Morphology and general characteristics of phages of chickpea rhizobia

Six rhizobiophages designated as RC1, RC2, RC3, RC4, RC5 and RC6, infective against six strains of chickpea Rhizobium were isolated from field soils. Seasonal incidence, morphology, host range and inactivation pattern of the phages to heat and UV-light were studied. Four investigated phages were differentiated into two morphological types; one with hexagonal head and a long flexible tail (RC1 and RC5), the other with hexagonal head and a very short tail (RC2 and RC3). Electron microscopic examination of phage RC1 infected cells revealed that phage multiplication occurred at one pole of the cell. Phage RC3 appeared to be more thermal sensitive than others and exhibited one component inactivation while relatively resistant phages (RC1 and RC2) revealed two component inactivation. The six phages could be grouped into two classes on the basis of UV sensitivity; relatively resistant (RC1, RC2 and RC5) and sensitive (RC3, RC4 and RC6).     

Phenotypic and molecular characterization of indigenous rhizobia nodulating chickpea in India

In a combined approach of phenotypic and genotypic characterization, 28 indigenous rhizobial isolates obtained from different chickpea growing regions in peninsular and northern India were analyzed for diversity. The field isolates were compared to two reference strains TAL620 and UPM-Ca142 representing M. ciceri and M. mediterraneum respectively. Phenotypic markers such as resistance to antibiotics, tolerance to salinity, temperature, pH, phosphate solubilization ability, growth rate and also symbiotic efficiency showed considerable diversity among rhizobial isolates. Their phenotypic patterns showed adaptations of rhizobial isolates to abiotic stresses such as heat and salinity. Two salt tolerant strains (1.5% NaCl by T1 and T4) with relatively high symbiotic efficiency and two P-solubilising strains (66.7 and 71 microg/ml by T2 and T5) were identified as potential bioinoculants. Molecular profiling by 16S ribosomal DNA Restriction Fragment Length Polymorphism (RFLP) revealed three clusters at 67% similarity level. Further, the isolates were differentiated at intraspecific level by 16S rRNA gene phylogeny. Results assigned all the chickpea rhizobial field isolates to belong to three different species of Mesorhizobium genus. 46% of the isolates grouped with Mesorhizobium loti and the rest were identified as M. ciceri and M. mediterraneum, the two species which have been formerly described as specific chickpea symbionts. This is the first report on characterization of chickpea nodulating rhizobia covering soils of both northern and peninsular India. The collection of isolates, diverse in terms of species and symbiotic effectiveness holds a vast pool of genetic material which can be effectively used to yield superior inoculant strains.     

Molecular diversity and phylogeny of rhizobia associated with wild legumes native to Xinjiang, China

A total of 111 rhizobial strains were isolated from wild legumes in Xinjiang, an isolated region of northwest China. Nine genomic species belonging to four genera of Rhizobium, Mesorhizobium, Ensifer, and Bradyrhizobium were defined among these strains based on the characterization of amplified 16S ribosomal DNA restriction analysis (ARDRA), restriction fragment length polymorphism (RFLP) analysis of 16S-23S rDNA intergenic spacers (IGS), 16S rRNA gene sequencing and multilocus sequence analysis (MLSA). Twenty-five nodC types corresponding to eight phylogenetic clades were divided by RFLP and sequence analysis of the PCR-amplified nodC gene. The acid-producing Rhizobium and Mesorhizobium species were predominant, which may be related to both the local environments and the hosts sampled. The present study also showed the limitation of using nod genes to estimate the host specificity of rhizobia.     

黄土高原近10年植被覆盖的动态变化及驱动力

基于Timesat的非对称高斯函数(AG)拟合法重建MODIS-NDVI数据,利用像元二分模型估算了黄土高原近10年的植被覆盖度(VC),并分析了年植被覆盖度的变化趋势和其与降水温度的相关性。研究结果表明:黄土高原植被覆盖度总体上呈现东南高西北低、由东南向西北递减的特征。其中森林生态系统平均覆盖度最高,灌木、草地生态系统次之,荒漠生态系统最低,空间差异明显。2010年森林生态系统植被覆盖度达到81.6%,主要包括太行山、吕梁山和秦岭地区。暖温带森林区植被组成以落叶阔叶林为主,覆盖度常年较高,为80%以上。西北部温带草原区,植被覆盖度达到38.8%。温带草地主要依水分梯度,由东南到西北分布有以旱生性多年生草本植物为主的典型草原,植被覆盖度呈现相应的递减趋势。黄土高原总面积78.6%的地区年植被覆盖度呈增加趋势;而占总面积19.4%的地区年植被覆盖度呈下降趋势。在空间分布上,植被覆盖度显著增加的区域主要分布在榆林至延安周边地区和秦岭一带;植被覆盖度显著减少区域沿兰州至银川呈条带状分布。     

