首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 62 毫秒
1.
The primary structure of the double-headed Bowman-Birk inhibitor (BBI) family and the antitryptic activity were investigated in cultivated and wild Phaseolus species. Two BBI types were identified; the first one inhibits trypsin and chymotrypsin (tc-BBI), the second one elastase and trypsin (et-BBI). Only tc-BBI was found in P. lunatus and P. parvulus, while none of BBI types, identified in this study, was found in P. leptostachyus. The deduced amino acid sequences revealed some polymorphisms within both tc-BBI and et-BBI binding loops that could affect the inhibitory activity. The trypsin inhibitor content showed a high variation with the lowest value recorded in P. lepthostachyus and the highest one observed in P. oligospermus. Southern blot analysis confirmed the absence of both BBI types in P. leptostachyus and suggests that in P. coccineus, P. dumosus and P. costaricensis, the two genes were clustered in a narrow genomic region of 1.3 kbp.  相似文献   

2.
The community structure and catabolic functional diversity of indigenous rhizosphere fluorescent pseudomonad isolates recovered from un-amended soil (control treated) and following long-term (6 years) swine compost application (compost treated) were studied. Soils collected for the pot experiments were from a Taiwanese experimental farm established in 1995 to study the long-term effects of crop rotation and organic amendment. In the pot experiments, corn seed was cultured; after the elongation stage, 13 and 32 indigenous rhizosphere fluorescent pseudomonad isolates were collected from compost-treated (n=13) and control-treated (n=32) soils. All isolates were classified by 16S rDNA restriction fragment length polymorphism (RFLP) and unweighted pair-group method using arithmetic averages analyses. Most (84.4%) of the control-treated soil isolates belonged to genotype A, which corresponded to Pseudomonas putida based on 16S rDNA sequences analysis. However, only 61.5% of compost-treated soil isolates were from genotype A; 30.7% of the isolates belonged to genotype B, whose 16S rDNA profile corresponded to Stenotrophomonas maltophilia. Differing catabolic potentials of the P. putida isolates from control- and compost-treated soils were evident; isolates from control-treated soils utilized organic acids including citric acid, cis-aconitic acid, and formic acid more actively than compost-treated soil isolates. Moreover, the latter isolates more efficiently utilized carbohydrates of i-erythritol and l-rhamnose than P. putida isolates from control-treated soil, consistent with the alteration in the catabolic functions of indigenous rhizosphere P. putida by long-term compost application.  相似文献   

3.
Non-legume crops grown in rotation with legumes usually have reduced N-fertilizer requirement, which has both economic and environmental benefits. In this study, we aimed to assess the indirect effect of Phaseolus vulgaris inoculation with two indigenous rhizobia strains on potato growth promotion and disease control in relation to inoculation effects on soil bacterial communities. T-RFLP profiling demonstrated that inoculation significantly increased the phylotype richness of the bacterial communities at the end of P. vulgaris life cycle. A significant difference in richness between simple and dual inoculation was found. Effects on bacterial structure are clearly sensed with both inoculants. Various bacteria like Halomonas, Arthrobacter, Rahnella, Actinobacterium and Frankia were enhanced by inoculation irrespective of the inoculant type. However, other bacteria like Clostridium, Bacillus, Stenotrophomonas and Xanthomonas were enhanced by rhizobial mono-inoculation only and not by co-inoculation with both strains. Some bacteria may potentially behave like plant growth promoting rhizobacteria (PGPR) towards potatoes grown in rotation with common bean, as indicated by the 32% increase observed in potato yield, and also by the 56% decrease in potato wireworm infection. Therefore, rhizobia inoculation may contribute to the rotational benefits of legumes in potato cropping systems not only by providing fixed nitrogen, but also by increasing microbial diversity and structure, potentially stimulating plant growth promoting rhizobacteria and enhancing disease control. However, these effects depend largely on inoculant formulation.  相似文献   

