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1.
Entomophthoralean-specific primers were used to estimate the occurrence of entomophthoralean species in the cereal aphid Sitobion avenae in Denmark. Sequencing documented for the first time the presence of Pandora kondoiensis in Denmark. Specific primers were designed and P. kondoiensis was identified on 12% of infested straws sampled in 2012.  相似文献   

2.
Capilliconidia, the asexual secondary spores of Neozygites parvispora (Zygomycetes, Entomophthorales) were produced in vitro either by entrapment of vegetative cells (hyphal bodies) in alginate pellets or after plating them onto water agar. Cultivation of the fungus for 3 days in a medium lacking hemolymph increased spore production 30 to 40-fold, and about 10% of the cells produced capilliconidia. The in vitro produced capilliconidia were infectious to Thrips tabaci and the fungus was reisolated from infected insects, thus completing its asexual life cycle under laboratory conditions. A decrease in capilliconidia production and a modification of the number of nuclei per spore were observed for isolates cultivated in vitro for more than 2 months, but subsequent host passages restored and increased sporulation efficiency without influencing the number of nuclei. Fungal cultures were stored at —80 °C for up to 7 months, and the capability to sporulate and infect T. tabaci was preserved. A bioassay procedure for infecting T. tabaci with N. parvispora is described, the first mycosed insects dying usually after 8 d of incubation.  相似文献   

3.
The immune system is essential to maintain the mutualistic homeostatic interaction between the host and its micro- and mycobiota. Living as a commensal, Saccharomyces cerevisiae could potentially shape the immune response in a significant way. We observed that S. cerevisiae cells induce trained immunity in monocytes in a strain-dependent manner through enhanced TNFα and IL-6 production upon secondary stimulation with TLR ligands, as well as bacterial and fungal commensals. Differential chitin content accounts for the differences in training properties observed among strains, driving induction of trained immunity by increasing cytokine production and direct antimicrobial activity both in vitro and in vivo. These chitin-induced protective properties are intimately associated with its internalization, identifying a critical role of phagosome acidification to facilitate microbial digestion. This study reveals how commensal and passenger microorganisms could be important in promoting health and preventing mucosal diseases by modulating host defense toward pathogens and thus influencing the host microbiota-immune system interactions.  相似文献   

4.
丛枝菌根对植物根际逆境的生态学意义   总被引:1,自引:0,他引:1  
李娇娇  曾明 《应用生态学报》2020,31(9):3216-3226
近年来,我国在菌根分子生物学、菌根营养学、菌根分类学和菌根生态学等方面取得了令人瞩目的研究成果,其中对丛枝菌根真菌(AMF)的研究居多。AMF能与大部分陆地植物根系形成共生关系,促进植物生长发育,提高植物抗逆性,在保持生态平衡、保护生态环境等方面发挥重要作用。本文主要从非生物胁迫(干旱胁迫、重金属污染、盐碱胁迫)和生物胁迫(致病菌和线虫侵染)方面介绍了AMF在植物根际逆境中发挥的生态功能及作用机制,提出了该研究领域尚存的不足之处和研究前景,为AMF后续研究提供参考。  相似文献   

