广谱抗真菌蛋白转基因水稻秸秆模拟还田对土壤真菌群落结构的影响

为探讨广谱抗真菌蛋白转基因水稻秸秆降解对土壤真菌群落结构的影响,本文在室温条件下进行田间秸秆还田模拟试验,设不添加秸秆(S)、添加转基因水稻‘转品1’秸秆(S-Z1)、添加转基因水稻‘转品8’秸秆(S-Z8)、添加非转基因水稻‘七丝软粘’秸秆(S-CK)4个土壤处理,采用传统的平板计数法和变性梯度凝胶电泳(denatured gradient gel electrophoresis,DGGE)技术,分析广谱抗真菌蛋白转基因水稻秸秆模拟还田过程中土壤可培养真菌数和土壤真菌群落的变化情况。平板计数结果表明,在秸秆降解的第40 d,转基因水稻秸秆处理(S-Z1、S-Z8)与非转基因水稻秸秆处理(S-CK)土壤之间的可培养真菌数差异显著,但秸秆降解中后期(50~90 d),S-Z1、S-Z8和S-CK之间土壤可培养真菌数的差异均不显著。真菌18S r RNA的PCR-DGGE图谱显示,S-Z1、S-Z8和S-CK在秸秆降解过程中没有显著不同的条带出现,仅有个别条带在亮度上存在差异。DGGE图谱条带多样性分析结果表明,在秸秆降解的个别时间段,S-Z1、S-Z8和S-CK之间在丰富度和Shannon-Wiener多样性指数上存在显著差异,而在秸秆降解的整个过程均匀度指数差异均不显著。对DGGE主要条带和差异性条带进行克隆测序后发现,子囊菌占最大比重,其次为担子菌、壶菌,而在转基因和非转基因土壤处理间亮度上存在差异的条带属于子囊菌。以上研究结果表明,广谱抗真菌蛋白转基因水稻秸秆降解对土壤真菌群落结构的影响是短暂的、不持续的。     

铜胁迫对抗虫转基因水稻根际土壤微生物的影响

根际土壤微生物群落是联系土壤环境与作物生长的重要纽带,也是转基因作物环境安全评价的主要指标,而Cu胁迫对转基因水稻根际土壤微生物的影响目前尚不清楚。本研究基于盆栽试验,采用高通量测序等技术研究Cu胁迫(Cu含量100 mg/kg)对抗虫转基因水稻华恢1号(HH)及其亲本非转基因水稻明恢63(MH)农艺性状及成熟期根际土壤微生物的影响,并以不施加Cu胁迫处理为对照。结果显示:Cu胁迫显著降低了水稻株高、生物量及产量;Cu胁迫改变了水稻根际土壤总氮、铵态氮含量及氧化还原电位值,而种植转基因水稻仅降低了根际土壤氧化还原电位值;Cu胁迫没有影响水稻根际土壤细菌丰度,但降低了细菌群落Alpha-多样性,改变了水稻根际土壤细菌群落组成和群落结构;相同Cu含量胁迫下,HH和MH水稻生长指标及根际土壤细菌群落结构及组成差异较小。上述研究表明,Cu胁迫抑制了水稻农艺性状及根际土壤细菌群落,但种植抗虫转基因水稻没有影响水稻植株及根际土壤细菌群落对Cu胁迫的抗性。     

种植转双价抗真菌基因水稻对根际微生物群落及酶活性的影响

对转几丁质酶和葡聚糖酶双价抗真菌基因抗病水稻七转39种植后的根际土壤微生物群落和酶活性进行了分析。研究结果表明,七转39根内生真菌和细菌数量显著低于非转基因阴性对照七丝软粘和常规水稻竹籼B,根际土壤中真菌和细菌数量也少于七丝软粘,与竹籼B数量接近。在水稻抽穗期测定,转基因水稻根际土壤过氧化氢酶、多酚氧化酶、蔗糖酶和脲酶活性以及可溶性有机质、氮、磷含量均与对照无显著差异。转基因水稻残体腐解过程中土壤腐殖酸含量变化与七丝软粘一致。与对照相比, 种植七转39未对下茬水稻的生长产生显著影响。     

