Stable isotopes and gut contents indicate differential resource use by coexisting asp (Leuciscus aspius) and pikeperch (Sander lucioperca)

Differential use of habitat and prey resources is an important mechanism that may allow coexistence of sympatric species. Unlike interactions between smaller cyprinid and percid fishes, the resource use by coexisting predatory asp (Leuciscus aspius) and pikeperch (Sander lucioperca) is relatively unknown. Here, gut content and stable isotope analyses were used to study ontogenetic dietary shifts and interspecific trophic niche overlap between asp and pikeperch coexisting in two reservoirs. The hypothesis that both species show an ontogenetic dietary shift from small invertebrates to large fish prey, but at the same time use different prey resources to reduce potential competitive interactions, was validated. The isotopic niches of the two predators showed no, or only a moderate, degree of overlap (0%–65%). The ontogenetic changes in the degree of interspecific isotopic niche overlap were different in the two reservoirs, suggesting that trophic segregation can be dynamic and variable among systems. Gut contents revealed that small (<100 mm standard length) asp consumed mostly terrestrial invertebrates and emerged aquatic insects, whereas small pikeperch foraged on zooplankton, larval and pupal stages of aquatic insects and fish. Larger individuals (>100 mm) of both species were predominantly piscivorous, with asp consuming more cyprinid prey and pikeperch more percid prey. Coexisting asp and pikeperch populations are able to utilise different prey resources, thereby reducing potential negative competitive interactions.     

油萝卜抗胞囊线虫基因的染色体定位及其在油菜附加系中的稳定性

【目的】油萝卜（2n=18,9条染色体分别被称作a～i）具有抗甜菜胞囊线虫的基因。探索油萝卜携带的抗甜菜胞囊线虫基因所在的染色体和外源的油萝卜染色体在油菜中的遗传稳定性。【方法】9个油菜附加系进行自花受粉,分别获得附加系的自交F2代。利用筛选的分子标记检测和原位杂交（FISH）检测附加染色体在F2代中的遗传稳定性;通过对9个油菜附加系F2代接种甜菜胞囊线虫的2龄幼虫,鉴定携带抗甜菜胞囊线虫基因所在的染色体。【结果】9个附加系自交F2代中的附加染色体遗传表现不一,5个油菜附加系的F2代中均有2条附加染色体,能稳定遗传;4个附加系的自交后代中附加染色体的遗传表现不稳定,部分后代中无附加染色体。FISH检测9个附加系自交F2代中的附加染色体表明：与分子标记检测的结果相符,并且4个不稳定的附加系中,有的自交后代虽然有附加染色体,但有1或2条。接种甜菜胞囊线虫测定结果表明,含有油萝卜染色体DD的油菜附加系对甜菜胞囊线虫的抗性水平与附加染色体的供体油萝卜相当,而其它8个附加系的自交后代未表现出抗性,与受体油菜相近。【结论】油萝卜的9条染色体分别附加到油菜中后,其遗传稳定性因附加的染色体而异,有的能稳定遗传,有的在自交后代中丢失1或2条;抗甜菜胞囊线虫的基因在d染色体上。     

Detection and quantification of <Emphasis Type="Italic">Tomato mosaic virus</Emphasis> in irrigation waters

A quantitative RT real-time PCR method was developed for the detection and quantification of Tomato mosaic virus (ToMV) in irrigation waters. These have rarely been monitored for the presence of plant pathogenic viruses, mostly due to the lack of efficient and sensitive detection methods. The newly developed method presented here offers a novel approach in monitoring the health status of environmental waters. ToMV was reliably detected at as low as 12 viral particles per real-time PCR reaction, which corresponds to the initial concentration of approximately 4.2 × 10^?10 mg (6,300 viral particles) of ToMV per ml of sample. The sensitivity of the method was further improved by including the Convective Interaction Media^® (CIM) monolithic chromatographic columns for quick and efficient concentration of original water samples. Seven out of nine water sources from different locations in Slovenia tested positive for ToMV, after concentrating the sample. Four samples tested ToMV-positive without the concentrating procedure. The presence and integrity of infective ToMV particles in the original sample, as well as in the chromatographic fraction, was confirmed using different methods from test plants, DAS ELISA to electron microscopy and real-time PCR. In this study, we propose a unique and simple diagnostic scheme for rapid, efficient, and sensitive monitoring of irrigation waters that could also be adopted for other plant, human or animal viruses.     

