Resistance quantitative trait loci originating from Solanum sparsipilum act independently on the sex ratio of Globodera pallida and together for developing a necrotic reaction

Plant resistance to nematodes is related to the ability of the host to reduce the development of nematode juveniles into females. Resistance to the potato cyst nematode (PCN) Globodera pallida, originating from the wild species Solanum sparsipilum, was dissected by a quantitative trait loci (QTL) approach. Two QTL explained 89% of the phenotypic variation. The QTL GpaV(s)spl on chromosome V displayed the major effect on the cyst number (coefficient of determination [R2] = 76.6%). It restricted G. pallida development to 16.2% of juveniles, 81.5% of males, and 2.3% of females. The QTL GpaXI(s)spl on chromosome XI displayed a lower effect on the cyst number (R2 = 12.7%). It restricted G. pallida development to 13.8% of juveniles, 35.4% of males, and 50.8% of females. Clones carrying both QTL restricted the nematode development to 58.1% juveniles, 41.1% of males, and 0.8% of females. We demonstrated that potato clones carrying both QTL showed a strong necrotic reaction in roots infected by nematodes, while no such reaction was observed in clones carrying a single QTL. This result underlines the importance to introgress together GpaV(s)spl and GpaXI(s)spl into potato cultivars, in order to reduce the density of this quarantine pest in soil and to decrease the risk of selecting overcoming G. pallida subpopulations.     

Lipopolysaccharides of Rhizobium etli strain G12 act in potato roots as an inducing agent of systemic resistance to infection by the cyst nematode Globodera pallida

Recent studies have shown that living and heat-killed cells of the rhizobacterium Rhizobium etli strain G12 induce in potato roots systemic resistance to infection by the potato cyst nematode Globodera pallida. To better understand the mechanisms of induced resistance, we focused on identifying the inducing agent. Since heat-stable bacterial surface carbohydrates such as exopolysaccharides (EPS) and lipopolysaccharides (LPS) are essential for recognition in the symbiotic interaction between Rhizobium and legumes, their role in the R. etli-potato interaction was studied. EPS and LPS were extracted from bacterial cultures, applied to potato roots, and tested for activity as an inducer of plant resistance to the plant-parasitic nematode. Whereas EPS did not affect G. pallida infection, LPS reduced nematode infection significantly in concentrations as low as 1 and 0.1 mg ml(-1). Split-root experiments, guaranteeing a spatial separation of inducing agent and challenging pathogen, showed that soil treatments of one half of the root system with LPS resulted in a highly significant (up to 37%) systemic induced reduction of G. pallida infection of potato roots in the other half. The results clearly showed that LPS of R. etli G12 act as the inducing agent of systemic resistance in potato roots.     

Preferential expression of a plant cystatin at nematode feeding sites confers resistance to Meloidogyne incognita and Globodera pallida

The expression patterns of three promoters preferentially active in the roots of Arabidopsis thaliana have been investigated in transgenic potato plants in response to plant parasitic nematode infection. Promoter regions from the three genes, TUB-1, ARSK1 and RPL16A were linked to the GUS reporter gene and histochemical staining was used to localize expression in potato roots in response to infection with both the potato cyst nematode, Globodera pallida and the root-knot nematode, Meloidogyne incognita. All three promoters directed GUS expression chiefly in root tissue and were strongly up-regulated in the galls induced by feeding M. incognita. Less activity was associated with the syncytial feeding cells of the cyst nematode, although the ARSK1 promoter was highly active in the syncytia of G. pallida infecting soil grown plants. Transgenic potato lines that expressed the cystatin OcIDeltaD86 under the control of the three promoters were evaluated for resistance against Globodera sp. in a field trial and against M. incognita in containment. Resistance to Globodera of 70 +/- 4% was achieved with the best line using the ARSK1 promoter with no associated yield penalty. The highest level of partial resistance achieved against M. incognita was 67 +/- 9% using the TUB-1 promoter. In both cases this was comparable to the level of resistance achieved using the constitutive cauliflower mosaic virus 35S (CaMV35S) promoter. The results establish the potential for limiting transgene expression in crop plants whilst maintaining efficacy of the nematode defence.     

