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 31 毫秒
1.
Field studies were conducted to assess the population and the spatial dynamics of the predatory bugMacrolophus costalis Fieber (Hemiptera: Miridae) and of its prey, the aphidMyzus persicae (Sulzer) (Hemiptera: Aphidoidea), on tobacco. From an untreated tobacco field in Tithorea (central Greece), tobacco leaves were collected from the upper and the lower half of the plants from June until September, in 1999 and 2000. The numbers ofM. costalis andM. persicae individuals per leaf were counted. Most aphids were observed during July and August (early and mid season), with densities dropping markedly in September. In contrast,M. costalis population densities increased late in the season (September). Significantly higher numbers of aphids were found on the upper half of the plants than on the lower half. In contrast, significantly moreM. costalis individuals were observed on the lower half. Iwao’s Regression Analysis was used in order to characterize the spatial pattern of the two species. According to this model, in both sampling seasons, aphids andM. costalis nymphs displayed an aggregated spatial pattern, whileM. costalis adults were found to be randomly distributed among sampling units. Although moreM. costalis individuals were recorded on leaves with relatively high aphid densities, this species did not react numerically to changes in prey density. In addition, a significant number of bugs were found on leaves with low aphid densities or no aphids at all. http://www.phytoparasitica.org posting Dec. 18, 2002.  相似文献   

2.
Cucumber mosaic virus (CMV) was isolated from a mosaic diseased plant of Eucharis grandiflora. The virus caused mosaic symptoms on leaves and slight distortion of flower petals in E. grandiflora by either mechanical or aphid inoculation. The virus was identified as a strain of CMV subgroup I from its biological and serological characteristics.  相似文献   

3.
The feeding behavior of the melon aphidAphis gossypii Glover (Homoptera: Aphididae) was monitored using the electrical penetration graph (EPG) technique on different melon (Cucumis melo L.) genotypes showing resistance to the aphid. The aphid-resistant genotypes used were PI-161375 and PI-414723, sources of theVat andAgr genes, respectively. TGR-1551, a newC. melo accession from Zimbabwe, was also tested. Our goal was to localize the tissues where the resistance factors are expressed and to determine if the resistance mechanisms operating in the three aphid-resistant accessions were the same. Our results indicated that the three selected lines have resistant factors located at the epidermis, mesophyll and vascular tissues. However, the behavior ofA. gossypii on TGR-1551 was different from the two other resistant accessions, as indicated by a longer phloem salivation phase (E1 phase). Many of the E1 phases observed for aphids feeding on TGR-1551 were not followed by phloem ingestion (E2 phase). These results suggest that TGR-1551 has a resistance mechanism that preventsA. gossypii from initiating ingestion from the phloem. Preference tests under free choice conditions also showed that aphids rejected accessions TGR-1551 or PI-414723 faster than PI-161375. Our results support the hypothesis thatAgr andVat are coding for different kinds of resistance strategies. Comparisons of aphid life history parameters also indicated that TGR-1551 is a very promising new source to breed for resistance againstA. gossypii. http://www.phytoparasitica.org posting Jan. 16, 2002.  相似文献   

4.
Crude ethanolic seed extracts ofAnnona muricata, A. squamosa (Annonaceae),Lansium domesticum andSandoricum koetjape (Meliaceae) collected from different locations and years in Maluku, Indonesia, were screened for inhibition of larval growth against the polyphagous lepidopteranSpodoptera litura (Noctuidae). Extracts ofA. squamosa were significantly more active (20-fold) than those ofA. muricata. A. squamosa collected from Namlea yielded the extracts with the greatest inhibitory activity. There were significant differences among locations for bothA. squamosa andA. muricata but not forL. domesticum andS. koetjape. Extracts ofA. squamosa, collected from Namlea, inhibited larval growth in a dose-dependent manner, with a dietary EC50 (effective concentration to inhibit growth by 50% relative to controls) of 191.7 ppm fresh weight. Extracts ofA. squamosa collected from individual trees in Namlea also varied in growth inhibitory effect againstS. litura andTrichoplusia ni larvae. This species is a candidate for development of a botanical insecticide for local use in Indonesia. http://www.phytoparasitica.org posting Dec. 1, 2003.  相似文献   