转基因抗虫棉对棉田土壤细菌数量及群落结构的影响

以转基因抗虫棉（GK12、33B）及其亲本对照（SM、5415）为材料,利用稀释平板法和基于rRNA基因PCR扩增的变性梯度凝胶电泳（DGGE）技术研究了棉田土壤中细菌数量和群落结构在转基因棉种植第一年的动态变化。结果表明：棉田土壤细菌数量随棉花生育期逐渐增加,于花铃中期达到最大值,转基因棉与其亲本之间细菌数量差异不显著。放线菌数量随生育期变化较小,转基因棉与其亲本之间在花铃中期出现显著差异。DGGE结果显示,转基因棉和亲本都存在丰富且相似的条带,聚类分析表明大多数转基因棉和亲本间条带相似性达80%以上,根据不同的生理期分成2个簇;主成分分析表明转基因棉和亲本细菌群落结构没有显著差异,但在不同生育期存在一定差异,表明生育期是影响细菌群落结构的主要因素,与聚类分析结果相吻合。研究结果初步说明转基因棉对棉田土壤细菌数量和群落结构没有显著影响。     

抗盐碱转基因大豆对根际与非根际土壤氨氧化古菌多样性的影响

采用PCR—DGGE技术,研究了抗盐碱转基因大豆（SRTS）对根际与非根际土壤氨氧化古菌（AOA）群落多样性的影响。结果表明,在非根际土壤中,SRTS的氨氧化古菌DGGE条带数、多样性指数显著高于其受体亲本黑农35和其他两种大豆处理,而均匀度指数较低;在根际土壤中,SRTS的DGGE条带数和多样性指数均高于其受体亲本,但并不显著,其均匀度指数则显著高于其他处理;每种大豆自身根际与非根际比较显示,SRTS非根际氨氧化古菌DGGE条带数、多样性指数明显高于根际,均匀度指数却低于根际,而其受体亲本与其他两个处理反之。聚类分析结果表明,SRTS的DGGE带谱与其他大豆处理差异较大,且自身非根际与根际处理差异显著,与其受体亲本黑农35相似性很低。测序结果表明,在SRTS处理中特有条带12、15和优势条带13、14均属于Uncultured crenarchaeote。在盐碱土壤生态系统中,SRTS提高了非根际土壤氨氧化古菌群落的多样性,但对根际土壤中氨氧化古菌的群落多样性有一定的抑制作用。     

再植枸杞根际真菌群落对长期连作的响应研究

受枸杞自身种植特点和道地产区土地资源限制,连作障碍已成为制约宁夏枸杞产业可持续发展的主要因素之一,导致严重的经济损失和生态问题。前期研究表明,连作能够显著影响再植枸杞根际土壤细菌的群落结构和多样性,但就连作对真菌群落结构和功能的影响目前仍不清楚。本文利用实时荧光定量PCR和高通量测序技术,研究连作对再植枸杞根际真菌群落丰度及多样性的影响。实时荧光定量PCR分析表明,与对照样地相比,连作显著促进再植枸杞根际及非根际土壤中细菌和真菌的丰度。但连作对真菌的促进作用明显高于细菌,导致细菌/真菌比例失衡,使再植枸杞根际及非根际土壤微生物环境偏向于真菌型。对测序结果的分析发现,所测定样地中枸杞根际及非根际土壤中的优势真菌门分别为子囊菌门、担子菌门、接合菌门、壶菌门及球囊菌门,其中连作地再植枸杞根际子囊菌门的相对丰度较对照样地显著降低,而接合菌门的相对丰度则显著增加(P0.05)。FUNGuild真菌功能预测也证实连作显著抑制再植枸杞根际土壤丛枝菌根真菌的相对丰度(P0.05)。基于距离的冗余分析(db-RDA)结果表明,土壤pH、电导率、硝态氮和有效磷含量是影响枸杞根际土壤真菌群落变化的主要因子(P0.05),而土壤硝态氮和有效磷含量则是解释非根际土壤真菌群落变化的主要因子(P0.05)。这些结果说明长期施用化肥可能是改变连作地再植枸杞根际土壤真菌群落结构及枸杞-真菌互作关系的主要因素之一。这一研究结果为理解枸杞连作障碍的形成机制提供理论基础。     

