Colonization of Ascaris lumbricoides eggs by the fungus Verticillium chlamydosporium Goddard.

The process of colonization of Ascaris lumbricoides eggs by the fungus Verticillium chlamydosporium was studied by scanning electron microscopy. The preparations were made by fractionation of egg suspension exposed to the fungus for four days and frozen in liquid nitrogen according to St?rba and Milácek (1986). Ovicidal fungus forms an abundant ramifying mycelial network in the area between the eggs. However, egg-shells are penetrated only by some hyphae without any penetration organs produced (simple hyphal penetration). In a liquid medium, after penetration, hyphae inside the eggs rapidly grow among inner structures of egg-shells and on the surface of developing larvae. In the next phase, hyphae colonize the developing larva. The eggs attacked by this fungus remain morphologically unchanged for a long time except the sites of penetration. Verticillium chlamydosporium is a fungus with unique ovicidal properties. It colonizes the eggs of Ascaris lumbricoides at all stages of embryo development and also attacks larvae inside the eggs.     

On the mechanism of penetration of ovicidal fungi through egg-shells of parasitic nematodes. Decomposition of chitinous and ascaroside layers.

The decomposition of egg-shells of Ascaris lumbricoides L. was studied microscopically using topochemical methods in a set of 32 strains of soil ovicidal fungi. It was found that even fungi displaying minimal chitinolytic activity in tests on purified chitin in vitro are able to dissolve chitin of egg-shells during the attack on live eggs. Fungi without any chitinolytic activity penetrate probably only the mechanically damaged eggs. None of the studied fungi was capable of degrading enzymatically the glycolipid (ascaroside) layer of the egg-shell which remained intact after digestion of all other components of the egg.     

Topical, residual and ovicidal contact toxicity of three reduced-risk insecticides against the European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae), on potato

BACKGROUND: The goal of the research was to gather efficacy data required to introduce reduced-risk insecticides in sustainable control programs for European corn borer, Ostrinia nubilalis Hubner, on potato. RESULTS: Laboratory tests confirmed that sprays of indoxacarb and novaluron at recommended field rates are as effective as spinosad against neonate larvae of O. nubilalis. However, there is evidence that higher rates would enhance the inhibition of chitin synthesis by novaluron. The three insecticides showed ovilarvicidal activity when applied to O. nubilalis egg masses 2 days prior to black head stage. The ovicidal activity of spinosad and novaluron was almost twice that of indoxacarb. At the recommended field rates, the residues of the three insecticides displayed contact toxicity to O. nubilalis larvae. Spinosad residues 16 h old or less provided the highest immediate (24 h after exposure) contact mortality, followed by indoxacarb and then by novaluron. Also, residues of spinosad had faster contact efficacy than indoxacarb, which had faster efficacy than novaluron. CONCLUSION: Spinosad, indoxacarb and novaluron have ovicidal properties, which could enhance O. nubilalis management programs. However, the contact residual toxicity is limited in duration and would likely only play a minor role in O. nubilalis control.     

20种杀虫剂对草地贪夜蛾的杀卵活性

在前期测定14种杀虫剂对草地贪夜蛾杀卵活性的基础上,本文采用浸渍法又测定了20种不同类型杀虫剂的杀卵活性,以期为草地贪夜蛾卵期防治药剂的选择提供更全面的参考。结果表明,所测的20种杀虫剂均具有一定的杀卵活性。在100 mg/L浓度下,溴氰菊酯、高效氯氰菊酯和乙基多杀菌素表现出出色的杀卵活性,能够完全抑制卵的孵化,杀虫双的杀卵活性最差,低于10%。而噻虫胺、氯虫苯甲酰胺、高效氯氟氰菊酯、多杀霉素、联苯菊酯、噻虫啉、氧乐果、噻虫嗪、甲氰菊酯、烯啶虫胺和啶虫脒的杀卵活性相对较好,其校正死亡率在70.95%～98.52%之间,毒死蜱、吡虫啉、辛硫磷、虫螨腈和杀虫单的杀卵活性相对较差,在42.26%～61.51%之间。在10 mg/L浓度下,噻虫胺、乙基多杀菌素和噻虫啉的杀卵活性均在70%以上,而杀虫双、毒死蜱和烯啶虫胺的杀卵活性低于15%。特别是在100 mg/L和10 mg/L浓度下,新烟碱类杀虫剂噻虫胺和噻虫啉对草地贪夜蛾表现出较高的杀卵活性,分别为98.52%、76.91%和89.37%、72.44%。上述药剂在田间对草地贪夜蛾的杀卵效果还有待进一步验证。     

