共查询到20条相似文献，搜索用时 40 毫秒
1.
ABSTRACT The burrowing nematode Radopholus similis is one of the most damaging pathogens on banana plantations. The role of phenolics in plant defense responses to the nematode was histochemically and ultrastructurally investigated in susceptible and partially resistant cultivars. Histochemical observations of healthy roots revealed that high levels of lignin, flavonoids, dopamine, cafeic esters, and ferulic acids were associated with a very low rate of nematode root penetration in the resistant cultivar. The presence of lignified and suberized layers in endodermal cells contributed to limit invasion of the vascular bundle by the pathogen. After infection, flavonoids were seen to accumulate early in walls of cells close to the nematode-migrating channel in both cultivars and in all tissues of the infected resistant roots including the vascular tissues. The labeling pattern obtained with the gold-complexed laccase and with anti-pectin monoclonal antibodies showed that phenolics were distributed in a loosened pectin-rich material surrounding the nematode. This study provides indications that constitutive phenolics in banana roots are associated with the limitation of host penetration and colonization by R. similis. Accumulation of flavonoids in response to infection was detected in the vascular tissues of susceptible plants and in all root tissues in the partially resistant plants. 相似文献
2.
玉米感染肿囊腐霉后寄主-病原物互作的超微结构研究 总被引：5，自引：0，他引：5
本文利用透射电镜,首次对玉米不同抗性寄主与肿囊腐霉(Pythium inflatum)相互作用中的寄主反应及菌丝在寄主内的发展进行了系统研究。结果表明:玉米苗期根部接种后,孢子迅速萌发成菌丝在根表蔓延,随即穿透根表皮,进入表皮细胞、皮层甚至感病寄主的维管束组织。与此同时,寄主相应的反应迅速,寄主反应采取如下方式:细胞壁的沉积物及乳突在真菌的入侵处形成,各种无定形物质或纤丝构成的质网包围入侵菌丝。沉积在寄主细胞壁上并在受侵染细胞内聚集的化合物可能是酚类物质,这些嗜锇酸的电子致密物是用来机械地加强细胞壁的强度及产生抗真菌的环境。寄主反应的早晚及程度的强弱决定着菌丝在寄主体内发展繁殖的程度及寄主抗性的强弱。抗病玉米自交系的反应程度及速度显著强于感病玉米。 相似文献
3.
The ability of nonpathogenic Fusarium oxysporum, strain Fo47, to trigger plant defense reactions was investigated using Ri T-DNA-transformed pea roots. Cytological investigations of strain Fo47-inoculated roots showed that the fungus grew actively at the root surface and colonized a number of epidermal and cortical cells, inducing marked host cell metabolic changes. In roots inoculated with pathogenic F. oxysporum f. sp. pisi, the pathogen multiplied abundantly through much of the tissues, whereas in Fo47-inoculated roots, fungal growth was restricted to the epidermis and the outer cortex. Invading cells of strain Fo47 suffered from serious alterations, a phenomenon that was not observed in control roots in which F. oxysporum f. sp. pisi grew so actively that the vascular stele was invaded within a few days. Strain Fo47 establishment in the root tissues resulted in a massive elaboration of hemispherical wall appositions and in the deposition of an electron-opaque material frequently encircling pathogen hyphae and accumulating in the noninfected xylem vessels. This suggests that the host roots were signaled to defend themselves through the rapid stimulation of a general cascade of nonspecific defense responses. The specific relationship established between strain Fo47 and the root tissues is discussed in relation to other types of plant-fungus interactions, including pathogenic and symbiotic associations. 相似文献
4.
Taissir Abou Al Fadil Alain Jauneau Yves Martinez Martina Rickauer Grégory Dechamp-Guillaume 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(1):93-103
Phoma macdonaldii, the causal agent of black stem disease of sunflower (Helianthus annuus), also attacks roots and collars of the plants, resulting in early death. Totally resistant lines do not exist for infection
of the aerial parts, but tolerant lines have been characterised. This paper presents a study on colonisation of a partially
resistant and a susceptible sunflower line by P. macdonaldii. The fungus was transformed with a constitutively expressed reporter gene encoding the jellyfish green fluorescent protein
via Agrobacterium tumefaciens, and colonisation of sunflower roots by this transformed strain was studied by various microscopy techniques including confocal
and scanning electron microscopy. The results show that penetration of the fungus into the root occurred through natural fissures
or through the epidermis and was similar in both lines. In contrast, the colonisation rate of the stele was reduced in the
partially resistant line, and the morphology of the fungal hyphae was also affected. The effect on hyphal morphology was strongest
in the stele, indicating a localised production of defence compounds in this line. 相似文献
5.
