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1.
Cellular responses in fungi and in susceptible or resistant hosts during fungus–plant interactions have been studied ultrastructurally
to examine their role in pathogenicity. Pathogenicity is determined in some saprophytic fungi by various factors: the production
of disease determinants such as the production of host-specific toxins (HSTs) or the extracellular matrix (ECM) by fungal
infection structures and H2O2 generation from penetration pegs. Three different target sites for HSTs have been identified in host cells in many ultrastructural
studies: plasma membranes, chloroplasts, and mitochondria. The mode of action of HSTs is characterized by the partial destruction
of the target structures only in susceptible genotypes of host plants, with the result that the fungus can colonize the host.
The infection structures of most fungal pathogen secrete ECM on plant surfaces during fungal differentiation, while the penetration
pegs of some pathogens produce reactive oxygen species (ROS) in the cell walls and plasma membranes. The pathological roles
of ECM and H2O2 generation are discussed here in light of ultrastructural evidence. Host and fungal characteristics in the incompatible interactions
include the rapid formation of lignin in host epidermal cell walls, failure of penetration pegs to invade lignin-fortified
pectin layers, the inhibition of subcuticular hyphal proliferation and the collapse of hyphae that have degraded cell walls
within pectin layers of the host. Apoptosis-like host resistant mechanism is also discussed. 相似文献
2.
Ana Alfaro-Fernández Amparo García-Luis 《European journal of plant pathology / European Foundation for Plant Pathology》2009,125(1):73-85
Muskmelon (Cucumis melo cv. Temprano Rochet) and autumn squash (Cucurbita maxima) seedlings were inoculated either with Acremonium cucurbitacearum or Monosporascus cannonballus, two of the soil-borne fungi implicated in ‘melon collapse’. Inoculation was achieved in two different ways: by growing the
plants in pots containing infested soil to study the histological changes produced in the infected tissues using light microscopy
and by growing seedlings in Petri dishes together with fungal colonies in order to observe the colonisation of the plant tissues
using scanning electron microscopy. Both muskmelon and autumn squash roots infected with A. cucurbitacearum showed a suberised layer in the epidermis and the outermost layers of the parenchymatic cortex, but these symptoms developed
earlier in the muskmelon plants. Muskmelon plants infected by this fungus also presented hypertrophy and hyperplasia, which
led to a progressive separation of the vascular bundles in the lower stems of the affected plants. This response was not observed
in autumn squash during the study. On the other hand, few histological changes were observed in tissues infected with M. cannonballus and only a slight increase in the size of cortical intercellular spaces was noted in the lower stems of muskmelon plants,
and infected autumn squash tissues remained free of these symptoms throughout the study. The scanning electron microscope
observations revealed that both fungi were able to colonise the tissues of the two host plants which were studied. A. cucurbitacearum colonised the epidermis and cortex of both muskmelon and autumn squash. The hyphae grew both inter- and intracellularly,
and the density of the colonisation decreased within the endodermis. The same colonisation of host plants was observed as
a result of M. cannonballus infection. The xylem vessel lumina of both muskmelon and autumn squash showed hyphae and tylose formation as a result of
both fungal infections. However, non-fungal structures were detected in the hypocotyl vascular tissues. The present study
demonstrates that both fungi are capable of infecting the tissues of a species which is resistant (autumn squash) and a species
which is susceptible (muskmelon) to melon collapse. 相似文献
3.
