Screening And Medium Optimization Of PGPR

At present,large quantities of chemical fertilizers and pesticides are used in agricultural production,which have a great influence on the soil environment and the quality of agricultural products.The extensive use of chemical fertilizers has led to a series of problems such as soil compaction and the decline of soil organic matter.Microbial fertilizers are called green fertilizers.Compared with traditional chemical fertilizers,they have the advantages of low cost,small pollution,and good effects.They are of great significance in reducing the use of chemical fertilizers and protecting the ecological environment,and have very good prospects for development.Protease-producing bacteria can secrete proteases to degrade macromolecular proteins in the soil to provide nutrients for crops.Auxin-producing bacteria can secrete growth-promoting substances and promote better and faster growth of crops.In this study,568 strains of protease producing strains were screened out from 1100 strains kept in the laboratory.There were 59 functionally stable strains,15 strains with good rescreening effect and 153 auxotrophic strains.Sixteen strains were preferred,83 strains were antagonistic to L.solanacearum,9 strains were functionally stable,and 4 strains had better rescreening effect.Through pot experiment,a total of 21 strains with better effect were selected.Among them,there were 10 strains of protease-producing bacteria with the strain numbers HYC6,JTYP1,JTYP2,JTYP3,FL55,DH10,GQJK5,GQJK17,FL18,and FL42.There were 15 strains of auxin-producing strains with the strain numbers HYC6,HN5,and YZ23.GQJK56,GQJK59,GQJK60,I25,I140,I157,I42,JP6,JTK21,JTYP2,JTYP3,FL18.The significance of plant height was analyzed using SPSS software.When p?0.01,the six strains JTYP1,JTK21,GQJK56,GQJK59,GQJK60,and I140 were significantly different from those of the control;the aboveground fresh weight was significantly analyzed.When p?0.01,the six strains FL18,FL42,GQJK56,I140,I25,and I42 were significantly different from the control;the aboveground dry weight was analyzed for significance.Significant analysis of dry weight on the ground,when p ? 0.01,JTYP1,JTYP2,FL18,GQJK56,GQJK60 5 strains compared with the control was significantly different;the root fresh weight analysis,when p ? 0.01,The 7 strains of DH10,GQJK5,FL18,FL42,GQJK60,I25,and I42 were significantly different from the control.In the dry weight of the root system,when p?0.01,DH10,FL18,FL42,JTYP3,GQJK60,and I42 These six strains were significantly different from the control;the significance analysis showed that when p?0.05,the stem diameters of 9 strains of HN5,JTYP1,YZ23,FL18,FL42,GQJK56,I140,I25,and I42 There was a significant difference from the control.In the combination of 6 different functional bacteria,the combination of JTYP1(Bacillus glycinifermentans)and GQJK56(Bacillus glycinifermentans)had the best promoting effect.The plant height increased by 181% compared to the control,the above-ground fresh weight increased by 199%,the above-ground dry weight increased by 207%,the fresh root weight increased by 42%,and the root dry weight increased by 52%.Two strains which were antagonistic to Ralstonia solanacearum were selected in the pot experiment.The strains were numbered PR10(Bacillus stratosphericus)and HYC1(Serratia marcescens).The relative control effect was 92.13% and 94.75%.The culture medium of Serratia marcescens HYC1 strain was optimized to determine the best fermentation medium for Serratia marcescens: soluble starch 3%,ammonium nitrate 0.75%,calcium carbonate 0.02%,optimal fermentation The conditions were 180 r/min speed,37 °C optimum temperature,pH optimum 7,and 5% optimal inoculum size.