5.
6.
  总被引:1,自引:0,他引:1  
Aim The search for possible factors influencing the spatial variation of grass quality is an important step towards understanding the distribution of herbivores, as well as a step towards identifying crucial areas for conservation and restoration. A number of studies have shown that grass quality at a regional scale is influenced by climatic variables. At a local scale, site factors and their interaction are considered important. In this study, we aimed at examining environmental correlates of grass quality at a local scale. The study also sought to establish if biotic factors interact significantly with abiotic factors in influencing a variation in grass quality. Location The study area is located in the Kruger National Park of South Africa. The study area stretches from west (22°49′ S and 31°01′ E) to east, (22°44′ S and 31°22′ E) covering an area of about 25 × 6 km in the far northern region of the Kruger National Park. Methods We collected environmental data such as soil texture, percentage grass cover and biomass as well as grass samples for chemical analysis from specific locations in the study area. In addition, a digital elevation model (DEM) with a resolution of 5 m was used to derive elevation, slope and aspect using a geographic information system (GIS), which were related to grass quality. We used correlation analysis and anova to relate environmental variables to grass quality. Multivariate analysis techniques were used to simultaneously analyse and explore the complex interactions between variables. Results and conclusions Our results indicate that there is a significant relationship between grass quality parameters and site‐specific factors such as slope, altitude, percentage grass cover, aspect and soil texture. Relatively, percentage grass cover and soil texture were more critical in explaining a variation in grass quality. Plant characteristics such as species type interact significantly with slope, altitude and geology in influencing nutrient distribution. The results of this study may give a better insight on foliar nutrient distribution patterns at a landscape scale in savanna rangelands. Furthermore, the results of this study may help in the selection of ancillary information, which could be used in conjunction with other data such as remotely sensed data to map grass quality – an important step towards understanding the distribution and feeding patterns of wildlife. However, we acknowledge that this study is based on one seasonal snapshot, therefore some slightly different findings may be obtained during other times of the year. Nevertheless, the study has revealed that under the conditions experienced during the study period, nutrient distribution varies with varying biotic and abiotic factors.  相似文献   

7.
The entomopathogenic fungi Zoophthora radicans and Pandora blunckii co-occur in field populations of Plutella xylostella and, therefore, are likely to interact during the infection process. We have investigated the possible outcomes of these interactions in the laboratory. Using four isolates, two of each fungal species, inter-specific interaction experiments were done in Petri dishes and on intact plants. In Petri dish experiments, larvae were inoculated directly using sporulating mats of mycelium, both species had the same opportunity to infect and only the relative concentration of conidia of each pathogen species applied was manipulated. In the intact plant experiments, larvae were placed onto fungus-contaminated plants, inoculation was passive and the probability of infection by either or both species of fungi depended on larval activity and proximity to inoculum. In the Petri dish experiment, the species with the largest concentration of conidia out-competed the other regardless of virulence, and results were similar in the intact plant experiment. The ecological implications for competition or co-existence of these two pathogens in the field are discussed.  相似文献   

8.
    
The ultrastructure of logarithmic-growing cells and of resting cells in laboratory cultures of Amphora coffaeformis (Ag.) Kütz. isolated from deep ocean water was examined using electron and light microscopy. The acid Phosphatase activity, chlorophyll a and lipid content were assessed at weekly intervals of resting cell formation during cold-dark treatment, simulating deep ocean water. Approximately 4 wk are required to complete resting cell formation. During the first week, the cytoplasm undergoes extensive transformation and lysosomal activity is observed. Large vacules decrease in size and many small ones develop, the mitochondria become fewer and one or more massive mitochondria appear possibly by fusion of smaller ones; the cytoplasm becomes densely granular. During the second and third week, the cytoplasm continues to contract, lipid bodies begin to develop and the plastid becomes densely stained. At the fourth week, the mature resting cell is formed containing one or more massive mitochondria, a well-formed plastid, and granular cytoplasm containing occasional lipid droplets. There is no change in frustule morphology and the cytoplasm does not produce a protective layer. The variation in chemical constituents correlates with microscopic structure of the cells. The fine structure of cells during growth resumption when exposed to light at 25 c is presented. Previous reports of viable, chlorophyll-containing cells at great depths in the ocean may be explained by the results reported in this paper.  相似文献   

9.
10.
    
《Mycoscience》2014,55(1):1-4
Species of the genus Acaulospora are partly characterized by the production of ‘acaulosporoid’ spores. The simultaneous formation of glomoid and acaulosporoid spores by some species in the Glomeromycota has been used as a basis for taxonomic classification. We report the presence of both glomoid and acaulosporoid spores in four Acaulospora species. Analysis of the 18S rRNA gene confirmed that only A. spinosa was present in a pot culture that produced two morphs. The functional significance of dimorphic spore production is unknown but the production of blastic spores is not a characteristic that can have any significance as a taxonomic character.  相似文献   

11.
    
