共查询到20条相似文献，搜索用时 15 毫秒
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T. Cao D. C. Rennie V. P. Manolii S. F. Hwang I. Falak S. E. Strelkov 《Plant pathology》2014,63(3):715-726
Plasmodiophora brassicae causes clubroot of crucifers. A quantitative PCR (qPCR)‐based protocol was developed to measure P. brassicae DNA in the roots of susceptible, intermediately susceptible, intermediately resistant and resistant Brassica hosts, and the non‐host wheat, at 5, 10, 15, 20 and 42 days post‐inoculation (dpi). The final reaction of each plant genotype was recorded as an index of disease at 42 dpi. Plasmodiophora brassicae DNA showed an increase in susceptible and moderately resistant hosts from 5 to 42 dpi, in contrast to a decrease in a highly resistant host and the non‐host wheat over the same period. Index of disease was significantly positively correlated with the amount of P. brassicae DNA in the roots at 5, 15, 20 and 42 dpi in one experiment, and at 10, 15, 20 and 42 dpi in a repeated experiment. Significant positive correlations also existed between the amounts of P. brassicae DNA in the roots at 42 dpi and those at 5, 10, 15 and 20 dpi in one experiment, and those at 10, 15 and 20 dpi in a repeated experiment. The results generated by the qPCR assay were validated by microscopic examination of roots inoculated with P. brassicae. The qPCR‐based protocol developed in this study allows for the accurate quantification of P. brassicae DNA in host root tissues as early as 5 dpi, and may serve as a useful tool to evaluate pathogen proliferation and development in the roots. 相似文献
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In Germany, sugar beet is often rotated with 2 years of cereal. Extensive fallow periods between cereal harvest and autumn primary tillage allow for a weed flora to develop. Broad‐leaved weeds could potentially be alternate hosts for the common nematode Heterodera schachtii, one of the most important pests of sugar beet. Between 2009 and 2012, annual weeds developing in cereal stubble fields during July to mid‐October in the season prior to sugar beet were surveyed, including known hosts of H. schachtii. Yearly weather patterns and agronomic practices possibly impacted weed species composition and weed population densities. During September, Chenopodium album, Cirsium arvense, Convolvulus arvensis, Mercurialis annua, Polygonum spp., Solanum nigrum and Sonchus spp. occurred at the highest frequencies. Weed hosts of H. schachtii were present, but densities, frequencies and uniformity were limited. In 2010 and 2011, staining for nematodes in roots revealed juvenile penetration of some weeds but few adult stages. No indication of nematode reproduction of H. schachtii was found on these weed hosts. A fairly stable weed flora was detected on stubble fields that could provide some carry over for weed species. An elevated risk for nematode population density build‐up on these weeds was not found and management of these weeds at the observed densities during the stubble period for nematological reasons appeared unnecessary. 相似文献
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Potato (Solanum tuberosum) production in Africa is rapidly expanding and becoming increasingly important. As its geographical production range broadens, so does its potential to host new pests and diseases. Following the discovery that potato can be affected by Scutellonema bradys, further studies were undertaken to assess its potential pathogenicity on potato under screenhouse and field conditions, and on marketed tubers. Potato plants inoculated with S. bradys produced tubers with substantial cracking and evident tuber rot, compared with tubers from uninoculated plants. Symptoms of nematode infection on tubers included a scaly appearance, surface cracking as well as deeper tissue cracks, distortions, and darkened surface patches. In most cases these patches were related to sub‐surface rot. Nematodes were recovered from the soil, roots and tubers of inoculated plants. Eight weeks after inoculation, the reproduction factor of the nematode was greatest (2·0) at the lowest inoculation rate assessed (1000 nematodes per 2·5‐L pot) and least (0·4) at the highest inoculation rate (5000 nematodes per pot). In the screenhouse, potato tuber weights were low and mostly unaffected by nematode inoculation rate, except at 5000 nematodes per pot. In the field, non‐inoculated plants yielded over nine times more tubers than plants inoculated with 2000 S. bradys. Low densities of S. bradys were also recovered from 10 of 15 (67%) samples collected from market stalls, indicating field infection. This study confirms that potato can host and be damaged by S. bradys, raising its prospect as a likely significant biotic constraint to the crop. 相似文献