萝卜-甘蓝型油菜中萝卜基因组的RAPD与dpRAPD分析效率研究

应用RAPD与dpRAPD方法鉴定萝卜-甘蓝型油莱中萝卜基因组,筛选了140条随机引物。结果表明,平均每条引物(组合)能产生的萝b基因组特异标记数dpRAPD高于RAPD,分别为1．69和1．33;在dpRAPD扩增产物中有77．6％谱带清晰易辨,略高于RAPD(75．4％)。两者所检测到的萝卜基因组标记大部分为各自特异的扩增产物。由于结合了荧光标记引物,dpRAPD反应产物可在Genetic Analyzer上分离检测,因此能检测到100bp以下的小片段DNA。     

Rickettsial Infection in Animals,Humans and Ticks in Paulicéia,Brazil

A previous study in Paulicéia Municipality, south‐eastern Brazil, reported 9.7% of the Amblyomma triste ticks to be infected by Rickettsia parkeri, a bacterial pathogen that causes spotted fever in humans. These A. triste ticks were shown to be associated with marsh areas, where the marsh deer Blastocerus dichotomus is a primary host for this tick species. During 2008–2009, blood serum samples were collected from 140 horses, 41 dogs, 5 opossums (Didelphis albiventris) and 26 humans in farms from Pauliceia Municipality. Ticks were collected from these animals, from vegetation and from additional wildlife in these farms. Overall, 25% (35/140) of the horses, 7.3% (3/41) of the dogs, 3.8% (1/26) of the humans and 100% (5/5) of the opossums were seroreactive (titre ≥64) to spotted fever group (SFG) Rickettsia spp. Multivariate statistical analysis indicated that horses that were allowed to forage in the marsh were 4.8 times more likely to be seroreactive to spotted fever group (SFG) Rickettsia spp than horses that did not forage in the marsh. In addition, horses that had been living in the farm for more than 8.5 years were 2.8 times more likely to be seroreactive to SFG Rickettsia spp than horses that were living for ≤8.5 years. Ticks collected from domestic animals or from vegetation included Amblyomma cajennense, Amblyomma coelebs, Amblyomma dubitatum, Dermacentor nitens and Rhipicephalus microplus. By PCR analyses, only one pool of A. coelebs ticks from the vegetation was shown to be infected by rickettsiae, for which DNA sequencing revealed to be Rickettsia amblyommii. Ticks (not tested by PCR) collected from wildlife encompassed A. cajennense and Amblyomma rotundatum on lizards (Tupinambis sp), and A. cajennense and A. triste on the bird Laterallus viridis. Our results indicate that the marsh area of Paulicéia offers risks of infection by SFG rickettsiae.     

Putative new species of the genus Dickeya as major soft rot pathogens in Phalaenopsis orchid production

Bacterial soft rots are a serious limitation to the production of orchids and other horticultural plants. Here, the characterization of causative bacteria isolated from Phalaenopsis orchids showing symptoms, from a commercial production site, is reported. The most commonly isolated bacteria were identified as Dickeya spp. Partial sequencing of 16S rDNA, fliC and dnaX showed diversity among the isolates and divided the isolates into two groups, with greatest similarity to previously reported undefined Dickeya lineages from orchids (UDL‐3 and UDL‐4). Two isolates (B16, S1) were sequenced using next‐generation sequencing, which has provided draft genomes of these two isolates for further studies (Ali? et al., 2015 ). Newly developed fliC‐based lineage‐specific quantitative real‐time PCR assays were used to distinguish among the lineages and to assess their relative abundances in diseased tissues. Virulence and aggressiveness comparison tests in vivo on Phalaenopsis orchids, potato plants and witloof chicory leaves indicated high virulence and extreme maceration potential of these novel Dickeya isolates, compared to a reference panel of other Dickeya spp. Pantoea cypripedii (formerly Pectobacterium cypripedii), which has previously been reported as a soft rot pathogen of orchids, was not detected, and isolates obtained from culture collections did not cause symptoms on artificially infected Phalaenopsis orchids.     

The effect of depth, distance from dam and habitat on spatial distribution of fish in an artificial reservoir

Abstract –  Spatial distribution of the fish community in the deep canyon-shaped Římov Reservoir, Czech Republic, was studied using overnight gillnetting fishing in 1999–2007. Effects of depth, distance from the dam to the tributary and habitat type (benthic and pelagic) on fish community structure, catch per unit of effort (CPUE), biomass per unit of effort (BPUE) and average weight were tested. Fish were recorded in all sampled depths and parts of the reservoir. Redundancy analysis revealed that effects of three environmental variables were significant and most variability was explained by depth, then by distance from the dam and habitat type. CPUE and BPUE of all species decreased with depth and responses of individual species to depth were similar for juvenile and adult fish. Number of species, CPUE and BPUE of all species except perch increased heading towards the tributary and peaked close to or at the tributary part of the reservoir. Responses of juvenile fish to distance from the dam differed from that of adult fish. Structure of fish community differed in benthic and pelagic habitats with species preferably occupying epipelagic (bleak, asp, rudd and juvenile bleak, roach and bream) or littoral waters (perch, pikeperch, ruffe, roach, bream and juvenile percids). This study showed that fish distribution in the reservoir followed distinct patterns, which were probably shaped by a combination of physiological constraints plus trade-off between food resources and competition.     