The Chinese government is considering ways to reconstruct Eucalyptus plantation monocultures in order to improve their ecosystem services. However, the effects of competition or facilitation of Eucalyptus on native species during the reconstruction have not been identified, especially during the formation of novel ecosystems. To better understand these relationships, in this study we tested the effects of competition and facilitation of Eucalyptus on three target species (Schima superba, Michelia macclurei, and Castanopsis fissa), in Eucalyptus plantations with different ages and understory vegetation. The results showed that the survival and growth of S. superba and M. macclurei were not sensitive to plantation age and understory removal treatment. The survival of C. fissa in understory removal was significantly higher and the growth of C. fissa increased gradually with increasing plantation age. The relative neighbor effect (RNE) index for growth indicated that the relationship between Eucalyptus and target species switched from competition to facilitation with an increase in plantation age. A redundancy analysis (RDA) showed that survival was positively correlated with soil water content and soil phosphorus. Growth was positively correlated with soil organic matter and soil nitrogen and negatively correlated with soil bulk density. Our results indicate that plantation age, understory vegetation, and species‐specific traits of target seedlings could change the competition and facilitation roles of Eucalyptus. Higher survival and growth rates indicated that C. fissa was an appropriate species for the reconstruction of mature Eucalyptus plantations and understory removal will benefit the process.  相似文献   

12.
  总被引:1,自引:0,他引:1  
The recent introduction and rapid spread of the tomato leaf miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) throughout Europe, Africa and the Middle East poses a severe threat to future cultivation of tomato and other Solanaceae. Among the best practicable means for effective and sustainable control of this invasive insect pest are entomopathogenic fungi, which can either prevent a further spread of this insect to new areas or keep population densities below an economic threshold level. Here, we report on the efficacy of a commercially available mycoinsecticide based on the entomopathogen Beauveria bassiana (Bals.) Vuill. (Ascomycota: Hypocreales) against all four larval stages of T. absoluta. In bioassays, high mortality rates and significantly reduced longevity of larvae were obvious when larvae had fed for a period of around 15 days on leaves with B. bassiana propagules present on the surface as an epiphyte with mortality values corrected for variance in control mortality of 90–100%. In addition, a second mode of action of B. bassiana against T. absoluta larvae was evident in bioassays in the form of an endophytic establishment of this fungus in treated tomato plants. Longevity of T. absoluta L4 larvae was significantly lower in individuals which had fed on surface‐sterilized tomato leaves obtained from plants treated 18 days before the bioassay with a B. bassiana suspension compared to larvae feeding on control plants treated with water. Corrected mortality reached values between 30% and 50% for all larval instars. Growth of tomato plants was not inhibited due to colonization by endophytic B. bassiana and a weak systemic translocation of fungal propagules in non‐treated leaves was evident in the assays. Accordingly, entomopathogenic fungi like B. bassiana express different modes of action again target insect pests, which is of particular relevance for the design of efficient management strategies for invasive pests like T. absoluta.  相似文献   

13.
安徽大别台区虫生真菌区系的物种多样性研究   总被引:7,自引:0,他引:7  
对安徽大别山区虫生真菌区系的物种多样性进行了研究。结果表明该地区虫生真菌资源十分丰富 ,共有虫生真菌 5 0种 ,隶属于 4目 4科 16属。科从大到小依次为麦角菌科 (Clavicipitaceae) (2 7种 ,占 5 4 % )、丝孢科 (Hy phomycetaceae) (15种 ,占 30 % )、虫霉科 (Entomophthoraceae) (5种 ,占 10 % )、束梗孢科 (Stilbellaceae) (3种 ,占 6 % )。含 3个种以上的优势属依次为虫草属 (Cordyceps) (2 6种 ,占 5 2 % )、拟青霉属 (Paecilomyces) (6种 ,占 12 % )、白僵菌属 (Beauveria) (3种 ,占 6 % ) ,共计 35种 ,占总种数的 70 % ;含 2个种的属为刺束梗孢属 (Akanthomyces)和虫瘟霉属 (Zoophthora) ;其余 11个属皆为单种属。优势种依次为粉拟青霉 (Paecilomycesfarinosus)、细脚拟青霉 (P .tenuipes)、下垂虫草 (Cordycepsnutans)、球孢白僵菌 (Beauveriabassiana)、金龟子绿僵菌小孢变种 (Metarhiziumanisopliaevar.anisopliae)。区系地理成分划分为 7大类型 :世界分布种 (42 .11% )、欧亚大陆分布种 (10 .5 3% )、亚热带—热带分布种 (5 .2 6 % )、东亚分布种 (7.89% )、东亚—新几内亚分布种 (5 .2 6 % )、中国—日本分布种 (5 .2 6 % )和特有成分 (2 3.6 8% ) ,表现出明显的东亚区系特征 ,而且本区及  相似文献   