The production of synthetic chemodisruptive peptides in planta disrupts the establishment of cyst nematodes

Root exudates from transgenic potato plants expressing a chemoreception-disruptive peptide inhibit acetylcholinesterase by up to 63 +/- 3%. This inhibition correlates strongly with the efficacy of the exudates as a presoak solution for infective juveniles of Heterodera glycines that leads to reduced root invasion. The establishment of developing Globodera pallida at 21 days post-infection in these transgenic plants was also suppressed in containment trials. Relative to controls, the best line showed a 47 +/- 5% reduction in developing females and had 188 +/- 25% more undeveloped infective juveniles. This suggests that disorientation of chemoreception occurs after initial root invasion. Line (e) showed the highest level of resistance with 61 +/- 4% in glasshouse trials conducted over a 9-week period. This result represents the combined effect on the number of cysts produced and the number of eggs each cyst contains. The level of control shown to saccate females was consistent in both the 21-day and 9-week post-infection studies. Another chemoreception-disruptive peptide, that binds to nematode nicotinic receptors in cholinergic neurones, provided a 52.6 +/- 1% reduction in the number of nematodes able to establish in transgenic hairy roots that expressed the peptide. This confirms that both chemoreception-disruptive peptides have efficacy in suppressing parasitism by cyst nematodes when expressed in planta at low concentrations.     

转Bt基因作物对非靶标土壤动物的影响

转Bt基因作物已经在世界范围内广泛种植.随着转基因作物的快速发展与推广,有必要深入研究其对土壤生态系统的影响.本文概述了转Bt作物对土壤动物群落以及蚯蚓、线虫、虫兆虫、螨类和甲虫等重要类群的种群动态影响的研究进展,介绍了转Bt基因作物的发展历史,分析了Bt蛋白进入土壤的途径及其在土壤环境中的残留与降解的动态,阐述了未来转Bt基因作物对非靶标土壤动物影响的生态风险分析的重要领域,旨在为研究转Bt基因作物对非靶标土壤动物影响提供参考.     

抗草甘膦转基因大豆对根际土壤细菌及根瘤菌的影响

转基因大豆是全球种植最广泛的转基因作物,抗除草剂是其最主要的转基因特性.微生物群落是土壤质量的监测指标之一,抗草甘膦转基因大豆及配施草甘膦是否影响大豆根际土壤细菌及根瘤菌群落尚不清楚.本研究基于大田试验,以非转基因亲本大豆‘中豆32’为对照(CK),分析转G10-epsps基因耐除草剂大豆SHZD32-01(GR)及配施草甘膦(GR+G)在大豆各生育时期对根际土壤细菌和根瘤菌的影响.结果表明: 与CK相比,GR、GR+G处理对苗期和成熟期根际土壤pH、总有机碳(TOC)、总氮(TN)、NH₄⁺-N含量等产生影响;GR处理显著增加结荚期根际土壤细菌群落丰度及多样性,GR+G处理显著增加结荚期根际土壤细菌群落多样性,但显著降低苗期和结荚期根际土壤细菌群落丰度;GR、GR+G处理改变了部分优势细菌类群的相对丰度,但不同生育期根际土壤优势细菌类群均为变形菌门、酸杆菌门、拟杆菌门、绿弯菌门、浮霉菌门和放线菌门;GR、GR+G处理改变了根瘤菌类群的相对丰度,但未影响慢生根瘤菌和中华根瘤菌两种主要大豆根瘤菌的相对丰度,且GR+G处理结荚期根际土壤根瘤菌相对丰度显著降低.环境因子分析显示,根际土壤放线菌和根瘤菌群落丰度主要受土壤pH影响.抗草甘膦转基因大豆或配施草甘膦显著影响结荚期根际土壤细菌和根瘤菌,但其影响随大豆的生长而消失.     

Relationship between saprotrophic growth in soil of different biotypes of Pochonia chlamydosporia and the infection of nematode eggs

