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 31 毫秒
1.
Sunflower (Helianthus annuus) stem canker caused by Diaporthe helianthi is one of the most important sunflower diseases in Croatia. Until recently, sunflower was the only known host for D. helianthi. In our research carried out in the area of Eastern Croatia, isolates of Diaporthe/Phomospis were collected from Xanthium italicum, X. strumarium and Arctium lappa. Using morphological, cultural and molecular ITS rDNA data, isolates from these weeds were identified as D. helianthi. The following isolates were used in the pathogenicity test: one isolate originated from sunflower (Su5/04), three from X. italicum (Xa2, Xa3 and Xa5), two from X. strumarium (Xa9 and Xa12), one from Xanthium sp. (Xa13) and one from A. lappa (Ar3). According to the results, it was determined that isolate Xa5 (originated from X. italicum) was the most pathogenic to sunflower stems. The average length of the lesion was 11.3 cm. The lowest level of pathogenicity was found in Xa9 (isolated from X. strumarium). The length of the lesion was 0.1 cm.  相似文献   

2.
The European bitterling, Rhodeus amarus, is a non-indigenous fish species in British fresh waters. It lays its eggs in unionid mussels which themselves are vulnerable to fouling by the non-indigenous zebra mussel, Dreissena polymorpha. Observations from an unmanipulated natural system showed that only 27% of zebra mussel-fouled Unio pictorum hosted bitterling, while 47% of unfouled U. pictorum hosted bitterling. We conducted a field experiment in the River Great Ouse catchment, Cambridgeshire, England in May–June 2007 and 2008 to quantify the impact of zebra mussels on bitterling load in host mussels. Zebra mussel-fouled unionids were significantly less likely to host bitterling than unfouled unionids. The number of unionids hosting bitterling did not differ significantly whether the zebra mussels fouling the unionid were alive or dead. Bitterling appeared to discriminate against zebra mussel-fouled unionids less as the 2007 breeding season advanced, potentially because preferred unfouled unionids had a higher bitterling load, and were therefore relatively lower quality hosts than at the start of the breeding season.  相似文献   

3.
Summary  Preparation of a catalogue of the plants of Colombia requires 30 new combinations in Stenostephanus Nees and five in Justicia L. to bring nomenclature up to date. Three new names Justicia littoralis J. R. I. Wood, J. albicans J. R. I. Wood and J. magdalenensis J. R. I. Wood are coined for Jacobinia lindaviana Rusby, Chaetothylax leucantha Leonard and Justicia disparifolia J. R. I. Wood respectively. The genus Pelecostemon Leonard is considered to belong to sect. Chaetothylax (Nees) V. A. W. Graham of Justicia L. Several species of Stenostephanus from Colombia and Venezuela are treated as synonyms of earlier species.  相似文献   

4.
We investigated the effects of temperature, photoperiod, food and host availability, and body size on the overwintering abilities of the egg parasitoid Anaphes nitens Girault (Hymenoptera, Mymaridae) under natural conditions. Seven groups of eighty females received one of four treatments (n = 20): (i) honey and hosts, (ii) water and hosts, (iii) honey, or (iv) water. Seven groups of forty males received only honey or water (n = 20). To test if short day-length is the main cue for larval dormancy, the experiment was replicated inside a climate chamber at 20°C and under a winter photoperiod. A. nitens overwinters because of quiescence or oligopause inside the hosts and increased adult longevity. Mean pre-emergence mortality was up to 26% indoors and 15.2% outdoors, males being more affected. Development time had a significant and positive effect on body size. Honey-fed females without hosts had the highest longevity (53 days). Mother’s diet and size affected development time, body size, longevity, and fecundity of the progeny. The results confirm the good adaptation of the parasitoid to the environmental conditions of NW Spain and its ability to synchronize its life cycle with the phenology of the host. Handling editor: Drik Babendreier.  相似文献   

5.
Cytoplasmic incompatibility (CI) is a reproductive phenotype induced by bacterial endosymbionts in arthropods. Measured as a reduction in egg hatchability resulting from the crossing of uninfected females with bacteria-infected males, CI increases the frequency of bacteria-infected hosts by restricting the fertilization opportunities of uninfected hosts in populations. Wolbachia, a type of alpha-proteobacteria, is well known as a CI inducer in a wide range of arthropod species, while Cardinium, a member of the phylum Bacteroidetes, is known to cause CI in one wasp and three spider mite species. In this study, dual infection with Cardinium and Wolbachia induced strong CI in a single host, Sogatella furcifera (Horváth), a planthopper species that is naturally infected with both bacteria. Specifically, infection with Cardinium alone was found to cause a 76 % reduction in egg development, and dual infection with Cardinium and Wolbachia a 96 % reduction, indicating that Cardinium induces CI and the dual infection raises the CI level. This study was the first to document reproductive alteration by Cardinium in a diploid host species.  相似文献   