ABSTRACT Port-Orford-cedar (POC) root disease, caused by Phytophthora lateralis, continues to kill POC in landscape plantings and natural forests in western North America. POC trees resistant to P. lateralis have been identified and propagated. Cytological observations of P. lateralis in susceptible and resistant roots and stems were made with light and transmission electron microscopy to identify resistance mechanisms. No differences in infection pathway and initial colonization were observed between susceptible and resistant roots, although there were differences in the rate and extent of development. Germ tubes formed appressoria, and penetration hyphae grew either between or directly through epidermal cell walls; inter- and intracellular hyphae colonized the root cortex. In susceptible roots, hyphae penetrated into the vascular system within 48 h of inoculation. In contrast, hyphae in roots of resistant seedlings grew more slowly in cortical cells and were not observed to penetrate to the vascular tissues. In resistant roots, infection was marked by general thickening of cortical cell walls, wall appositions around penetrating hyphae, collapse of cortical cells, and accumulation of osmophillic granules around hyphae. In susceptible stems, hyphae grew inter- and intracellularly in all cells of the secondary phloem except fiber cells, but were concentrated in sieve and parenchyma cells in the functional phloem. The pattern of penetration and colonization of hyphae was similar in the resistant stems, except that hyphae were found in the fiber cells of the xylem. In resistant stems, there were fewer hyphae in the functional phloem, and cytological changes such as damaged nuclei and disintegrated cytoplasm were evident. Structural changes in resistant stems included collapsed cells, wall thickening, secretory bodies, apposition of electron dense materials, and crystals in cell walls. 相似文献
6.
N. Wuyts † G. Lognay M. Verscheure M. Marlier D. De Waele R. Swennen 《Plant pathology》2007,56(5):878-890
Resistance in banana roots against the burrowing nematode Radopholus similis has been correlated in the past with the phenylpropanoid pathway of secondary metabolism, but quantitative chemical analyses to support histological data are lacking. Therefore, healthy and infected roots of two susceptible (Grande naine and Obino l'ewai) and three resistant cultivars (Yangambi km5, Pisang jari buaya and Calcutta 4) were extracted and chemically analysed for their lignin content and phenylpropanoid profile using a quantitative lignin assay, high performance liquid chromatography and liquid chromatography/mass spectrometry. Through histochemical staining phenylpropanoids were localized in root tissue. Compared to the susceptible cultivars, the resistant cultivars had constitutively significantly higher levels of lignin in the vascular bundle and cell-wall bound ferulic acid esters in the cortex. Infection-induced lignification was observed in the vascular bundles of all cultivars. The catecholamine dopamine was identified as a major metabolite in banana roots. Levels varied from 2·8 to 8·4 mg per g root fresh weight and were significantly higher in the resistant cultivars. Other compounds, tentatively identified as anthocyanidin-related, were present in high quantities and may, besides dopamine, make up the substrates for polyphenol oxidation products in necrotic tissue. 相似文献
7.
Akira Masunaka Kazuhiro Nakaho Masao Sakai Hideki Takahashi Shigehito Takenaka 《Journal of General Plant Pathology》2009,75(4):281-287
The biocontrol agent Pythium oligandrum (PO) can suppress bacterial wilt caused by Ralstonia solanacearum (RS) in tomato. To understand the primary biocontrol mechanisms of bacterial wilt by PO, we pretreated tomato plants with
sterile distilled water or preinoculated them with PO, followed by inoculation with RS, then observed PO and RS in fixed sections
of tomato tissues using a confocal laser-scanning microscope and fluorescence labeling until 14 days after the inoculation
with RS. Horizontal and vertical movement of RS bacteria was frequently observed in the xylem vessels of roots and stems of
tomato plants (cv. Micro-Tom) that had not been inoculated with PO. In plants that were preinoculated with PO, the movement
of RS was suppressed, and bacteria appeared to be restricted to the pit of vessels, a reaction similar to that observed in
resistant rootstocks. PO colonization was mainly observed at the surfaces of taproots, the junctions between taproots and
lateral roots, and the middle sections of the lateral roots. PO was not observed near wound sites or root tips where RS tended
to colonize. However, RS colonization was significantly repressed at these sites in PO preinoculated plants. These observations
suggest that the induction of plant defense reactions is the main mechanism for the control of tomato bacterial wilt by PO,
not direct competition for infection sites. 相似文献
8.