5.
The aims of this study were to select bacterial isolates from the non-rhizophere of maize soil and to examine their antagonistic activity against Aspergillus section Flavi strains. The first selection was made through ecophysiological responses of bacterial isolates to water activity (aw) and temperature stress. Subsequently, an Index of Dominance test (ID), ecological similarity and inhibition of the lag phase prior to growth, growth rate and aflatoxin B1 accumulation were used as criteria. From the first assay nine bacterial strains were selected. They grew well at 25 and 30 °C, with growth optima between 0.982 and 0.955 aW using 48 h of incubation. There was ecological similarity between the bacterial strains Bacillus subtilis (RCB 3, RCB 6), Pseudomonas solanacearum RCB 5, Amphibacillus xylanus RCB 27 and aflatoxigenic Aspergillus section Flavi strains at 0.982 at 25 °C. The predominant interaction between all selected bacteria and fungi in dual culture was mutual intermingling at 0.982. Mutual inhibition on contact and mutual inhibition at a distance was observed at 0.955 aw, between only four bacteria and some Aspergillus strains. Bacillus subtilis RCB 55 showed antifungal activity against Aspergillus section Flavi strains. Amphibacillus xylanus RCB 27, B.␣subtilis RCB 90 and Sporolactobacillus inulinus RCB 196 increased the lag phase prior to growth and decreased the growth rate of Aspergillus section Flavi strains. Bacillus subtilis strains (RCB 6, RCB 55, RCB 90) and P. solanacearum RCB 110 inhibited aflatoxin accumulation. Bacillus subtilis RCB 90 completely inhibited aflatoxin B1 accumulation at 0.982 aW. These results show that the bacterial strains selected have potential for controlling Aspergillus section Flavi over a wide range of relevant environmental conditions in the stored maize ecosystem.  相似文献   

6.
Pepper mottle virus, genus Potyvirus, was first identified in Japan based on particle morphology, host range, aphid transmission, and molecular classification using the nucleotide sequence of the coat protein gene and 3-untranslated region.  相似文献   

7.
Among the factors affecting the quality and yield of garlic production, blue mold caused by -- Penicillium spp. -- is responsible for economical losses in many countries. Allicin, present in garlic bulbs, has been suggested as having antifungal activity against some Penicillium species. This study was conducted to evaluate the response of garlic accessions against Penicillium hirsutum infection and to compare this response with bulb allicin content. Twelve garlic accessions were inoculated with P. hirsutum, and assayed in greenhouse and growth chamber experiments. Plant growth parameters and the fungal production of conidia were evaluated. Significant differences were found among the accessions. Accessions Castaño and Morado were most resistant whereas AR-I-125 and Fuego were always severely affected by the disease. A low correlation was found (r = 0.17) between allicin content and tolerance, indicating that allicin is not the main factor involved in the resistance against P. hirsutum.  相似文献   

8.
Severe rot of leaves, peduncles and flowers caused by Gibberella zeae (anamorph: Fusarium graminearum) was found on potted plants of hyacinth (Hyacinthus orientalis), a liliaceous ornamental, in greenhouses in Kagawa Prefecture, Japan, in January 2001. This disease was named “Fusarium rot of hyacinth” as a new disease because only the anamorph, F. graminearum, was identified on the diseased host plant. The authors contributed equally to this work. The fungal isolate and its nucleotide sequence data obtained in this study were deposited in the Genebank, National Institute of Agrobiological Sciences and the DDBJ/EMBL/GenBank databases under the accession numbers MAFF239499 and AB366161, respectively.  相似文献   