The infection process of Fusarium avenaceum on wheat spikes and the alteration of cell wall components in the infected host tissue were examined by means of electron microscopy and cytochemical labelling techniques following spray inoculation at growth stage (GS) 65 (mid-flowering). Macroconidia of the pathogen germinated with one to several germ-tubes 6–12 h after inoculation (hai) on host surfaces. The germ-tubes did not penetrate host tissues immediately, but extended and branched on the host surfaces. Hyphal growth on abaxial surfaces of the glume, lemma and palea was scanty 3–4 days after inoculation (dai) and no direct penetration of the outer surfaces of the spikelet was observed. Dense mycelial networks formed on the inner surfaces of the glume, lemma, palea and ovary 36–48 hai. Penetration of the host tissue occurred 36 hai by infection hyphae only on the adaxial surfaces of the glume, lemma, palea and upper part of ovary. The fungus penetrated the cuticle and hyphae extended subcuticularly or between the epidermal wall layers. The subcuticular growth phase was followed by penetration of the epidermal wall, and hyphae spread rapidly inter- and intracellularly in the glume, lemma, palea and ovary. During this necrotrophic colonization phase of the wheat spike, a series of alterations occurred in the host tissues, such as degeneration of cytoplasm and cell organelles, collapse of host cells and disintegration of host cell walls. Immunogold labelling techniques showed that cell walls of spike tissues contained reduced amounts of cellulose, xylan and pectin near intercellular hyphae or infection pegs compared to walls of healthy host tissues. These studies suggest that cell wall degrading enzymes produced by F. avenaceum facilitated rapid colonization of wheat spikes. The different penetration properties of abaxial and adaxial surfaces of the spikelet tissues as well as the two distinct colonization strategies of host tissues by F. avenaceum are discussed. The penetration and colonization behaviour of F. avenaceum in wheat spikelets resembled that of F. culmorum and F. graminearum, although mycotoxins produced by F. avenaceum differed from those of the latter two Fusarium species. 相似文献
4.
An interaction between the fungal pathogenSphaeropsis sapinea (Fr.) Dyko & Sutton, causal organism of Sphaeropsis canker, and the Israeli pine bast scaleMatsucoccus josephi (Homoptera: Margarodidae), causal agent of pine decline, was studied, since both were prevalent on Aleppo pine (Pinus halepensis) stands.Sphaeropsis sapinea was isolated from larvae (stage II) and molts of the Israeli pine bast scale collected in four Aleppo pine stands. When Aleppo
pine saplings were infested with pine bast scale and subsequently inoculated withS. sapinea most plants died, whereas mortality of seedlings inoculated withS. sapinea alone without previous scale infestation was negligible. Scale infestation of saplings without subsequent fungal inoculation
caused the death of one third of the plants. Wounding of pine shoot apices by removal of needle fascicles enhanced infection
byS. sapinea. The results support the assumption thatM. josephi can play an important role in transmitting the fungal inoculum to the host tree as well as enabling its penetration to the
shoots through wounds in the bark.
http://www.phytoparasitica.org posting Dec. 20, 2004. 相似文献
5.
Graziella Berta Simonetta Sampo Elisa Gamalero Nadia Massa Philippe Lemanceau 《European journal of plant pathology / European Foundation for Plant Pathology》2005,111(3):279-288
Rhizoctonia solani root-rot is a major soilborne disease causing growth and yield depression. The ability of Glomus mosseae BEG12 and Pseudomonas fluorescens A6RI to suppress this soilborne disease in tomato was assessed by comparing the shoot and root growth of plants infested with R. solani 1556 when protected or not by these beneficial strains. The epiphytic and parasitic growth of the pathogenic R. solani 1556 was compared in the presence and absence of the biocontrol agents by microscopical observations allowing the quantification of roots with hyphae appressed to epidermal cells (epiphytic growth) and of roots with intraradical infection (parasitic growth). The root architecture of the tomato plants under the different experimental conditions was further characterized by measuring total root length, mean root diameter, number of root tips and by calculating degree of root branching. G. mosseae BEG12 and P. fluorescens A6RI fully overcame the growth depression caused by R. solani 1556. This disease suppression was associated with a significant decrease of the epiphytic and parasitic growth of the pathogen together with an increase of root length and of the number of root tips of inoculated tomato plants. The combined effects of G. mosseae BEG12 and P. fluorescens A6RI on pathogen growth and on root morphogenesis are suggested to be involved in the efficient disease suppression. 相似文献
6.