14.
The daily and seasonal distribution of airborne fungal particles was recorded in a high altitude tropical zone. Sampling was carried out in the southern part of Mexico City. An Andersen air sampler was used over a period of six months. Ten minutes sampling for each set of plates was done at fixed schedule: 07:30, 14:00 and 19:00 hours. The sampler was placed 10 m above the ground. Daily variation was found to be associated with the season, weather and atmospheric stability. The highest value of mold counts (3195 CFU m−3) was recorded in the evening on October, a transitional month between the rainy and the dry seasons, the lowest (45 CFU m−3) at noon during the rainy season. Mold counts were significantly correlated with temperature, having negative signs both in the morning and at noon, and being positive in the evening. The abundance of only three genera was recorded.Cladosporium, was isolated more frequently, and its abundance at 14:00 h was of 38%;Alternaria represented 4.0%, at 14:00 h, andAspergillus 3.0% at 7:30 h. Fifteen species belonging to the latter genera were identified and most of them are considered as opportunistic molds of clinical significance.  相似文献   

15.
    
  1. Parasitoids represent the third trophic level in plant-insect food webs. They develop in or on herbivorous insects at the second trophic level, which in turn feed on plants that constitute the first trophic level. This food web system might be affected by agricultural landscape and practices.
  2. We studied the phenology and population density of Aphis fabae (Hemiptera: Aphididae) and determined the impact of parasitoids in organic fields of beans and beet plants.
  3. Twenty leaves per field were collected weekly. For each leaf, the total number of aphids, apterous and alate morphs, the number of mummies, and mortality of aphids were recorded.
  4. Our results showed that the phenology of A. fabae varied throughout the season with maximal numbers observed at the beginning of summer. In addition, the production of alate morphs and the proportion of parasitism were positively correlated to an increase in aphid densities.
  5. Six parasitoid species were recorded attacking A. fabae in the field, with Lysiphlebus fabarum and Binodoxys angelicae (Hymenoptera: Aphidiinae) being the most abundant parasitoids.
  6. Field characteristics and availability of host plants in the surroundings affected A. fabae density. Lysiphlebus fabarum and B. angelicae appeared to be good biocontrol candidates against A. fabae.
  相似文献   

16.
休眠孢子的形成对于赤潮藻种群的保存、延续以及分布扩散等均具有重要的意义。通过单因子营养限制研究氮、硅对赤潮藻扁面角毛藻(Chaetoceros compressus)休眠孢子形成的影响,结果表明:培养基中氮的初始浓度对休眠孢子的出现时间有一定影响。氮的初始浓度越低,休眠孢子出现的时间越早:反之,氮的初始浓度越高,休眠孢子出现的时间越晚。氮缺乏是硅藻形成休眠孢子的必需条件之一,当培养基中氮含量低于10μmol·L^-1时,扁面角毛藻可以形成休眠孢子。氮缺乏诱发的休眠孢子的形成需要大量的硅,当培养基中硅含量低于23μmol·L^-1时,即使氮缺乏,扁面角毛藻也几乎不再继续形成休眠孢子。这说明硅藻休眠孢子的形成不仅受氮浓度的影响,还与硅浓度有关。  相似文献   

17.
    