9.
A new hymenopteran aphid parasitoid species (Praon uroleucon sp. n.) fromUroleucon sp. infestingCarduus acanthoides L. is described from Yugoslavia. It is diagnosed and illustrated with scanning electron microscope photographs and line drawings. The new species is placed in thePraon dorsale species group, and a key to species of that group is provided. http://www.phytoparasitica.org posting Dec. 9, 2002.  相似文献   

10.
Eighteen toxins produced byFusarium species were tested at different concentrations onOrobanche ramosa seeds to evaluate their effectiveness in inhibiting germination. Many of the toxins were active at the highest concentration used. Seven of them,viz. fusarenon X, nivalenol, deoxynivalenol, T-2 toxin, HT-2 toxin, diacetoxyscirpenol and neosolaniol, were highly active at 10μM, causing 100% inhibition of germination. Many of them were still active when assayed at a concentration ten times lower, with T-2, HT-2, nivalenol, neosolaniol and diacetoxyscirpenol still able to cause total inhibition; the last mentioned was very active also at 0.1μM, causing more than 90% inhibition. The results show that the use of toxic secondary metabolites could represent a useful alternative strategy in the management of parasitic weeds, by interfering with the induced germination process, and that fungal culture extracts could be an interesting source of new compounds acting as natural and original herbicides. http://www.phytoparasitica.org posting Sept. 18, 2002.  相似文献   

11.
Ageratum conyzoides L. is an annual herb in the tropics and subtropics whose extracts are known to possess pharmacological and biocidal activity. We report on the bioactivity of a secondary metabolite (a chromene) isolated from the shoots ofA. conyzoides against some plant pathogenic fungi. Organic solvent extracts from the shoots were tested for antifungal activity against the plant pathogenic fungiRhizoctonia solani, Sclerotium rolfsii, Botryodiplodia theobromae, Phomopsis theae andFusarium species growingin vitro on potato dextrose agar medium. The cruden-hexane extract completely inhibited the growth ofR. solani andS. rolfsii. Then-hexane extract was chromatographed over a column of silica gel followed by activity-guided fractionation to give an antifungal principle. Structure elucidation by detailed analysis of1H,13C NMR and mass spectroscopy identified the active compound as precocene II. The growth ofR. solani andS. rolfsii was completely inhibited by precocene II at a concentration of 80–100 ppm. The sclerotia ofR. solani andS. rolfsii were also completely suppressed by 150 ppm of precocene II. Sub-culture of these inhibited fungi onto precocene II-free medium restored growth of the fungus, indicating that precocene II is fungistatic. Crude or refined extracts fromA. conyzoides offer the possibility of biocontrol of plant pathogenic fungi. http://www.phytoparasitica.org posting Feb. 11, 2004.  相似文献   

12.
Population structure of Eleusine isolates of Pyricularia oryzae (Magnaporthe oryzae) was examined using DNA markers. On the basis of rDNA sequences, Eleusine isolates were divided into two groups. One group clustered with Triticum isolates, while the other clustered with Eragrostis isolates. This grouping was supported by DNA fingerprinting with three repetitive elements: MGR586, MGR583, and grasshopper. These results suggest that the population of Eleusine isolates is composed of at least two groups that evolved independently from the original population of P. oryzae. Most of the isolates that were collected just after an outbreak of finger millet blast in the 1970s had almost identical fingerprint profiles although they were collected in distant prefectures. This result supports the idea that the outbreak was caused by seed transmission of a particular strain of Eleusine isolates.  相似文献   