Interactions between lettuce and a green fluorescent protein (GFP)-expressing, race 1 isolate of Verticillium dahliae, were studied to determine infection and colonization of lettuce cultivars resistant and susceptible to Verticillium wilt. The roots of lettuce seedlings were inoculated with a conidial suspension of the GFP-expressing isolate. Colonization was studied with the aid of laser scanning confocal and epi-fluorescence microscopes. Few differences in the initial infection and colonization of lateral roots were observed between resistant and susceptible cultivars. Hyphal colonies formed on root tips and within the root elongation zones by 5 days, leading to the colonization of cortical tissues and penetration of vascular elements regardless of the lettuce cultivar by 2 weeks. By 8 to 10 weeks after inoculation, vascular discoloration developed within the taproot and crown regions of susceptible cultivars well in advance of V. dahliae colonization. Actual foliar wilt coincided with the colonization of the taproot and crown areas and the eruption of mycelia into surrounding cortical tissues. Advance colonization of stems, pedicels, and inflorescence, including developing capitula and mature achenes was observed. Seedborne infection was limited to the maternal tissues of the achene, including the pappus, pericarp, integument, and endosperm; but the embryo was never compromised. Resistant lettuce cultivars remained free of disease symptoms. Furthermore, V. dahliae colonization never progressed beyond infected lateral roots of resistant cultivars. Results indicated that resistance in lettuce may lie with the plant's ability to shed infected lateral roots or to inhibit the systemic progress of the fungus through vascular tissues into the taproot. 相似文献
9.
ABSTRACT Histochemical staining, beta-glucuronidase (GUS) activity, or placing roots on agar were methods used to characterize interactions between the pathogenic fungus, Fusarium oxysporum f. sp. lycopersici, and the nonpathogenic biocontrol F. oxysporum strain 70T01 with respect to colonization behaviors, interaction sites, and population densities on tomato roots. Mycelia of strain 70T01, a genetic transformant expressing stable GUS activity, hygromycin B resistance, and effective disease control, were localized in epidermal and cortex cell layers of tomato roots in a discontinuous and uneven pattern. In contrast, mycelia of F. oxysporum f. sp. lycopersici were found in the vascular bundles. Thus, direct interactions between the two fungi likely happen in the root surface cell layers. Colonization density of strain 70T01 was related to the inoculation density but decreased with distance from the inoculation site. Host defense reactions, including increased cell wall thickness or papilla deposits, were adjacent to 70T01 hyphae. Experiments done in soil showed that strain 70T01 densities in roots were highest at inoculation zones and barely detectable for root segments more than 2 cm away from the inoculation sites. F. oxysporum f. sp. lycopersici densities were lowest at 70T01 inoculation zones and highest (>10 times) where strain 70T01 was not directly applied. Newly elongating roots where strain 70T01 did not reach were available for infection by the pathogen. The higher strain 70T01 density was always found when the plants were simultaneously infected by F. oxysporum f. sp. lycopersici, suggesting that F. oxysporum f. sp. lycopersici has as much influence in predisposing the plant to colonization by strain 70T01 as strain 70T01 has on providing disease protection against the pathogen. 相似文献
10.
中国小黑豆抗源对大豆孢囊线虫4号生理小种抗性机制的研究Ⅱ.抗感品种根部合胞体超微结构的比较 总被引：1，自引：0，他引：1
接种大豆孢囊线虫4号生理小种后4、9、14天,对我国小黑豆抗源灰皮支黑豆和元钵黑豆及感病对照鲁豆1号根部形成的合胞体组织的超微结构进行了研究。结果发现:感病品种的合胞体细胞较大、靠近木质部导管一侧有内生长,各种细胞器丰富,内质网数量多形体长、多为光滑型;抗病品种合胞体细胞较小,核糖体较多,内质网小而少、多为粗糙型,细胞内出现较多的类脂肪体,在侵染早期,细胞质快速降解,有时发现细胞质膜与细胞壁发生分离。 相似文献
11.
中国小黑豆抗源对大豆孢囊线虫4号生理小种抗性机制的研究Ⅱ.抗感品种根部合胞体超微结构的比较 总被引：6，自引：0，他引：6
接种大豆孢囊线虫4号生理小种后4、9、14天,对我国小黑豆抗源灰皮支黑豆和元钵黑豆及感病对照鲁豆1号根部形成的合胞体组织的超微结构进行了研究。结果发现:感病品种的合胞体细胞较大、靠近木质部导管一侧有内生长,各种细胞器丰富,内质网数量多形体长、多为光滑型;抗病品种合胞体细胞较小,核糖体较多,内质网小而少、多为粗糙型,细胞内出现较多的类脂肪体,在侵染早期,细胞质快速降解,有时发现细胞质膜与细胞壁发生分离。 相似文献
12.