Four isolates of the entomopathogenic fungus Metarhizium anisopliae were tested for their potential to control the biting midge Culicoides brevitarsis, the principal vector of bluetongue virus in Australia. Adult C. brevitarsis died three to eight days after walking on paper substrate treated with 0.7 g/m2 conidia of any of the isolates, indicating that M. anisopliae has potential as a surface treatment or topical application control strategy. Incorporation of the fungus into freshly excreted cattle dung at rates of between 0.25 and 1 g conidia/kg reduced the emergence of adult midges by up to 98.5% compared to untreated dung indicating that M. anisopliae has the potential to control C. brevitarsis larvae in cattle dung. Three of the isolates produced similar mortality rates on adult and immature C. brevitarsis while the fourth isolate produced lower, but still significant, mortality rates on adult and immature stages.  相似文献   

18.
    
The seasonal and vertical distributions of Acanthostomella norvegica are described from two fjord-like bays in insular Newfoundland, Canada. Resting spores are figured and described.  相似文献   

19.
在室内评价了球孢白僵菌对烟蚜茧蜂生命参数及控害效果的影响。分别在烟蚜茧蜂寄生桃蚜后不同时间进行高剂量(1900孢子/mm2)接菌,检测蚜虫感病率和寄生蜂形成的僵蚜率及僵蚜出蜂率。结果表明,球孢白僵菌对僵蚜率和僵蚜出蜂率的影响随接菌时间不同而变化。在烟蚜茧蜂寄生前1d、寄生当天和寄生后3d接菌,蚜虫感病率分别为59.6%、56.2%和34.8%;与对照相比,僵蚜率分别下降94%、59%和47%,僵蚜出蜂率分别减少83%、54%和49%。在寄生后5d或7d接菌,僵蚜率和僵蚜出蜂率不受明显影响,但蚜虫感病率降低到8.2%以下。对蚜尸内白僵菌菌体含量检测表明,随着烟蚜茧蜂寄生后接菌时间的推移,菌体数量迅速下降。寄生蜂寄生后5d或7d接菌,蚜尸内几乎检测不到菌体。直接喷雾接菌烟蚜茧蜂,成蜂寿命缩短4d左右,且81.8%的蜂尸受白僵菌感染。接菌后的寄生蜂对蚜虫寄生率几乎无影响,但寄生蜂在蚜虫体内的存活时间缩短了27.8%。  相似文献   

20.
球孢白僵菌对烟蚜茧蜂生命参数及控害效果的影响   总被引:1,自引:0,他引:1  
在室内评价了球孢白僵菌对烟蚜茧蜂生命参数及控害效果的影响。分别在烟蚜茧蜂寄生桃蚜后不同时间进行高剂量(1900孢子/mm2)接菌,检测蚜虫感病率和寄生蜂形成的僵蚜率及僵蚜出蜂率。结果表明,球孢白僵菌对僵蚜率和僵蚜出蜂率的影响随接菌时间不同而变化。在烟蚜茧蜂寄生前1d、寄生当天和寄生后3d接菌,蚜虫感病率分别为59.6%、56.2%和34.8%;与对照相比,僵蚜率分别下降94%、59%和47%,僵蚜出蜂率分别减少83%、54%和49%。在寄生后5d或7d接菌,僵蚜率和僵蚜出蜂率不受明显影响,但蚜虫感病率降低到8.2%以下。对蚜尸内白僵菌菌体含量检测表明,随着烟蚜茧蜂寄生后接菌时间的推移,菌体数量迅速下降。寄生蜂寄生后5d或7d接菌,蚜尸内几乎检测不到菌体。直接喷雾接菌烟蚜茧蜂,成蜂寿命缩短4d左右,且81.8%的蜂尸受白僵菌感染。接菌后的寄生蜂对蚜虫寄生率几乎无影响,但寄生蜂在蚜虫体内的存活时间缩短了27.8%。  相似文献   

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