13.
Mutants of Botrytis cinerea and Ustilago maydis highly resistant to fludioxonil were isolated at a high frequency, after nitrosoguanidine or UV mutagenesis, respectively, and selection on media containing fludioxonil. Tests on the response of mutant strains to high osmotic pressure resulted in the identification of two fludioxonil-resistant phenotypes (FLDosm/s and FLDosm/r), regarding the sensitivity to high osmolarity. Approximately 95% of fludioxonil-resistant mutants were found to be more sensitive to high osmotic pressure than the wild-type parent strains. Genetic analysis of phenylpyrrole-resistance in the phytopathogenic basidiomycete U. maydis, showed that fludioxonil-resistance was coded by three unlinked chromosomal loci (U/fld-1, U/fld-2 and U/fld-3), from which only the U/fld-1 mutation coded an osmotic sensitivity similar to that of the wild-types. Cross-resistance studies with fungicides from other chemical groups showed that the mutations for resistance to phenylpyrroles affect the sensitivity of mutant strains to the aromatic hydrocarbon and dicarboximide fungicides, but not to the benzimidazoles, anilinopyrimidines, phenylpyridinamines, hydroxyanilides or the sterol biosynthesis inhibiting fungicides. A study of fitness parameters in the wild-type and fludioxonil-resistant mutants of B. cinerea, showed that all osmotic sensitive (B/FLDosm/s) isolates had significant reductions in the characteristics determining saprophytic fitness such as mycelial growth, sporulation, conidial germination and sclerotial production. Contrary to that, with the exception of mycelial growth, the fitness parameters were unaffected or only slightly affected in most of the osmotic resistant (B/FLDosm/r) isolates. Tests on cucumber seedlings showed that the osmotic-sensitive strains were significantly less pathogenic compared with the wild-type and B/FLDosm/r strains of B. cinerea. Preventative applications of the commercial products Saphire 50 WP (fludioxonil) and Rovral 50 WP (iprodione) were effective against lesion development on cotyledons by the wild-type and the mutant strains of B. cinerea that were resistant to the anilinopyrimidine cyprodinil (B/CPL-27) and to the hydroxyanilide fenhexamid (B/FNH-21), but ineffective, even at high concentrations, against disease caused by the fludioxonil-resistant isolates (B/FLD) and a mutant strain resistant to the dicarboximide iprodione (B/IPR-1). Experiments on the stability of the fludioxonil-resistant phenotype showed a reduction of resistance, mainly in osmotic-sensitive isolates, when the mutants were grown on inhibitor-free medium. A rapid recovery of the high resistance was observed after mutants were returned to the selection medium. Studies on the competitive ability of mutant isolates against the wild-type parent strain of B. cinerea, by applications of a mixed conidial population, showed that, in vitro, all mutants were less competitive than the wild-type strain. However, the competitive ability of osmotic-resistant mutants was higher than the osmotic-sensitive ones. Furthermore, competition tests, in planta, showed a significant reduction of the frequency of both phenylpyrrole-resistant phenotypes, with a respective increase in the population of the wild-type strain of the pathogen.  相似文献   

14.
The role of the self-sown shrubsDittrichia viscosa (L.) W. Greuter andRubus ulmifolius Schott as reservoirs of aphid parasitoids was investigated. In the field studies conducted,D. viscosa grew adjacent to crops of durum wheat and barley andR. ulmifolius grew adjacent to cotton. The relative abundance of the parasitoids of(a) Capitophorus inulae (Passerini) onD. viscosa, (b) Rhopalosiphum padi (Linnaeus) on durum wheat and barley,(c) Aphis ruborum (Börner) onR. ulmifolius, and(d) Aphis gossypii Glover on cotton in various parts of Greece, was assessed during the years 1996–2000. In 2000, the fluctuation of parasitization of the above four aphid species was recorded and the action of the aphidophagous predators of the family Coccinellidae was studied. It was observed thatAphidius matricariae Haliday predominated onC. inulae andR. padi in all sampling cases. In contrast,Lysiphlebus fabarum (Marshall) was the dominant species parasitizingA. ruborum onR. ulmifolius andA. gossypii on cotton in Thessaly (central Greece) and Macedonia (northern Greece), whereasLysiphlebus confusus Tremblay et Eady andBinodoxys acalephae (Marshall) were the dominant parasitoid species in Thrace (northern Greece).Coccinella septempunctata Linnaeus was the most abundant coccinellid species on durum wheat, whereasAdonia variegata (Goeze) predominated on cotton. However, coccinellid individuals were scarce on bothD. viscosa andR. ulmifolius. The present study indicated that these two shrubs can be regarded as useful reservoirs of aphid parasitoids.  相似文献   