The diet and growth of larval and juvenile pikeperch (Stizostedion lucioperca (L.)): A comparative study of fishponds and a reservoir

Diet of larval and juvenile pikeperch (Stizostedion lucioperca) reared in ponds wasinvestigated and compared with the diet ofpikeperch from a reservoir. The standard lengthof first feeding pikeperch larvae in ponds was6.1 mm, on average, and although rotifers werepresent in the diet, their numericalcontribution can be considered asinsubstantial. Rotifers were soon replaced bynauplii of cyclopoid copepods, which werehighly positively selected and contributedlargely to the diet up to a larval length of 10 mm.Daphnia spp. were consumed from the onsetof exogenous feeding, but were not positivelyselected until 15 mm. Anothersmaller cladoceran Bosmina longirostriswas highly negatively selected and did notcontribute significantly to the diet. A clearpositive selection for larger relatively tosmaller prey and a preference for Daphniafrom a body length of 15 mm onwards could beobserved. In the reservoir, rotifers were notfound in the diet of pikeperch larvae even inthe smallest individuals. Dominant food itemswere nauplii and 1st copepodite instar ofEudiaptomus gracilis and Cyclopsspp. Cladocerans – Daphnia galeata andto a lesser extent Diaphanosomabrachyurum appeared in the pikeperch diet at alength of about 10 mm. A shift from copepods toDaphnia spp. and especiallyLeptodora kindtii could be recognised inpikeperch at a length of 20 mm. When comparing ourdata from nursing ponds with the data fromímov reservoir, similar trends in dietcomposition were observed.Growth of pikeperch was found significantlyfaster in nursing ponds than in the reservoir.Slow growth of reservoir pikeperch was probablyan artefact due to the prolonged spawningperiod in the reservoir. Larvae and juvenilesfrom later spawnings decreased the average sizeof the population over the studied period. Innursing ponds lowest average standard length atharvest was found in the pond with the highestnumbers of fish, and vice versa in the pondwith the lowest numbers the largest standardlength was recorded. This result corresponds tothe increased intracohort food competitionamong juvenile pikeperch with increasingstocking density.     

Development of a complete set of disomic rape-radish chromosome-addition lines

After crosses of multiple rape-radish chromosome additions with rape, nine different monosomic additions (2n = 4x = 38 + 1) of individual radish chromosomes, a–i, were isolated, having the genomic background of winter oil seed rape and radish cytoplasm. Extra chromosomes were identified with RAPD markers, specific for individual radish chromosomes. All radish-plasmic monosomic additions, except that of chromosome f, had low seed production due to pistilloid stamens. Rape cytoplasm was substituted by crossing the monosomic additions as pollinators to rape followed by reselection of the radish chromosome additions. The monosomic additions in rape cytoplasm showed normal male fertility. Average transmission rates of radish chromosomes via egg cells and pollen cells were 37% and 27%, respectively. Lowest male transmission was found for chromosomes e and f with 0.04 and 0.01. Monosomic additions were self-pollinated to produce disomic additions. Monosomic and disomic addition progenies were discriminated by a prescreening with quantitative double primer (dp) RAPDs and cytological confirmation of preselected candidates by FISH analysis using a Raphanus-specific probe. Usability of this complete set of nine disomic rape-radish additions (2n = 4x = 38 + 2) was discussed.     

Effect of combined nitrogen and sulphur fertilization on yield and qualitative parameters of Camelina sativa [L.] Crtz. (false flax)

Abstract

Camelina (Camelina sativa (L.) Crtz., false flax) is described as a species requiring fewer inputs than other oilseed crops thus making it an interesting alternative in sustainable cropping systems. As information on the combined effects of nitrogen and sulphur on camelina yield and quality parameters is meagre, a pot fertilization experiment was carried out with nitrogen applied as NH₄NO₃ at three increasing rates equivalent to a range from 63 up to 127 kg ha^?1. These treatments were combined with sulphur additions applied as (NH₄)₂SO₄ to achieve a soil sulphate content of 25 or 45 mg kg^?1, respectively (equivalent to 75 and 135 kg S ha^?1). The medium and high nitrogen rates combined with the low sulphur fertilization level increased the number of branches per plant compared with the lowest nitrogen fertilization at the same sulphur rate. Camelina seed yield increased with increasing nitrogen doses at the same low sulphur level, whereas straw yield increased only at the highest rate of nitrogen. Thousand-seed mass increased at the highest nitrogen dose and with the low sulphur application rate. In addition, the increase in nitrogen fertilization reduced seed oil content from 39.8% to 37.1%. A highly negative correlation was observed between oil and protein content of seeds. Nitrogen fertilization increased total oil yield and total protein yield. Differences in crop parameters between the sulphur treatments were not significant statistically, although the higher sulphur treatment tended to increase seed yield as well as oil and protein content compared with the low sulphur treatment. Thus, the combined application of N and S as mineral fertilizers is only recommended when growing camelina on sulphur-deficient soils if the aim is to achieve both high oil and protein production.