Primary succession over sixty years on hundred-year old islets in Lake Hjälmaren,Sweden

New islands were created as a result of an artificial lowering of the water table of Lake Hjälmaren in 1882–1886 and the floras of 40 such islands have been monitored ever since plant colonization started in 1886. Data used in this paper are from belt-transects across ten of these islands which were analysed in 1927–29 and reanalysed in 1986. During this 60-year period shading by trees has increased and shading and litter accumulation have affected the ground flora. Succession includes aspects of both convergence and divergence. Species of dry, open sites and shore species have been excluded from the island interiors, making these parts of the islands more similar, but there has simultaneously been an increased variability of vegetation types of shaded, mesic habitats. There have been no consistent trends in beta-diversity between the two surveys. Differences in successional patterns between island interiors and shore habitats are attributed to an outward migration of plant species and to differences in disturbance regimes.     

Phenotypic and molecular characterization of chickpea rhizobia isolated from different areas of Tunisia

Several phenotypic markers were used in this study to determine the biodiversity of rhizobial strains nodulating Cicer arietinum L. in various areas of Tunisia. They include symbiotic traits, the use of 21 biochemical substrates, and tolerance to salinity and pH. In addition, restriction fragment length polymorphisms (RFLPs) of PCR-amplified 16S rDNA were compared with those of reference strains. Numeric analysis of the phenotypic characteristics showed that the 48 strains studied fell into three distinct groups. This heterogeneity was highly supported by the RFLP analysis of 16S rRNA genes, and two ribotypes were identified. Chickpea rhizobia isolated from Tunisian soils are both phenotypically and genetically diverse. Results showed that 40 and 8 isolates were assigned, respectively, to Mesorhizobium ciceri and Mesorhizobium mediterraneum.     

Phenotypic and molecular characterization of chickpea rhizobia isolated from different areas of Morocco

AIMS: To determine the biodiversity of rhizobial strains nodulating Cicer arietinum L. in representative soils from various areas of Morocco. METHODS AND RESULTS: Symbiotic traits, utilization of 49 carbohydrate sources, resistance to antibiotics and heavy metals, tolerance to salinity, to extreme temperatures and pH were studied as phenotypic markers. In addition, restriction fragment length polymorphism (RFLP) of PCR-amplified 16S rDNAs were compared with those of reference strains. Numerical analysis of the phenotypic characteristics showed that the 48 strains studied fell into three distinct groups. RFLP analysis of 16S rRNA genes revealed an additional heterogeneity and four ribotypes were identified. CONCLUSIONS: Chickpea rhizobia isolated from Moroccan soils are both phenotypically and genetically diverse. Most of these rhizobia belong to the Mesorhizobium genus. However, some strains originating from a particular soil appeared to have 16S rRNA genes similar to Sinorhizobium as well as very distinct auxanographic characteristics compared with Mesorhizo- bium isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: A well characterized collection of chickpea-nodulating rhizobia in representative soils of Morocco has been generated, which can be used to develop efficient inoculants for this crop. This is the first report evidencing that chickpeas may be nodulated by bacteria from the Sinorhizobium genus.     

Biodiversity of populations of phosphate solubilizing rhizobia that nodulates chickpea in different Spanish soils