15.
This study examines the effects of a vegetable fungicide on sugar beet powdery mildew (Erysiphe betae) and cucumber powdery mildew (Erysiphe cichoracearum). The formulations consisting of a dispersion of Brassicaceae meal in vegetable or mineral oils on infected leaves of sugar beet, reared in the greenhouse, and of musk melons cultivated under plastic tunnels, were tested in comparison to each oil taken separately. Both formulations containing Brassicaceae meals, caused 94% of conidia to be distorted while for the untreated group only 2% were distorted. Furthermore, the leaf area infected by E. betae was 56% for untreated plants and 2.7 and 9.9% respectively, for plants treated with meal containing mineral and vegetable oil. Vegetable oil considered separately or with Brassicaceae meals showed no phytotoxicity, while the formulations based on mineral oil showed a significantly lower fresh and dry weight on tomato plants. The low level or absence of phytotoxicity of plants treated with vegetable oil formulations suggests that to improve the efficacy of powdery mildew control, they could be used mixed with sulphur. The efficiency of the vegetable formulations in the powdery mildew control observed during these trials encourages further investigation on other parasitic fungi and foliar pathogens.  相似文献   

16.
The impacts of elevated CO2 and soil water on the population dynamics, adult fecundity and nymphal period of the bird cherry-oat aphidRhopalsiphum padi (Linnaeus) were evaluated in three experiments: (i)Combined effects of CO 2 and soil water on aphid populations. Spring wheat was grown in pots at three CO2 concentrations (350, 550 and 700 ppm) and three soil water levels (40%, 60% and 80% of field water capacity, FWC) in field open-top chambers (OTC) and infested with the bird cherry-oat aphid. Aphid population dynamics were recorded throughout the growing season; at the same time, adult fecundity and duration of the nymphal period were recorded. Chemical composition of spring wheat leaves was also analyzed. (ii)Indirect effects of CO 2 concentrations and soil water on aphid adult fecundity and nymphal period. The experiment was conducted with the leaf discs method in the laboratory. Aphids were reared on leaf discs excised from the treated wheat in OTC with different CO2 and soil water levels. (iii)Direct effects of CO 2 concentrations on aphid adult fecundity and nymphal period. Aphids were reared on leaf discs excised from the wheat grown under natural conditions. The experiment was conducted with the leaf disc method in OTC with the three CO2 concentrations. It was found that the direct effect of CO2 concentration on aphid population parameters was minor. CO2 and soil water affected aphid population indirectly through their effects on wheat characteristics. The aphid population under 550 ppm CO2 was far larger than the one under 350 ppm CO2, whereas the population under 700 ppm CO2 was slightly higher than that under 550 ppm CO2. The largest aphid population was obtained with the 60% soil water treatment, regardless of CO2 treatment. The effects of CO2 concentration on aphid population were, however, not significantly correlated with soil water level. Adult fecundity increased with CO2 concentration, the highest fecundity being achieved under 60% FWC treatments. The nymphal period was not affected by CO2 concentration. The shortest period occurred under 60% FWC. Atmospheric CO2 and soil water had significant effects on the chemical composition of the wheat leaves. Aphid population size was positively correlated with leaf water content, concentrations of soluble proteins, soluble carbohydrates and starch, and negatively correlated with DIMBOA and tannins concentrations. http://www.phytoparasitica.org posting Oct. 20, 2003.  相似文献   

