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1.
The etiology of a new soft rot disease of tulips, causing leaf spots, leaf blight, neck and bulb rot in Konya, Turkey, was investigated. This disease occurred in tulip fields grown for seed bulbs of various varieties in 2002. Bacteria were isolated from the lesions on leaf, bud neck and bulbs and the causal bacterium was identified asPectobacterium carotovorum on the basis of biochemical and physiological tests. Cells were Gram-negative, rod-shaped, fermentative, potato-rot positive. Colonies were capable of growth at 37°C. On nutrient agar the colonies were creamy-white. The isolates were non-fluorescent on King’s B medium, positive for acetoin production, gelatin liquefaction, acid-production-from-lactose, and catalase; and negative for gas from glucose, reducing substances from sucrose, and phosphatase activity. Additionally, tests for egg yolk (lecithin), sensitivity to erythromycin, and pigmentation on yeast dextrose carbonate agar were negative; growth on 5% sodium chloride was positive. All the bacterial isolates obtained from the leaf, bud neck and bulbs produced the original symptoms following inoculation to the susceptible tulip variety ‘Gander’. The rate of damage caused by this bacterium was evaluated on several tulip varieties under field and storage conditions. Gander was the most susceptible variety in the field whereas ‘Salmon Parrot’ exhibited the highest rate of bulb rot in storage. Disease severity was lower in 2003 than 2002. http://www.phytoparasitica.org posting May 14, 2006.  相似文献   

2.
Greenhouse and field evaluations of onion for resistance to Fusarium basal rot caused byFusarium oxysporum f.sp.cepae were conducted on cultivars ‘Akgün 12’ and ‘Rossa Savonese’ previously described as resistant at the seedling stage. In the greenhouse experiments inoculations were carried out on seeds or soil; in the field experiments evaluation was performed on onion sets from plants grown in naturally infested soils. Akgün 12 and to a lesser extent Rossa Savonese were resistant to the disease at the bulb stage in all experiments. Results were also consistent with those obtained from a previous screening at the seedling stage. Onion sets were also extracted and fractionated by thin layer chromatography to determine their content of antifungal compounds. Extracts were characterized by the expression of distinct antifungal components, which may be involved in resistance to the pathogen. http://www.phytoparasitica.org posting July 14, 2004.  相似文献   

3.
Two distinct races ofDitylenchus dipsaci in Israel were identified: one, which infects and damages onion and garlic, reproduces on pea, but does not infect phalaris grass; and a second, which infects and damages phalaris—and, probably, also ‘Saia’ oats—but fails to infect onion and garlic. A new ‘garlic’ race of the nematode does not appear to have been introduced into Israel together with the ‘Lavinia’ garlic cultivar, as previously speculated, but rather the introduced Lavinia clone is highly susceptible to the existing ‘onion and garlic’ race ofD. dipsaci.  相似文献   

4.
The effect of environmental factors on the development of each stage ofPeronospora destructor (Berk.) Caspary on onions is reviewed. For sporulation to take place, a period of light must precede the period of darkness and high humidity in which spores are formed. Spores are discharged when the relative humidity (RH) is increasing or decreasing, and over a wide range of temperatures. Their discharge is triggered by exposure to red-infrared radiation and by vibration of the leaf. Dissemination of spores follows a daily periodic cycle and spores can be blown by wind over long distances. Duration of spore survival depends on temperature, RH and, especially, the absence of strong radiation. The rate of spore germination is highest at 10°C and declines with the rise in temperature. Germ tubes develop in liquid water, and a continuous period of wetness is required for infection to be completed. Systemic infection is common in cooler climates, where necks of onion bulbs are slow to dry. The principal sources of downy mildew infection by wind-borne spores are systemically infected propagation material, onion volunteer plants, and neighboring older crops.  相似文献   

5.
Fusarium proliferatum can occur on a wide range of economically important vegetable plants but its role in disease is not always well established. In 2000 and 2001, from forty-one field samples of wilting onion and garlic plants in Serbia, F. proliferatum as the predominant fungal species was isolated from root and bulbs. Seventy isolates were firstly characterized for their sexual fertility and were shown to be mostly members of Gibberella intermedia (sixty-seven of seventy isolates, the remaining three isolates were unfertile), the sexual stage of F. proliferatum (syn. mating population D of G. fujikuroi complex). A selected set of eleven F. proliferatum isolates from both hosts were also tested for their pathogenicity and toxigenicity. Although onion and garlic plants were susceptible to all isolates, onion plants showed a significantly higher disease severity index. Six of the eleven isolates of F. proliferatum produced fumonisin B1 from 25 to 3000 μg g−1, and beauvericin from 400 to 550 μg g−1; ten isolates produced fusaric acid from 80 to 950 μg g−1 and moniliformin from 50 to 520 μg g−1. Finally, all isolates produced fusaproliferin up to 400 μg g−1. These results confirm F. proliferatum as an important pathogen of garlic and onion in Europe and that there is a potential mycotoxin accumulation risk in contaminated plants of both garlic and onion.  相似文献   

