转基因棉花种植对根际土壤微生物群落功能多样性的影响

应用Biolog方法对两种转基因棉花及其亲本非转基因棉花根际土壤微生物的单一碳源利用水平进行了比较分析,探讨转基因棉花种植对其根际土壤微生物群落功能多样性的影响.结果表明：与非转基因亲本相比,在苗期、蕾期、吐絮期、衰老期转基因棉花种植对根际土壤微生物群落碳源利用能力、Shannon功能多样性指数和均匀度指数的影响均不显著,而在花铃期根际土壤微生物群落碳源利用能力和Shannon功能多样性指数显著降低.主成分分析表明,花铃期转基因棉花与非转基因棉花根际土壤微生物碳源利用在两主成分轴上的分异较大,碳源利用模式差异显著.     

连作条件下毛鸡骨草根际土壤微生物群落功能多样性变化特征

毛鸡骨草是治疗肝病的重要中草药之一,而连作障碍致其产量和品质下降。从主产区广西玉林分别采集正茬、重茬和连作三年的毛鸡骨草根际土壤样品,以种植前水稻土壤为对照,采用Biolog GN2 平板碳源分析技术,研究连作条件下根际土壤微生物群落功能多样性变化特征,以揭示其连作障碍的原因。结果表明,连作导致根际土壤微生物功能多样性显著降低,微生物利用各类碳源的能力下降。主成分分析(PCA)表明,不同种植年限的毛鸡骨草根际土壤微生物群落结构之间存在显著差异,且均与种植前对照明显不同,而同一种植年限不同生长期土壤微生物碳代谢群落结构虽有差异,但并不显著。相关分析表明,其产量与微生物功能多样性指数(如Shannon,Simpson,Mclntosh)以及平均吸光值(AWCD)值正相关,而与第一主成分(PC1)呈显著负相关,说明连作条件下其产量的降低在一定程度上与土壤微生物功能多样性的降低和群落结构的改变有关。     

棉花长期连作对新疆土壤细菌群落结构的影响

新疆部分棉区发生连作障碍后与其他地区有所不同,能自发恢复并长期保持高产、稳产,为了查明该类棉田土壤细菌群落结构在连作障碍发生及自发恢复整个过程中的演替规律。以未开垦土地作为对照,利用16S rRNA-PCR-DGGE(polymerase chain reactiondensity gradient gel electrophoresis)法对比研究了新疆阿克苏棉区分别连作1、3、5、10、15和20a棉田1—30 cm深度土壤细菌群落结构组成。结果表明未开垦土地细菌多样性指数丰富度最高,多样性和均匀度指数最低。随着棉花连作年限的延长,土壤细菌群落丰富度指数不断下降,而多样性和均匀度指数逐渐增大。当连作年限继续延长至10a后各指数出现恢复或趋于达到一个新的相对稳定状态。聚类分析显示7个样品分别聚为3簇,其中连作3a的样品差异最大,相似度仅有44%,而连作10a后的样品和对照较为相似。主成分分析也有类似的结果。对比回收的部分序列显示,序列间相似性在88%以上,分属于Microbacterium、Uncultured Chloroflexi bacterium、TM7 Phylum sp.Canine、Flavobacteria等4个不同菌属。分析认为棉花长期连作对该地区土壤细菌群落结构组成影响很大,但随着连作年限延长至5a以后,细菌群落结构组成能自发趋于稳定和回升。此外,对比棉田细菌群落结构整体变化规律和棉花产量的增减及病虫害发生规律发现,在棉花长期连作过程中两者有很强的关联性。     