Ultrastructure of eggs of Ascaris lumbricoides Linnaeus, 1758. I. Egg-shells

Under the light microscope the chitin-protein layer of egg-shells in ascarids appears to be a regular, hyaline and nonstructural layer of 1.5 to 2.00 microns in thickness. The outer uterine layer is usually removed during the preparation. The lipid (ascaroside) layer covers the inner surface of the chitinous layer and seems to be irregularly undulated and regularly thick over the whole surface, with the thickness up to 1 micron. In electron micrographs the fibrous structure of the lipid layer is not evident as a rule. This is probably due to washing the lipids away from this layer during the dehydration of deeper layers of egg-shells that are imperfectly fixed with glutaraldehyde. A very low permeability of the egg-shells is typical of geohelminth eggs. The layer lipid shows a distinct lamellate structure only after a prolonged fixation with osmium at higher temperature. This is supported by the studies using the method of freeze-fracturing.     

菜豆锈菌侵染过程的显微和超微观察

 本文报道了通过微分干涉衬显微镜、荧光显微镜及扫描电镜和透射电镜所观察到的菜豆锈菌的侵入和扩展过程。菜豆锈菌夏孢子萌发多产生1个芽管,偶尔也产生双芽管。芽管以气孔侵入为主,也可从表皮直接侵入。侵入前形成或不形成明显的附着胞。气孔侵入的芽管首先在气孔腔内形成气孔下囊,再进一步分化出圆形的膨大体,由膨大体产生1~2支初生菌丝。初生菌丝与叶肉细胞壁接触后分化出吸器母细胞,吸器母细胞进入叶肉细胞内部形成吸器。初生侵染菌丝在产生吸器母细胞的部位的后部产生分枝,形成次生侵染菌丝在叶肉细胞间蔓延。     

Structural Characterisation of the Interaction between Triticum aestivum and the Dothideomycete Pathogen Stagonospora nodorum

The interaction between Stagonospora nodorum and a susceptible wheat cultivar was investigated using a range of microscopic techniques. Germination of pycnidiospores occurred approximately 3 h after making contact with the leaf surface and was followed by attempted penetration 8–12 h later. Penetration was observed through stomata and also directly through periclinal and anticlinal epidermal cell walls. Penetration down the anticlinal cell walls appeared to occur without a differentiated penetrating structure whilst structures identified as either lateral appressoria or hyphopodia were typically present when penetrating over a periclinal cell wall. Once inside the leaf, the fungus continued to grow for the next 4–5 days colonising all parts of the leaf except the vascular bundles. Only in the later phase of the infection was total host cell collapse apparent. Evidence of polyphenolic compounds was observed. The infection cycle was completed within 7 days as indicated by sporulation on the leaf surface. These results have allowed us to understand how the fungus physically interacts with the leaf and will help the overall understanding of the infection process.     

Studies on the Infection Process of Fusarium Culmorum in Wheat Spikes: Degradation of Host Cell Wall Components and Localization of Trichothecene Toxins in Infected Tissue

After single spikelet inoculation, the infection process of Fusarium culmorum and spread of fungal hyphae in the spike tissues were studied by scanning and transmission electron microscopy. While hyphal growth on outer surfaces of the spike was scanty and no successful penetration was observed, the fungus developed a dense mycelium on the inner surfaces and effectively invaded the lemma, glume, palea and ovary by penetration pegs. During the inter- and intracellular spreading of the fungus, marked alterations in the host tissues were observed, including degeneration of cytoplasm, cell organelles, and depositions of electron dense material between cell wall and plasmalemma. Ultrastructural studies revealed that host cell walls in proximity of the penetration peg and in contact with hyphae were less dense or transparent which suggested that cell wall degrading enzymes were involved in colonisation of host tissues by fungal hyphae. Enzyme- and immunogold-labelling investigations confirmed involvement of extracellular enzymes, that is cellulases, xylanases and pectinases, in degradation of cell wall components. Localization studies of trichothecenes indicated that toxins could be detected in host tissues at an early stage of infection.     