长期不同养分缺乏对冬油菜土壤微生物群落组成及多样性的影响

为探明长期不同养分缺乏对冬油菜根际与非根际土壤细菌和真菌群落组成结构及多样性的影响,以江汉平原中稻 -冬油菜田间定位试验为研究对象,选取施磷钾肥不施氮肥(-N)、施氮钾肥不施磷肥(-P)、施氮磷肥不施钾肥(-K)和施用氮磷钾肥(NPK)4个处理,于成熟期采集各处理冬油菜非根际土壤(标记为 0)和根际土壤(标记为 1)。基于 Illumina MiSeq高通量测序技术对土壤样本的细菌 16S rDNA和真菌 ITS进行扩增、测序,并结合生物信息学分析根际和非根际土壤中细菌和真菌群落组成和多样性。结果表明:长期养分的投入缺乏造成土壤 pH和养分含量均有不同程度的降低。相比非根际土壤,冬油菜根际土壤的有机质、有效磷和速效钾含量有富集的趋势,而缓效钾差异不显著。长期平衡施肥(NPK处理)条件下,油菜根际土壤的细菌多样性比非根际土壤高,而根际真菌多样性低于非根际土壤。门分类水平上,各处理土壤中的细菌优势物种是绿弯菌门、酸杆菌门和变形菌门,平均相对丰度分别为 30.9%、25.7%和 17.6%;真菌优势物种是子囊菌门和担子菌门,平均相对丰度分别为 52.0%和 6.3%。相比 NPK处理,-N、-P和 -K处理对冬油菜根际和非根际细菌、根际真菌群落分布有显著影响,但对非根际真菌群落分布无明显作用,从而导致各处理的优势属种类型和相对丰度差异显著。冗余分析结果表明,pH、速效钾和有效磷含量对土壤细菌群落结构的影响最为显著,而有机质和碱解氮含量对真菌群落结构的影响最为明显。可见,长期不同养分缺乏会显著改变冬油菜根际细菌和真菌群落的组成结构及其多样性,尤其是缺磷、缺氮,其次是缺钾。因此,平衡施肥仍是维持农田微生物生态系统平衡与稳定的重要措施。     

转基因玉米双抗12-5对根际土壤酶活性及 微生物多样性的影响

采用田间试验研究了转基因玉米瑞丰1号-双抗-12-5(RF1-12-5)种植对根际土壤酶活性、微生物群落的影响,可为RF1-12-5的环境释放和商业化应用提供科学的安全性评价数据支持。研究结果表明:①在5个生育期内,RF1-12-5与其非转基因对照品种瑞丰1号(RF1)根际土壤碱性蛋白酶、脲酶和酸性转化酶活性均没有显著性差异;RF1-12-5根际土壤过氧化氢酶活性在收获期、碱性磷酸酶活性在乳熟期显著低于RF1,其他生育期差异不显著。②在5个生育期内,RF1-12-5与RF1根际土壤微生物群落的Shannon多样性指数、McIntosh均匀度指数和Simpson优势度指数均不存在显著性差异,主成分分析未发现RF1-12-5与RF1根际微生物功能多样性存在规律性差异。     

