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1.
An interactive relationship between vitiviruses and grapevine leafroll viruses was characterized in grapevine. Grapevine viruses A and B (GVA and GVB) were found more frequently in the presence of co-infecting Grapevine leafroll associated viruses (GLRaV-1, ?2 or ?3) than in their absence. The titers of the vitiviruses in co-infection with leafroll viruses were found to be higher than were their titers in the absence of leafroll virus infection. The occurrence of vitivirus-associated stem-pitting symptoms was correlated with leafroll virus co-infection. Specific pairing associations on the species level were found between different viti- and leafroll virus species: GVB was associated preferentially with GLRaV-2; GVA was associated preferentially with GLRaV-1 and GLRaV-3. In contrast to the increase in vitivirus titer seen with leafroll virus co-infection, the incidence and titer of grapevine leafroll virus appeared to be unaltered by vitivirus co-infection. The potential for a synergistic enhancement of grapevine disease in co-infected vines is discussed.  相似文献   

2.
The transmission of two closteroviruses associated with grapevine leafroll, GLRaV-1 and GLRaV-3, from grapevine to grapevine by the mealybugs, Pseudococcus longispinus and P. calceolariae (Homoptera: Pseudococcidae) was studied. Controlled transmission experiments using the first and third instars of each insect were conducted twice during the 1993–94 growing season to investigate the consequence of virus accumulation within the donor vine leaf tissue on the incidence of virus transmission to healthy recipient vines. Transmission of GLRaV-1 and GLRaV-3 was determined by ELISA testing recipient vines in July 1994 and March 1995. GLRaV-3 was transmitted to recipient vines by P. longispinus and P. calceolariae first instars only. An increase in virus titre within the season did not significantly alter the transmission rate of GLRaV-3 by either P. longispinus or P. calceolariae first instars. P. longispinus and P. calceolariae failed to transmit GLRaV-1 to recipient vines.  相似文献   

3.
Eucalyptus globulus, a non-native species, is currently the most abundant forest species in Portugal. This economically important forest tree is exploited mainly for the production of pulp for the paper industry. The community of Botryosphaeriaceae species occurring on diseased and healthy E. globulus trees was studied on plantations throughout the country. Nine species from three different genera were identified, namely Botryosphaeria (B. dothidea), Diplodia (D. corticola and D. seriata) and Neofusicoccum (N. australe, N. algeriense, N. eucalyptorum, N. kwambonambiense, N. parvum and Neofusicoccum sp.). Of these, N. algeriense, D. corticola and D. seriata are reported for the first time on E. globulus, while N. algeriense, N. eucalyptorum and N. kwambonambiense correspond to first reports in Portugal. The genus Neofusicoccum was clearly dominant with N. australe and N. eucalyptorum being the most abundant species on both diseased and healthy trees. In artificial inoculation trials representative isolates from all nine species were shown to be pathogenic to E. globulus but there were marked differences in aggressiveness between them. Thus, D. corticola and N. kwambonambiense were the most aggressive while B. dothidea and D. seriata were the least aggressive of the species studied.  相似文献   

4.
A new species in the genus Ditylenchus, D. stenurus n. sp. collected from western Iran, is described and illustrated herein based on morphological and molecular studies. The new species is characterised by a body length of 772 (663–863) μm, delicate stylet 6 (5–7) μm long, six lines in the lateral field. Median bulb of pharynx well-developed, muscular with crescentic valve. Post-vulval uterine sac well-developed, 35 (30–45) μm long, female tail elongate-conoid, becoming narrow suddenly with finely rounded terminus. The new species comes close in morphology and morphometrics to five known species of the genus, namely D. arachis, D. caudatus, D. clarus, D. myceliophagus, and D. nanus. DNA sequencing data was obtained on the partial 18S, D2/D3 expansion segments of the 28S rRNA gene and internal transcribed spacer (ITS). The phylogenetic relationships of this species with other Ditylenchus spp. using partial 18S–rDNA and D2/D3 indicated that D. stenurus n. sp. clustered together with several species belongs to the D. triformis-group i. e. D. africanus, D. destructor and D. halictus: all sharing a rounded tail terminus and six lines in lateral fields.  相似文献   

5.
Aureobasidium isolated from Vitis vinifera (cv Chardonnay) grapevine tissues were characterised using morphological and molecular techniques. Species level identification of 29 isolates was accomplished by partial amplification and sequencing of the ITS region (ITS1–5.8S–ITS2) using universal primers ITS1 and ITS4. A comparison of nucleotide sequences using BLAST followed by phylogenetic analysis revealed that all isolates examined were Aureobasidium pullulans. Strain level discrimination of a total of 100 epiphytic Aureobasidium isolates including three reference strains was successfully carried out using two inter simple sequence repeat (ISSR) primers, (AAC)5 and (GTG)5 and the Intron Splice Junction R1 (ISJ-R1) primer in which 24, 24 and 15 scorable bands were produced for each primer, respectively. The high level of genetic variation recorded among the isolates further highlighted the high levels of strain diversity among A. pullulans residing on grapevines. Thirty-two epiphytic Aureobasidium isolates were examined for their ability to inhibit the growth of Greeneria uvicola, responsible for bitter rot of grapes. Using an in-vitro dual-culture antagonism assay, all isolates inhibited the growth of G. uvicola (Isolates DAR 77272 and DAR 77273) with inhibition ranging from 15 to 85%. Three Aureobasidium isolates were then examined for their ability to inhibit G. uvicola when co-inoculated onto detached berries, leaves and grape bunches growing on potted vines in a glass house. All isolates reduced the severity of bitter rot infection. The results indicate that A. pullulans has the potential to suppress bitter rot of grapes.  相似文献   