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This study investigated the ability of Neofusicoccum luteum to infect wounded shoots, trunks, pruned cane ends, leaf surfaces, buds, berries and roots, and its further progression into stem tissues. All tissue types were susceptible to infection except roots, with highest incidences in trunks (100%), cane ends (100%), shoots (92%) and buds (88%), indicating that in New Zealand, N. luteum is primarily a trunk and shoot pathogen. In trunks, there were no external symptoms, although N. luteum could be reisolated from 60 to 70 cm acropetally from the inoculation site after 4 months, by which time the pathogen had progressed into side shoots which became necrotic. Wounded and non‐wounded buds became infected; most were killed, with basipetal progression of the pathogen into the supporting shoots. Berries wounded and inoculated at the pre‐bunch closure stage were susceptible to N. luteum infection, with isolation incidence increasing over the season and peaking at harvest, when infected berries became mummified and produced pycnidia with many conidia. The pathogen was also able to progress from berries into bunch stems and supporting canes. Results from this research have indicated that N. luteum infection can occur in all aerial grapevine tissues and progress to young stem tissues where it causes wood necrosis. Growers should remove mummified berries from vineyard trash to ensure that pruning and trimming times do not coincide with rainy periods when conidia are released and dispersed. Furthermore, the susceptibility of buds to N. luteum infection indicates the need for fungicide sprays before budburst in spring. 相似文献
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Contrasting canopy and fibrous root damage on Swingle citrumelo caused by ‘Candidatus Liberibacter asiaticus’ and Phytophthora nicotianae 
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下载免费PDF全文 Huanglongbing (HLB), associated with the phloem‐limited bacterium ‘Candidatus Liberibacter asiaticus’ (Las), is devastating trees in citrus orchards of Florida. Additionally, Phytophthora nicotianae, omnipresent in citrus soils, causes root rot that reduces water and nutrient uptake by fibrous roots. To investigate fibrous root damage and replacement and canopy size in relation to infection of fibrous roots by Las and P. nicotianae, rootstock seedlings of Swingle citrumelo (Citrus paradisi × Poncirus trifoliata) were inoculated with Las or P. nicotianae in two greenhouse pot trials. Phytophthora nicotianae caused root damage within 5 weeks post‐inoculation, which led to greater reduction of canopy size than for Las‐infected seedlings by the end of the experiment. Las increased accumulation of fibrous root biomass at 5 weeks post‐root trimming (wpt) in the 2014 trial and at 11 wpt in the 2015 trial. New root length was not consistently increased by Las. Reduced total leaf area of symptomless Las‐infected seedlings compared to noninoculated controls might be due to the combined effect of altered carbohydrate allocation between shoots and roots and altered leaf morphology. 相似文献
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Naceur Djébali Haythem Mhadhbi Claude Lafitte Bernard Dumas Marie-Thérèse Esquerré-Tugayé Mohamed Elarbi Aouani Christophe Jacquet 《European journal of plant pathology / European Foundation for Plant Pathology》2011,131(4):559-571
The biochemical processes underlying the expression of resistance in the roots of Medicago truncatula against Aphanomyces euteiches infection was investigated, with emphasis on oxidative stress. The levels of H2O2, superoxide dismutase, peroxidase, ascorbate peroxidase, catalase, soluble phenolics and lignin were measured in the roots
of two lines, A17 partially resistant and F83005.5 susceptible to A. euteiches at three infection stages; penetration of the epidermis (1 dpi), colonization of the cortex (3 dpi) and invasion of the root
stele (6 dpi). A rapid and large decrease of the H2O2 levels in A17 roots occurred. However, in F83005.5 roots, the decrease in H2O2 levels was delayed until 3 dpi. In A17 roots, the activities of ascorbate peroxidase, peroxidase and catalase were induced
as early as 1 dpi, whereas a general decrease in the activity of the four antioxidant enzymes was observed in F83005.5 roots.