黑土农田施加AM菌剂对大豆根际菌群结构的影响

为揭示在黑土农田条件下施加丛枝菌根(AM)菌剂对作物根际微生物群落的影响,试验以大豆为研究对象,田间播种时分别施加根内球囊霉(Glomus intraradices,GI)和摩西球囊霉(Glomus mosseae,GM)两种AM菌剂,以单施化肥处理(F)和不施加AM菌剂及化肥处理(CK)作为对照,采用传统与现代分子生物学手段,研究大豆根际土壤中菌群结构及根系内AM真菌多样性。结果表明:GI、GM处理的大豆菌根侵染率最高达到78.3%和86.6%;GI、GM、F处理的大豆根际土壤中可培养细菌、真菌和放线菌三大菌群的数量与CK处理相比显著提高(p0.05)。分离大豆结荚期根际土壤中AM真菌孢子,共获得Acaulospora属真菌3种,Glomus属真菌7种,孢子密度均较低,G.intraradices和G.mosseae均为各自处理的优势种群。对大豆结荚期根系和根际土壤PCR-DGGE图谱条带的丰度及优势条带测序分析,结果表明根际土壤中的AM真菌菌群数明显高于根系中AM真菌的菌群数量,GI处理的大豆根际土壤中AM真菌丰度值最大,GM处理大豆根系里的AM真菌丰度值最大,F处理的根际土壤中总AM真菌的数量最少;施加AM菌剂处理的大豆根系及根际土壤中的优势菌群分别为外源施加的两种AM真菌。     

转CryIAb水稻对稻田杂草群落组成及多样性的影响

尽管基因工程技术可以增加作物产量, 但转基因作物是否对农田生态产生影响受到广泛关注。本研究通过田间定位试验, 应用群落生态学方法研究了转CryIAb基因抗虫水稻"Mfb"连续2年在传统栽培和半野生条件下对稻田杂草群落组成及多样性的影响。调查结果显示: 转CryIAb基因稻"Mfb"与非转基因稻"明恢86"田间杂草种类没有显著差异。稻田杂草的频度和密度与栽培方式有关, 半野生稻田杂草的频度和密度显著高于传统稻田, 但相同栽培条件下, 转基因稻"Mfb"与非转基因稻"明恢86"田间杂草频度和密度在整个生长期内均无显著差异。半野生稻田物种丰富度(Sr)指数明显大于传统稻田; 相同栽培条件下, 相同生长时期抗虫转基因水稻"Mfb"与其非转基因对照"明恢86"对稻田杂草群落丰富度的影响差异不显著。稻田杂草群落优势度(D)、均匀度(J)以及多样性(H)各处理、各生长时期内转基因稻与非转基因稻相比均没有显著差异。稻田杂草Shannon-Wiener多样性指数变化无明显规律, 相同栽培方式相同生长期的抗虫转基因水稻"Mfb"与其非转基因对照"明恢86"的Shannon-wiener指数差异不显著。综合上述分析, 转CryIAb基因抗虫稻对稻田杂草群落的组成及多样性没有显著影响。     

Two-year field study shows little evidence that PPO-transgenic rice affects the structure of soil microbial communities

There is global concern about the environmental consequences associated with transgenic crops. Their effects on the soil ecosystem are of special interest when assessing ecological safety and integrity. Although many efforts have been made to develop crops genetically modified to have resistance to protoporphyrin oxidase (PPO)-inhibiting herbicides, little is known about their influence on soil microbial communities. We conducted a 2-year field study and an analysis via terminal restriction fragment length polymorphism (T-RFLP) to assess the impacts of PPO-transgenic rice on bacterial and fungal communities. In the first year we sampled the rhizosphere and surrounding bulk soil, while in the second year we sampled rhizosphere soil only. No differences were observed in the diversity indices and community composition of microbial communities between transgenic rice and its parental non-transgenic counterpart (cultivar Dongjin). Instead, community variation was strongly dependent on growth stage and year. Therefore, we observed no adverse effects by these crops of modified rice on the microbial community composition in paddy soils.     

