首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 875 毫秒
1.
  相似文献   

2.
Surveys of Impatiens and Verbena species in local nurseries in Fredericton, Canada and Verbena species in New Delhi, India showed widespread infection of Citrus exocortis viroid (CEVd) in vegetatively-propagated and seed-grown plants. To determine viroid seed transmission, samples of eight varieties of Impatiens and 11 varieties of Verbena were obtained from four commercial sources. All 19 samples collected contained viroid infection irrespective of variety. The presence of viroid in non-germinated seed was 21%, while the transmission rate in seedlings was 66% in Impatiens walleriana in 2006. Following 2 years of seed storage, the respective figures were 6% and 26%. Similarly, in Verbena x hybrida the presence of viroid in seed was 13% in 2006 with a seed-transmission rate in seedlings of 28%, while the respective figures after 2 years of storage were 5% and 45%.  相似文献   

3.
The patterns and progress of disease caused by multiple infections of Cucumber mosaic virus (CMV), Pepper mild mottle virus (PMMoV) and Pepper mottle virus (PepMoV) and their effects on growth of pepper plants (Capsicum annuum L.) were investigated in this study. Each virus induced distinct symptoms, but more severe symptoms, including reduced growth rates, were observed when pepper plants were simultaneously infected by more than one virus. When CMV was included in multiple viral inoculations, co-inoculations and sequential inoculations, PepMoV and PMMoV symptoms were observed but the symptoms characteristic of CMV were not masked, even though CMV titre did not increase greatly. In multiple viral infections, PepMoV titre and CMV did not increase significantly, but PMMoV titre gradually increased in most cases. Growth rates of pepper plants were greatly reduced during the 30 to 40-day post-inoculation period under both single-infection and multiple-infection conditions, but multiple viral infections of CMV pre-inoculated peppers were affected to a greater extent. A significant reduction in fruit size and fruit number was observed in single and multiple viral inoculations, and fruit malformation rates were high in CMV single-infection and multiple viral infections with CMV.  相似文献   

4.
Wasabi (Wasabia japonica) is grown for its highly-valued rhizome which is used as a condiment in Japanese food. Symptoms of vascular blackening in the rhizome were first observed in 2005 in plants grown in British Columbia, Canada. Microscopic observations and microbial isolation from infected tissues revealed that most of the xylem tracheid cells were blackened and bacteria were consistently associated with symptomatic plants. The bacterium most frequently recovered was identified as Pectobacterium carotovorum subsp. carotovorum (Pcc) using BioLog™ and sequencing of a specific ~510 bp IGS region. Pathogen-free plants obtained using meristem-tip micropropagation were inoculated with a wasabi isolate of Pcc. Vascular blackening symptoms developed in the rhizome after 8 weeks when the rhizome was first wounded by stabbing or cutting, or if the roots were pre-inoculated with Pythium species isolated from rhizome epidermal tissues, followed by inoculation with Pcc at 1 × 108 cells ml−1. Xylem tracheid cells were blackened and Pcc was reisolated from all diseased tissues. The highest frequency of rhizome vascular blackening occurred at 22°C and 27°C and these tissues occasionally succumbed to soft rot at higher temperatures, but not when inoculated tissues were incubated at 10°C. The rooting medium used by growers for vegetative propagation of wasabi was shown to contain Pcc but the pathogen was not recovered from the irrigation water. Entry of Pcc through wounds on wasabi rhizomes and the host tissue response result in symptoms of vascular blackening.  相似文献   

5.
The predatory insect Anthocoris minki Dohrn (Heteroptera: Anthocoridae) is an indigenous Anthocoris species for the biological control of pests in pistachio orchards. The pistachio psylla Agonoscena pistaciae Burckhardt and Lauterer (Homoptera: Psyllidae) is an important insect pest in pistachio trees in Turkey. Similarly, Brachycaudus (Thuleaphis) amygdalinus (Schouteden) (Hemiptera: Aphididae) is a pest of almond trees that is considered as alternative prey for A. minki when pistachio psylla are not available in early spring on pistachio trees. The development time, survival percentage of immature stages, longevity, fecundity, prey consumption, and life table parameters of A. minki fed on A. pistaciae and B. amygdalinus nymphs were determined at 25 ± 1°C, 70 ± 5% r.h., and a 16 h:8 h (L:D) photoperiod under laboratory conditions. The nymphal survival rate was significantly higher when nymphs were fed on A. pistaciae (an average of 96.7%) than on B. amygdalinus (an average of 71.4%). The development time of A. minki was significantly shorter when nymphs were fed on B. amygdalinus (10.3 days) as opposed to A. pistaciae (11.0 days). No significant differences among prey species were found for longevity and fecundity. The total female longevity and fecundity of A. minki was 38.0 days and 247.2 eggs, respectively, when nymphs were fed on A. pistaciae; and 35.4 days and 233.0 eggs, respectively, when nymphs were fed on B. amygdalinus. On average, 104.4 A. pistaciae and 77.7 B. amygdalinus nymphs were consumed during the nymphal development time for A. minki. Adults of A. minki consumed significantly more psyllids than aphids throughout their life span. The greater difference did not significantly inpact the longevity and fecundity of A. minki. Females of A. minki consumed an average of 631.0 A. pistaciae and an average of 273.3 B. amygdalinus nymphs, while female predators consumed significantly more prey than males. The intrinsic rate of increase (r m ) of A. minki fed on A. pistaciae (0.174) was significantly greater than those fed on B. amygdalinus (0.148). The successful development and reproduction of both A. pistaciae and B. amygdalinus indicates that they are suitable prey for A. minki.  相似文献   