Within rhizobia, two species nodulating chickpea, Mesorhizobium ciceri and Mesorhizobium mediterraneum, are known as good phosphate solubilizers. For this reason, we have analysed the ability to solubilize phosphate of a wide number of strains isolated from Cicer arietinum growing in several soils in Spain. The aim of this work was to analyse microbial populations nodulating chickpea, that are able to solubilize phosphates, using molecular techniques. In the present work we analyzed 19 strains isolated from effective nodules of C. arietinum growing in three soils from the North of Spain. Nineteen strains showed ability to solubilize phosphate in YED-P medium. These strains were separated into 4 groups according to the results obtained by 879F-RAPD fingerprinting. The 16S rDNA sequencing of a representative strain from each group allowed the identification of strains as belonging to the genus Mesorhizobium. Strains from groups I and II showed a 99.4% and 99.2% similarity with M. mediterraneum UPM-CA142^T, respectively. The strains from group III were related to M. tianshanense USDA 3592^T at a 99.4% similarity level. Finally, the strain from group IV was related to M. ciceri USDA 3383^T with a 99.3% similarity. The LMW RNA profiles confirmed these results. Strains from groups I and II showed an identical LMW RNA profile to that of M. mediterraneum UPM-CA142^T; the profile of strains from group III was identical to that of M.␣tianshanense USDA 3592^T and the profile of strains from group IV was identical to that of M. ciceri USDA 3383^T. Different 879F-RAPD patterns were obtained for strains of the group I, group II and the M.␣mediterraneum type strain (UPM-CA142^T). The 879-RAPD patterns obtained for group III also differed from the pattern shown by M. tianshanense USDA 3592^T. Finally, the patterns between group IV and M. ciceri USDA 3383^T were also different. These results suggest that groups I and II may be subspecies of M. mediterraneum, group III a subspecies of M. tianshanense and group IV a subspecies of M. ciceri. Nevertheless, more studies are needed to establish the taxonomic status of strains isolated in this study.     

Seasonal succession of phytoplankton in Lake Yogo over 2 years: effect of artificial manipulation

We studied the seasonal variation in concentrations of nutrients and phytoplankton in Lake Yogo for 2 years, from May 2000 to May 2002, in order to clarify the seasonal succession of phytoplankton and the effect of various manipulations on it. It was revealed that in spite of the installation of aeration systems and the pumping of mesotrophic water from Lake Biwa during the summer season, the trophic state of Lake Yogo overall has not improved during the past few decades. However, the pumping of water from Lake Biwa did affect the concentrations of nutrients and the periods of cyanobacterial bloom during the summer. The pumping period was different in each year, and the cyanobacterial bloom occurred during the period without pumping in both years. The aeration destratification was not strong enough to prevent cyanobacterial blooms. Cyanobacteria and Bacillariophyceae contributed most to the phytoplankton biomass in both years. Aphanizomenon, Anabaena, and Microcystis were the main genera among cyanobacteria. The bloom of Aphanizomenon or Anabaena occurred early in the summer, and was then replaced by Microcystis. Aphanizomenon was almost always present, and often formed bloom even in winter. The seasonal succession of Bacillariophyceae was almost the same in both years and was well categorized: winter-growing species such as Aulacoseira pusilla (F. Meister) Tuji et Houki and species of Thalassiosiraceae, spring-growing species such as Asterionella formosa Hassall, Fragilaria crotonensis Kitton, and Synedra cf. acus, and fall-growing species such as Aulacoseira ambigua (Grunow) Simonsen, and Aulacoseira granulata (Ehrenb.) Simonsen.     

Genotypic alteration and competitive nodulation of Mesorhizobium muleiense against exotic chickpea rhizobia in alkaline soils

Mesorhizobium muleiense, Mesorhizobium mediterraneum and Mesorhizobium ciceri are chickpea (Cicer arietinum L.) rhizobia that share a high similarity of the symbiotic genes nodC and nifH, but they have different geographic distributions. M. muleiense has been isolated and found only in alkaline soils of Xinjiang, China, whereas the other two strains have been found in the Mediterranean and India. To investigate the species stability of M. muleiense during natural evolution and its capability of competitive nodulation against the other two exotic species, re-sampling of nodules in the field and competition experiments between the three species were conducted. The results showed that the predominant microsymbiont associated with chickpea grown in Xinjiang was still M. muleiense, but the predominant genotypes of M. muleiense had changed significantly during the four years since a previous survey. The data also showed that M. mediterraneum and M. ciceri were more competitive than the residential strain of M. muleiense CCBAU 83963^T in sterilized vermiculite or soils from Xinjiang. However, in non-sterilized soils, M. muleiense was the predominant nodule occupier. These results indicated that natural or adapting evolution of M. muleiense was occurring in fields subjected to changing environmental factors. In addition, the biogeography and symbiotic associations of rhizobia with their host legumes were also influenced by biological factors in the soil, such as indigenous rhizobia and other organisms.     