4.
We examined the bean rhizobia community other than the predominant species Rhizobium etli present in soils of a region that is part of the range occupied by the host in Northwest Argentina, which showed Rep and 16S rDNA RFLP polymorphism. Two populations represented by isolates T29N3L and T44N22P were found to be distinct chromosomal genotypes and closely related to species Rhizobium tropici and Agrobacterium rhizogenes. Their symbiotic genes were analyzed and found to cluster with those from R. tropici as well as with rhizobia isolated from leguminous trees. Three nodulation metabolites produced by T44N22P were detected which are tetra- and pentameric chitocompounds, N-methylated, O-carbamoylated, and N-substituted either by a C18:0 or C18:1 acyl chain at their non-reducing end, and all them sulphated at the reducing end. Isolates T29N3L and T44N22P exhibited broad host range but unlike T29N3L, only T44N22P was able to efficiently nodulate Medicago truncatula.  相似文献   

5.
Twenty-eight Rhizobium strains were isolated from the root nodules of faba bean (Vicia faba L.) collected from 11 governorates in Egypt. A majority of these strains (57%) were identified as Rhizobium leguminosarum bv. viciae (Rlv) based on analysis of a nodC gene fragment amplified using specific primers for these faba bean symbionts. The strains were characterized using a polyphasic approach, including nodulation pattern, tolerance to environmental stresses, and genetic diversity based on amplified ribosomal DNA-restriction analysis (ARDRA) of both 16S and 23S rDNA. Analysis of tolerance to environmental stresses revealed that some of these strains can survive in the presence of 1% NaCl and a majority of them survived well at 37 °C. ARDRA indicated that the strains could be divided into six 16S rDNA genotypes and five 23S rDNA genotypes. Sequence analysis of 16S rDNA indicated that 57% were Rlv, two strains were Rhizobium etli, one strain was taxonomically related to Rhizobium rubi, and a group of strains were most closely related to Sinorhizobium meliloti. Results of these studies indicate that genetically diverse rhizobial strains are capable of forming N2-fixing symbiotic associations with faba bean and PCR done using nodC primers allows for the rapid identification of V. faba symbionts.  相似文献   

6.
The 18S–28S and 5S rDNA sites are useful chromosome landmarks and provide valuable evidence about genome organization and evolution. This investigation was the first attempt to study the dynamics, distribution and directionality of rDNA gains and losses, as well as to understand the contribution of site number variation in the speciation of the genus Citrullus. In this study, we employed fluorescent in situ hybridization (FISH), using the18S–28S and 5S rDNA gene loci, to evaluate the differences between the (1) cultivated type watermelon C. lanatus var. lanatus (sweet watermelon), (2) the “bitter” desert watermelon C. colocynthis (colocynth) that is indigenous to the deserts of northern Africa, the Middle East and Asia, (3) the C. lanatus var. citroides (citron) “Tsamma” or “cow watermelon” that is known as and is indigenous to southern Africa, (4) and C. rehmii that thrive in the Namibian Desert. The FISH analyses showed that the sweet watermelon and colocynth have similar rDNA configuration. The sweet watermelon and colocynth genomes contain two 18S–28S rDNA gene loci, each located on a different chromosome, and one 5S rDNA locus which is co-localized with one of the 18S–28S rDNA gene loci. On the other hand, the C. rehmii has one 18S–28S rDNA locus and one 5S rDNA locus positioned on different chromosomes, while the citron has one18S–28S rDNA and two 5S rDNA loci, each located on a different chromosome. A FISH analysis of F1 (citron × sweet watermelon) chromosome spreads revealed uniparental homeologous rDNA gene copies pertaining to the sweet watermelon versus the citron chromosomes, with the sweet watermelon chromosome containing the 18S–28S and 5S rDNA locus versus the citron homologue chromosome that has the 5S rDNA locus, but not the 18S–28S rDNA locus. Genomic in situ hybridization (GISH) analysis, using the entire citron genome as a probe to be differentially hybridized on sweet watermelon chromosome spreads, revealed that the citron genomic probes mainly hybridize to subtelomeric and pericentromeric regions of the sweet watermelon chromosomes, suggesting extensive divergence between the citron and sweet watermelon genomes. The FISH and GISH cytogenetic analysis here indicate major differences in genome organization between the cultivated watermelon type sweet watermelon and its counterpart citron that thrive in southern Africa and considered a useful germplasm source for enhancing disease and pest resistance in watermelon cultivars.  相似文献   