6.
Three Australian native animal species yielded 60 samples composed of three indigenous ticks. Hosts included twelve koalas, two echidnas and one wombat from Victoria, and ticks were of the species Ixodes tasmani (n = 42), Bothriocroton concolor (n = 8) and B. auruginans (n = 10), respectively. PCR screening and sequencing detected a species of Coxiella, sharing closest sequence identity to C. burnetii (>98%), in all B. auruginans, as well as a species of Rickettsia, matching closest to R. massiliae, in 70% of the same samples. A genotype sharing closest similarity to Rickettsia bellii (>99%) was identified in three female B. concolor collected from one of the echidnas. Three samples of I. tasmani, taken from three koalas, yielded different genotypes of Rickettsiella. These results represent the first detection of the three genera in each tick species and identify a high level of previously undetected bacterial diversity in Australian ticks.  相似文献   

7.
Summary  A taxonomic revision of the palm genus Podococcus (Arecaceae) is presented. Two species are recognised: P. barteri, a species relatively widespread in a coastal band from Nigeria to the D. R. Congo and P. acaulis, a species previously considered conspecific to P. barteri, almost exclusively confined to Gabon. The taxonomic history, morphology, distribution and conservation status of the genus and each species are discussed  相似文献   

8.
The cabbage bugs Eurydema rugosa Motschulsky and Eurydema dominulus (Scopoli) (Heteroptera: Pentatomidae: Strachiini) possess a number of crypts in a posterior region of the midgut, which are filled with bacterial symbiont cells. Here we characterized the gut symbionts of Eurydema stinkbugs using molecular phylogenetic and histological techniques. Specific gammaproteobacteria were consistently identified from the posterior midgut of E. rugosa representing nine populations and E. dominulus representing six populations, respectively. The bacterial 16S rRNA gene sequences were identical within the species but slightly different (98.2% sequence identity) between the species. Molecular phylogenetic analysis revealed that the Eurydema symbionts formed a well-defined monophyletic group in the Gammaproteobacteria. The symbionts were phylogenetically distinct from the gut symbionts of the stinkbug families Acanthosomatidae, Plataspidae, Parastrachiidae, Scutelleridae, and other pentatomid species, suggesting multiple evolutionary origins of the gut symbiotic bacteria among diverse stinkbugs. In situ hybridization confirmed that the symbiont is located in the cavity of the midgut crypts. Aposymbiotic insects of E. rugosa, which were produced by egg surface sterilization, were viable but suffered retarded growth, reduced body weight, and abnormal body color, suggesting the biological importance of the symbiont for the host.  相似文献   

9.
West Indian marsh grass, Hymenachne amplexicaulis Rudge (Nees) (Poaceae), is an emergent wetland plant that is native to South and Central America as well as portions of the Caribbean, but is considered invasive in Florida USA. The neotropical bug, Ischnodemus variegatus (Signoret) (Hemiptera: Lygaeoidea: Blissidae) was observed feeding on H. amplexicaulis in Florida in 2000. To assess whether this insect could be considered as a specialist biological control agent or potential threat to native and cultivated grasses, the host specificity of I. variegatus was studied under laboratory and field conditions. Developmental host range was examined on 57 plant species across seven plant families. Complete development was obtained on H. amplexicaulis (23.4% survivorship), Paspalum repens (0.4%), Panicum anceps (2.2%) and Thalia geniculata (0.3%). Adults survived 1.6 times longer and laid 6.6 times more eggs on H. amplexicaulis than the other species. Oviposition on suboptimal host species was positively related to I. variegatus density under multiple choice conditions. Results from field experiments indicated that H. amplexicaulis had higher densities of I. variegatus than other species. Spill-over to suboptimal hosts occurred in an area where H. amplexicaulis was growing in poor conditions and there was a high density of I. variegatus. Thus, laboratory and field studies demonstrate that I. variegatus had higher performance on H. amplexicaulis compared to any other host, and that suboptimal hosts could be colonized temporarily. Handling Editor: John Scott. An erratum to this article can be found at  相似文献   