6.
In the present study, the pathogenicity of 36 isolates of Guignardia species isolated from asymptomatic ‘Tahiti’ acid lime fruit peels and leaves, ‘Pêra-Rio’ sweet orange leaves and fruit peel lesions, and a banana leaf were characterized. For pathogenicity testing, discs of citrus leaves colonized by Phyllosticta citricarpa under controlled laboratory conditions were kept in contact with the peels of fruit that were in susceptible states. In addition, pathogenicity was related to morphological characteristics of colonies on oatmeal (OA) and potato dextrose agar (PDA). This allowed the morphological differentiation between G. citricarpa and G. mangiferae. Polymerase chain reactions (PCRs) were also used to identify non-pathogenic isolates based on primers specific to G. citricarpa. A total of 14 pathogenic isolates were detected during pathogenicity tests. Five of these were obtained from leaf and fruit tissues of the ‘Tahiti’, which until this time had been considered resistant to the pathogen. Given that the G. citricarpa obtained from this host was pathogenic, it would be more appropriate to use the term insensitive rather than resistant to categorize G. citricarpa. A non-pathogenic isolate was obtained from lesions characteristic of citrus black spot (CBS), indicating that isolation of Guignardia spp. under these conditions does not necessarily imply isolation of pathogenic strains. This also applied to Guignardia spp. isolates from asymptomatic citrus tissues. Using fluorescent amplified fragment length polymorphism (fAFLP) markers, typically pathogenic isolates were shown to be more closely related to one another than to the non-pathogenic forms, indicating that the non-pathogenic isolates display higher levels of genetic diversity.  相似文献   

7.
Dry mycelium (DM) of killedPenicillium chrysogenum and its water extract (DME) were used to induce resistance in cotton plants againstFusarium oxysporum f.sp.vasinfectum (Fov). Results showed that the efficacy of either DM or DME in controlling the disease depends on both the concentration and the mode of application. DM amended to the soil at 0.25–2% (w/w) provided 32–75% protection againstFov. Soil drench with 2–5% DME (w/v) and pre-sowing seed soakage with 5–10% DME provided 51–77% and 28–35% protection against the wilt disease, respectively, whereas no protection was obtained with foliar sprays of 1–10% DME. DM and its water extract had no direct antifungal activity on growth ofFov in vitro, suggesting that disease control with DM or DME resulted from the induction of natural defense mechanisms in the cotton plants. Soil drench with 5% DME was as effective as 2% DM powder in inducing resistance againstFov, implying that the resistance-inducing substances were mostly water-soluble. Four cotton cultivars with various genetic resistance levels againstFov were tested at the seedling stage: two resistant ‘Pima’ cultivars and two susceptible ‘Acala’ cultivars. The level of protection achieved in the two susceptible cultivars with DME was equal to, or higher than, that of the two resistant cultivars treated with water. Innate and induced peroxidase activity in cotyledons or hypocotyls and roots coincided with the level of genetic resistance and DME-induced resistance, respectively. Based on our results, an integrated control strategy ofFov with both genetic resistance and induced resistance is suggested.  相似文献   

8.
The spider mites Tetranychus urticae Koch and Panonychus ulmi (Koch) (Tetranychidae) cause severe economic losses to vegetable farms and deciduous fruit orchards in Turkey. One of their predators, the ladybird beetle Stethorus gilvifrons (Muls.) (Col., Coccinellidae), aggregates on mite-infested patches of plants. The present study assessed whether there is a role for herbivore-induced plant volatiles (HIPVs) and/or odors emitted directly from these two mite species in the aggregative response of ladybird beetles. The olfactory responses of the predator females to volatiles from T. urticae- and/or P. ulmi-infested sweet pepper (four cultivars, viz. ‘Demre’, ‘Yalova Carliston’, ‘Kandil Dolma’ and ‘Yag Biberi’), kidney bean (cv. ‘Barbunya’) and apple (M9 rootstock) were investigated using a two-choice olfactometer. Our results showed that HIPVs emitted from both T. urticae- and P. ulmi-infested plants significantly attracted S. gilvifrons adults for all plants except the sweet pepper cv. Yag Biberi. In addition, it was found that volatiles from apple plants infested by T. urticae and, especially, P. ulmi are more attractive for S. gilvifrons females than those emitted by other infested plants. The results also suggest that the odors of T. urticae adults and their products might influence the attraction of S. gilvifrons females.  相似文献   