6.
A viral disease was found in Nagano Prefecture, Japan, on statice (Limonium sinuatum) with chlorotic leaf spot, necrotic stunt, and dwarfing. Spherical virus particles 30 nm in diameter were isolated from infected plants and statice seedlings and caused identical symptoms 4 weeks after mechanical inoculation. Nucleotide and deduced amino acid sequences of the coat protein showed 98% and 98.7% identities with those of Grapevine Algerian latent virus (GALV) nipplefruit strain. This is the first report in Japan of a viral disease on statice caused by GALV. The nucleotide sequence data reported here are available in the DDBJ/EMBL/GenBank databases under accession AB461854.  相似文献   

7.
Pepper (Capsicum annuum) is an important crop worldwide. In Israel, approximately 2,500 ha are grown all year round for the local and export markets. Herein, we report the identification of a viral pathogen causing a new devastating disease in pepper crops. The disease syndrome includes shortening of stem internodes, interveinal yellowing, and upward rolling of the leaf blade, accompanied by fruit discoloration and size reduction. Virus purification from infected plants yielded isometric particles, 25 nm in diameter. The causal agent of the disease was tentatively named Pepper yellow leaf curl virus (PYLCV). The virus cross-reacted in DAS ELISA with antisera against Cucurbit aphid-borne yellows virus and Potato leafroll virus, members of the Polerovirus genus. The partial nucleotide sequence obtained from the cloned viral coat protein and movement protein genes indicated 92% identity at the amino acid level with Tobacco vein distortion virus (TVDV), another member of the Polerovirus genus. However, the host range of PYLCV is significantly different from the host range described for TVDV. Based on our findings, the taxonomic status of PYLCV is discussed.  相似文献   

8.
Sweet pepper (Capsicum annuum) is a popular crop worldwide and an asymptomatic host of the begomovirus (Geminiviridae) Tomato yellow leaf curl virus (TYLCV). A previous study showed that TYLCV could be transmitted by the seeds of tomato plants, but this phenomenon has not been confirmed in other plants. In 2015, four different cultivars of sweet pepper (‘Super Yellow,’ ‘Super Red,’ ‘Sunnyez’ and ‘Cupra’) known to be susceptible to TYLCV were agro-inoculated with a TYLCV infectious clone. Three months after inoculation, the leaves of the ‘Super Yellow’ cultivar showed 80% (8/10) susceptibility and the other three sweet pepper cultivars showed 30 to 50% susceptibilities. All of the ‘Super Yellow’ seed bunches (five seeds per bunch) from plants whose leaves were confirmed to be TYLCV-infected were also TYLCV-infected (8/8). The seeds of other cultivars showed 20 to 40% susceptibilities. Virus transmission rates were also verified with 10 bunches of seedlings for each cultivar (five seedlings per pool). Eight bunches of ‘Super Yellow’ seedlings (8/10) were confirmed to be TYLCV-infected and one to three bunches of each of the other cultivar seedlings were also infected. Viral replication in TYLCV-infected seeds and seedlings was confirmed via strand-specific amplification using virion-sense- and complementary-sense-specific primer sets. This is the first report of TYLCV seed transmission in sweet pepper plants and among non-tomato plants. Because sweet pepper is an asymptomatic host of TYLCV, seeds infected with TYLCV could act as a silent invader of tomatoes and other crops.  相似文献   