The levels of soluble phenolics and lignin were increased in A17 roots at 3 and 6 dpi, respectively. The H2O2 levels were negatively correlated to ascorbate peroxidase, catalase and lignin production at 1, 3 and 6 dpi, respectively
in A17 roots. Physiological concentrations of H2O2 found in M. truncatula infected roots had no detrimental effect on the in vitro growth of this oomycete. Our data suggest that H2O2 does not have a direct antimicrobial effect on M. truncatula resistance to A. euteiches, but is involved in cell wall strengthening around the root stele, preventing pathogen invasion of the vascular tissues. 相似文献
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Effect of temperature on resistance to Potato virus Y in potato cultivars carrying the resistance gene Rychc 下载免费PDF全文
下载免费PDF全文 The effect of cultivation temperatures on the resistance reaction to three Potato virus Y strains (PVYO, PVYN and PVYNTN) in potato cultivars carrying Rychc was examined. When potato plants carrying Rychc were cultivated at 22 °C, a few small necrotic spots developed on inoculated leaves by 5 days after mechanical inoculation (dpi), and systemic infection of a few symptomless plants was confirmed at 28 dpi by IC‐RT‐PCR. At 28 °C, distinct necrotic spots developed on inoculated leaves by 5 dpi, and systemic symptoms occasionally appeared at 28 dpi. Thus, high temperature weakens Rychc‐conferred resistance. However, the incidence of systemic infection and the titre of virus in resistant cultivars at 28 °C were lower than in a susceptible cultivar. In graft inoculation under high summer temperatures, some plants developed necrosis on the leaves and stem, but PVY was barely detected by RT‐PCR in leaves on potato carrying Rychc. When seedlings from progeny tubers of plants that were inoculated with PVY and grown in a greenhouse at >30 °C in the daytime were examined by ELISA and IC‐RT‐PCR, PVY was not detected in cultivars carrying Rychc. These results show that Rychc confers an extreme resistance to PVY strains occurring in Japan. 相似文献
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Marta I. Francis Alma Peña James H. Graham 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(4):571-578
A detached leaf protocol for rapid screening of germplasm for resistance to citrus canker (Xanthomonas citri subsp. citri, Xcc) and citrus bacterial spot (Xanthomonas alfalfae subsp. citrumelonis, Xac) was developed to evaluate limited quantities of leaf material. Bacterial inocula of Xcc or Xac at 104, 105, or 108 cfu ml−1 were injection-infiltrated into the abaxial surface of disinfested, immature leaves of susceptible and resistant genotypes.
Inoculated detached leaves were placed on the surface of 0.5% water agar plates and incubated at 28°C under a 12 h photoperiod.
Likewise, inocula were infiltrated into attached leaves of greenhouse plants. At high inoculum concentrations of Xcc or Xac (108 cfu ml−1), resistant cultivars of kumquat developed a hypersensitive-like reaction within 3 days post inoculation (dpi). At 105 cfu ml−1, populations 14 dpi were <104 per inoculation site. In canker-susceptible Citrus spp. (‘Duncan’ grapefruit and ‘Rough’ lemon), water-soaked areas occurred by 3 dpi and typical canker lesions developed by
7 to14 dpi. Concentration of Xcc recovered from inoculation sites was approximately 105 cfu ml−1 by 14 dpi. In citrus bacterial spot-susceptible citrus (‘Swingle’ citrumelo and grapefruit), symptoms developed within 7 dpi.