Fusarium species are soil-borne fungal pathogens that produce a variety of disease symptoms when attacking crop plants. The mode of root colonization of Eucalyptus viminalis seedlings by a pathogenic F. oxyporum strain (Foeu1) at the ultrastructural level and changes in cell wall pectin during host pathogen interactions are described. Root systems of E. viminalis plants were inoculated with F. oxysporum in an in vitro model system. Hyphae of F. oxysporum adhered to the outer epidermal cell walls through fibrillar material, and after penetration they spread into the internal tissues. They developed intercellularly and intracellularly in the root cortex and invaded vascular tissues. Papillae were induced, and the host plasma membrane ruptured in colonized cells, causing rapid host tissue and cell damage. Changes in distribution and occurrence of nonesterified and methyl-esterified pectins were evaluated after root colonization by F. oxysporum using two monoclonal antibodies, JIM 5 and JIM 7, respectively. Nonesterified pectin in control roots was mainly localized in the epidermal cell walls and middle lamellae in parenchymal cortex, whereas methyl-esterified pectin accumulated more in primary cell walls of the cortex and phloem. Decreases in immunodetected nonesterified and methyl-esterified pectins were associated with extensive plant tissue degradation after root colonization by the pathogenic fungus. 相似文献
7.
Z. Kang H. Buchenauer 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(7):653-660
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. 相似文献
8.
Parasitic plants are becoming a severe constraint on major agricultural crops in Mediterranean and tropical countries and
the efficacy of available means of control is minimal. The problem is particularly severe in field pea, which is very sensitive
to standard glyphosate treatments and in which little resistance has been identified. Systemic Acquired Resistance (SAR) has
proven to be effective as a tool for controlling plant pathogens, including fungi, bacteria and viruses, but only recently
has this phenomenon started to be evaluated as a control strategy against parasitic weeds. The present studies were conducted
to evaluate the potential of SAR activation for broomrape control in pea. The effect of salicylic acid, glutathione and benzothiadiazole
(BTH) in three different application methods was studied. Foliar application of 0.6–1.0 mM BTH, in the form of Bion 50 (50%
a.i.), reduced broomrape infection under controlled conditions (growth chamber and greenhouse) by limiting the success in
attachment and retarding the development of established tubercles.
http://www.phytoparasitica.org posting Dec. 1, 2003. 相似文献
9.
Nonpathogenic isolates of Fusarium oxysporum can be successful antagonists of pathogenic forms of the same fungal species that commonly attacks crop plants. The characteristics that distinguish nonpathogenic from pathogenic forms are not well understood. In this study, the mode of root colonization of Eucalyptus viminalis seedlings by a nonpathogenic F. oxysporum strain is described at the ultrastructural level. Root systems of E. viminalis plants were inoculated with nonpathogenic F. oxysporum strain Fo47 in an in vitro model system. Changes in the occurrence of nonesterified and methyl-esterified pectins in colonized E. viminalis roots were evaluated by in situ immunolabeling using two monoclonal antibodies, JIM 5 and JIM 7. Modes of penetration and root colonization patterns in E. viminalis seedlings by the nonpathogenic fungus were similar to those described for pathogenic forms of F. oxysporum. However, root interactions differed in that the nonpathogenic fungus did not induce host tissue damage. No papilla-like appositions were observed in host cells in response to invading hyphae, which did not disrupt the host plasma membrane in many cases, suggesting that a biotrophic relationship was established. Root colonization by the nonpathogenic strain did not induce alteration in JIM 7 labeling of methyl-esterified pectin in E. viminalis cell walls, whereas nonesterified pectin was detected to a significantly greater extent in cell walls of roots colonized by the fungus. Pectin components decreased slightly only at points of hyphal contact with host cells. Because nonpathogenic strains utilize pectin in pure culture, host control over enzyme activity or production by the fungi may at least partly explain their compatible interactions with host tissues. 相似文献
10.
11.