A 3-year field investigation of impacts of Monsanto’s transgenic Bt-cotton NC 33B on rhizosphere microbial communities in northern China

Monsanto’s Bt-cotton NC 33B, planted in northern China for more than one decade, effectively controls cotton bollworms and decreases the use of chemical insecticides. Because of the concern about undesirable ecological side-effects of transgenic Bt-cottons, it is important to assess Bt-cotton NC 33B’s effects on soil microorganisms in this zone. Microbial communities in the rhizosphere soil of Bt and non-Bt cottons were monitored under field conditions by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprints of eubacteria, fungi and actinomycetes at six growth stages after three-year cultivation. Results showed that the population sizes and community structures of eubacteria, fungi and actinomycetes in rhizosphere soil were markedly affected by natural variations in the environment related to cotton growth stages. However, there was no significant difference in eubacterial, fungal and actinomycete population size and community structures in rhizosphere soil between NC 33B and its non-transgenic parent. In general, Bt-cotton NC 33B did not show evident effects on microbial communities in the rhizosphere soil under field conditions after three-year cultivation. This study provides a theoretical basis for environmental impact monitoring of transgenic Bt cottons.     

Transgenic Bt rice does not affect enzyme activities and microbial composition in the rhizosphere during crop development

Use of transgenic crops, including those expressing the insecticidal Cry protein from Bt, is increasing at a rapid rate in worldwide. Field and laboratory studies of transgenic Bt crops have been carried out to detect the persistence and activity of the Cry protein in soil and its effect on soil microorganisms to assess their risks to environment. However, there were few studies that evaluate the seasonal effects of Bt rice on rhizosphere soil microbial communities compared to those of insecticides commonly applied in paddy soil for the control of lepidopteran insects. In this study, seasonal effects of transgenic rice expressing the Cry1Ab insecticidal protein active against lepidoperan pests and the insecticide triazophos [3-(o,o-diethyl)-1-phenyl thiophosphoryl-1,2,4-triazol] on soil enzyme activities and microbial communities were compared under field conditions. During a 2-year field study, rhizosphere soil samples of transgenic-Bt rice (Bt), non-Bt parental rice (Ck) and non-Bt parental rice with triazophos (Ckp) applied were taken at four stages in the rice developmental cycle: seedling, booting, heading and maturing. Microbial processes were investigated by measuring different biochemical activities including those involved in C and P cycling. Denaturing gradient gel electrophoresis (DGGE) and terminal-restriction fragment length polymorphism (T-RFLP) analyses were used to compare rhizosphere microbial compositions. Some occasional and inconsistent effects of the application of triazophos on the bacterial composition in the rhizosphere soil of rice plant were found at the booting and heading stages as compared with that of transgenic-Bt rice. There were no statistically significant differences (P>0.05) in phosphatase activity, dehydrogenase activity, respiration, methanogenesis or fungal community composition in rhizosphere soil between Bt, Ck and Ckp over the rice cropping cycle. However, seasonal variations in the selected enzyme activities and microbial community composition in the rhizosphere soil of Bt, Ck and Ckp were clearly detected. These results suggested that the changes in rhizophere soil microbial community composition associated with the crop growth stage overweighed the application of triazophos and the cry1Ab gene transformation. KMD1 (Bt) rice expressing the cry1Ab gene had no measurable adverse effect on the key microbial processes or microbial community composition in rhizophere soil over 2 years of rice cropping.     

Molecular identification of methane oxidizing bacteria in a Japanese rice field soil

By using cultivation-independent techniques, community changes of methane-oxidizing bacteria (MOB) in rice bulk soils were investigated under field conditions in a Japanese rice field. The representative soil samples were collected during the typical rice growing season and nonrice growing period all year round. Statistical characterization of denaturing gradient gel electrophoresis (DGGE) community patterns of MOB pmoA/amoA functional gene fragments showed that MOB community structures in the rice bulk soils remained largely unchanged throughout the investigated period. The total intensity of six common DGGE bands that appeared consistently throughout the investigated period accounted for 64% of the total intensity of all 18 different DGGE bands detected. The low squared distance of the Ward cluster analysis of the DGGE pattern and the high Sorensen similarity coefficient (81%) also implied the high similarity of the MOB community structures. The stable MOB community structure did not couple well with the wide variation of soil water contents all year round. Sequencing analysis of the nine characteristic bands including six common bands revealed the presence of Type I, Type II methanotrophs, and β-proteobacterial ammonia oxidizers in rice bulk soils. In comparison with MOB type species, three DGGE bands showed a wide variation of the highly conserved amino acid residues, implying the presence of novel MOB bacteria inhabiting the rice bulk soil. The high diversity of MOB composition suggested that rice bulk soils might serve as an ideal reservoir for the dynamic changes of MOB in a rice field ecosystem in response to environment changes.     