Ovicidal activity of juvenile hormone mimics in the bean bug,Riptortus pedestris

Insect juvenile hormone (JH) mimics (JHMs) are known to have ovicidal effects if applied to adult females or eggs. Here, we examined the effects of exogenous JHMs on embryonic development of the bean bug, Riptortus pedestris. The expression profiles of JH early response genes and JH biosynthetic enzymes indicated that JH titer was low for the first 3 days of the egg stage and increased thereafter. Application of JH III skipped bisepoxide (JHSB₃) or JHM on Day 0 eggs when JH titer was low caused reduced hatchability, and the embryos mainly arrested in mid- or late embryonic stage. Application of JHMs on Day 5 eggs also resulted in an arrest, but this was less effective compared with Day 0 treatment. Interestingly, ovicidal activity of synthetic JHMs was much lower than that of JHSB₃. This study will contribute to developing novel insecticides that are selective among insect species.     

Infection of Norway spruce (Picea abies (L.) Karst.) seedlings with Pythium irregulare Buism. and Pythium ultimum Trow.: histological and biochemical responses

We have studied the reaction of Picea abies seedlings to infection with Pythium. The highly virulent species Pythium ultimum and the less virulent species Pythium irregulare germinated on the root and hypocotyl surface, formed appressoria and penetrated through the stomata as well as through the epidermis. No major differences in the growth of both fungal species were observed during the early events of colonization. The less virulent species formed about 25% more appressoria suggesting that the fungus experienced difficulties with penetration. Differences were observed in the response of the host plant to infection. Autofluorescence, possibly related to deposition of lignin or lignin-like materials increased more in cortical and endodermal tissue colonized with the highly virulent P. ultimum than with the less virulent P. irregulare. Chitinase activity was highest in the tissues most extensively colonized by the fungus. In addition, a systemic increase of chitinase activity was also detected. Interestingly, chitinase activity increased systemically in cotyledons which were never in contact with the pathogen, indicating the translocation of a systemic signal. Salicylic acid was also detected in spruce seedlings; its level increased in roots during infection with the less virulent P. irregulare.     

柴油及其与阿维菌素复配对柑橘全爪螨卵的作用

室内测定了柴油对柑橘全爪螨卵的毒力及其与阿维菌素复配植物油基新型乳油的杀卵作用。结果表明,柴油对柑橘全爪螨卵的LC50为2790.39μg/mL;两种柴油与阿维菌素复配新型乳油1000、750和500倍液3种浓度下的杀卵率均高于90%,其中添加了印楝油的复配剂3浓度的杀卵率与对照药剂24%螺虫乙酯SC 3000倍液相当。     

Ultrastructural Studies of the Mode of Penetration by Phoma macdonaldii in Sunflower Seedlings

ABSTRACT An ultrastructural investigation of the artificial inoculation of sunflower with Phoma macdonaldii conidia was undertaken using light, scanning, and transmission electron microscopy to elucidate the host-parasite relationship. The behavior of the conidia deposited on the cotyledon petiole was investigated at various time intervals after inoculation. Conidia adhesion and germination were observed first. The cotyledon petiole was invaded by the fungus directly through the cuticle and via stomata. Externally, the spore and germ tube were covered with a mucilaginous polysaccharide sheath of a cotton-like appearance and of variable thickness. At the time of penetration, the host cuticle was perforated mechanically. The cuticle was slightly depressed and no enzymatic alteration could be observed. The fungus did not form appressoria on the surface of the host tissues but developed an infection peg. As soon as the cuticle barrier was crossed, the fungus rapidly colonized the host parietal layer. In a first step, the plasmalemma of the host cell appeared to be stuck against the cell wall. As soon as the fungus passed through the epidermal cell wall to reach the host cytoplasm, the plasmalemma was disrupted, and the subsequent rapid breakdown of cell integrity favored the colonization of the tissues by the pathogen.     