9.
We developed a method to detect Acidovorax avenae subsp. citrulli from cucurbit seeds that is more sensitive than conventional growing-out methods. Seeds were cultivated in test tubes for 2 weeks, and the bacteria grew semi-selectively on the seeds and seedlings. The plants were then vigorously shaken in water to suspend bacterial cells, and the suspension was spread on a selective medium for identifying the bacterium by colony appearance. The method is suitable for research purposes to evaluate the percentage of seeds infested with the bacteria, but not to detect bacterial contamination in commercial lots with thousands of seeds.  相似文献   

10.
The efficacy of a seed treatment of oilseed rape (OSR) (Brassica napus) with the rhizobacteria Serratia plymuthica (strain HRO-C48) and Pseudomonas chlororaphis (strain MA 342) applied alone or in combination against the blackleg disease caused by Leptosphaeria maculans was tested with different cultivars. Seeds were soaked in bacterial suspensions (bio-priming) to obtain log10 6–7 CFU seed−1. Cotyledons were inoculated with a 10 ul droplet of L. maculans spore suspension of log10 7 spores ml−1 and the disease index (size of lesions) was evaluated 14 days later. A mean disease reduction of 71.6% was recorded for S. plymuthica and of 54% for P. chlororaphis. The combined treatment was not superior to the treatment with S. plymuthica alone. The reduction of the disease caused by S. plymuthica was independent of the cultivar’s susceptibility, whereas the control effect recorded with P. chlororaphis increased with decreasing cultivar resistance to blackleg disease. The bacterial colonization of OSR was restricted to the roots and hypocotyl. No significant difference in bacterial colonization of the rhizosphere was observed between different cultivars, nor between single or combined bacterial seed treatments.  相似文献   

11.
The pathogenicity and reproductive fitness of Pratylenchus coffeae and Radopholus arabocoffeae from Vietnam on coffee (Coffea arabica) seedlings cv. Catimor were evaluated in greenhouse experiments. The effect of initial population densities (Pi = 0, 1, 2, 4, 8, 16, 32, 64, 128, and 256 nematodes per cm3 soil) was studied for both species at different days after inoculation (dai). The data were adjusted to the Seinhorst damage model Y = m + (1-m).zPi-T. Tolerance limit (T) for P. coffeae was zero for the height and the diameter of the coffee plants. For the diameter, the T-value for R. arabocoffeae was 25.6 for 30 and 60 dai and 12.8 for 90 and 120 dai. After 4 months T was zero. The low tolerance limits indicate that Arabica coffee is highly intolerant to both nematode species. At the end of the experiment (180 dai), all plants were infected and most were dead when inoculated with R. arabocoffeae at initial densities of 32, 64, 128 and 256 nematodes/cm3 soil. For P. coffeae plant death was already observed at the lowest inoculation densities. Growth of coffee was reduced at all inoculation levels for both species. Pratylenchus coffeae and R. arabocoffeae caused intense darkening of the roots, leaf chlorosis and a strong reduction of root and shoot growth. It was observed that P. coffeae mainly destroyed lateral roots rather than tap roots, whereas R. arabocoffeae reduced tap root length rather than the lateral roots. At the lowest inoculum densities, the reproduction factor of P. coffeae was 2.38 and 2.01 for R. arabocoffeae, indicating that arabica coffee is a host for both species. Plant growth as expressed by shoot height and shoot and root weight measured 60 dai was negatively correlated with nematode (both species) density as expressed by the geometric mean of nematode numbers at 30 and 60 dai.  相似文献   

12.
Results of a greenhouse Armillaria ostoyae inoculation experiment, designed for screening resistant Pinus pinaster genotypes and for exploring the role of different phenotypic traits in seedling susceptibility, are reported. The experiment included 39 open-pollinated pine families that comprised a random subset of the breeding population of P. pinaster in Galicia (NW Spain). We employed a non-parametric survival-time analysis to analyze patterns of survival times during 14 months after inoculation with a local A. ostoyae strain. Results indicate (i) a significant correlation between seed weight and tree susceptibility, with seedlings originating from large seeds being more susceptible, (ii) a positive family mean correlation between secondary root weight and size and median life expectancy, and (iii) genetic variation of tree tolerance to A. ostoyae, with some families surviving significantly longer than others. Less susceptible families could be used in breeding programmes or directly in forest plantations to reduce the losses caused by A. ostoyae. Large within-family variation in tolerance to the disease was also observed, suggesting that non additive genetic variance was also important. Although being infected, 32 out of the 1200 inoculated trees survived the fungus infection. These tolerant genotypes comprise an attractive collection to further investigate genetic, phenotypic and environmental factors affecting pine susceptibility to Armillaria root rot.  相似文献   