The ecology of Pochonia chlamydosporia in soil and its interaction with both plant and nematode hosts are important for the successful exploitation of the fungus as a biological control agent. Differences in saprotrophism and parasitism were assessed for biotypes of P. chlamydosporia, which had originated from the eggs of cyst or root‐knot nematodes. Colonisation in soils of different textures (compost, sandy loam and loamy sand) measured by the numbers of colony‐forming units, differed greatly. Most biotypes were more abundant in sterilised soil of the different textures compared with non‐sterilised soils. The proportion of nematode eggs parasitised in a baiting technique demonstrated that biotypes had host preferences. Those biotypes that originated from root‐knot nematodes (RKN‐biotypes) infected significantly more Meloidogyne hapla eggs than Globodera pallida eggs, whereas biotypes from cyst nematodes (CN‐biotypes) parasitised more G. pallida eggs than M. hapla eggs. Differences in virulence between biotypes in an in vitro assay in which the fungi were placed directly onto the egg masses of M. hapla and those differences observed in the baiting technique showed similar trends. There was a negative linear correlation between the growth of the eight biotypes in soil and the proportion of eggs they infected in compatible interactions (i.e. fungal biotype originated from the same nematode genus as the target eggs). Those biotypes that infected most nematode eggs colonised soil the least extensively, suggesting that virulence may have a fitness cost. However, the relationship between saprotrophic growth and virulence is complex. The relative abundance of the different biotypes in soil in Petri dish assays was similar to that under glasshouse conditions using potato but not tomato as the plant host. Chlamydospores of some biotypes applied to soil significantly reduced (>50%) the population densities of M. hapla on tomato and of G. pallida on potato plants. Some biotypes that were both effective and virulent are good candidates for biological control of specific nematode pests. Data presented here and elsewhere indicate that RKN‐biotypes have different host preferences to CN‐biotypes; the specific primers based on the vcp1 gene from P. chlamydosporia rapidly confirmed the host origin of seven of the eight biotypes.     

Mapping QTLs for resistance to the cyst nematode Globodera pallida derived from the wild potato species Solanum vernei

Resistance to the potato cyst nematode (PCN) species Globodera pallida, derived from the wild diploid potato species Solanum vernei, has been investigated. This source of resistance, which is effective against all of the major pathotypes of G. pallida and Globodera rostochiensis, has been assumed to be due to several genetic factors, but it has proved difficult to deploy effectively in breeding strategies for potato cultivars. Diploid and tetraploid potato populations segregating for 'vernei' resistance were analysed. At the tetraploid level, a bulk segregant analysis (BSA) approach was employed and detected AFLP markers linked to a resistance QTL on potato linkage group V. Conventional linkage analysis of a diploid population identified QTL on linkage groups V and IX. A marker linked to a QTL on linkage group V has been converted to a single-locus PCR-based marker, which can be used to detect the presence of the QTL in diploid and tetraploid potato germplasm. Moreover, there is evidence that one of the AFLPs detected by BSA appears to be specific to an introgressed segment of DNA from S. vernei. These results are compared with those obtained from other studies on resistance to the PCN species G. pallida.     

Effective delivery of a nematode‐repellent peptide using a root‐cap‐specific promoter

The potential of the MDK4‐20 promoter of Arabidopsis thaliana to direct effective transgenic expression of a secreted nematode‐repellent peptide was investigated. Its expression pattern was studied in both transgenic Arabidopsis and Solanum tuberosum (potato) plants. It directed root‐specific β‐glucuronidase expression in both species that was chiefly localized to cells of the root cap. Use of the fluorescent timer protein dsRED‐E5 established that the MDK4‐20 promoter remains active for longer than the commonly used constitutive promoter CaMV35S in separated potato root border cells. Transgenic Arabidopsis lines that expressed the nematode‐repellent peptide under the control of either AtMDK4‐20 or CaMV35S reduced the establishment of the beet cyst nematode Heterodera schachtii. The best line using the AtMDK4‐20 promoter displayed a level of resistance >80%, comparable to that of lines using the CaMV35S promoter. In transgenic potato plants, 94.9 ± 0.8% resistance to the potato cyst nematode Globodera pallida was achieved using the AtMDK4‐20 promoter, compared with 34.4 ± 8.4% resistance displayed by a line expressing the repellent peptide from the CaMV35S promoter. These results establish the potential of the AtMDK4‐20 promoter to limit expression of a repellent peptide whilst maintaining or even improving the efficacy of the cyst‐nematode defence.     