10.
In this study, the methanol extract of Arthrospira (Spirulina) platensis was examined for acute and subchronic toxicities. The extract did not produce any sign of toxicity within 7 days after feeding it at a single high dose of 6 g kg−1 body weight to female and male Swiss mice. For the subchronic toxicity test, the extract at doses of 6, 12, and 24 mg kg−1 body weight was orally administered to six male and six female Wistar rats daily for 12 weeks. Throughout the study period, we did not observe any abnormalities on behavior, food and water intakes, and health status among the treated animals. The hematology and clinical chemistry parameters of treated groups did not significantly differ from those of the controls in both sexes. Postmortem examination of the test groups also showed no abnormalities in both gross and histological findings. These results thus suggest that the methanol extract of A. platensis did not cause acute or subchronic toxicity in our experimental animals.  相似文献   

11.
Complete mitochondrial cytochrome b sequences of 54 species, including 18 newly sequenced, were analyzed to infer the phylogenetic relationships within the family Cyprinidae in East Asia. Phylogenetic trees were generated using various tree-building methods, including Neighbor-joining (NJ), Maximum Parsimony (MP) and Maximum Likelihood (ML) methods, with Myxocyprinus asiaticus (family Catostomidae) as the designated outgroup. The results from NJ and ML methods were mostly similar, supporting some existing subfamilies within Cyprinidae as monophyletic, such as Cultrinae, Xenocyprinae and Gobioninae (including Gobiobotinae). However, genera within the subfamily “Danioninae” did not form a monophyletic group. The subfamily Leuciscinae was divided into two unrelated groups: the “Leuciscinae” in East Asia forming as a monophyletic group together with Cultrinae and Xenocyprinae, while the Leuciscinae in Europe, Siberia, and North America as another monophyletic group. The monophyly of subfamily Cyprininae sensu Howes was supported by NJ and ML trees and is basal in the tree. The position of Acheilognathinae, a widely accepted monophyletic group represented by Rhodeus sericeus, was not resolved.  相似文献   

12.
An investigation was conducted to understand the influence of host size on the reproductive performance of Nesolynx thymus, an ecto-pupal parasitoid of the uzi fly, Exorista bombycis, inflicting 10–20% loss to silkworm crops in the southern silk producing states of India. Two day-old adults of N. thymus were allowed to parasitize pupae of M. domestica, categorized into big and small at a parasitoid-host ratio of 1:20. After parasitoid adult eclosion, data on parasitization rate, developmental duration, male, female and total adult recovery per pupa and per female, sex ratio, adult size and adult longevity were recorded. The performance of first generation adults as influenced by host size was also recorded by allowing the first generation adults to parasitize three day-old pupae of E. bombycis. The parameters female and total progeny production per female, sex ratio, longevity, body length and wing span of males, females, head width of male, and abdomen length of female increased significantly with host size. No impact of host size was observed on performance of first generation adults.  相似文献   

13.
Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae) is an ectoparasitoid of several stored-product insect pests. Very little information has been published on its biology and development in host larvae, which typically are concealed within seeds. We documented the development of P. cerealellae within fourth instar larvae of its concealed host, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) infesting cowpea seeds. The preimaginal life stages of the parasitoid were characterized for the first time using morphological structures revealed by microscopic techniques including scanning electron microscopy. Pteromalus cerealellae produces hymenopteriform eggs and larvae. Eggs hatch into 13-segmented first instar larvae with peripneustic condition of spiracles. The larvae have simple, tusk-like mandibles, whereas the mandibles of the pupae and the adults are of the conventional toothed types. Using statistical analyses of the sizes of the larval mandibles and head capsules in conjunction with reliable characters such as the number of exuviae on the body of parasitoid larvae, cuticular folding, and excretion of the meconium, we recorded four larval instars for P. cerealellae. The data showed significant positive correlations between larval mandible lengths and widths of larval head capsules, as well as between mandible lengths and larval instars, suggesting that mandible length is a good predictor of the number of instars in P. cerealellae. Developmental time from egg to adult emergence was ∼12 d for females and ∼11 days for males at 30 ± 1°C, 70 ± 5% r.h. and 12L:12D photoperiod.  相似文献   

14.
Summary   Erythroxylum longisetulosum I. Loiola & M. F. Sales and E. timothei I. Loiola & M. F. Sales (sect. Rhabdophyllum) from north-eastern Brazil are described and illustrated, and their taxonomic and ecological relationships are discussed.  相似文献   