Populations of Xac after inoculation at 105 cfu ml−1 were comparable to Xcc in susceptible hosts 14 dpi (>105). The detached leaf assay is useful for the characterization and differentiation of lesion phenotype for each Xanthomonas pathogen permitting rapid screening of germplasm resistance based on the quantification of number of lesions and bacterial
concentration. 相似文献
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Interactions between Serratia plymuthica A30 and a blackleg‐causing biovar 3 Dickeya sp. were examined. In a potato slice assay, S. plymuthica A30 inhibited tissue maceration caused by Dickeya sp. IPO2222 when co‐inoculated at a density at least 10 times greater than that of the pathogen. In glasshouse experiments, population dynamics of the antagonist and of the pathogen in planta were studied by dilution plating and confocal laser scanning microscopy (CLSM) using fluorescent protein‐tagged strains. Pathogen‐free minitubers were vacuum‐infiltrated with DsRed‐tagged Dickeya sp. IPO2222 and superficially treated during planting with a water suspension containing GFP‐tagged S. plymuthica A30. A30 reduced the blackleg incidence from 55% to 0%. Both the pathogen and the antagonist colonized the seed potato tubers internally within 1 day post‐inoculation (dpi). Between 1 and 7 dpi, the population of A30 in tubers increased from 101 to c. 103 CFU g?1 and subsequently remained stable until the end of the experiment (28 dpi). Populations of A30 in stems and roots increased from c. 102 to c. 104 CFU g?1 between 7 and 28 dpi. Dilution plating and CLSM studies showed that A30 decreased the density of Dickeya sp. populations in plants. Dilution plating combined with microscopy allowed the enumeration of strain A30 and its visualization in the vascular tissues of stem and roots and in the pith of roots, as well as its adherence to and colonization of the root surface. The implications of these finding for the use of S. plymuthica A30 as a biocontrol agent are discussed. 相似文献
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Reducing the build‐up of Plasmodiophora brassicae inoculum by early management of oilseed rape volunteers 下载免费PDF全文
下载免费PDF全文 Clubroot of oilseed rape (OSR), caused by Plasmodiophora brassicae, is a disease of increasing economic importance worldwide. Previous studies indicated that OSR volunteers, Brassica crops and weeds play a critical role in the predisposition of the disease. To determine the effect of timing of foliar application of the herbicide glyphosate or mechanical destruction of OSR volunteers in reduction of clubroot severity and resting spore production, a series of studies was conducted under controlled conditions with a susceptible OSR cultivar and an isolate of P. brassicae. Plants were inoculated by injecting a spore suspension beside the root hairs at growth stage 11–12 (BBCH scale) and were terminated at 7 (early) or 21 (late) days post‐inoculation (dpi). Under controlled conditions, the first symptoms on roots were observed as early as 7 dpi. The early application of glyphosate as well as early mechanical destruction resulted in significant (P ≤ 0.05) reduction in the development of clubroot symptoms, root fresh weight and the number of resting spores?g root. Furthermore, the effect of volunteer management on clubroot severity in the succeeding OSR was studied by inoculating plants with the resting spores obtained from treated clubbed roots. Inoculated OSR exhibited root clubs similar to the initial symptoms after 35 dpi. Plants that were inoculated with spore suspension from early treated roots resulted in significant reductions in clubroot incidence and severity. Conversely, plants inoculated with the spore suspension from the late treated roots displayed levels of clubroot similar to the plants inoculated with the spore solutions of positive controls. 相似文献
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Northern leaf blight is a lethal foliar disease of maize caused by the fungus Exserohilum turcicum. The aim of this study was to elucidate the infection strategy of the fungus in maize leaves using modern microscopy techniques and to understand better the hemibiotrophic lifestyle of E. turcicum. Leaf samples were collected from inoculated B73 maize plants at 1, 4, 9, 11, 14 and 18 days post-inoculation (dpi). Samples were prepared according to standard microscopy procedures and analysed using light microscopy as well as scanning (SEM) and transmission electron microscopy (TEM). Microscopic observations were preceded by macroscopic observations for each time point. The fungus penetrated the leaf epidermal cells at 1 dpi and the disease was characterized by chlorotic leaf flecks. At 4 dpi the chlorotic flecks enlarged to form spots, and at 9 dpi hyphae were seen in the epidermal cells surrounding the infection site. At 11 dpi lesions started to form on the leaves and SEM revealed the presence of hyphae in the vascular bundles. At 14 dpi the xylem was almost completely blocked by hyphal growth. Hyphae spread into the adjacent bundle sheath cells causing cellular damage, characterized by plasmolysis, at 18 dpi and conidiophores formed through the stomata. Morphologically, lesions started to enlarge and coalesce leading to wilting of leaves. This study provides an updated, detailed view of the infection strategy of E. turcicum in maize and supports previous findings that E. turcicum follows a hemibiotrophic lifestyle. 相似文献