Varietal effects of eight paired lines of transgenic Bt maize and near-isogenic non-Bt maize on soil microbial and nematode community structure

A glasshouse experiment was undertaken to provide baseline data on the variation between conventional maize (Zea mays L.) varieties and genetically modified maize plants expressing the insecticidal Bacillus thuringiensis protein (Bt, Cry1Ab). The objective was to determine whether the variation in soil parameters under a range of conventional maize cultivars exceeded the differences between Bt and non-Bt maize cultivars. Variations in plant growth parameters (shoot and root biomass, percentage carbon, percentage nitrogen), Bt protein concentration in shoots, roots and soil, soil nematode abundance and soil microbial community structure were determined. Eight paired varieties (i.e. varieties genetically modified to express Bt protein and their near-isogenic control varieties) were investigated, together with a Bt variety for which no near-isogenic control was available (NX3622, a combined transformant expressing both Bt and herbicide tolerance) and a conventional barley (Hordeum vulgare L.) variety which was included as a positive control. The only plant parameter which showed a difference between Bt varieties and near-isogenic counterparts was the shoot carbon to nitrogen ratio; this was observed for only two of the eight varieties, and so was not attributable to the Bt trait. There were no detectable differences in the concentration of Bt protein in plant or soil with any of the Bt-expressing varieties. There were significant differences in the abundance of soil nematodes, but this was not related to the Bt trait. Differences in previously published soil nematode studies under Bt maize were smaller than these varietal effects. Soil microbial community structure, as determined by phospholipid fatty acid (PLFA) analysis, was strongly affected by plant growth stage but not by the Bt trait. The experimental addition of purified Cry1Ab protein to soil confirmed that, at ecologically relevant concentrations, there were no measurable effects on microbial community structure.     

转植酸酶基因玉米种植对土壤线虫群落的影响

土壤是生态系统中物质循环和能量转化的重要场所,转基因作物外源基因对土壤非靶标生物的影响已经引起人们的广泛关注.我国转植酸酶基因玉米(即自交系BVLA430101)于2009年9月27日获得了生物安全证书,该转植酸酶基因玉米可提高饲料利用效率,减少动物粪便造成的环境污染.本文以转植酸酶基因玉米(简称转基因玉米)和常规对照亲本玉米(简称对照玉米)为试验材料,通过大田试验研究了转基因玉米和对照玉米种植对土壤线虫群落组成与生态指标的影响.结果表明： 转基因玉米和对照玉米大田土壤分别分离出29个属和26个属的线虫.与对照玉米相比,转基因玉米种植田食细菌线虫相对多度与数量、捕/杂食线虫数量和土壤线虫总数,以及群落多样性指数等都有升高的趋势,而植食线虫相对多度与线虫总成熟度指数呈降低趋势.重复测量方差分析表明,整个生长季节内转基因玉米与对照玉米田间不同营养类群土壤线虫相对多度与数量及生态指标均无显著差异;而T检验分析表明,玉米乳熟期转基因玉米田食细菌线虫、捕/杂食线虫数量和土壤线虫总数显著高于对照玉米田,这可能与乳熟期转基因玉米田土壤总氮含量显著升高有关.     

What constitutes a population for the plant parasitic nematode Globodera pallida in its native area (Peru)?

Although numerous species are distributed in discrete populations easily recognised by geographical barriers, continuous populations are a common feature of plants or marine organisms. This is particularly true for soil organisms as their habitat is continuous and their range cannot easily be assessed as they are buried below ground. In the case of organisms for which standard methods such as Capture/Mark/Recapture cannot be used, population genetics provide a straightforward approach to delimitate populations. In this study, we have pursued this topic with a soil-dwelling nematode (Globodera pallida), which parasitises potato roots and is indigenous to South America. Potential barriers to gene flow were identified using the analysis of the F(ST)/(1-F(ST)) ratio against geographical distance and spatial autocorrelation combined with model-based clustering algorithm. Inside regions, neither genetic differentiation nor isolation by distance (IBD) occur among fields less than 50 km distant. We hypothesise that the large amount of gene flow revealed by the absence of genetic structure of this organism could be due to large passive dispersion inside an agronomic area where G. pallida has a continuous distribution and is found at high density. The first evidence of genetic differentiation appeared when a field was separated from others by an area free of farms (where G. pallida is absent or rare). Among regions, a high genetic structure coupled with an IBD pattern occurs as the consequences of the limitations of passive dispersal across deep valleys or high mountains. To our knowledge, this is the first study identifying the spatial limit of a population for a plant nematode parasite.     