Performance of chickpea,lentil and lupin nodulated with indigenous or inoculated rhizobia micropartners under nitrogen,boron, cobalt and molybdenum fertilization schedules

Chickpea (Cicer arietinum), lentil (Lens esculenta) and lupin (Lupinus albus) responded to inoculation with their respective symbiotants:Rhizobium loti, Rhizobium leguminosarum biovarviceae andBradyrhizobium sp. (Lupinus) alone or with (NH₄)₂SO₄ at 30 ppm N. Soil application of Na₂MoO₄.2H₂O at 3 ppm Mo, CoCl₂.6H₂O at 2 ppm Co²⁺ or Na₂B₄O₇.10H₂O at 1 ppm B with 0 and 30 ppm N increased nodule weight and plant dry weight and N-content 60 days after sowing and seed yield, seed size and the N and P contents of seed. Nodule numbers slightly decreased with application of such chemicals. Mo enhanced performance of the three plants more than Co and B. Yield, total N and P-contents of lupin were comparable with those of chickpea or lentil and lupin had the highest levels of both N₂-fixation and N absorption from the fertilizer. IndigenousR. leguminosarum biovarviceae was more established in the soil compared with the other two, chickpea and lupin, micropartners.     

Paeonia in Xinjiang,China

The present paper deals with the genus Paeonia in Xinjiang, whose taxonomy has been confused. Based on the field observation, population sampling and the examination of herbarium specimens, a taxonomical revision is made in this paper. Two species are recognized, i. e. Paeonia anomala L. and P. sinjiangensis K. Y. Pan. P. altaica K. M. Dai et T. H. Ying is reduced to P. sinjiangensis and P. hybrida (= P. anomala var. intermedia) is reduced to P. anomala. The diagnostic characters of the two species are described and illustrated, and a map of their distribution in Xinjiang is presented. A key to these two species is provided here. 1. Roots straight, not thickened; sepals all caudate, less frequently one or very rarely two non-caudate ................................................ 1. P. sinjiangensis K. Y. Pan. 2. Roots fusiform or tuberous; inner three sepals non-caudate, less frequently one of them caudate .............................................................. 2. P. anomala L. key words Xinjiang; Paeonia; P. anomala; P. sinjiangensis; revision     

Comparison of chickpea rhizobia isolates from diverse Portuguese natural populations based on symbiotic effectiveness and DNA fingerprint

Aims:  To test the hypothesis that differences in chickpea yields obtained in four distinct Portuguese regions (Beja, Elvas- Casas Velhas , Elvas- Estação Nacional de Melhoramento de Plantas (ENMP) and Évora) could be due to variation between the natural rhizobia populations.
Methods and Results:  Estimation of the size of the different rhizobial populations showed that Elvas-ENMP population was the largest one. Elvas-ENMP population also revealed a higher proportion of isolates carrying more than one plasmid. Assessment of genetic diversity of the native rhizobia populations by a DNA fingerprinting PCR method, here designated as DAPD (Direct Amplified Polymorphic DNA), showed a higher degree of variation in Elvas-ENMP and Beja populations. The symbiotic effectiveness (SE) of 39 isolates was determined and ranged 13–34%. Statistical analysis showed that SE was negatively correlated with plasmid number of the isolate.
Conclusions:  The largest indigenous rhizobia population was found in Elvas-ENMP. DAPD pattern and plasmid profile analysis both suggested a higher genetic diversity among the populations of Elvas-ENMP and Beja. No relationship was found between SE of the isolates and their origin site.
Significance and Impact of Study:  The large native population, rather than the symbiotic performance of individual rhizobia, could contribute to the higher chickpea yields obtained in Elvas-ENMP.     

The evolution of Helicobacter pylori antibiotics resistance over 10 years in Beijing, China