草地贪夜蛾抗药性现状及化学防治策略

本文就草地贪夜蛾抗药性研究的历史、现状以及如何进行化学防治进行了比较系统的分析。针对国内外草地贪夜蛾发生的现状,从抗药性程度及交互抗性、种群遗传、抗药性机制以及化学防治的关键技术等方面进行了讨论。提出了化学防治要尽量做到药剂品种、时间和空间的配合;掌握好药剂防治的两个窗口期,一是害虫本身敏感的窗口期即从孵化到3龄初,二是孵化后到钻蛀前;分阶段选择适宜药剂类型用于化学防治。除了考虑杀虫剂作用机制类别外,作用方式也要考虑。卵高峰期施用具有触杀活性的药剂配合具有杀卵活性的药剂添加具有渗透功能的助剂,孵化高峰期施用触杀药剂配合胃毒药剂,后期大龄幼虫可以考虑胃毒药剂为主的化学防治策略。     

A light and scanning-electron microscopic study of infection of tomato plants by virulent and avirulent races of Cladosporium fulvum

Infection of tomato plants byCladosporium fulvum Cooke was studied using light and scanning-electron microscopy. Races 1.2.3 and 4 ofCladosporium fulvum were used, whereas tomato cultivars, carrying the Cf2 gene (susceptible to race 1.2.3 and immune to race 4) and the Cf4 gene (immune to race 1.2.3 and susceptible to race 4) served as differentials. No differences were observed in growth between compatible and incompatible combinations during germination, subsequent formation of runner hyphae and stomatal penetration. Runner hyphae did not show directional growth towards stomata. Penetration usually occurred on the third or fourth day after inoculation. In compatible combinations the fungus grew intercellularly, often in close contact with spongy mesophyll cells. Under optimal conditions it did not cause visible damage to plant cells during early stages of infection. Under suboptimal conditions in winter, the host cells often reacted with callose deposition, but growth of the fungus did not appear to be inhibited. Ten to twelve days after inoculation conidiophores emerged through the stomata and produced conidia. In incompatible combinations fungal growth was arrested one to two days after penetration and confined to stomata and surrounding cells. Very soon the host cells, in contact with the fungus, deposited extensive amounts of callose. Later these cells turned brown and collapsed. At the surface of the host cells, contacted by fungal hyphae, abundant extracellular material could be observed by scanning-electron microscopy. Removing the epidermis of leaves before inoculation delayed the resistant response. On stripped leaves the rate of fungal growth was equal for both interactions up to ten days after inoculation, but the incompatible combination lacked sporulation.     

Fusarium mangiferae localization in planta during initiation and development of mango malformation disease

Mango malformation disease (MMD), caused by Fusarium mangiferae, is a major constraint to mango production, causing significant yield reduction resulting in severe economic impact. The present study characterizes fungal localization in planta during initiation and development of vegetative and floral malformation. Young mango trees were artificially inoculated with a green fluorescent protein (GFP)‐expressing strain of F. mangiferae. Shoots and buds were sampled periodically over a period of more than a year and localization of the GFP‐expressing fungi was determined using confocal microscopy. Fungal localization appears to be epiphytic: mycelia remained in close contact with the plant surface but did not penetrate the tissue. In vegetative malformation and in young inflorescences, the fungus was confined to protected regions between scales, young leaf bases and buds. Fungal colonization was only very rarely detected on open leaves or on exposed shoot sections. In developed flowers, mycelia were localized mainly to protected regions at the base of the flower organs. Upon development of the inner flower organs, specific mycelial growth occurred around the anthers and the style. Mycelial penetration through the stylar tract into aborting carpels was observed. For several months, mycelia were confined to the surface of the organs and were not detected within plant tissues. Only at later stages, transient saprophytic growth of the fungus was detected causing the malformed inflorescences to senesce and collapse, concurrent with dispersion of conidia. Implications of the present study on MMD in natural field infections are discussed.     