7.
The diversity of Paenibacillus polymyxa populations associated with the rhizosphere of durum wheat was investigated in Algerian soils sampled in regions where wheat had been cultivated for 5 and 26 years (Hamiz, H5 and Z26), 70 years (Algiers, D70), and more than 2 000 years (Tiaret, T2000 and K2000). A total of 111 strains were isolated by immunotrapping and identified as P. polymyxa using an API50CHB kit and restriction analysis of the amplified 16S rDNA gene. The phenotypic characteristics of the P. polymyxa populations were compared and the strains found not to cluster according to their origin. The longer the history of wheat cultivation, the lower the phenotypic diversity and the higher the frequency of nitrogen-fixing strains. Population genetic diversity, evaluated by ERIC-PCR, showed the same trends as phenotypic diversity. The distribution of ERIC genotypes among the different populations studied were compared using Pearson’s Chi-squared test. The strains isolated in D70, Z26, and H5 derived from soil populations sharing the same genetic structure, but those isolated in T2000 and K2000 each stemmed from a population with a specific genetic structure. These data suggest that the genetic structure of P. polymyxa populations has been affected by long-term wheat cultivation.  相似文献   

8.
Potentilla alba L. is a valuable medicinal plant widely used in folk and traditional medicine and particularly promising in complex treatment of thyroid pathology. Natural resources of this species are insufficient due to ever-growing use in contemporary medicine. Comprehensive investigations of different P. alba populations are essential for the successful extension of P. alba plantings. Aiming for a better understanding of karyotype structure, chromosome behaviour in meiosis and developing new diagnostic characters, we performed molecular cytogenetic characterization and leaf structure and ultrastructure analyses of two introduced P. alba samples originating from different habitats. Based on chromosome morphology, distribution of 45S/5S rDNA and DAPI-banding patterns, all chromosomes in the karyotypes were identified and the P. alba chromosomal idiogram was constructed. Our findings confirmed P. alba karyotype stability and also revealed several diagnostic characters of this species: the features of cells of upper and lower leaf epidermis, the presence of calcium oxalate druses and three types of leaf indumentum, essential for evaluation of genetic diversity in different populations, validation of raw materials and further selection progress. The meiotic abnormalities were detected probably related to low pollen activity and indicated the advantages of vegetative propagation in the development of a P. alba plantation system.  相似文献   

9.
《Applied soil ecology》2007,35(3):488-501
Carrot cavity spot (CCS) is characterised by the appearance of small sunken elliptical lesions on the tap root. It is caused by a complex of Pythium species, but the species diversity and interactions within the complex have never been studied for modelling CCS epidemics. The diversity of a pathogenic Pythium community was assessed during 3 consecutive years in a field experiment after an initial artificial soil infestation with P. violae. 1241 lesions were examined, yielding 728 Pythium isolates. Conventional microbiological methods and restriction polymorphism of the internal transcribed spacer regions of the rDNA of 209 representative Pythium isolates allowed us to identify 655 isolates as belonging to six Pythium species, including P. violae and five indigenous species (P. sulcatum, P. intermedium, P. sylvaticum/irregulare, P. coloratum, and P. ultimum). Biological traits, such as pathogenicity, optimum temperature for mycelial growth and saprophytic survival of the inoculum, explained the fluctuations in the composition of the complex over 17 successive samplings during the 3-year period, most notably the prevalence of first P. violae and then P. sulcatum. P. violae and P. sulcatum were occasionally isolated in mixture from single lesions (10.4% and 9.6%, respectively). Other species were more frequently isolated in mixture: 30.8% for P. intermedium, 33.8% for P. sylvaticum/irregulare, 42.9% for P. ultimum, and 66.7% for P. coloratum. A contingency analysis allowed us to define ‘major’ and ‘minor’ species on both pathological and ecological criteria (frequency of occurrence in the complex, pathogenicity and ability to induce lesions by themselves), and demonstrated that infection by one ‘major’ pathogen species (P. violae or P. sulcatum) is not positively correlated with the presence of a second Pythium species. The ratio between ‘observed’ and ‘expected’ mixed infection frequency under the assumption of independent infection (mir) was less than 1 for P. violae, P. sulcatum, P. intermedium, and P. sylvaticum/irregulare (P < 0.05). For all Pythium species, there was a negative linear relationship between mir and pathogenicity (R2 = 0.638): the less a Pythium species was pathogenic on carrot, the more often it was isolated from a CCS lesion in mixture with at least one other species. The non-significance of interactions between species during the infection phase suggests that CCS epidemics can be analysed as if they were caused by a single Pythium species.  相似文献   

