Study On The Effect Of Soil Texture On The Degree Of Apple Replant Disease

In this study,pot experiment and field validation were combined to study the occurrence degree and mechanism of apple replant disease(ARD)in the apple orchards with different soil textures.So we can adopt appropriate control measures according to the severity of ARD.The pot experiment was carried at the National Apple Engineering Center Experimental Station of Shandong Agricultural University,College of Horticulture,Shandong Agricultural University and State Key Laboratory of Crop Biology in 2017 and 2018.The soils of three different soil texture were from Laizhou,Yantai,the Malus hupehensis Rehd.seedings were used as experimental material.The field experiment was conducted from 207 to 2018 in the villages of Dashaling(37.40° N 120.09° E),Fengmaozhai(37.41° N 120.07° E),and Wantou(37.09° N 119.80° E)in Laizhou city,which is located in Yantai city in Shandong Province,China.Healthy two-year-old seedlings with consistent growth were selected,of which the root stock was T337 and the scion was Yanfu3.The experiment consisted of six treatments: Methyl bromide applied to sandy loam soil(SX),replanted sandy loam soil(SL),methyl bromide applied to loam soil(FX),replanted loam soil(FL),methyl bromide applied to clay loam soil(WX),and replanted clay loam soil(WL).The main experimental results are as follows:1.In pot culture experiments,we can see that the most difference occured between methyl bromide fumigation and its replanted soil treatment in clay loam soil,which indicated that the degree of ARD in clay loam soil was the most serious.Compared with their respective controls,the fresh weight of plants in the methyl bromide fumigated sandy loam,loam,and clay loam increased by 85.7%,59.6% and 104%,respectively.The dry weight of plants increased by 87.9%,54.4% and 98.9%,respectively.2.In the pot experiment,Root stress was most serious in replanted clay loam soil.In the three different texture treatments,the difference of root protective enzymes,the root respiration rates and the MDA contents were the greatest in clay loam.The most harmful fungi mainly in F.oxysporum was in replanted clay loam soil.The copy number of F.oxysporum decreased by 70.1%,66.3% and 87.5%,respectively,and the copy number of F.oxysporum was the highest in the replanted clay loam soil.3.Through the determination of the biomass under methyl bromide fumigation and replanting in soil of different textures,it can be found that the biomass of the bromide fumigation treatments was significantly higher than that of the control in the three different textured soils.In 2017 and 2018,there were significant differences in plant height,stem diameter,number of branches,and branch length between methyl bromide fumigation and replanted treatments,and the difference was largest in clay loam,followed by sandy loam,and loam.There were significant differences in urease,sucrase and phosphatase activities between methyl bromide fumigation and replanted treatments,among which the clay loam showed the greatest difference,followed by sand loam and loam.The trend is consistent in the two years.4.Based on high-throughput sequencing of fungi in soil samples,fungal richness and diversity were highest in clay loam,followed by sandy loam,and loam.Compared with their respective controls,the Chao1 index in the treatment with methyl bromide fumigation in sandy loam,loam and clay loam decreased by 17.21%,17.03%,and 18.18%,respectively.The Ace index decreased by 17.59%,15.88%,and 18.40%,respectively;the Shannon index increased by 14.57%,13.75%,and 17.97%,respectively,and the Simpson index decreased by 33.77%,31.79%,and 44.13%,respectively.5.At the phylum level,soil fungi in the three soil textures were mainly composed of Ascomycota,Basidiomycota,Zygomycota and Glomeromycota.Blastocladiomycota,Chytridiomycota and Rozellomycota could be detected in part of the treatments.Ascomycota dominated all soil fungal communities.The relative abundances in SX,SL,FX,FL,WX,and WL were 62.99%,81.29%,53.24%,79.31%,41.83%,and 57.10%,respectively.At the genus level,a total of 66 fungal genera were detected.The relative abundance of Fusarium in SX,SL,FX,FL,WX and WL was 7.33%,19.32%,2.70%,4.24%,10.71% and 23.87%,respectively.Based on q-PCR analysis,there were significant differences in the number of Fusarium oxysporum and Fusarium solani between methyl bromide fumigation and replanted treatments,i.e.,clay loam > sandy loam > loam.Fusarium was the main pathogen causing ARD.This shows that ARD is the most serious under replanted clay loam condition.6.The results of four samples in the field showed that there were significant differences in the total phenolic acids between methyl bromide fumigation and replanted treatments,among which the clay loam showed the greatest difference,followed by sand loam and loam.The contents of phlorizin,phloretin,cinnamic acid and p-hydroxybenzoic acid were also highest in clay loam,followed by loam and lowest in sandy loam.As time goes on,the total amount of phenolic acid accumulated in the soil gradually increased,and the contents of phlorizin,phloretin,cinnamic acid and p-hydroxybenzoic acid also gradually increased.