15.
The level of fluctuating asymmetry (FA), which is defined as random deviations from perfect bilateral symmetry in the morphological traits of an organism, increases with increasing developmental instability, and it may be used as an indicator of environmental and/or genetic stresses. This study attempted to relate FA levels in the opercular plates of the barnacle Amphibalanus (Balanus) amphitrite with shore height and body trace metal concentrations. Barnacles were collected from both low and mid shores at six coastal locations with various degrees of marine pollution in Hong Kong. Four opercular traits, namely scutum length, tergum length, scutum width, tergum width were measured in the specimen while concentrations of five common trace metals (Cd, Cu, Cr, Mn and Zn) were determined in their body tissues using inductively coupled plasma-atomic emission spectrophotometry. Among the four traits, only tergum length and scutum width fulfilled the assumption of FA while their measurement errors were low. Across all sites, mid-shore A. amphitrite consistently exhibited a significantly higher FA level in scutum width than that in low-shore barnacles, but FA levels in tergum length were similar between the two shore heights. These results suggested that FA was trait-dependent, and mid-shore barnacles were possibly under high physical stress, such as desiccation and high temperature, leading to high developmental instability. Although no positive association was observed between FA and metal contamination in low-shore A. amphitrite, FA level in tergum length significantly increased with decreasing body concentration of manganese (Mn) in these barnacles. Such a negative relationship may be explained by the mechanism of bioaccumulation and physiological role of Mn in A. amphitrite with respect to the formation of barnacle shell plates. Handling editor: T. P. Crowe  相似文献   

16.
17.
A genetic transformation system has been developed for callus cells of Crataegus aronia using Agrobacterium tumefaciens. Callus culture was established from internodal stem segments incubated on Murashige and Skoog (MS) medium supplemented with 5 mg l−1 Indole-3-butyric acid (IBA) and 0.5 mg l−1 6-benzyladenine (BA). In order to optimize the callus culture system with respect to callus growth and coloration, different types and concentrations of plant growth regulators were tested. Results indicated that the best average fresh weight of red colored callus was obtained on MS medium supplemented with 2 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.5 mg l−1 kinetin (Kin) (callus maintenance medium). Callus cells were co-cultivated with Agrobacterium harboring the binary plasmid pCAMBIA1302 carrying the mgfp5 and hygromycin phosphotransferase (hptII) genes conferring green fluorescent protein (GFP) activity and hygromycin resistance, respectively. Putative transgenic calli were obtained 4 weeks after incubation of the co-cultivated explants onto maintenance medium supplemented with 50 mg l−1 hygromycin. Molecular analysis confirmed the integration of the transgenes in transformed callus. To our knowledge, this is the first time to report an Agrobacterium-mediated transformation system in Crataegus aronia.  相似文献   

18.
Summary  A new monotypic bamboo genus Phuphanochloa (Poaceae: Bambusoideae) from north-eastern Thailand is described, together with a new species, P. speciosa.  相似文献   

19.
Ustilago esculenta is a biotrophic smut fungus that parasitizes Zizania latifolia, an edible aquatic vegetable of the southern China region. Infection results in swelling of the upper parts of the Z. latifolia culm which are called jiaobai and have a unique flavor and delicacy and are popular among Chinese. The infection process of Z. latifolia by U. esculenta was investigated with light and electron microscopy. Distribution of hyphae was uneven in plants; hyphae were mainly present in the swollen upper parts (jiaobai), the nodal regions of mature culms and old rhizomes and buds or shoots. Hyphae were rare in the internodes of mature culms and were fewer in the internodes of old rhizomes. All new buds produced on the nodes of culms and rhizomes were infected by hyphae in November before and in March after overwintering. The hyphae grew into the buds from the parent nodes via intervascular tissues only or via parenchyma tissues and vascular bundles. Hyphae extended within and between the host cells and frequently formed hyphal aggregations or clusters, not only in the mature tissues but also in developing tissues. The typical interface between the fungal hyphal wall and invaginated host plasma membrane comprised a sheath. The sheath surrounding a hyphae comprised an outer electron-opaque matrix and an inner electron-dense layer. The electron-opaque matrix layers were thicker in jiaobai tissues, ranging from 0.28 to 0.85 μm. The electron-dense hyphal coatings were more conspicuous in the young buds or shoots and mature culms than in the jiaobai. The intercellular hyphae caused large cavity formation between the cells or rupture of host cell walls, for gaining entry into host cells. The broken host cell wall fused with the electron-opaque matrix of the hyphal sheath as an interactive interface. The teliospore wall and wall ornamentation development was the same in postmature jiaobai tissues with sporadic sori and in the huijiao (jiaobai tissues containing the massive sori), but a sheath enveloping the teliospore was more transparent in the process of teliospore development in the jiaobai than in the huijiao.  相似文献   

20.
Summary  Two new species of Rhynchospora, R. acanthoma and R. rupestris, are described and illustrated. Their geographical distributions are discussed. The status of R. exilis and its synonymy is clarified.  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