9.
Phoma macdonaldii is one of the most important pathogens of sunflower (Heliantus annuus) in France. In order to determine the inheritance of resistance to the disease, five sunflower genotypes with wide genetic variability for resistance to two ‘collar’ and two ‘root’ Phoma isolates were crossed in a diallel programme. Four separate experiments were undertaken under controlled conditions. In each one, the response of parental genotypes and their F1 hybrids were evaluated with one of the four Phoma isolates. Analysis of variance was performed to determine the effects of genotype on disease severity score when inoculated with ‘collar’ or ‘root’ Phoma isolates and showed significant variability among parents and F1 hybrids for disease severity score. Diallel analysis showed that general combining ability (GCA) and specific combining ability (SCA) effects for resistance to ‘collar’ and ‘root’ Phoma isolates were highly significant for each of the four isolates indicating that both kinds of gene effects were important in controlling the resistance. The GCA/SCA ratios were more than one for three out of four isolates showing that additive genetic effects were more important than non-additive effects for resistance to three of the studied Phoma isolates. Hence, conventional breeding methods could be recommended to achieve genetic improvement to such ‘collar’ and ‘root’ Phoma isolates.  相似文献   

10.
The huanglongbing (HLB) disease of citrus trees, caused by Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, was first reported in Brazil in March, 2004. The presence of the disease has caused serious concerns among growers. Pruning experiments were conducted to determine if removal of symptomatic branches or the entire canopy (decapitation) would eliminate infected tissues and save HLB-affected trees. Pruning was done in five blocks on a total of 592 3- to 16 year-old ‘Valência’, ‘Hamlin’ or ‘Pêra’ sweet orange trees showing no symptoms or with two levels of symptom severity. Ten decapitated trees per block were caged and all trees were treated with insecticides to control the psyllid vector, Diaphorina citri. Mottled leaves reappeared on most symptomatic (69.2%) as well on some asymptomatic (7.6%) pruned trees, regardless of age, variety, and pruning procedure. Presence of the pathogen (Ca. Liberibacter americanus) in all symptomatic trees was confirmed by PCR. In general, the greater the symptom severity before pruning the lower the percentage of trees that remained asymptomatic after pruning.  相似文献   

11.
In a study of date fruit damage caused byOligonychus spp., we investigated whether the cultivar affects phenology, and on what hosts the mites over-winter. Samples were taken from ‘Deglet Noor’, ‘Barhi’ and ‘Medjool’ trees from mid-April through mid-September during the years 1999–2002. In the ground-cover mites were monitored by collecting Bermuda grass (Cynodon dactylon) under each sampling tree. Over 99% of the mites collected on Deglet Noor and Barhi fruit were identified asO. afrasiaticus. Mean population levels ofO. afrasiaticus reached ten mites or more (initiation of infestation) on Medjool in the second half of May, whereas on Deglet Noor this did not occur before the first week of July. On Barhi the initiation of infestation varied between plots and years, ranging from the second half of May to the beginning of July, but always occurred earlier than Deglet Noor. Mite populations on the pinnae remained low from June through October, not exceeding seven mites per pinna, whereas on fruit strands they reached peak populations of approximately 4000 mites per strand. The sex ratio (proportion of females) ofO. afrasiaticus on fruit of all three cultivars was highly female-biased, usually above 0.85. During winter,O. afrasiaticus was found on Bermuda grass in the orchard ground-cover as well as on fronds of all three cultivars. http://www.phytoparasitica.org posting Jan. 30, 2003.  相似文献   

12.
Differentin vivo resistance/susceptibility levels of 14 carnation cultivars toFusarium oxysporum f.sp.dianthi race 2, the causal agent of Fusarium wilt disease of carnation, were also expressed in anin vitro system and assayed as the degree of fungal colonization of callus cultures at 20° C. Temperature influenced thein vitro expression of carnation resistance. An incubation temperature of 27° C increased the colonization of calli derived from both the susceptible (‘Corrida’ and ‘Ambra’) and the resistant (‘Pulcino’ and ‘Pallas’) cultivars. At 15°C, the colonization of calli derived from Pulcino and Pallas diminished significantly more than for Ambra and Corrida. Inhibition of fungal growth on resistant calli was correlated to retardation in hyphal development. Both scanning electron microscopy and light microscopy observations showed that hyphae did not penetrate into carnation cells.  相似文献   