Objectives: To evaluate Helicobacter pylori antibiotics resistance evolution from 2000 to 2009 to amoxicillin, clarithromycin, metronidazole, tetracycline, levofloxacin and moxifloxacin in Beijing, China. Methods: A total of 374 H. pylori strains isolated from 374 subjects who had undergone upper gastrointestinal endoscopy from 2000 to 2009 were collected and examined by E‐test method for antibiotics susceptibility. Results: The average antibiotics resistance rates were 0.3% (amoxicillin), 37.2% (clarithromycin), 63.9% (metronidazole), 1.2% (tetracycline), 50.3% (levofloxacin) and 61.9% (moxifloxacin). Overall resistance to clarithromycin, metronidazole, and fluoroquinolone increased annually (from 14.8 to 65.4%, 38.9 to 78.8%, and 27.1 to 63.5%, in 2000 or 2006–2007 to 2009, respectively). The secondary resistance rates were much higher than primary rates to these antibiotics, which also increased annually in recent 10 years. Conclusions: The trend of clarithromycin, metronidazole, and fluoroquinolone resistance of H. pylori increased over time and the resistance to amoxicillin and tetracycline was infrequent and stable in Beijing. Clarithromycin, metronidazole, and fluoroquinolone should be used with caution for H. pylori eradication treatment.     

Patchiness, collapse and succession of a cyanobacterial bloom evaluated by synoptic sampling and remote sensing

Spatial patchiness and collapse of the cyanobacterium, Nodulariaspumigena, were evaluated in saline Pyramid Lake, Nevada, bytwo synoptic ground surveys and Landsat remote sensing. Horizontalvariation of surface water chlorophyll a during the first surveyranged from 3.6 to 9790 mg m^–3 and Nodularia biovolumewas between 416?10³ and 347?10⁶ µm³ ml^–1. Differencesin spatial and temporal resolution between synoptic ground surveys({small tilde}10m, hours) and Landsat imagery (80m, seconds)yielded a poor correlation when data were matched by commonground location. A regression model for estimating chlorophyllfrom Landsat radiance was developed by pairing equivalent frequenciesfrom cumulative relative frequency distributions of both variables.Wind driven advection precipitated bloom collapse shortly afterthe first synoptic sample and Nodularia mineralization producedhigh epilimnetic ammonium concentrations. Ammonium, silica fromfluvial sources, and density differences between river and lakewater masses stimulated succession to a Chaetoceros elmoreibloom within 8 days of the first synoptic survey. The 16 dayfly by interval of Landsat is too long to document such short-termbloom succession. Landsat imagery is most applicable for evaluatinginstantaneous, basin-scale horizontal patchiness and averagelakewide chlorophyll concentrations, while frequent synopticground surveys yield more accurate estimates of meso- and micro-scalephytoplankton patchiness and species succession.     

Detection of ribosomal DNA sites in lentil and chickpea by fluorescent in situ hybridization.

Hybridization sites of an rDNA probe coding for the 18S, 5.8S, and 26S genes were detected on lentil and chickpea somatic chromosomes using fluorescent in situ hybridization. One pair of hybridization sites was detected in cultivated lentil Lens culinaris L. and wild lentil L. orientalis (Boiss.) Hand.-Mazz., and in both the hybridization sites of the ribosomal probe correspond to the secondary constriction. In cultivated chickpea Cicer arietinum three pairs of rDNA sites were detected and in the wild C. reticulatum two pairs were detected. The karyotypic relationship between the cultivated C. arietinum and its wild progenitor C. reticulatum is discussed.     

Moisture changes over the past 467 years in the central Hexi Corridor,northwestern China

The long-term characteristics of precipitation in arid and semi-arid areas are of great interest because these areas are very sensitive to climate change and human activities. The Hexi Corridor is an arid and semi-arid region in northwestern China that also is an important sector of the Silk Road Economic Belt; despite the region’s dependence on precipitation, annually resolved, long-term moisture records are still lacking for this region. Here, a standard tree-ring width chronology spanning 1484–2015 AD is developed for the Hexi Corridor using Qilian juniper (S. przewalskii Kom.). The chronology is used to reconstruct moisture changes in the region over the past 467 years. Correlation analyses indicate that the tree-ring width index has a significant positive correlation with the June SPEI (standardized precipitation evapotranspiration index) on a twelve-month time scale (r=0.73, n=65, p<0.001). We used this information to build a transfer function that explains 52.5% of the variance in the SPEI reconstructed for the period from 1549 CE to 2015 CE. Our study area experienced clear alternations between dry and wet periods. Especially long wet periods include 1600–1650 AD and 1762–1804 AD; long dry periods include 1670–1693 AD, 1917–1970 AD, and 1990–2015 AD. The 1920s was the most severe period of drought in the last 467 years. The results of wavelet analysis and running correlation analysis indicate that the atmospheric circulation system experienced a notable shift around the 1800s, after which point the role of the westerly system grew more pronounced.