Screening And Identification Of Paenibacillus Polymyxa GRY-11 And Its Effect On Apple Replant Disease

This study screened an antagonistic bacterium that can alleviate apple replant disease from the healthy apple rhizosphere soil in a continuous cropping apple orchard.Molecular biology identification,morphological observation,and physiological and biochemical experiments were conducted to study its functional characteristics.Pot and field experiments were conducted to verify its effectiveness in preventing and controlling apple replant disease.The main results are as follows:1.Screening and identification of Paenibacillus polymyxa.Conduct a confrontation test between the initially screened bacteria and the four pathogenic bacteria Fusarium moniliforme,rot skin,sharp spore,and stratification preserved in the laboratory,and select the bacteria that have antagonistic effects against these four fusarium species,named GRY-11.Analyze the morphology of the GRY-11 strain,and conduct physiological and biochemical tests to preliminarily determine that it is a Bacillus like bacterium.Then,conduct tree building analysis on its 16 s RNA sequence,and determine that it is a Bacillus polymyxoides strain.2.The ability of Paenibacillus polymyxa GRY-11 to antagonize and produce extracellular enzymes.The inhibitory rates of strain GRY-11 against the four pathogenic Fusarium species were 80.0%,71.6%,75.0%,and 70.0%,respectively,with an antagonistic coefficient of gradeⅠ.GRY-11 strain produced a transparent circle of 10 mm on starch medium,and formed obvious small water droplets on nitrogen fixation medium and silicate medium.3.Paenibacillus polymyxa GRY-11 bacterial fertilizer of Bacillus mucilaginosus can improve the plant height,ground diameter,and branching amount of continuous cropping Malus hupehensis Rehd.seedlings.Sampling and analysis of pot experiments showed that compared with continuous cropping,the biomass of the tested seedlings increased after treatment with GRY-11 bacterial fertilizer.The indicators for July were measured,and the plant height,ground diameter,new weight,and dry weight after treatment with GRY-11 bacterial fertilizer were 1.39 times,1.84 times,3.70 times,and 2.34 times higher than those of continuous cropping,respectively.Compared with continuous cropping soil,the application of multi sticky GRY-11 microbial fertilizer resulted in a root length,root surface area,root tip number,and root volume that were 1.91 times,1.69 times,1.18 times,and 1.24 times higher than those of continuous cropping treatment.The GRY-11 microbial fertilizer treatment was1.14 times,1.36 times,1.16 times,and 1.21 times higher than that of the microbial fertilizer carrier treatment.4.Paenibacillus polymyxa GRY-11 bacterial fertilizer reduces the content of phenolic acids in continuous cropping soil.Phenolic acids were extracted and analyzed from August soil.Compared with the continuous cropping control treatment,the treatment with GRY-11 bacterial fertilizer reduced benzoic acid,phloretin,phloretin,and cinnamic acid by 41.4%,33.48%,52.17%,and 25,00%,respectively.5.Paenibacillus polymyxa GRY-11 bacterial fertilizer can improve the main enzyme activity of soil.The enzyme activity in soil was increased by GRY-11 bacterial fertilizer.In July,the activities of sucrase,catalase,neutral phosphatase,and other enzymes in soil were1.52,1.83,and 1.47 times higher than those in continuous cropping soil control(CK1),respectively;In August,soil enzyme T1 treatment was 1.84 times,3.11 times,and 2.05 times higher than CK1 treatment.Paenibacillus polymyxa GRY-11 bacterial fertilizer can increase the root activity and antioxidant enzyme activity of Malus hupehensis Rehd.seedlings.In August,the activities of POD,CAT,and SOD enzymes were 1.77,1.30,and 1.31 times higher than those of continuous cropping(CK1),and the content of MDA was detected to have decreased by 42%.6.Paenibacillus polymyxa GRY-11 bacterial fertilizer can significantly reduce the number of soil fungi and increase the number of bacteria.In July,the bacterial content of GRY-11 bacterial fertilizer treatment(T1)was 3.81 times that of the control group,and the fungal content was 61.5% lower than that of the control group.The bacterial content of T1 treatment was 7.6 times that of fungi.In August,the bacterial content was 3.24 times higher than the control,and the fungal content decreased by 66%.7.It can improve the apple replant disease of two-year apple grafted seedlings in the field.Treatment with Paenibacillus polymyxa GRY-11 microbial fertilizer can promote the increase of biomass of continuous cropping two-year grafted seedlings.The plant height,ground diameter,branching amount,branch length,and stem circumference of the bacterial fertilizer treatment(T1)in Qixia region were 1.37,1.29,1.31,2.98,and 1.49 times higher than those of the continuous cropping control(CK1).The change trend of various treatment indicators in Penglai region was consistent with that in Qixia.Soil enzyme activity increased and continuous cropping barriers were effectively improved.