高通量测序分析冻融期碳源输入方式对土壤线虫群落的影响

植物碳源输入途径变化对土壤生物群落的影响研究是目前学术界关注的热点问题。为探究温带森林生态系统碳源输入方式对土壤线虫群落的影响,通过Illumina MiSeq技术分析了不同碳源输入方式下土壤线虫群落组成和多样性的变化。研究结果显示:所有处理(凋落物和根系同时输入;仅根系输入;仅凋落物输入;无碳源输入)中共发现土壤线虫68属,其中食细菌线虫的相对丰度最大;各碳源输入方式中仅凋落物输入处理对线虫群落组成的影响最为明显,表现为:与凋落物和根系同时输入处理相比,仅凋落物输入处理中食细菌线虫的相对丰度明显增加,食真菌线虫的相对丰度显著降低以及捕食杂食线虫的相对丰度显著增加。从线虫群落的多样性指数角度看,无碳源输入处理中土壤线虫群落的多样性指数(H'')下降,优势度指数(Dom)增高;仅凋落物输入处理中均匀度指数(J)最高。从线虫群落的生态指数角度看,仅凋落物输入处理的线虫群落成熟度指数(MI)最高;各碳源输入处理的分解过程均以细菌分解通道为主。研究表明,土壤线虫群落受到碳源输入变化的调节,仅凋落物输入处理比仅根系输入处理对土壤线虫群落的影响更大。无碳源输入处理的物种多样性明显下降,仅凋落物输入处理的土壤食物网更加稳定。研究结果丰富了森林土壤线虫多样性的研究内容,并为高通量测序技术在土壤线虫方面的研究提供方法和数据的支持。     

Generation of transgenic plantain (Musa spp.) with resistance to plant pathogenic nematodes

Plant parasitic nematodes impose a severe constraint on plantain and banana productivity; however, the sterile nature of many cultivars precludes conventional breeding for resistance. Transgenic plantain cv. Gonja manjaya (Musa AAB) plants, expressing a maize cystatin that inhibits nematode digestive cysteine proteinases and a synthetic peptide that disrupts nematode chemoreception, were assessed for their ability to resist nematode infection. Lines were generated that expressed each gene singly or both together in a stacked defence. Nematode challenge with a single species or a mixed population identified 10 lines with significant resistance. The best level of resistance achieved against the major pest species Radopholus similis was 84% ± 8% for the cystatin, 66% ± 14% for the peptide and 70% ± 6% for the dual defence. In the mixed population, trial resistance was also demonstrated to Helicotylenchus multicinctus. A fluorescently labelled form of the chemodisruptive peptide underwent retrograde transport along certain sensory dendrites of R. similis as required to disrupt chemoreception. The peptide was degraded after 30 min in simulated intestinal fluid or boiling water and after 1 h in nonsterile soil. In silico sequence analysis suggests that the peptide is not a mammalian antigen. This work establishes the mode of action of a novel nematode defence, develops the evidence for its safe and effective deployment against multiple nematode species and identifies transgenic plantain lines with a high level of resistance for a proposed field trial.     

Overexpression of glutamate decarboxylase in transgenic tobacco plants confers resistance to the northern root-knot nematode

Previous research suggests that the endogenous synthesis of gamma-aminobutyrate (GABA), a naturally occurring inhibitory neurotransmitter, serves as a plant defense mechanism against invertebrate pests. Here, we tested the hypothesis that elevated GABA levels in engineered tobacco confer resistance to the northern root nematode (Meloidogyne hapla). This nematode species was chosen because of its sedentary nature and economic importance in Canada. We derived nine phenotypically normal, homozygous lines of transgenic tobacco (Nicotiana tabacum L.), which contain one or two copies of a full-length, chimeric tobacco glutamate decarboxylase (GAD) cDNA or a mutant version that lacks the autoinhibitory calmodulin-binding domain, under the control of a chimeric octopine synthase/mannopine synthase promoter. Regardless of experimental protocol, uninfected transgenic lines consistently contained higher GABA concentrations than wild-type controls. Growth chamber trials revealed that 9–12 weeks after inoculation of tobacco transplants with the northern root-knot nematode, mature plants of five lines possessed significantly fewer egg masses on the root surface when the data were expressed on both root and root fresh weight bases. Therefore, it can be concluded that constitutive transgenic expression of GAD conferred resistance against the root-knot nematode in phenotypically normal tobacco plants, probably via a GABA-based mechanism.     