ABSTRACT Research on the mechanisms employed by the biocontrol agent Trichoderma virens to suppress cotton (Gossypium hirsutum) seedling disease incited by Rhizoctonia solani has shown that mycoparasitism and antibiotic production are not major contributors to successful biological control. In this study, we examined the possibility that seed treatment with T. virens stimulates defense responses, as indicated by the synthesis of terpenoids in cotton roots. We also examined the role of these terpenoid compounds in disease control. Analysis of extracts of cotton roots and hypocotyls grown from T. virens-treated seed showed that terpenoid synthesis and peroxidase activity were increased in the roots of treated plants, but not in the hypocotyls of these plants or in the untreated controls. Bioassay of the terpenoids for toxicity to R. solani showed that the pathway intermediates desoxyhemigossypol (dHG) and hemigossypol (HG) were strongly inhibitory to the pathogen, while the final product gossypol (G) was toxic only at a much higher concentration. Strains of T. virens and T. koningii were much more resistant to HG than was R. solani, and they thoroughly colonized the cotton roots. A comparison of biocontrol efficacy and induction of terpenoid synthesis in cotton roots by strains of T. virens, T. koningii, T. harzianum, and protoplast fusants indicated that there was a strong correlation (+0.89) between these two phenomena. It, therefore, appears that induction of defense response, particularly terpenoid synthesis, in cotton roots by T. virens may be an important mechanism in the biological control by this fungus of R. solani-incited cotton seedling disease. 相似文献
13.
ABSTRACT Digestive cysteine proteinases have been isolated from plant-parasitic nematodes as well as coleopteran and hemipteran insects. Phytocystatins, inhibitors of cysteine proteinases, are found in a number of plants where they may play a role in defense against pathogens and pests. The cDNAs of the phytocystatins from rice, oryzacystatin I (OC-I) and oryzacystatin II (OC-II), were expressed in alfalfa (Medicago sativa) plants under the control of the potato protease inhibitor II (PinII) promoter and the plants were evaluated for resistance to the root-lesion nematode (Pratylenchus penetrans). A PinII-beta-glucuronidase (GUS) gene was introduced into alfalfa to determine the pattern of gene expression from this promoter. Constitutive GUS expression was observed in leaf and root vascular tissue, and in some plants, expression was observed in leaf mesophyll cells. Mechanical wounding of leaves increased GUS expression approximately twofold over 24 h. Inoculation with root-lesion nematodes resulted in localized GUS expression. Populations of root-lesion nematodes in alfalfa roots from one line containing the PinII::OC-I transgene and one line containing the PinII::OC-II transgene were reduced 29 and 32%, respectively, compared with a transgenic control line. These results suggest that oryzacystatins have the potential to confer increased resistance to the root-lesion nematode in alfalfa. 相似文献
14.
ABSTRACT Field-grown winter wheat was inoculated with a beta-glucuronidase-transformed isolate of Cephalosporium gramineum in two field seasons to elucidate the mode of infection in resistant and susceptible cultivars. Colonization of viable root epidermis and cortical cells occurred as soon as 15 days postinoculation and the pathogen was found in the vascular tissues by 20 days postinoculation, well before freezing soil temperatures occurred. Penetration occurred directly through the root epidermis and through wounds adjacent to emerging secondary roots. The pathogen also penetrated through root cap cells and colonized meristematic tissues near root tips to gain access to the vascular system. Lower stem base colonization was observed where the pathogen penetrated directly through the epidermis, wounds, or senescent tissues. Appressorium-like structures, which appeared to aid penetration of cell walls, were often found within cells of both roots and stems after initial colonization. The mechanisms of resistance were not apparent, but less colonization occurred in resistant than in susceptible cultivars. 相似文献
15.
Forty-five onion (Allium cepa) cultivars were evaluated for disease resistance to the fungal pathogen Pyrenochaeta terrestris (pink root disease). Forty-three Iranian cultivars and two commercially exotic resistant cultivars (Texas Early Grano and
Yellow Sweet Spanish) were grown in a glasshouse for two successive years (2003 and 2004) in Isfahan, Iran. Susceptibility
of the cultivars was determined using a scale of 0–3. Six cultivars had significantly lower susceptibility of pink root compared
to the exotic ones. High susceptibility tended to be associated with high mean scores (2–3), and the highly resistant cultivars
had the lowest scores (0–1). In addition, the 45 examined cultivars were ranked from 1 to 45 according to their markedly differing
reactions to P. terrestris, which differed markedly. Of 32 cultivars that were less resistant, 30 with an intermediate status or tolerance (1–2) differed
considerably in their rank order. No pink root symptoms were seen in the early stages, but on blotter paper or wheat-straw
agar some roots turned pink with no pycnidia formation, whereas on potato dextrose agar medium (PDA) with a few fresh healthy
and sterile onion roots on the surface, mycelia and pycnidia were recovered. Variance and cluster analysis showed similar
results among the cultivars with various levels of resistance, tolerance and susceptibility as determined by scoring scales. 相似文献
16.