施用棉秆炭对新疆连作棉花根际土壤微生物群落结构和功能的影响

以棉秆移除(NPK)和棉秆还田(NPKS)为对照,采用平板计数、Biolog和DGGE等3种方法,研究了棉秆移除基础上施用常量棉秆炭(22.50 t·hm^-2,NPKB-1)和增量棉秆炭(45.00 t·hm^-2,NPKB-2)对新疆连作棉花根际土壤微生物数量、群落功能和结构多样性的影响.结果表明：与NPK和NPKS处理相比,棉秆炭施用显著增加了连作棉田根际土壤中细菌和放线菌数量;NPKB-1处理真菌数量显著高于NPK处理,但增量棉秆炭NPKB-2处理与NPK处理差异不显著;2个棉秆炭处理的真菌数量均低于NPKS处理.棉秆炭处理AWCD值较高,显著提高了微生物丰富度指数,可促进利用糖类、氨基酸类和羧酸类碳源的微生物生长,尤其是利用与根系分泌物相关的酚酸类碳源的微生物.DGGE电泳结果表明,施用棉秆炭(尤其是增量棉秆炭)后,土壤细菌DGGE图谱条带数增多,增加了土壤中芽单胞菌门、酸杆菌门、变形菌门和放线菌门中一些菌群的丰度.UPGMC聚类分析表明,NPKB-2处理明显区别于其他处理,而NPKS、NPK和NPKB-1处理细菌群落结构相似.表明高量施用棉秆炭可显著提高棉花根际土壤微生物多样性,并明显改变土壤细菌群落结构,对连作棉田生态系统健康有改善作用.     

不同连作年限怀牛膝根际土壤理化性质及微生物多样性

以不同连作年限怀牛膝根际土壤为材料,采用土壤农化分析技术和磷脂脂肪酸生物标记法,对土壤理化性质以及根际微生物群落结构进行分析。结果表明:怀牛膝连作会使大部分大量元素(全磷、碱解氮、速效磷和速效钾)含量上升,而全氮、全钾的变化并无明显趋势。全量钙、全量镁、全量锰和有效锌的含量也会随着连作年限的增加而增加。研究发现,怀牛膝连作1a的土壤与对照相比,根际土壤微生物群落结构差别不大,但是与连作10a和30a的土壤相比微生物多样性却发生了明显变化。土壤中总PLFAs、细菌、革兰氏阴性菌Gram(-)及真菌含量都随连作年限增加而明显上升,微生物多样性增加,且革兰氏阳性菌Gram(+)/革兰氏阴性菌Gram(-)的比值随着连作年限的增加而下降。此外,土壤中一些嗜热解氢杆菌和真菌等参与土壤物质循环和木质素降解的微生物类群数量明显增加,假单胞菌等有益微生物类群也显著增多,这是牛膝连作促进作用的生物学基础。研究用药用植物怀牛膝证明了植物根际微生物结构和功能多样性对植物连作促进或连作抑制作用的产生与控制的生态学意义。     

不同连作年限土壤对茄子土壤生物学活性的影响及其嫁接调节

探讨了不同连作年限土壤对茄子根际土壤微生物数量、土壤酶活性的影响及其相关性和嫁接对重要相关因子的调节作用。结果表明:随着连作年限的增加,茄子根际土壤细菌数量和放线菌数量呈下降趋势,真菌数量呈增加趋势;根际土壤中的过氧化氢酶、过氧化物酶、多酚氧化酶、蛋白酶的活性呈降低趋势;土壤微生物数量和土壤酶活性之间有显著的相关性。其中过氧化氢酶、过氧化物酶、多酚氧化酶、蛋白酶是影响根际土壤中细菌和放线菌数量的主要因子,蛋白酶是影响根际土壤中真菌数量的主要因子。嫁接能提高土壤酶活性,缓解连作土壤带来的胁迫。     

大豆连作对土体和根际微生物群落功能的影响

试验采用Biolog方法在大田试验条件下研究了不同连作年限大豆在结荚期和收获期根际和土体微生物群落功能多样性的变化.试验结果表明,在结荚期和收获期根际微生物群落功能多样性、均匀度指数和AWCD均显著高于土体.在结荚期迎茬和连作8a的土体微生物多样性、AWCD均高于正茬和连作4a土体;在收获期正茬和迎茬处理的土体微生物多样性、AWCD高于连作4a和8a.结荚期迎茬、连作4a和8a处理的根际微生物群落AWCD均显著高于收获期,说明在大豆植株生长旺盛的结荚期微生物群落的根际效应比收获期更明显.在这两个生长期降解氨基酸,糖类和羧酸类碳源的微生物可能是连作影响的主要土体微生物类群.     