10.
Ginseng is an important medicinal plant, but almost no genomic information is known for it. For the primary step to understand the Panax genome, we inspected the chloroplast genome sequence diversity and used that to infer the evolution of Panax species using them. We inspected a total of 101 intergenic spacers (IGS) covering 44,563 bp (96.8 % of the total IGS) from four Panax species. Diversity was inspected by three steps: gel electrophoresis, high resolution melting (HRM) analysis, and further confirmation by sequencing. Even though low levels of InDel polymorphism were detected by gel electrophoresis, high levels of reproducible polymorphisms were identified by HRM analysis. Sequencing of the HRM-polymorphic spaces and pair-wise multiple sequence alignments revealed up to 247 sequence variations between species. We have identified 62 IGS showing polymorphism between species. Among them, the trnE-trnT, trnT-psbD, ndhF-rpl32, and rpl14-rpl16 spaces are more informative for studying the diversity of Panax relatives. Phylogenetic analysis and molecular evolution studies revealed that P. notoginseng is most diverged from the other Panax species, with a nucleotide substitution rate of 0.0039. P. quinquefolius shows a close relationship with P. ginseng and P. japonicus, with a nucleotide substitution rate of 0.0009. Meanwhile, no sequence variation was detected between P. ginseng and P. japonicus. Calculation of molecular clocks revealed that P. notoginseng diverged more than 1.30 million years ago from the other Panax species and then, P. quinquefolius diverged from P. ginseng by migration in the American continent more than 0.29 million years ago.  相似文献   

11.
This study determined the cell density in the field and the biological activity of culturable phosphate-solubilizing microorganisms (PSMs) present in the Elaeis guineensis Jacq. rhizosphere at two locations in a commercial plantation. Promising isolates found in two soils under different agronomic management conditions were selected. We first calculated the cell density of cultivable PSMs grown in SRS medium (Sundara-Rao and Sinha, 1963) supplemented with the insoluble phosphate sources Ca3(PO4)2, AlPO4, and FePO4. Twenty-two bacteria, ten filamentous fungi, and eight yeast isolates were found. The 16 isolates with the clearest P solubilization halo in Petri dishes were selected to estimate their P solubilization potential in SRS medium with Ca3(PO4)2. No solubilization activity was registered using AlPO4 or FePO4 as the P sources. Ten of the isolates presented solubilization efficiencies between 20 and 82%. Some of these isolates showed high percentages of identity with the 16S and ITS rDNA sequences of the genera Aspergillus, Penicillium, Klebsiella, Burkholderia, and Staphylococcus according to the NCBI and EzTaxon-e databases. The solubilization activity of the isolates was associated with a decrease in the pH and the release of organic acids, such as gluconic, citric, succinic, and acetic acids. Gluconic acid was mainly released by the genera Aspergillus and Penicillium, and these isolates also showed the highest solubilization activities (82 and 80%, respectively). Therefore, these isolates were selected as the most promising isolates present in the oil palm rhizosphere for phosphate solubilization.  相似文献   