Community structure of microeukaryotes in a rice rhizosphere revealed by DNA-based PCR-DGGE

Rice roots provide a specific habitat for microorganisms in the rhizosphere of a submerged field through supply of oxygen and organic matter. Many studies have focused on the microbial community in the rice rhizosphere, but less is still known about the microeukaryotic community structure of rice rhizosphere. This study explored the microeukaryotic community structure of a rice rhizosphere through denaturing gradient gel electrophoresis (DGGE) targeting 18S rRNA gene. The rice roots and the rhizosphere soil samples, which were collected from a field under rice-wheat rotation system, were separately analyzed. To characterize the rice rhizosphere-specific community, the bulk soil of rice field and the wheat rhizosphere samples were also examined. DGGE fingerprints showed that the microeukaryotic community of rice roots were distinct from the community of the bulk soil and showed a temporal shift with the growth stage. The rhizosphere soil community was distinct from the root and bulk soil communities, but this could be explained by that the root and bulk soil communities were shared in the rhizosphere. The rice rhizosphere community was also distinct from those in the wheat rhizosphere. Microeukaryotes that characterized the rice rhizosphere (roots and the rhizosphere soil) community could be affiliated to Polymyxa, flagellates, and oomycetes, which suggested that microeukaryotes with various ecological roles, e.g., parasites, bacterial grazers, and decomposers, inhabit the rice rhizosphere. The results showed that the rice root and its growth stages are key factors shaping the microeukaryotic community structure in the rhizosphere.     

In situ dynamics of soil fungal communities under different genotypes of potato, including a genetically modified cultivar

Fungi are key to the functioning of soil ecosystems, and exhibit a range of interactions with plants. Given their close associations with plants, and importance in ecosystem functioning, soil-borne fungi have been proposed as potential biological indicators of disturbance and useful agents in monitoring strategies, including those following the introduction of genetically modified (GM) crops. Here we report on the impact of potato crop varieties, including a cultivar that was genetically modified for its starch quality, on the community composition of the main phyla of fungi in soils, i.e. Ascomycota, Basidiomycota and Glomeromycota in rhizosphere and bulk soil. Samples were collected at two field sites before sowing, at three growth stages during crop development and after the harvest of the plants, and the effects of field site, plant growth stage and plant cultivar (genotype) on fungal community composition assessed using three phylum-specific T-RFLP profiling strategies and multivariate statistical analysis (NMDS ordinations with ANOSIM test). In addition, fungal biomass, arbuscular mycorrhizal colonization of roots and activities of extracellular fungal enzymes (laccases, Mn-peroxidases and cellulases) involved in degradation of lignocelluloses-rich organic matter were determined. Fungal community compositions, densities and activities were observed to differ significantly between the rhizosphere and bulk soil. The most important factors determining fungal community composition and functioning were plant growth stage for the rhizosphere communities and location and soil properties for the bulk soil communities. The basidiomycetes were the most numerous fungal group in the bulk soils and in the rhizosphere of young plants, with a shift toward greater ascomycete numbers in the rhizosphere at later growth stages. There were no detectable differences between the GM cultivar and its parental cultivar in terms of influence on fungal community structure of function. Fungal community structure and functioning of both GM- and parental cultivars fell within the range of other cultivars at most sampling moments.     