13.
The effect of microclimate variables on development ofClonostachys rosea and biocontrol ofBotrytis cinerea was investigated on rose leaves and crop residues. C.rosea established and sporulated abundantly on inoculated leaflets incubated for 7–35 days at 10°, 20° and 30°C and then placed on paraquat—chloramphenical agar (PCA) for 15 days at 20°C. On leaflets kept at 10°C, the sporulation after incubation on PCA increased from 60% to 93% on samples taken 7 to 21 days after inoculation, but decreased to 45% on material sampled after 35 days. A similar pattern was observed on leaves incubated at either 20° or 30°C. The sporulation ofC. rosea on leaf disks on PCA was not affected when the onset of high humidity occurred 0, 4, 8, 12 or 16 h after inoculation. However, sporulation was reduced to 54–58% on leaflets kept for 20–24 h under dry conditions after inoculation and before being placed on PCA. The fungus sporulated on 68–74% of the surface of leaf disks kept for up to 24 h at high humidity after inoculation, but decreased to 40–51% if the high humidity period before transferral to PCA was prolonged to 36–48 h. The growth ofC. rosea on leaflets was reduced at low inoculum concentrations (103 and 104 conidia/ml) because of competition with indigenous microorganisms, but at higher concentrations (105 and 106 conidia/ml) the indigenous fungi were inhibited. Regardless of the time of application ofC. rosea in relation toB. cinerea, the pathogen’s sporulation was reduced by more than 99%. The antagonist was able to parasitize hyphae and conidiophores ofB. cinerea in the leaf residues. AsC. rosea exhibited flexibility in association with rose leaves under a wide range of microclimatic conditions, and in reducingB. cinerea sporulation on rose leaves and residues, it can be expected to suppress the pathogen effectively in rose production systems.  相似文献   

14.
Scytalidium wilt, caused by Scytalidium lignicola, has become prevalent on ‚Star Ruby’ grapefruit in orchards in the Jordan Valley, an area with a warm climate in the north of Israel. It occurs in the summer in certain years, soon after extreme hot and dry weather conditions have prevailed for several consecutive days, but not in other years with regular summer temperatures. The effect of temperature conditions before and after inoculation with S. lignicola on disease development on ‚Star Ruby’ was studied in greenhouse chambers with three day/night temperature regimes: ‚Very Hot’ (47 °C/34 °C); ‚Hot’ (36 °C/28 °C); and ‚Moderate’ (30 °C/20 °C). Among the pre-inoculation regimes, ‚Very Hot’ was most conducive to infection, whereas the ‚Hot’ regime sustained canker development only when followed by a ‚Very Hot’ post-inoculation regime. The moderate pre-inoculation conditions appeared to have a negligible, if any, effect on canker development, even with a ‚Very Hot’ post-inoculation regime. Wilt developed in infected saplings if they were exposed to the ‚Very Hot’ temperature regime either pre- or post-inoculation, but did not develop under the cooler conditions. Saplings of ‚Star Ruby’ exposed to a ‚Very Hot’ regime developed heat-stress symptoms, similar to those observed on ‚Star Ruby’ in the Jordan Valley. Under a constant ‚Very Hot’ regime, both canker expansion and subsequent foliar wilt developed on ‚Flame’, but not on ‚Marsh Seedless’ or ‚Rio Red’ grapefruit. The study confirmed an hypothesis that predisposition induced by extremely hot temperature is a prerequisite for infection of susceptible hosts by S. lignicola.  相似文献   

15.
Forty vineyards from four wine making regions of Spain were sampled at three different growth stages in 2002 and 2003. The aim was to study the fungi associated with grapes and their ability to produce ochratoxin A (OTA) on synthetic media. Among the total mycoflora, 464 (7.7%) and 648 (10.8%) Aspergillus section Nigri (black aspergilli) strains were isolated in 2002 and 2003, respectively, and were classified into three groups: isolates with uniseriate heads, A. niger aggregate and A. carbonarius. The latter presented the highest percentage of OTA-positive strains (82% in 2002 and 76% in 2003) and produced the highest levels of toxin (2.5–25 μg g−1). The sampling year, sampling date, the region and their interactions presented significant differences in the number of black aspergilli isolated. Most black aspergilli were found in 2003 and at harvest. A positive correlation between the number of black aspergilli found in grapes and the temperature in the field was found. Grapes from 2003, the warmest year, and from Costers del Segre, the warmest region, were significantly the most contaminated. No significant correlation between black aspergilli presence and other meteorological factors such as relative humidity or rainfall could be established. Musts from all the vineyards were also analysed in both years, although no OTA was found in either year.  相似文献   