12.
We characterized nif gene structure of Paenibacillus polymyxa strain P2b-2R, an endophytic diazotroph that can provide up to 79 % of foliar N in lodgepole pine through biological nitrogen fixation. We amplified a 388-bp internal nifH gene fragment from P2b-2R using the single specific primer–polymerase chain reaction (SSP-PCR) and performed a Southern blot analysis of Pst I/HindIII-digested genomic DNA to evaluate the sequence, copy number, and location in the nif gene operon. This strain was found to possess a single copy of the nifH gene with nifB located directly upstream of nifH and D. Phylogenetic analyses of the full nifH, partial nifB, and nifD, and 16s rDNA (rrs) gene sequences indicated that P2b-2R was part of a monophyletic cluster with other members of the genus Paenibacillus and suggest that nifH is transmitted horizontally while nifD is transmitted vertically. Our results provide the first full nifH sequence from a P. polymyxa strain and indicate that arrangement of genes in the P2b-2R nif operon is consistent with those observed in other species of the genus Paenibacillus.  相似文献   

13.
Consensus nematode 18S ribosomal DNA primers were designed by aligning available 18S sequences and identifying a variable region flanked by highly conserved regions. These primers were then used to amplify nematode 18S rDNA from whole soil community DNA extracted from a range of European grassland types. Cloning of the PCR amplicons (778 bp) followed by restriction digest analysis (RFLP) resulted in the recovery of 34 unique nematode sequences from the four grasslands studied. Comparison of these data with the limited number of 18S rDNA nematode sequences currently held in on-line databases revealed that all of the sequences could be assigned to known nematode taxa albeit tentatively in some cases. Two of the sequences recovered from the site in the Netherlands (wet, hay-grassland) were recovered in a clade that included a sequence of the genus Trichodorus whilst other sequences from this site showed similarity with 18S rDNA sequences of the genus Prismatolaimus (five sequences), Xiphinema (one sequence) and Enoplus (one sequence). Of the remaining sequences, two showed some affinity with Mylonchulus (UK, upland peat), four with Steinernema (UK) and one sequence with Mesorhabditis (Hungary, east European Steppe). Three sequences from the Netherlands and one from Hungary were recovered in a clade that included a sequence of the genus Pratylenchoides whilst three further sequences from the Netherlands and two from Hungary were recovered in a clade encompassing the genus Globodera. Of the remaining nine sequences, two (NL6, NL62) formed a distinct lineage within the Adenophorea with 90% bootstrap recovery in a paraphyletic clade that included sequences of Prismatolaimus and Trichodorus. Seven sequences (three from the Netherlands, three from the UK and one from Greece) were left unassigned though the tree topology suggested some relationship (58% bootstrap recovery) with the genus Cephalobus. To assess whether primers used to amplify 18S rDNA might be used to fingerprint genetic diversity in nematode communities in soil, the environmental sequence data were used to design a second set of primers carrying a GC-clamp. These primers amplified a 469 bp fragment internal to the region flanked by the primer set used to derive the nematode trees and were used to amplify 18S rDNA for subsequent analysis using denaturing gradient gel electrophoresis (DGGE). DGGE analysis of six major European grassland types revealed considerable genetic diversity between sites. However, the relationships seen with the DGGE data were inconsistent with previous studies where the same soils had been characterized with respect to functional and morphological diversity. To confirm that this second set of primers was amplifying nematode sequences, selected bands on the DGGE gels were extracted, PCR amplified and sequenced. The final alignment was 337 bases. These analyses revealed the presence of sequence signatures from the genera Paratrichodorus, Plectus, Steinernema, Globodera, Cephalobus and Pratylenchoides.  相似文献   

