangeable magnesium,soil phosphatese activity,soil invertase activity etc was increased.Analysis of soil bacterial community structure showed that the diversity of soil bacterial community was increased and improved when applied with bio-organic fertilizer.Meanwhile,the abundance of beneficial bacterium was increased,such as Desulfovibrio,Cupriavidus,Sphingomonas,etc.Analysis of RDA showed that the factors such as organic matter,nitrate nitrogen and content of available Fe²⁺were the main factors which affected the soil bacterial community.In conclusion,the applicationcation of bio-organic fertilizer could improve the content of soil availabile nutrients,soil bacterial community structure,and the agronomic character of peach.