不同土壤质地对平邑甜茶幼苗连作障碍程度的影响

Effects of Different Soil Textures on the Degree of Replanted Disease of Malus hupehensis Rehd

【目的】以平邑甜茶幼苗作为试材,研究不同土壤质地苹果园连作障碍发生程度及其差异机制,以便根据连作障碍可能发生的严重程度采用适宜的防治措施。【方法】取烟台莱州3种不同质地老果园土,在盆栽条件下设置连作砂壤土、连作壤土、连作黏壤土及各个质地土壤对应溴甲烷熏蒸处理,共6个处理,测定不同处理盆栽幼苗的生物量、土壤微生物数量、土壤酶活性、根系保护性酶活性、丙二醛(MDA)含量,使用实时荧光定量(qPCR)技术检测老果园土壤中主要有害真菌的数量变化。因3种土壤条件不同,故分别以3种土壤溴甲烷处理与各自连作处理上述指标的差异来表示连作障碍发生的程度,差异越大,连作障碍程度越严重。同时采用高效液相色谱法测定3种连作土壤中的酚酸类物质含量。【结果】与各自连作对照相比,黏壤土、砂壤土和壤土溴甲烷熏蒸处理植株干样质量分别提高了98.9%、87.9%和54.4%,说明黏壤土连作与溴甲烷处理差异最大,连作障碍程度最严重。与各自连作对照相比,黏壤土、砂壤土、壤土溴甲烷熏蒸处理植株的根系保护酶活性均显著提高,根呼吸速率显著增加,MDA含量明显降低。其中超氧化物歧化酶(SOD)活性分别是各自连作对照的2.63、1.80和1.53倍;过氧化物酶(POD)活性分别是连作的3.02、2.01和1.62倍,过氧化氢酶(CAT)活性分别是连作的3.25、2.61和2.11倍。黏壤土根系保护性酶差异最大,说明在连作黏壤土条件下,根系胁迫更严重。与各自连作对照相比,黏壤土、砂壤土、壤土溴甲烷熏蒸处理植株根呼吸速率分别提高了91.3%、69.4%和36.0%;MDA含量分别降低了51.3%、48.9%和33.1%。脲酶活性分别比连作降低了68.2%、64.2%和54.4%;磷酸酶活性分别比连作降低了25.6%、18.6%和8.18%。黏壤土、砂壤土和壤土溴甲烷熏蒸处理比各自连作对照真菌数量降低了85.8%、58.1%和72%,尖孢镰孢菌拷贝数比各自连作处理分别降低了87.5%、70.1%和66.3%,且连作黏壤土条件下尖孢镰孢菌拷贝数最多。连作条件下黏壤土的实测酚酸总量最高,为41.30 mg·kg^(-1)。【结论】3种不同土壤质地中,黏壤土酚酸类物质含量高、土壤中尖孢镰孢菌为主的有害真菌最多、根系胁迫最严重,最终表现为连作平邑甜茶幼苗与溴甲烷熏蒸处理的生物量差异最大,而壤土则相反。

【Objective】The occurrence degree and mechanism of apple replant disease(ARD) in the apple orchards with different soil textures were studied with the Malus hupehensis Rehd. seedlings as experimental material, so as to adopt appropriate control measures according to the severity of ARD.【Method】Pot experiment including six treatments, which were the replanted sandy loam soil and its methyl bromide fumigation treatment, the replanted loam soil and its methyl bromide fumigation treatment,and the replanted clay loam soil and its methyl bromide fumigation treatment, was carried out. And the soils were from Laizhou,Yantai. The biomass, root protective enzymes activities and malonaldehyde(MDA) contents of M. hupehensis seedlings, changes of the number of soil bacteria, fungi and actinomycetes, and soil enzyme activities were measured by conventional method. The number of the F. oxysporum was detected by a real-time quantitative PCR detection system. Because of the three different soil conditions, the differences of the above indicators between the three soil treatments of methyl bromide fumigation and their replanted soil treatments were used to indicate the degree of ARD. The greater of the difference, the more serious the ARD was. At the same time, the content of phenolic acids of three kind of soils was determined by high performance liquid chromatography.【Result】 Compared with their respective controls, the dry weight of plants in the methyl bromide fumigated clay loam, sandy loam soil and loam soil increased by98.9%, 87.9%, and 54.4%, respectively. From the results, we could see that the most difference occurred between the replanted soil and its methyl bromide fumigation 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 plants treated with methyl bromide fumigation in clay loam, sandy loam and loam significantly increased the root activity of superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) and decreased the MDA content. The activity of SOD was 2.63, 1.80 and 1.53 times higher than that of the control, POD activity was 3.02, 2.01 and1.62 times higher than that of the control and CAT activity was 3.25, 2.61 and 2.11 times higher than that of the control, respectively.The difference of root protective enzymes was the greatest in clay loam, which indicated that root stress was more serious in the replanted clay loam soil. Compared with their respective controls, the root respiration rates of clay loam, sandy loam and loam treated with methyl bromide fumigation increased by 91.3%, 69.4% and 36.0%, respectively. MDA content decreased by 51.3%,48.9% and 33.1%, respectively. Urease activity decreased by 68.2%, 64.2% and 54.4%, respectively, and phosphatase activity decreased by 25.6%, 18.6% and 8.18%, respectively, compared with their respective controls. The amount of fungi treated with methyl bromide fumigation in clay loam, sandy loam soil and loam soil decreased by 85.8%, 58.1% and 72%, respectively. The copy number of F. oxysporum decreased by 87.5%, 70.1% and 66.3%, respectively, and the copy number of F. oxysporum was the highest in the replanted clay loam soil. Under replanted conditions, the total phenolic acid content in clay loam soil was the highest, which was 41.30 mg·kg-1.【Conclusion】 Among three soils of different texture, the degree of ARD was the most serious in clay loam soil on account of the highest total content of phenolic acid, the most harmful fungi mainly in F. oxysporum and the most serious root stress,while the degree of ARD in loam soil was the slightest.