连作对芝麻根际土壤微生物群落的影响

采用稀释平板计数法研究了不同连作年限处理芝麻根际土壤细菌、真菌、放线菌、芽孢杆菌、尖孢镰刀菌(FO)和青枯劳尔氏菌(RS)数量的变化情况。结果表明,随着连作年限的增加,芝麻根际土壤中细菌和放线菌的数量下降,而真菌的数量则呈上升趋势。新种芝麻地根际土壤芽孢杆菌数量显著高于连作2a处理和连作5a处理,而连作2a处理又显著高于连作5a处理;连作5a芝麻根际土壤尖孢镰刀菌数量显著高于新种地、轮作1a和连作2a等3个处理;轮作1a、连作2a及连作5a等3个处理青枯劳尔氏菌数量显著高于新种地处理。说明连作导致土壤微生物环境恶化,引起根际微生物区系结构发生定向改变。连作2a与轮作1a相比,各菌群(类群)数量差异均不显著。     

连作对白肋烟根际土壤细菌群落多样性的影响

以种植白肋烟1年、2年和4年的土壤为研究对象,采用末端限制性片段长度多态性(T-RFLP)技术分析根际土壤细菌群落的动态变化.结果表明:白肋烟根际土壤细菌群落香农指数和丰富度指数随着种植年限的增加呈现出先增后减的趋势,连作4年后细菌群落的多样性水平显著降低,细菌群落结构较单一.随着种植年限的增加,根际土壤细菌群落与对照的相似性指数逐渐降低.种植年限为1年、2年的土壤和对照土壤中放线菌门放线菌纲是优势类群,种植年限为4年的土壤中放线菌纲所占的比例下降,而厚壁菌门的芽孢杆菌纲成为优势类群.白肋烟连作使根际鞘氨醇单胞菌属和链霉菌属等益生菌数量减少、蜡状芽孢杆菌等潜在致病菌增加,破坏了烟草根际土壤微生物群落的平衡,使其微生态环境恶化.     

加工番茄连作对农田土壤酶活性及微生物区系的影响

通过盆栽试验,研究了连作及活性炭处理对加工番茄土壤微生物数量及土壤酶活性的影响。结果表明:加工番茄连作对其微生物区系及土壤酶活性产生一定影响。随连作年限的增加,过氧化氢酶活性呈上升趋势,而脲酶、多酚氧化酶、蔗糖酶、磷酸酶活性呈下降趋势,通过活性碳处理后,脲酶、土壤蔗糖酶、多酚氧化酶、磷酸酶活性比对照(未活性炭处理)增加,而过氧化氢酶活性降低。随连作年限的增加,连作2a和3a的细菌数量分别比1a降低12.1%和16.8%,真菌数量连作2a和3a分别比种植1a时提高20%和60%,放线菌数量连作2a和3a土壤中分别是种植1a的1.04倍和1.12倍,通过活性碳处理后,细菌的数量在连作2a和3a时分别比对照增加5.8%和1.6%,放线菌和真菌数量比对照分别降低13.0%、23.1%和8.3%、50%。反硫化细菌数量随连作年限延长而增加,硝酸细菌和好氧性自身固氮菌数量减少。可见通过活性炭处理可减轻自毒物质对加工番茄土壤酶和微生物的影响,从而缓解加工番茄连作障碍。     

生物炭对温室黄瓜不同连作年限土壤养分和微生物群落多样性的影响

以温室黄瓜连作6年和10年土壤添加质量比为5%生物炭为处理,以不添加生物炭为对照,采用桶栽的方法,研究了生物炭对不同年限连作土壤养分和微生物群落多样性的影响.结果表明: 与连作土壤相比,生物炭处理的连作6年土壤的黄瓜单株产量提高11.4%,连作10年土壤产量提高62.8%.施入生物炭显著降低了2种连作土壤容重,显著提高了有机质、速效磷含量、阳离子交换量(CEC)和pH;显著提高了土壤细菌数量和细菌/真菌,降低了真菌和尖孢镰刀菌数量,使土壤类型由真菌型向细菌型转变,尤其对连作10年土壤作用最为明显,土壤细菌和细菌/真菌分别是未处理的2.00和3.64倍,真菌和尖孢镰刀菌数量分别是未处理的54.8%和55.9%.土壤微生物群落碳源利用分析表明,10年连作土壤施入生物炭可显著提高土壤微生物活性、Shannon指数和均匀度指数,分别是未处理的1.50、2.14和1.31倍,同时显著提高了土壤微生物对糖类、氨基酸类、酚酸类和胺类碳源的利用强度,分别是未处理的1.62、1.81、1.74和1.93倍.相关性分析表明,土壤容重、速效磷含量、CEC和pH 4个指标对微生物群落变化的影响较显著.综上,生物炭通过对连作土壤理化性质及土壤微生物生态系统的改善,优化了黄瓜根区环境,促进了黄瓜产量的提高,缓解了温室黄瓜连作障碍.     