16.
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   

17.
An outbreak of the pine processionary moth (PPM),Thaumetopoea pityocampa Schiff. (Lepidoptera: Thaumetopoeidae), began in spring 1998 and lasted 5 years in aPinus brutia Ten. (Calabrian pine) stand. Tree volume and volume elements increments were examined throughout a PPM outbreak cycle from 1981 to 2003, for an even aged, pure, undisturbed, young Calabrian pine stand. Tree ring chronologies of ‘control’ Calabrian pine, which was not defoliated by PPM during the period of 1998–2003, were used to estimate potential growth characteristics in the ‘host’ Calabrian pine (moderate and high defoliation groups) for current and past outbreaks. Increment cores were collected from 70 host and 78 control dominant or co-dominant trees and annual radial growth indices from 1981–2003 were calculated for each defoliation group in a 41 point sampling. Growth functions were defined as the cumulative sum of radial, height, and volume increment, and graphically compared between host Calabrian pine (3 moderate and one high), four control Calabrian pine and one host Crimean pine (Pinus nigra Arnold) sample trees. At least three severe outbreak periods were identified (from 1981–86; 1992–97; and 1998–2003), much of the study area being severely affected by PPM. Tree ring evidence suggests that large scale (in 1981, 1992, 1998) and partial (in 1988) outbreaks occurred in the study area. Negative inflections of host radial growth curves relative to control height and volume indicated PPM activity. The periodic average diameter growth reductions (in %) in 1981, 1988, 1992 and 1998, respectively, were 0, 13, 5 and 0 for control, 12, 8, 7 and 2 for moderate, and 18, 5, 0 and 7 for high defoliation groups. Outbreaks appear to be associated with dry winter and spring weather prior to the autumn and winter in which feeding occurs. http://www.phytoparasitica.org posting Sept. 28, 2004.  相似文献   

18.
Single-ascospore-derived isolates ofMycosphaerella fijiensis Morelet from false horn ‘Agbagba’ plantain leaves obtained from five different villages in southern Nigeria were stimulated to mate under artificial conditions. Pairs of isolates were incubated under blacklight on potato dextrose agar (PDA) with surface-sterilized plantain leaves or on PDA with autoclaved plantain leaves. Some isolates were observed to be sexually compatible by their ability to produce spherical to bulb-shaped fruiting body structures (FBS) and ascospores on pairing. FBS were observed to measure between 39–65 μm (smallest diameter) and 39–104 μm (largest diameter; mean 55.3×71.1 μm) in diameter, whereas ascospore lengths measured between 13.0 and 14.9 μm. Length of incubation time required for FBS production was dependent on the pair of isolates involved, the average being 40.1 days. With some pairs, ascospores were observed after 35 days of incubation. http://www.phytoparasitica.org posting Dec. 16, 2002.  相似文献   

19.
The development time and parasitization rate ofDiaeretiella rapae (M’Intosh) onBrevicoryne brassicae (L.) feeding on differentBrassica cultivars was studied in the laboratory at 20°C. The shortest development time from egg to adult parasitoid was 11.6 days on cabbage cv. ‘Yalova 1’ and the longest was 12.1 days on turnip cv. ‘Antep’ and rapeseed cv. local variety. Females lived significantly longer than males on the host plants used in the study. Females and males had the shortest longevity on rapeseed at 11.1 and 5.1 days, respectively. The highest percent parasitism ofB. brassicae byD. rapae was found on cabbage (40.20%), and the lowest was recorded on turnip (32.64%). Our results demonstrate that parasitism rate could be influenced by the plant quality, probably due to the nutritional status of the aphids or to toxic compounds ingested through the plant. Cabbage, cauliflower and broccoli were found to be suitable plants for the parasitoid, considering the development time of pre-adults, and the parasitization rate ofD. rapae onB. brassicae. http://www.phytoparasitica.org posting Jan. 23, 2007.  相似文献   

20.
Pratylenchus thornei densities were monitored in field plots of two winter wheat cultivars in a dry farming area of southern Spain. Samples were taken fortnightly during the wheat-growing season and from the following dry fallow. Under bread wheat cv. ‘Yecora’, densities ofP. thornei increased for 5 to 6 months and then were maintained or slightly decreased thereafter, surviving the summer dry fallow in an anhydrobiotic state (78.2% and 85.3% survival in soil and roots, respectively). Under durum wheat cv. ‘Donpedro’, nematode densities decreased over the growing season, although densities within the roots increased during the first 2 months of the wheat-growing period, indicating that nematodes could penetrate the roots of this cultivar but were unable to reproduce. These observations suggest resistance of wheat cv. Donpedro toP. thornei.  相似文献   

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