13.
CAP-34, a protein from Clerodendrum aculeatum inducing systemic antiviral resistance was evaluated for control of Papaya ringspot virus (PRSV) infection in Carica papaya. In control plants (treated with CAP-34 extraction buffer) systemic mosaic became visible around 20 days that intensified up to 30 days in 56% plants. During this period, CAP-34-treated papaya did not show any symptoms. Between 30 and 60 days, 95% control plants exhibited symptoms ranging from mosaic to filiformy. In the treated set during the same period, symptoms appeared in only 10% plants, but were restricted to mild mosaic. Presence of PRSV was determined in induced-resistant papaya at the respective observation times by bioassay, plate ELISA, immunoblot and RT-PCR. Back-inoculation with sap from inoculated resistant plants onto Chenopodium quinoa did not show presence of virus. The difference between control and treated sets was also evident in plate-ELISA and immunoblot using antiserum raised against PRSV. PRSV RNA was not detectable in treated plants that did not show symptoms by RT-PCR. Control plants at the same time showed a high intensity band similar to the positive control. We therefore suggest that the absence/delayed appearance of symptoms in treated plants could be due to suppressed virus replication.  相似文献   

14.
In a field experiment between 2004 and 2006, 14 winter wheat varieties were inoculated with either a mixture of three isolates of F. poae or a mixture of three isolates of F. avenaceum. In a subsequent climate chamber experiment, the wheat variety Apogee was inoculated with individual single conidium isolates derived from the original poly conidium isolates used in the field. Disease symptoms on wheat heads were visually assessed, and the yield as well as the fungal incidence on harvested grains (field only) was determined. Furthermore, grains were analysed using LC-MS/MS to determine the content of Fusarium mycotoxins. In samples from field and climate chamber experiments, 60 to 4,860 μg kg−1 nivalenol and 2,400 to 17,000 μg kg−1 moniliformin were detected in grains infected with F. poae and F. avenaceum, respectively. Overall, isolate mixtures and individual isolates of F. avenaceum proved to be more pathogenic than those of F. poae, leading to a higher disease level, yield reductions up to 25%, and greater toxin contamination. For F. poae, all variables except for yield were strongly influenced by variety (field) and by isolate (climate chamber). For F. avenaceum, variety had a strong effect on all variables, but isolate effects on visual disease were not reflected in toxin production. Correlations between visual symptoms, fungal incidence, and toxin accumulation in grains are discussed.  相似文献   

15.
Two novel aspects of Tomato chlorotic dwarf viroid (TCDVd) are reported, namely that TCDVd was detected in symptomless plants of Vinca minor, a trailing ground cover surviving at subzero temperatures (−12°C); and that TCDVd was seed-borne in tomato and detected in high percentages in tomato seeds and seedlings. Soaking seeds in a low concentration of sodium hypochlorite did not eliminate the viroid. The sequence analysis showed that the TCDVd isolate consists of 360 nucleotides and has sequence identity between 96% to 99% with isolates of TCDVd from other hosts.  相似文献   

16.
The volatile antimicrobial substance allicin (diallylthiosulphinate) is produced in garlic when the tissues are damaged and the substrate allicin (S-allyl-l-cysteine sulphoxide) mixes with the enzyme alliin-lyase (E.C.4.4.1.4). Allicin undergoes thiol-disulphide exchange reactions with free thiol groups in proteins and it is thought that this is the basis of its antimicrobial action. At 50 μg ml-1, allicin in garlic juice inhibited the germination of sporangia and cysts and subsequent germ tube growth by Phytophthora infestans both in vitro and in vivo on the leaf surface. Disease severity in P. infestans-infected tomato seedlings was also reduced by spraying leaves with garlic juice containing allicin over the range tested (55–110 μg ml−1) with an effectiveness ranging from approximately 45–100%. Similarly, in growth room experiments at concentrations from 50–1,000 μg ml−1, allicin in garlic juice reduced the severity of cucumber downy mildew caused by Pseudoperonospora cubensis by approximately 50–100%. These results suggest a potential for developing preparations from garlic for use in specialised aspects of organic farming, e.g. for reducing pathogen inoculum potential and perhaps for use under glass in horticulture.  相似文献   