Treatments with prohexadione-calcium led to lowered incidence of fire blight, scab and other diseases in pome fruit trees and other crop plants. In addition to acting as a growth regulator, prohexadione-calcium interferes with flavonoid metabolism and induces the accumulation of the 3-deoxycatechin luteoliflavan in shoots of pome fruit trees. Luteoliflavan does not possess any remarkable antimicrobial activity. Therefore luteoforol, its unstable and highly reactive precursor, has been tested in vitro for its bactericidal and fungicidal activities. Luteoforol was found to be highly active against different strains of Erwinia amylovora, the causal agent of fire blight, and all other bacterial and fungal organisms tested. Phytotoxic effects were also observed in pear plantlets. The results obtained indicate that prohexadione-calcium induces luteoforol as an active principle with non-specific biocidal properties. It is proposed that luteoforol is released upon pathogen attack from its cellular compartment and inhibits further disease development by destroying pathogen cells as well as by inducing a hypersensitive-like reaction in the host plant tissue. This mechanism would be closely analogous to the one known for structurally related phytoalexins in sorghum. 相似文献
12.
为明确红颈常室茧蜂Peristenus spretus Chen et van Achterberg定位寄主绿盲蝽Apolygus lucorum(Meyer-Dür)时利用的挥发性信息物质来源,利用Y型昆虫嗅觉仪测定了红颈常室茧蜂雌雄成虫对绿盲蝽3龄若虫及其为害寄主植物棉株以及雌性红颈常室茧蜂成虫、绿盲蝽成虫对苗期和花期的棉花、蓖麻的选择行为。结果表明,与干净空气(空白对照)相比,雌性红颈常室茧蜂对绿盲蝽3龄若虫、健康棉株的选择行为无显著差异,绿盲蝽3龄若虫为害的棉株对雌性红颈常室茧蜂具有显著的吸引作用,但在为害后去虫和未去虫处理间无显著差异;雄性红颈常室茧蜂对各处理均无明显的选择行为。与健康或为害后去虫的苗期棉花相比,雌性绿盲蝽成虫显著趋向花期蓖麻;而雌性红颈常室茧蜂只趋向于为害后的花期蓖麻。雌性红颈常室茧蜂对为害后去虫的花期棉花和花期蓖麻的选择行为显著高于相应的苗期植株。这表明雌性红颈常室茧蜂主要利用绿盲蝽若虫为害后寄主植物释放的挥发性信息物质来定位寄主绿盲蝽,且其对花期寄主植物的选择行为与绿盲蝽成虫具有一致性。 相似文献
13.
为探索丛枝菌根(arbuscular mycorrhiza,AM)真菌与植食性昆虫的相互作用,将摩西管柄囊霉(Funneliformis mosseae BEG167,Fm)、根内球囊霉(Glomus intraradices BEG141,Gi)和地表球囊霉(Glomus versiforme Berch,Gv)3种AM真菌以及甜菜夜蛾Spodoptera exigua分别接种至花生和番茄上,通过测定AM真菌的侵染定殖和甜菜夜蛾的生长发育指标分析AM真菌与甜菜夜蛾的相互作用。结果显示,甜菜夜蛾取食菌根花生植株后,Fm、Gv和Gi的侵染率和泡囊数均有增加,侵染率分别是未取食的1.15、1.10和1.11倍,而Fm的泡囊数增加最显著,是未取食的1.27倍。在菌根番茄植株上,Fm和Gv的侵染率显著增加,分别是未取食的1.24倍和1.94倍,Fm、Gv和Gi的泡囊数均显著增加,分别是未取食的1.50、1.98和1.42倍。甜菜夜蛾取食菌根花生和菌根番茄植株后,幼虫存活率下降,幼虫历期和蛹期明显延长;Fm对其影响最显著,甜菜夜蛾在花生上的存活率、幼虫历期和蛹期分别为26.67%、26.78 d和10.67 d,在番茄上分别为35.52%、24.33 d和10.39 d,与取食非菌根植株处理差异显著。表明甜菜夜蛾能在一定程度上促进AM真菌的侵染和定殖,而AM真菌能抑制甜菜夜蛾的生长和发育,但其影响因AM真菌种类而不同。 相似文献
14.
15.