Plants of the eucalypt. Eucalyptus marginata. selected through a glasshouse screening procedure for resistance or susceptibility to Phytophthora cinnamomi , were established in tissue culture and micropropagated. After inoculation with P. cinnamomi , root lesions in clonal lines selected as resistant (RR) to P. cinnamomi were restricted and became contained within four days after inoculation while lesions in roots of those lines susceptible (SS) to P. cinnamomi continued to extend rapidly. Activity of phenylalanine ammonialyase (PAL) was increased above controls in root segments of the RR lines 48 h after inoculation with P. cinnamomi while activity in unselected seedlings and the SS lines was reduced or unchanged. After inoculation, lignin concentration was increased and reached high levels compared with uninoculated control levels in roots of the two RR lines tested. Constitutive levels of phenolics in roots of the RR lines were up to 94% higher than in seedling roots and levels were further increased after inoculation. Levels of phenolics in the other lines and seedlings were unaltered by inoculation. A line derived from resistant seedlings from a susceptible family (RS) had the highest constitutive levels of lignin, which were further increased after inoculation. Resistance to P. cinnamomi in clonally propagated E. marginata seedlings is based on similar mechanisms to those of field resistant species. 相似文献
17.
Callose and β‐1,3‐glucanase inhibit Phytophthora cinnamomi in a resistant avocado rootstock 
下载免费PDF全文
下载免费PDF全文 N. van den Berg J. B. Christie T. A. S. Aveling J. Engelbrecht 《Plant pathology》2018,67(5):1150-1160
Phytophthora root rot (PRR) of avocado, caused by Phytophthora cinnamomi, is a significant threat to sustainable production wherever the crop is grown. Resistant rootstocks in combination with phosphite applications are the most effective options for managing this disease. Recently, the mechanisms underpinning PRR resistance have been investigated by the avocado community. Here, biochemical assays and confocal and scanning electron microscopy were used to investigate early defence responses in PRR resistant and ‐susceptible avocado rootstocks. Zoospore germination and subsequent hyphal growth for the pathogen were significantly inhibited on the surface of resistant avocado roots. When penetration occurred in the resistant R0.06 rootstock, callose was deposited in the epidermal cells, parenchyma and cortex of roots. In addition, β‐1,3‐glucanase was released early (6 h post‐inoculation, hpi) in response to the pathogen, followed by a significant increase in catalase by 24 hpi. In contrast, susceptible R0.12 roots responded only with the deposition of lignin and phenolic compounds incapable of impeding pathogen colonization. In this study, PRR resistance was attributed to a timely multilayered response to infection by P. cinnamomi. 相似文献
18.
19.
To increase understanding of the interactions between Brachypodium distachyon (purple false brome) and its pathogens, six diploid and two hexaploid Plant Introductions (PI) lines were assessed for their resistance/susceptibility to nine economically important fungal pathogens and two species of insect pests affecting closely related grass species. Naturally occurring variation in resistance was found, with two lines being the most resistant and one line being the most susceptible to most of the insects and pathogens tested. Evidence was found for differential activation of key genes in pathogen defense response pathways between susceptible and resistant lines. 相似文献
20.
1983-2007年,对南方稻区水稻区域试验品种、组合的白叶枯病抗性进行了研究。结果表明,在1 805个参试品种、组合中,78个表现抗白叶枯病,抗病品种频率为4.3%;其中,常规水稻74个,占抗病品种的94.9%。在1 219个籼型杂交水稻中,抗病的组合3个,中抗的76个,抗病和中抗组合频率分别为0.2%和6.2%。不同类型和不同生态型水稻的抗病品种频率差异显著,晚粳>早籼>中籼>晚籼;常规水稻>杂交水稻。籼型杂交水稻中抗病组合频率为:杂交晚稻>杂交早稻>杂交中稻。1990-2004年,17个抗或中抗白叶枯病的优良水稻新品种、组合通过国家审定。 相似文献