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Assessment of inoculation methods for screening black alder resistance to Phytophthora ×alni 下载免费PDF全文
下载免费PDF全文 Identification of resistance to Phytophthora ×alni could provide the basis for a management strategy against alder decline in riparian ecosystems in Europe. This study aimed to test methods to evaluate the resistance of riparian alders to the disease, and to screen alder genotypes for resistance. Phytophthora ×alni isolates were compared for their aggressiveness (lesion length on stem) and sporulation capacity (sporangia). While no difference in lesion lengths was found between isolates, sporangia production was dependent on isolate, highlighting the need for careful selection of isolates used for zoospore inoculation methods. Inoculation tests carried out at different periods of the year revealed a seasonal change in susceptibility to the disease, with the period from June to September being the most efficient for inoculation tests. Stem‐wounded inoculations, carried out on excised shoots, were unreliable for evaluating the level of resistance of alder genotypes to P. ×alni infection, with divergent results between two successive years or between two inoculation periods during the same year. In contrast, a method that mimics the natural conditions of infection, based on flooding of rooted cuttings in artificially infected river water, was found promising. Another method, based on the inoculation of foliated terminal shoots with zoospore suspensions, was found to be repeatable and could be used for high‐throughput analyses. Altogether, the results show a continuous resistance response from highly susceptible to moderately resistant genotypes. This suggests that breeding might be a useful strategy to manage alder decline caused by P. ×alni. 相似文献
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S. Zarei S. M. Taghavi H. Hamzehzarghani E. Osdaghi J.R. Lamichhane 《Plant pathology》2018,67(3):660-670
The population dynamics of Xanthomonas arboricola pv. pruni (Xap) and X. citri subsp. citri (Xcc) was assessed on over three dozen plant species/genotypes under field and greenhouse conditions. Both Xap and Xcc multiplied on red nightshade, black nightshade, bindweed, Chenopodium, common bean and wheat up to 20 days post‐inoculation (dpi) under greenhouse conditions. A high bacterial growth rate was observed on all (alfalfa, bindweed, Chenopodium, field mustard, millet and prickly lettuce) but one (liquorice) plant species tested under field conditions. Xap successfully proliferated on both lemon and sweet lemon up to 140 dpi, attaining a population density even higher than that of Xcc. The latter showed an increased growth rate on GxN, GF677, Ghisella 6 and Mariana 2624 rootstocks up to 140 dpi. While Xap and Xcc did not grow on pomegranate and common fig, they had a steady population growth on apple and pear plants up to 140 dpi, although the final population sizes were smaller than those observed on lemon and sweet lemon plants. The results suggest that a large number of non‐host plant species could support epiphytic populations of Xap or Xcc, which may have implications for plant disease epidemiology. 相似文献
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C. L. C. Lelivelt J. Hoogendoorn 《European journal of plant pathology / European Foundation for Plant Pathology》1993,99(1):13-22
The development ofHeterodera schachtii Schm. (beet cyst nematode, BCN) juveniles in roots of resistant and susceptible genotypes belonging to cruciferous crop species and hybrids was studied from 4 to 28 days after inoculation. No difference in root penetration by larvae was observed between resistant and susceptible plants.The development of nematodes in roots from resistant plants ofRaphanus sativus L., resistant xBrassicoraphanus Sageret and a resistant hybrid xBrassicoraphanus x Brassica napus L. was similar. BCN resistance in these three sources of plant material appeared to be related to an increased male:female nematode ratio as compared to the ratio found in susceptibleR. sativus plants.Also in resistant plants ofSinapis alba L. and a resistant intergeneric hybridS. alba x B. napus the increase in male:female nematode ratio, as compared to the ratio found for susceptibleS. alba cultivars and a susceptible intergeneric hybridS. alba x B. napus, seemed to be related with the observed resistance. In roots of the resistantS. alba and of a resistant hybridS. alba x B. napus, however, BCN resistance might also be due to a slower development of larvae and increased necrosis of root cells at the site of larval penetration. 相似文献