The growth behaviour of several Alternaria species on leaf discs of host and nonhost plants was examined by u.v. microscopy. Specific patterns of development were found for the pathogens. Differences in development which correlated to host specificity, or which differentiated specialized pathogens from weak or opportunistic pathogens, were obvious only after attempted penetration. Thus, little variation was observed amongst different plants for individual Alternaria species in the rate of germination, in the extent of germ-tube growth or in the frequency of appressorium production. However, plant responses to attempted penetration, which included the formation of callose-containing papillae, callose deposition in the walls of attacked cells and their neighbours and cell necrosis, varied with specific pathogen–plant interactions. Callose deposition occurred at sites of both successful and unsuccessful penetrations and may, therefore, not be a determining factor in the plant–pathogen interactions examined. A biplot technique is used to illustrate the different degrees of host specificity apparent at pre- and post-penetration stages of fungal development. 相似文献
16.
Root parasitic plants of the family Orobanchaceae cause severe damage to important agricultural crops worldwide. These parasitic weeds are difficult to control since most of their lifecycle occurs belowground. This hinders the diagnosis of infection and normally when irreversible damage has been caused to the crop. Therefore, new and more effective control strategies against these parasitic weeds should be focused on the initial stages of the interaction. Using tomato-Phelipanche ramosa as model system, we have explored the host response during the initial phase of parasitic infection by monitoring the expression of marker genes of different defense-related hormonal pathways. Two different colonization stages were selected and analyzed by quantitative real-time PCR. The data suggest that the three principal defense regulating hormonal pathways - salicylic acid (SA), jasmonic acid (JA) and abscisic acid (ABA) - are induced after infection, being therefore, likely involved in the defense response against these root parasites. In addition, an induction of the strigolactone (SL) biosynthesis genes SlD27 and SlCCD8 was observed. Our results suggest a complex regulation of plant defenses during the early stages of plant-parasite interaction involving the classical defense hormones, and suggest an additional role of the parasite germination stimulants SLs at this post-attachment stage. 相似文献
17.
为室内大量繁殖中华卵索线虫Ovomermis sinensis,采用个体由大到小的斜纹夜蛾Spodoptera litura、棉铃虫Helicoverpa armigera和黏虫Mythimna separata作为宿主,测定被中华卵索线虫寄生后3种宿主的体长和体重,研究宿主种类对中华卵索线虫有效率、雌雄比和体长的影响以及寄生强度对线虫雌雄比的影响。结果显示,被中华卵索线虫寄生后,斜纹夜蛾、棉铃虫和黏虫生长减缓。在相同感染比例下（除宿主与线虫比为1∶15外）,3种宿主的线虫有效率之间差异不显著。当寄生强度为5时,3种宿主体内脱出的中华卵索线虫均为雌线虫;当寄生强度从10增到40时,斜纹夜蛾、棉铃虫和黏虫所脱出的雌性比分别由100.0%、90.0%、83.9%降为0;相同寄生强度下,从斜纹夜蛾体内脱出的雌性比显著高于从棉铃虫与黏虫体内脱出的雌性比。斜纹夜蛾、棉铃虫和黏虫体内脱出雌线虫和雄线虫平均体长分别为14.8、13.8、12.8 cm和8.0、7.5和7.5 cm。当中华卵索线虫与宿主按照比例20∶1～25∶1侵染斜纹夜蛾、按照15∶1侵染棉铃虫和黏虫时,能获得线虫最适雌雄比（1∶1... 相似文献
18.