14.
A total of 98 non-symbiotic endophytic bacterial strains isolated from soybean root nodules were classified into eight rDNA types in ARDRA analysis and 21 BOX types in BOX-PCR. The phylogenetic analysis of 16S rDNA identified these strains as Pantoea, Serratia, Acinetobacter, Bacillus, Agrobacterium, and Burkholderia. Limited genetic diversity was revealed among these bacteria since most of the strains (85.7%) were found in three very similar rDNA types corresponding to Pantoea agglomerans, and many strains shared the same BOX-PCR patterns. The inoculation of nodule endophytes had no significant effects on the growth and nodulation of soybean, but most of the strains produced indoleacetic acid (IAA), could solubilize mineral phosphate, and could fix nitrogen, implying that they are a valuable pool for discovering plant growth promoting bacteria. Our results demonstrated that the nodule endophytes were common in soybean and their diversity was affected by the plant's character and the soil conditions. The 99% similarities found in the nifH genes of Bradyrhizobium japonicum and of the endophytic Bacillus strains strongly indicated that horizontal transfer of symbiotic genes happened between the symbiotic bacteria and the endophytes.  相似文献   

15.
Summary Seven wildPetunia species including 2n = 18 species (P. parviflora Jussieu,P. linearis Hook.) and those with 2n = 14 (P. parodii Steene,P. axillaris Lam.,P. integrifolia Hook.,P. inflata R.E. Fries,P. violacea Lindl.) and tenPetunia hybrida horticultural lines were compared for polymorphisms in rDNA genes using the four restriction enzymesEcoRI,BamHI,HindIII andXhoI. All the unit types found in the lines pre-existed in the wild forms. There are two different sizes of either 11.45 or 11.6 kb./The 2n = 18 species are closely related to the 2n = 14 species, thus making thePetunia genus homogeneous. Moreover, it is likely thatP. hybrida lines originated in several kinds of crosses between these species. We constructed a dendrogram for all the 15 rDNA unit types found. Two main branches of the tree result from the presence or the absence ofHindIII sites. The main branch is divided according to variability at theEcoRI andBamHI sites. Taking into account the existence of several loci which carry one unit type only, we consider whether or not exchanges might occur between loci. Lines carrying two unit types and lines carrying three unit types support such a hypothesis.XhoI andBamHI fragments enable us to distinguish two types of 5S DNA corresponding to 2n = 18 and 2n = 14 species, respectively.P. hybrida lines and each 2n = 14 wild species carry one of the types only, that corresponds to one 5S DNA locus. The most parsimonious phylogenetic trees whatever the species chosen as the outgroup, do not fit with our knowledge ofPetunia and with taxonomy. This is likely because only few loci formed the basis of these phylogenetic constructions.  相似文献   

16.
Saccaromonospora viridis is a thermophilic actinomycetes organism which is found in mushroom compost, as well as being a causal agent of mushroom worker's lung (MWL) and other hypersensitivity pneumonitis conditions, including farmer's lung. Phenotypically, it is difficult to distinguish the seven species described for this genus based solely on chemtaxonomic characterization, therefore it was the aim of this study to examine partial 16S rDNA PCR amplification and direct sequencing, as an improved molecular means of identification of Saccharomonospora viridis, associated with MWL. The approach adopted in this study was to identify hypervariable regions within the 16S rRNA gene, which could be employed as signature sequences of the seven individual species within this genus and to employ highly conserved flanking primers to allow initial PCR amplification, prior to direct DNA sequencing of the 16S rDNA amplicon, in a partial 16S rDNA-sequence typing technique. Four universal 16S rDNA primer combinations [P11P/P13P, PSL/PSR, XB1(SV)/PSR and XB1(SV)/P13P] were compared for their ability to identify an unknown thermophilic Saccharomonospora organism from MWL. All PCR primer combinations coupled with direct sequencing allowed for the successful identification of the MWL isolate as S. viridis, demonstrating that universal 16S rDNA PCR primer pairs examined, including the P11P/P13P primer pair, flank regions within the 16S rRNA gene, of sufficient hypervariability to be able to reliably differentiate S. viridis from the other species within this genus. This approach may therefore be useful in the identification of Saccharomonospora spp. associated with composting, as well as with allergic alveolitis or pneumonitis associated occupational exposure in agricultural and horticultural environments, including mushroom production.  相似文献   