17.
Anthracnose of tomato caused by Colletotrichum coccodes is a devastating disease of ripe fruits. This pathogen may also infect tomato roots, stems and leaves. In the present study, C. coccodes is shown to be capable of contaminating seeds collected from artificially inoculated tomato fruits. Seedlings germinating from these infected seeds exhibited disease symptoms and therefore may transmit the pathogen to the next crop. The proportion of infected seeds ranged between 20% and 63% in all C. coccodes isolates tested and correlated with the aggressiveness of the isolates to tomato fruits. Fungicidal treatment of the collected seeds reduced, but did not eliminate, seed infection. A transgenic C. coccodes isolate expressing green fluorescent protein was used to visualize the pathogen. Mycelium was observed both on surfaces of the seed coat and within 1% of the embryos.  相似文献   

18.
Root-knot nematodes (RKN) are obligate parasite species of the genus Meloidogyne that cause great losses in Arabica coffee (Coffea arabica L.) plantations. Identification of resistant genotypes would facilitate the improvement of coffee varieties aiming at an environmental friendly and costless nematode control. In this work, the C. arabica genotype ‘UFV 408-28’ was found to be resistant to the most destructive RKN species M. incognita. Pathogenicity assays indicated that the highly aggressive populations of M. incognita races 1, 2 and 3 were not able to successfully reproduce on ‘UFV 408-28’ roots and displayed a low gall index (GI = 2). An average reduction of 87% reduction of the M. incognita population was observed on ‘UFV 408-28’ when compared to the susceptible cultivar ‘IAC 15’. By contrast, ‘UFV 408-28’ was susceptible to the related species M. exigua and M. paranaensis (GI = 5 and 4, respectively). Histological observations performed on sections of UFV408-28 roots infected with M. incognita race 1 showed that nematode infection could be blocked right after penetration or during migration and establishment stages, at 6 days, 7 days and 8 days after infection (DAI). Fluorescence and bright field microscopy observations showed that root cells surrounding the nematodes exhibited HR-like features such as accumulation of phenolic compounds and a necrotic cell aspect. In the susceptible ‘IAC 15’ roots, 6 DAI, feeding sites contained giant cells with a dense cytoplasm. Necrotic cells were never observed throughout the entire infection cycle. The HR-like phenotype observed in the ‘UFV 408-28’—M. incognita interaction suggests that the coffee resistance may be mediated by a R-gene based immunity system and may therefore provide new insights for understanding the molecular basis of RKN resistance in perennial crops.  相似文献   

19.
A new disorder exhibiting flower crinkle on Phalaenopsis orchids bearing white flowers has been observed in Taiwan, China and Japan for several years. This disorder decreased the flower longevity and was considered as a physiological syndrome. The objective of this study was to identify and characterize the real causal agent of this new Phalaenopsis disorder. Five plants of Phalaenopsis hybrids “V3” (Phal. Yukimai × Phal. Taisuco Kochdian) with flower crinkle symptoms were collected and tested by enzyme-linked immunosorbent assay with antisera against 18 viruses. The extract of leaves and flowers from one diseased plant (96-Ph-16) reacted positively only to antiserum against Odontoglossum ringspot virus (ORSV), while those from the other four plants (96-Ph-7, 96-Ph-17, 96-Ph-18 and 96-Ph-19) reacted positively to the antisera against ORSV and Cymbidium mosaic virus (CymMV). Five ORSV isolates, one each from flowers of those five diseased Phalaenopsis orchids, were established in Chenopodium quinoa. A CymMV culture was isolated from the flowers of one of the ORSV/CymMV mix-infected Phalaenopsis orchids (96-Ph-19). To determine the causal agent of the flower crinkle disease, healthy Phalaenopsis seedlings were singly or doubly inoculated with the isolated ORSV and/or CymMV. Results of back inoculation indicated that ORSV is the sole causal agent of the crinkle symptom on petals of Phalaenopsis orchid. The CP gene of the ORSV isolates from this study shared 97.3–100% nucleotide identity and 96.2–100% amino acid identity with those of 41 ORSV isolates available in GenBank. This is the first report demonstrating ORSV as the sole virus causing flower crinkle disease on Phalaenopsis orchids.  相似文献   

20.
Yeast-like fungi were isolated from lesions on azuki bean (cv. Shin-Kyotodainagon) seeds that had been sucked by bean bugs in Kyoto Prefecture, Japan. On the basis of morphological and physiological characteristics and sequence data of the internal transcribed spacer (ITS) regions including the 5.8S rDNA, these yeasts were identified as Eremothecium coryli and E. ashbyi. Pathogenicity of those yeasts was confirmed by a reinoculation test. To our knowledge, this is the first report of the occurrence of yeast spot in azuki bean in Japan. The nucleotide sequence data reported are available in the GeneBank/EMBL/DDBJ database as accessions AB478291–AB478309 for E. coryli AZC1–19 and AB478310–AB478317 for E. ashbyi AZA1–8.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号