Manchanahally Shivanna Meera Manchanahally Byrappa Shivanna Koji Kageyama Mitsuro Hyakumachi 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(4):421-430
Initial experiment on the reactions of five Japanese cultivars of cucumber toColletotrichum orbiculare infection in the greenhouse revealed that cv Suyo and Gibai were susceptible and moderately susceptible, respectively, while cv Shogoin fushinari and Sagami hanjiro were resistant to infection byC. orbiculare; cv Ochiai fushinari was moderately resistant. The ability of 16 plant growth promoting fungi (some isolates belonged to species ofPhoma and some non-sporulating isolates) isolated from zoysiagrass rhizospheres to induce systemic resistance in the above five cucumber cultivars was tested by growing plants in potting medium infested with barley grain inocula of PGPF in the greenhouse. The second true leaves of 21-day-old plants were challenge inoculated withC. orbiculare and disease assessed. Nine, out of 16 isolates, caused significant reduction of disease caused byC. orbiculare in at least two cultivars.Phoma isolates (GS8-1 and GS8-2) and non-sporulating isolates (GU21-2, GU23-3, and GU24-3) significantly reduced the disease in all the five cultivars. The disease suppression in cucumber was due to the induction of systemic resistance, since the inducer(s) and the pathogen were separated spatially and that the inducer did not colonize aerial portions. The resistance induced by certain isolates in a susceptible cultivar was less than that in a resistant cultivar. Disease suppression caused by isolate GU21-2 was similar to theC. orbiculare induced control in certain cultivars. The average rate of expansion of lesion diameter on leaves due toC. orbiculare was slower due to induction with the selected plant growth promoting fungi compared to the uninduced control plants. Roots of four cultivars were colonized by only three isolates, however, roots of one cultivar (Suyo) was colonized by five isolates suggesting the cultivar-specific root colonization ability.Abbreviations cv
cultivar(s)
- PGPF
plant growth promoting fungal isolates
- PGPR
plant growth promoting rhizobacteria 相似文献
19.
Yeon Kyeong Lee Jeum Kyu Hong Sigrun Hippe-Sanwald Byung Kook Hwang 《Physiological and Molecular Plant Pathology》2000,57(6)
The compatible interaction of pepper stems with Phytophthora capsici showed more rapid and severe disease development than did the incompatible interaction, although pathogen penetration styles of host cells in compatible and incompatible interactions were similar to each other. Treatment with
-β-amino- n -butyric acid (BABA) protected the pepper plants against P. capsici infection. Reduced hyphal growth and sporangial formation were found after P. capsici infection in BABA-induced resistant and incompatible reactions. One of the most noticeable ultrastructural features of the BABA-induced resistant reaction was the formation of electron-dense wall appositions. The thick and dense wall appositions that encased the haustoria restricted haustorial development, thus leading to limitation of further pathogen penetration into inner plant tissues. A main host response in the incompatible interaction was the occlusion of cortical cells with an amorphous material. Plugging of the intercellular spaces in the cortical cells with electron opaque material was frequently observed in the incompatible interaction, but not in the compatible interaction. Another common feature of the BABA-induced resistant and incompatible reactions was degeneration of mitochondrial structure within penetrating hyphal cytoplasm. The mitochondrial structure in the BABA-induced resistant or incompatible reactions had no distinct double membrane layer and well-shaped cristae. 相似文献
20.
多堆柄锈菌侵染玉米的细胞学及超微结构特征 总被引：2，自引：1，他引：1
为明确玉米对多堆柄锈菌Puccinia polysora侵染后病理反应的细胞学特征,利用扫描和透射电镜技术分析了玉米自交系与多堆柄锈菌互作中二者的细胞变化过程。多堆柄锈菌对玉米的侵染主要以直接穿透叶片表皮侵入为主,少量可从气孔和细胞间隙侵入。接种后,病菌夏孢子在感病自交系叶片上快速并大量萌发,在叶表生长蔓延并侵入表皮组织细胞,7 d后形成夏孢子堆;在抗病自交系上,病菌萌发、菌丝生长均受到明显抑制,少量入侵的病菌也由于寄主细胞死亡而导致菌丝和夏孢子干瘪死亡。侵染早期在感病寄主细胞间隙出现菌丝并穿透细胞壁,在胞内产生分枝菌丝,此时寄主细胞结构正常;随着菌丝进一步扩展,叶绿体等结构发生紊乱,被侵染细胞逐渐死亡。在抗病自交系上,接菌24 h后寄主即出现过敏性坏死反应,侵入位点与周围细胞快速坏死,抑制菌丝生长蔓延;叶绿体中清晰可见深色颗粒状物质;72 h后细胞壁外侧产生大量致密的深色结晶体,应为与抗病反应相关的酚类物质。表明抗多堆柄锈菌的玉米材料可能存在2种抗病途径,即寄主与病菌互作中由分子识别引起的免疫反应和病菌侵入后的系统防卫反应。 相似文献