17.
Our previous studies of the native rhizobial population associated with peanut nodules in the Córdoba soils of Argentina revealed that this population is highly diverse and includes slow- and fast-growing isolates. The native fast-growing isolates NCHA22 and NET30 were selected on the basis of their plant growth promoting properties and their chromosomal genotypes were determined by 16S rDNA sequencing. NCHA22 and NET30 16S rDNA alleles were found to cluster with those of Rhizobium tropici group IIB and Rhizobium giardinii bv. giardinii strain H152, respectively. We have now characterized these isolates by analyzing the glnA and nifH genes to clarify their taxonomic position. These studies confirmed that fast-growing isolates belonging to species earlier described as bean symbionts were obtained from nodules of a leguminous plant that has been described as efficiently nodulated exclusively by slow-growing rhizobial strains.  相似文献   

18.
The rDNA PCR–RFLP of foxtail millet (Setaria italica) germ-plasm collected throughout Eurasia and from a part of Africa was investigated with five restriction enzymes according to our previous study. Foxtail millet germ-plasms were classified by length of the rDNA IGS and RFLP; clear geographical differentiation was observed between East Asia, the Nansei Islands of Japan-Taiwan-the Philippines area, South Asia and Afghanistan-Pakistan. We also found evidence of migration of foxtail millet landraces between the areas. We calculated diversity index (D) for each region and found that center of diversity of this millet is East Asia such as China, Korea and Japan.  相似文献   

19.
Understanding microbial responses to crop rotation and legacy of cropping history can assist in determining how land use management impacts microbially mediated soil processes. In the literature, one finds mixed results when attempting to determine the major environmental and biological controls on soil microbial structure and functionality. The objectives of this research were to: (1) Qualitatively and quantitatively measure seasonal and antecedent soil management effects on the soil microbial community structure in the rhizosphere of a subsequent tomato crop (Solanum lycopersicum) and (2) Determine phylum scale differences between the rhizosphere and bulk soil microbial community as influenced by the antecedent hairy vetch (Vicia villosa), cereal rye (Secale cereale), or black plastic mulch treatments. In this report, we use terminal restriction fragment length polymorphisms in the 16s rDNA gene to characterize changes in microbial community structure in soil samples from a field replicated tomato production system experiment at USDA-ARS Beltsville Agricultural Research Center, Beltsville, MD, USA. We found season of the year had the strongest influence on the soil microbial community structure of some of the major microbial phyla. Although we monitored just a few of the major microbial phyla (four Eubacteria and Archaea), we found that the effects of the tomato plant on the structural composition of these phyla in the rhizosphere differed dependent on the antecedent cover crop. Increased understanding of how agricultural factors influence the soil microbial community structure under field conditions is critical information for farmers and land managers to make decisions when targeting soil ecosystem services that are microbially driven.  相似文献   

20.
Eubacterial cellular endoparasites belonging to the genus Wolbachia (Rickettsiales) are extremely widespread symbionts of Arthropoda and Nematoda. Their ability to manipulate the reproductive behavior of the host is of particular importance to the fauna of the deep soil horizon, an environment in which parthenogenesis-inducing symbionts can play a crucial role in shaping population dynamics and speciation processes. In this study, three novel cases of infection in parthenogenetic Collembola (Parisotoma notabilis, Neelus murinus and Megalothorax minimus) are described. Sequences for molecular markers 16S rDNA and ftsZ were obtained for each species; their phylogenetic affinities with known Wolbachia supergroups were established using Bayesian inference. The analysis confirmed the presence of a Wolbachia strain belonging to the supergroup E, already reported from Folsomia candida and the Tullbergiidae, in the isotomid P. notabilis, while the Neelipleona M. minimus and N. murinus host a well differentiated strain which is phylogenetically distinct from supergroup E. Multiple events of Wolbachia infection in springtails as well as a richer diversity of the symbiont strains in soil arthropods were hereby confirmed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号