Analysis of bacterial communities on alkaline phosphatase genes in soil supplied with organic matter

Abstract

We studied the effects of the application of organic matter (OM) and chemical fertilizer (CF) on soil alkaline phosphatase (ALP) activity and ALP-harboring bacterial communities in the rhizosphere and bulk soil in an experimental lettuce field in Hokkaido, Japan. The ALP activity was higher in soils with OM than in soils with CF, and activity was higher in the rhizosphere for OM than in the bulk soil. Biomass P and available P in the soil were positively related to the ALP activity of the soil. As a result, the P concentration of lettuce was higher in OM soil than in CF soil. We analyzed the ALP-harboring bacterial communities using polymerase chain reaction based denaturing gradient gel electrophoresis (DGGE) on the ALP genes. Numerous ALP genes were detected in the DGGE profile, regardless of sampling time, fertilizer treatment or sampled soil area, which indicated a large diversity in ALP-harboring bacteria in the soil. Several ALP gene fragments were closely related to the ALP genes of Mesorhizobium loti and Pseudomonas fluorescens. The community structures of the ALP-harboring bacteria were assessed using principal component analysis of the DGGE profiles. Fertilizer treatment and sampled soil area significantly affected the community structures of ALP-harboring bacteria. As the DGGE bands contributing to the principal component were different from sampling time, it is suggested that the major bacteria harboring the ALP gene shifted. Furthermore, there was, in part, a significant correlation between ALP activity and the community structure of the ALP-harboring bacteria. These results raise the possibility that different ALP-harboring bacteria release different amounts and/or activity of ALP, and that the structure of ALP-harboring bacterial communities may play a major role in determining overall soil ALP activity.     

Response of soil microbial abundance and diversity in Sacha Inchi (Plukenetia volubilis L.) farms with different land-use histories in a tropical area of Southwestern China

Land-use conversion affects the soil community and microbial abundance, which are essential dynamic indicators of soil quality and sustainability. However, little to no work has been performed to analyse the impact from different land-use histories (i.e. fallow, tea, rice, banana, and maize) on the microbial abundance and diversity in the soil of sacha inchi (Plukenetia volubilis L.). Real-time quantitative PCR (qPCR) was performed to quantify soil bacterial and fungal abundance. Denaturing gradient gel electrophoresis (DGGE) combined with cloning and sequencing was used to assess the microbial communities. Our results showed that the bacterial and fungal abundance in fallow land-use conversion soils was significantly lower than that in the other four land-use conversion soils (tea, rice, banana, and maize). Moreover, the highest abundance of bacteria and fungi was detected in the soils converted from maize to sacha inchicultivation. In addition, canonical correspondence analysis (CCA) showed that the total N and pH were significantly related to bacterial and fungal community structures. These results suggest that land-use conversion from maize fields to sacha inchi farms is an effective way to maintain the soil microbial quantity and hence the sustainability of the soil.     

转BADH基因大豆对盐碱土壤氮素转化的影响

以转甜菜碱醛脱氢酶(betaine aldehyde dehydrogenase)基因(BADH)大豆、非转基因亲本‘黑农35’、野生大豆、当地栽培种‘抗线王’、耐盐碱性较差品种‘合丰50’等5种大豆品种为材料,在典型盐碱土封闭种植,于大豆苗期、花荚期、鼓粒期和成熟期取根际土,采用经典方法测定氮素转化过程相关的细菌数量、生化功能及速效氮含量等指标的动态变化,为揭示转BADH基因大豆对土壤氮素转化的影响机制提供理论支持。结果表明:与非转基因亲本相比,转BADH基因大豆对苗期和花荚期根际土壤固氮菌数量有促进作用,但抑制苗期和花荚期根际土壤氨化细菌数量,对硝化细菌数量无显著性影响;显著促进成熟期大豆根际土壤固氮作用强度,对大豆苗期、花荚期和鼓粒期根际土壤氨化作用强度有显著抑制作用,显著促进各生育时期硝化作用强度;转BADH基因大豆苗期和花荚期根际土壤铵态氮含量显著降低,对鼓粒期根际土壤铵态氮含量无显著性影响,成熟期根际土壤铵态氮含量显著增高,大豆苗期、鼓粒期和成熟期根际土壤硝态氮含量显著升高,花荚期根际硝态氮含量显著降低。研究结果说明,转BADH基因大豆通过调节苗期、花期根际土壤氮素转化功能菌数量和生化过程强度进而影响氮素转化。