Pasteuria endospores from Heterodera cajani (Nematoda: Heteroderidae) exhibit inverted attachment and altered germination in cross-infection studies with Globodera pallida (Nematoda: Heteroderidae)

The Pasteuria group of Gram-positive, endospore-forming bacteria are parasites of invertebrates and exhibit differences in host specificity. We describe a cross-infection study between an isolate of Pasteuria from pigeon pea cyst nematode, Heterodera cajani, which also infects the potato cyst nematode, Globodera pallida, from the United Kingdom. A proportion of the attached endospores, 13% on H.?cajani and 22% on G.?pallida adhere to the cuticle in an inverted orientation. Inverted and conventionally attached endospores germinated and produced bacillus-like rods that completed their life cycle in 相似文献   

A method for estimating the contribution of seed potatoes, machinery and soil tare in field infestations with potato cyst nematodes on a national scale

In order to make a cost benefit analysis for the management of the potato cyst nematodes Globodera rostochiensis and G. pallida, we developed a method to estimate the relative importance of three basic distribution channels of potato cyst nematodes: seed potatoes, machinery and soil tare. The baseline is determined by the area planted with potatoes, the area infested with potato cysts, the proportion of resistant potato cultivars and the distribution of cysts trough different channels. This quantification forms a basis for the evaluation of the effects of different control measures for potato cyst nematode on a national scale. The method can be useful as an example for application in other countries.     

Effects of native and exotic range‐expanding plant species on taxonomic and functional composition of nematodes in the soil food web

Due to climate warming, many plant species shift ranges towards higher latitudes. Plants can disperse faster than most soil biota, however, little is known about how range‐expanding plants in the new range will establish interactions with the resident soil food web. In this paper we examine how the soil nematode community from the new range responds to range‐expanding plant species compared to related natives. We focused on nematodes, because they are important components in various trophic levels of the soil food web, some feeding on plant roots, others on microbes or on invertebrates. We expected that range expanding plant species have fewer root‐feeding nematodes, as predicted by enemy release hypothesis. We therefore expected that range expanders affect the taxonomic and functional composition of the nematode community, but that these effects would diminish with increasing trophic position of nematodes in the soil food web. We exposed six range expanders (including three intercontinental exotics) and nine related native plant species to soil from the invaded range and show that range expanders on average had fewer root‐feeding nematodes per unit root biomass than related natives. The range expanders showed resistance against rather than tolerance for root‐feeding nematodes from the new range. On the other hand, the overall taxonomic and functional nematode community composition was influenced by plant species rather than by plant origin. The plant identity effects declined with trophic position of nematodes in the soil food web, as plant feeders were influenced more than other feeding guilds. We conclude that range‐expanding plant species can have fewer root‐feeding nematodes per unit root biomass than related natives, but that the taxonomic and functional nematode community composition is determined more by plant identity than by plant origin. Plant species identity effects decreased with trophic position of nematodes in the soil food web.     

转mapk双链RNA干扰表达载体黄瓜对根际土壤细菌多样性的影响

随着RNA干扰技术的发展,通过植物表达病原物特异的dsRNA来防治植物病害的转基因作物越来越多.转根结线虫mapk双链RNA表达载体的黄瓜能够通过RNA干扰作用沉默线虫的mapk基因,对根结线虫具有良好的防治效果.为了评价该转基因黄瓜的安全性,明确mapk双链RNA干扰表达载体转基因黄瓜植株对根际土壤细菌多样性的影响,采用16S rRNA基因克隆文库方法对非转基因黄瓜和转基因黄瓜土壤细菌群落多样性进行分析.结果表明,非转基因黄瓜土壤细菌文库包含124个OTU(可操作分类单元),转基因黄瓜土壤细菌文库包含122个OTU.2个文库共同拥有的OTU为115个.2个文库都包含1 3个类群细菌,Acidobacteria、Actinobacteria、Armatimonadetes、Bacteroidetes、candidate division BRC1、Chloroflexi、Firmicutes、Gemmatimonadetes、Nitrospira、Planctomycetes、Proteobacteria、Verrucomicrobia、unclassified_Bacteria. 其中 Proteobacteria、Bacteroidetes 、Chloroflexi和Acidobacteria是优势菌群.其他细菌类群数量相对较少.在纲分类水平上,两个文库包含的细菌类群一致,且各类群细菌比例差异不大.在Acidobacteria门中,Acidobacteria_Gp6为优势菌群.在Bacteroidetes门中,Sphingobacteria纲细菌数量最多.在Chloroflexi门中,unclassified Chloroflexi细菌最多.在Proteobacteria门中,其中Betaproteobacteria纲的细菌数量最多.从多样性指数角度分析,两种土壤细菌群落的Shannon、Simpson和Chao值差异不大.总体来看,两种土壤细菌类群差异不显著,转基因黄瓜未对根际土壤细菌群落产生明显影响.