草地贪夜蛾卵块在玉米植株上的空间分布

本研究调查了草地贪夜蛾卵块在田间玉米植株上的空间分布,发现草地贪夜蛾卵块主要分布于植株中部,即玉米小喇叭口期倒3叶与倒4叶、吐丝期倒5叶与倒6叶上卵块最多,在小喇叭口期主要分布在叶正面,吐丝期主要分布于叶背面,距叶尖平均距离分别为23.4 cm和35.2 cm。为玉米上草地贪夜蛾卵的调查和防治提供了参考。     

马铃薯晚疫病初侵染源的研究初报

 在土壤中存活的病原菌,能凭借土壤水分的扩散作用而被动地移动,在试验室的条件下,最远可横向移动15厘米,在田间的自然条件下,可移动20厘米,但是在土壤下层的病原菌,不能向土面移动。
在土壤中的病原菌,有可能被中耕除草,特别是培土起垄等栽培措施,将土壤中的病原菌,翻到土壤表面,直接接触或被雨水溅泼到寄主植株的下部叶片,在有水滴的情况下,侵入并形成数量较多的中心病株。
据理推测:这种初侵染途径的可能性,是不容忽视的。     

禾顶囊壳小麦变种对小麦种子根的侵染过程

 光镜和电镜观察表明,禾顶囊壳小麦变种(Gaeumannomyces graminis var.tritici,小麦全蚀病菌)对小麦种子根的侵染过程可分为侵入前、侵入表皮层、进入皮层和进入中柱等4个连续阶段。麦根接菌后在15℃下培养,48 h后侵入表皮层细胞,60 h后进入皮层,120 h后进入中柱。病原菌主要以侵染菌丝直接侵入表皮层,表皮细胞间隙和根毛基细胞是主要侵入部位,少数由附着枝侵入。菌丝穿透细胞壁有明显的酶解作用特征,菌丝先端前方胞壁上还产生电子密物质。皮层细胞是病原菌定殖和发展的主要场所,病原菌还能离解胞间层,形成胞外空间,特别有利于菌丝和菌丝束的扩展。在侵入位点的寄主细胞壁和质膜之间,形成多种形状的木质管,其数量与侵入菌丝的数目相对应,但木质管不能阻止菌丝进入细胞。菌丝进入中柱后,可阻塞导管和筛管。小麦细胞发生退行性病变,尤以细胞壁膨大崩坏和早期质壁分离最明显,细胞间隙还产生性质不明的黄色物质。     

Effect of triflumuron on two species of nitidulid beetles,Carpophilus hemipterus andUrophorus humeralis

Egg hatch of two nitidulids,Carpophilus hemipterus L. andUrophorus humeralis F., was affected by the chitin synthesis inhibitor triflumuron (Alsystin; BAY SIR 8514)via the adult stage of the beetle. This occurred by exposure to treated diets, by a brief dip of the adults in aqueous dilutions of the toxicant, or by contact with a treated plastic netting cage. Exposure of adults ofC. hemipterus for 24 h to 0.0125%, 0.00125%, 0.00025% or 0.000125% and ofU. humeralis to 0.0125% a.i.-treated diets completely prevented hatch of eggs laid during the subsequent 48 h on an untreated diet. Although at first sterile eggs were obtained with adults of either nitidulid species transferred to an untreated diet after 24 h exposure to the 0.0125%-treated diet, egg viability gradually recovered. The speed of recovery and the course of mortality of larvae that hatched from eggs laid by treated adults, indicated thatC. hemipterus was more susceptible thanU. humeralis to triflumuron. DippingC. hemipterus adults — males or females — in 0.0125% a.i. triflumuron also resulted in complete prevention of egg hatch. Similar results were obtained by a 1-h contact of adults with treated cages. Triflumuron had no direct ovicidal activity against the two species at the concentrations used but was very effective against larvae of both species. At 0.0125% a.i., 3-5-mm-long larvae ofU. humeralis were more tolerant than newly hatched larvae and than 3-5-mm-long larvae ofC. hemipterus. Application of 0.0125% a.i. triflumuron in a date palm grove did not prevent fruit infestation by nitidulid adults but, due to prevention of egg hatch, almost no larval development was observed.     

荸荠茎点霉秆枯病菌侵染过程的超微观察

<正>荸荠(Eleocharis dulcis),又称马蹄,为莎草科多年生草本植物,是一种具有食用和药用价值的水生蔬菜。近年来,随着荸荠在我国种植面积的不断扩大,病害发生也呈逐年上升趋势。荸荠茎点霉秆枯病是2009年在湖北省荸荠产区发现的一种新病害,由Phoma bellidis侵染引起,该病在湖北省团风地区发生尤为严重,对荸荠的产量和品质造成严重影响;病害一般在8~12月发生,发病初期在荸荠茎秆上产生圆形或梭形红褐色小斑,随后病斑沿茎