施用生物质炭和羊粪对宿根连作茶园根际土壤微生物的影响

茶树长期宿根连作会导致土壤酸化严重、土壤营养不平衡、根际土壤微生态结构恶化.研究生物质炭、羊粪对宿根连作茶树生长以及土壤微生物群落结构和功能的影响,探讨其对宿根连作茶树土壤环境的调节效果,可为宿根连作茶园土壤微生态的改善提供理论依据.本研究以宿根连作20年的茶园土壤为对象,利用Biolog技术和磷脂脂肪酸(PLFA)方法,研究施用生物质炭(40 t·hm^-2)和羊粪替代部分化肥对连作茶树产量和品质、土壤化学性质、根际土壤微生物群落功能和结构的影响.结果表明:施用生物质炭、羊粪1年后酸化茶园土壤的p H和土壤养分显著提高,并提高了茶叶产量.与常规施肥相比,施用生物质炭、羊粪替代部分化肥处理显著提高了茶树根际土壤微生物的碳源代谢活性和微生物多样性,对胺类、碳水化合物和聚合物的相对利用有所增加.生物质炭和羊粪处理的根际土壤总PLFA含量分别比常规施肥处理提高了20.9%和47.5%,羊粪处理还显著降低了总饱和/总单一不饱和脂肪酸比例.生物质炭和羊粪可改善茶园土壤酸化状况和土壤肥力,对宿根连作茶树的生长具有促进作用,两种措施均不同程度地增加了土壤微生物的代谢活性和微生物量、提高了多样性指数、改善了微生物群落结构.施用生物质炭和羊粪可作为调节宿根连作茶园根际土壤微生态的有效措施.     

16S rRNA-Based PCR-DGGE Analysis of Actinomycete Communities in Fields with Continuous Cotton Cropping in Xinjiang, China

The purpose of this study was to examine the variations in the microbial community structure of soil actinomycetes in fields with continuous cropping of cotton in Xinjiang Autonomous Region, China. Soil samples were collected from four depths in fields with 7-year continuous cotton cropping. The community structure of soil actinomycetes was examined using the 16S rRNA-based polymerase chain reaction–density gradient gel electrophoresis (PCR-DGGE) techniques. The microbial diversity indices of the soil samples from different depths generally decreased along with the period of continuous cotton cropping. When the period of continuous cropping of cotton reached 5 years, the diversity indices rose again and gradually stabilized at a level slightly lower than that of soils with original ecology (i.e., 0-year cotton cropping). Cluster analysis showed that at the 1–20-cm depth, the actinomycete community structure of the soil subjected to 1-year cotton cropping was similar to that of soil subjected to 0-year cotton cropping, whereas that of soils after 3-year continuous cotton cropping showed high similarity. At the 21–40-cm depth, the actinomycete community structure showed various changes but generally recovered to its original pattern after repeated fluctuations. Principal component analysis showed that at the 1–30-cm depth, the actinomycete community structure varied similarly regardless of the period of continuous cotton cropping. In contrast, there were no clear actinomycete community structure variation trends at the 31–40-cm soil depth. Homology comparison of sequences recovered from the DGGE bands showed that the obtained sequences shared similarities >88 %. Alignment with the known homologous sequences indicated a lack of microorganisms related to soil-borne cotton diseases. Continuous cotton cropping exerted significant influences on the community structure of soil actinomycetes in Xinjiang Autonomous Region, which were largely determined by the soil depth and the period of continuous cotton cropping. The microbial diversity of soil actinomycete communities gradually recovered after 5-year continuous cropping. Thereafter, a new actinomycete community structure that was beneficial for continuous cropping of cotton was formed and stabilized each year.     