17.
Pectinases extract (PE) from the fermentation product ofPenicillium oxalicum BZH-2002 was tested for its ability to induce protection against scab caused byCladosporium cucumerinum on cucumber (Cucumis sativus L.) plants. Seedlings with one true leaf were sprayed with various concentrations of PE (10–200 units ml−1) 3 days before inoculation withC. cucumerinum. Results showed that the induced local protection against the pathogen was dose-dependent when the concentrations of PE were between 20 and 120 units ml−1; systemically induced resistance against the pathogen was not observed. Boiled PE had a slight effect on disease reduction. Commercial pectinases prepared fromAspergillus niger showed lower protection against scab compared with PE when they were used at the same concentration of enzyme activity. No inhibitory activity was observed on conidial germination or germ-tube growth ofC. cucumerinum. PE was further evaluated for its enhancement of defense-related enzymes. Peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) increased in cucumber seedlings after treatment with PE. PO and PPO remained at a higher level in PE-pretreated seedlings throughout the experiment period whether pathogen-inoculated or non-inoculated, whereas PAL activity began to decrease 2 days after PE treatment. http://www.phytoparasitica.org posting July 14, 2004.  相似文献   

18.
In some areas of Japan, yellow spots with white pustules on leaves, stems, petioles, peduncles and calyces were found on Ipomoea nil, I. triloba, I. lacunosa and I. hederacea var. integriuscula. We demonstrated that the diseases on I. nil, I. triloba and I. lacunosa were caused by host-specific strains of Albugo ipomoeae-panduratae and defined three forma speciales of the fungus, respectively, for the three Ipomoea species: “f. sp. nile”, “f. sp. trilobae” and “f. sp. lacunosae”. Because the diseases were new to Japan, we coined the Japanese name “shirosabi-byo”, which means white rust. We also showed that the disease on I. hederacea var. integriuscula was caused by A. ipomoeae-hardwickii. We named this new disease “white rust (shirosabi-byo in Japanese)”.  相似文献   

19.
A potyvirus tentatively named Ornithogalum virus 3 (OV-3) was successfully isolated by single-aphid transmissions from O. thyrsoides mix-infected with OV-3, Ornithogalum mosaic virus (OrMV) and Ornithogalum stripe mosaic virus (OrSMV). OV-3, a flexuous, rod-shaped particle of ca. 690 nm, was sap and aphid transmissible. The virus had a narrow host range and caused necrotic mosaic on O. thyrsoides under cold conditions. We therefore propose the name Ornithogalum necrotic mosaic virus (OrNMV) for OV-3. A synergistic increase in symptom severity was apparent on O. thyrsoides mix-infected with OrSMV/OrNMV, but not with either OrMV/OrNMV or OrMV/OrSMV. The nucleotide sequence data reported is available in the DDBJ/EMBL/GenBank databases under accession number AB282754.  相似文献   

20.
The plasmid pUFZ75 conferred constitutive GFP expression on the bacterial pathogen Xanthomonas euvesicatoria (syn. X. campestris pv. vesicatoria). Colonisation of the tomato phyllosphere and invasion of tomato leaves by X. euvesicatoria was examined using both fluorescence and confocal laser scanning microscopy. Xanthomonas euvesicatoria established a limited population on the tomato leaf surface, primarily occupying the depressions between epidermal cells and around the stomata, prior to invasion of the leaf via the stomata and subsequent growth within the substomatal chamber and the leaf apoplast. Additionally, hrp-gfp fusions were used to report on the temporal and spatial expression of hrp genes during epiphytic colonisation and invasion. Xanthomonas euvesicatoria cells carrying hrpG- and hrpX-gfp reporter constructs were not fluorescent in vitro on non-hrp-inducing LB agar but did exhibit a low level of fluorescence on the leaf surface within 24 h of inoculation, particularly in the vicinity of stomata. Cells carrying hrpG- and hrpX-gfp fusions exhibited high levels of fluorescence 72 h after inoculation in the substomatal chamber and the leaf apoplast. Cells carrying the hrpF-gfp fusion were slightly fluorescent on LB agar and showed no further increase in fluorescence on the leaf surface by 24 h after inoculation, but did show a significant increase in fluorescence 72 h after inoculation in the substomatal chamber and apoplast. The apparent low-level induction of the regulators hrpG and hrpX on the tomato leaf surface may suggest that some of the genes of the X. euvesicatoria HrpG/HrpX regulon are up- or down-regulated prior to invasion of the stomata while still on the leaf surface.  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