Effects of continuous cucumber cropping and alternative rotations under protected cultivation on soil microbial community diversity

The diversity of soil microbial communities as affected by continuous cucumber cropping and alternative rotations under protected cultivation were evaluated using community level physiological profiles (CLPP) and random amplified polymorphic DNA (RAPD) analysis. The soils were selected from six cucumber cropping systems, which cover two cropping practices (rotation and continuous cropping) and a wide spectrum for cucumber cropping history under protected cultivation. Shannon–Weaver index and multivariate analysis were performed to characterize variations in soil microbial communities. Both CLPP and RAPD techniques demonstrated that cropping systems and plastic-greenhouse cultivation could considerably affect soil microbial functional diversity and DNA sequence diversity. The open-field soil had the highest Shannon–Weaver index (3.27 for CLPP and 1.50 for RAPD), whereas the lowest value occurred in the 7-year continuous protected cultivation soil (3.27 for CLPP and 1.50 for RAPD). The results demonstrated that continuous plastic-greenhouse cultivation and management can cause the reduction in the species diversity of the biota. Higher Shannon–Weaver index and coefficients of DNA sequence similarity were found in soils under rotation than those under continuous cropping. Cluster analysis also indicated that microbial community profiles of continuous cultivation soils were different from profiles of rotation soils. The reduction in diversity of microbial communities found in continuous cultivation soils as compared with rotation soils might be due to the differences in the quantity, quality and distribution of soil organic matter. Section Editor: D. E. Crowley     

大棚蔬菜轮/连作系统土壤肥力与微生物因子综合评价

从土壤肥力与微生物因子探索连茬障碍机理,以期为其提供科学依据。研究草莓番茄轮作(RST)、番茄连作4年(CT4)和番茄连作10年(CT10)3种蔬菜种植模式根际与非根际土壤微生物区系及生理菌群,并对土壤肥力与微生物生物因子进行主成分分析。结果表明根际土壤微生物三大类群和生理菌群数量均高于非根际,根际效应显著。番茄连作根际与非根际土壤细菌和放线菌数量呈现先增加后减少趋势;真菌数量呈线型增加趋势,CT4和CT10在根际与非根际较RST分别增加9.09%和2.11%、75.48%和57.72%。番茄连作根际土壤硝化细菌和好气性自生固氮菌数量的减少,氨化细菌与好气性纤维素分解菌在短期连作表现为增加长期减少的变化趋势;解钾菌、无机磷和有机磷细菌数量在根际与非根际土壤均减少。在6种研究的种植模式中,RST根际土壤状况最好,其次为CT4的根际与RST非根际土壤,CT10的根际土壤、CT4与CT10非根际土壤状况最差。结论是蔬菜连作造成土壤质量下降,连作年限越长下降越显著。     

桑树-大豆间作对盐碱土碳代谢微生物多样性的影响

针对桑树-大豆间作可缓解盐碱土危害的特点,利用Biolog^TM技术研究了桑树-大豆间作对盐碱土作物根际碳代谢微生物多样性的影响.结果表明：表征土壤微生物代谢活性的平均颜色变化率(AWCD)在桑树-大豆间作下明显高于桑树单作和大豆单作,其中间作大豆的AWCD最高,单作桑树最低.桑树-大豆间作的土壤微生物均匀度指数高于单作,而土壤微生物的多样性指数和优势度指数在间作和单作之间差异不显著,说明桑树-大豆间作改变了盐碱土根际微生物群落结构组成,提高了根际微生物群落多样性.主成分分析表明,桑树-大豆间作和单作下土壤微生物的碳源利用模式出现分异,主要碳源为糖类、羧酸和聚合物类物质等.盐碱土pH和盐度是制约微生物群落多样性的主要因素,间作有效降低了土壤pH和盐度,促进了土壤微生物群落多样性的提高.     

Transgenic Bt cotton has no apparent effect on enzymatic activities or functional diversity of microbial communities in rhizosphere soil

A transgenic Bt cotton (Sukang-103) and its non-Bt cotton counterpart (Sumian-12) were investigated to evaluate the potential risk of transgenes on the soil ecosystem. The activities of urease, phosphatase, dehydrogenase, phenol oxidase, and protease in cotton rhizosphere were assayed during the vegetative, reproductive, and senescing stages of cotton growth and after harvest. A Biolog system was used to evaluate the functional diversity of microbial communities in soils after a complete cotton growth cycle. Enzymatic activities in soils amended with cotton biomass were also assayed. Results showed that there were few significant differences in enzyme activities between Bt and non-Bt cottons at any of the growth stages and after harvest; amendment with cotton biomass to soil enhanced soil enzyme activities, but there were no significant difference between Bt and non-Bt cotton; the richness of the microbial communities in rhizosphere soil did not differ between Bt and the non-Bt cotton, and close to that of control soil; the functional diversity of microbial communities were not different in rhizosphere soils between Bt and non-Bt cotton. All results suggested that there was no evidence to indicate any adverse effects of Bt cotton on the soil ecosystem in this study.