6.
This paper reviews the contribution of vector activity and plant age to virus spread in potato crops. Determining which aphid species are vectors is particularly important for timing haulm destruction to minimize tuber infection by potato virus Y (PVY). Alate aphids of more than 30 species transmit PVY, and aphids such asRhopalosiphum padi, that migrate in large numbers before flights of the more efficient vector,Myzus persicae, appear to be important vectors. Differences in methodology, aphid biotypes and virus strains prevent direct comparisons between estimates of vector efficiencies obtained for aphids in different countries in north western Europe.M. persicae is also the most efficient vector of potato leafroll virus (PLRV), but some clones ofMacrosiphum euphorbiae transmit PLRV efficiently toNicotiana clevelandii and potato test plants. The removal of infected plants early in the season prevents the spread of PLRV in cool regions with limited vector activity. The proportion of aphids acquiring PLRV from infected potato plants decreases with plant age, and healthy potato plants are more resistant to infection later in the season. Severe symptoms of secondary leafroll developed on progeny plants of cv. Maris Piper derived from mother plants inoculated with PLRV in June or July of the previous year. Progeny plants derived from mother plants inoculated in August showed only mild symptoms, but the concentration of PLRV in these plants was as high as that in the plants with severe symptoms.  相似文献   

7.
Two hymenopteran parasitoids of the cactus scale Diaspis echinocacti (Bouché) (Hemiptera: Diaspididae) on Opuntia ficus-indica (L.) Mill. (Cactaceae) are recorded in Greece. Aphytis debachi Azim, 1963 (Aphelinidae) is first recorded for Europe and Plagiomerus diaspidis Crawford, 1910 (Encyrtidae) is first recorded for Greece. Preliminary data on phenology and natural enemies of the scale D. echinocacti on O. ficus-indica are presented. Parasitism of D. echinocacti by P. diaspidis reached 86% in southern Greece (Kalamata) and parasitism by A. debachi reached 9.3% and 12% in Kalamata and Athens, respectively. Two predators, Cybocephalus fodori Endrödy-Youga (Coleoptera: Nitidulidae) and a mite species (Prostigmata: Bdellidae), were found to be associated with D. echinocacti.  相似文献   

8.
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   

9.
Bois noir (BN) is an important grapevine yellows endemic to the Euro-Mediterranean basin caused by ‘Candidatus Phytoplasma solani’ (‘Ca. P. solani’), a non culturable plant pathogenic Mollicute. Bois noir symptoms could be associated with ‘Ca. P. solani’ in two Azerbaijanian vineyards where disease incidence and severity were recorded for five local Vitis vinifera cultivars. In order to gain insight into the epidemiology of Bois noir in Azerbaijan, ‘Ca. P. solani’ isolates infecting plants were characterized by multi-locus sequence analysis and their secY and stamp gene sequences compared to that of the strains detected in other plants and in local Cixiidae planthoppers. Genotypes were determined for two non-ribosomal house-keeping genes, namely tuf and secY, as well as two variable markers namely Stamp and mleP1 genes, that respectively encode the antigenic membrane protein AMP and a 2-Hydroxycarboxylate transporter. The Azerbaijanian BN phytoplasma isolates corresponded to three tufB and secY genotypes. A finer differentiation of Azerbaijanian ‘Ca. P. solani’ isolates was obtained with mleP1 as five different mleP1 genetic variants were found. Finally, Stamp gene allowed differentiating four new genotypes in grapevine among the 10 new Stamp genotypes detected in various plants in Azerbaijan. The preliminary survey for infected insects conducted in northern Azerbaijan, led to the identification of Hyalesthes obsoletus and Reptalus noahi as potential vectors for two ‘Ca. P. solani’ new genotypes phylogenetically distant from the known genetic clusters. Altogether these results indicate an important genetic diversity of BN phytoplasmas in Azerbaijan that certainly result from spread through local insect vectors.  相似文献   

10.
Several vineyards in Rías Baixas and one in the Ribeira Sacra (Spain) were monitored and the spatial pattern of leafroll-diseased grapevine was analysed at several dates. Unidimensional aggregation analysis (ordinary runs), bidimensional analysis, and disease gradients analysis were used as methods of study of spatial aspects of epidemics of GLRaV. At very low insect populations the mealybug Planococcus citri transmitted the GLRaV-3 from infected plants to healthy ones planted between them in an experimental plot at Beluso; an initial focus of leafroll-infected grapevines was detected 2 years after planting at the area where the vectors had been located infesting the old plants. Within 8 years some new foci appeared and coalesced, and the incidence reached >80%. In three commercial plots where no vectors were observed, the spatial analysis of the diseased plants showed three different situations. In Meaño, the study of the evolution of the spatial patterns of diseased plants between 1992 and 2005 suggested slow vectorial field transmission of GLRaV-3. In Goián the analysis for only 2 years suggested random distribution; therefore the viruses were arriving with the planting material, but the runs analysis of some lines suggested incipient spread of GLRaV-3. In Portomarín the incidence of both GLRaV-2 and 3 was low and their distribution was random, without any evidence of field spread. These examples of the study of the spatial analysis of leafroll-infected plants may be helpful to determine whether or not spread of the viruses is occurring, and the best control measures to take.  相似文献   

11.
The occurrence and distribution of Dothistroma needle blight (DNB) on Pinus mugo was studied in 2014–2015 around the Slovakia. In total, 42 localities were investigated both native and planted ones. Symptoms of DNB were observed on 35 localities only on planted shrubs. All these 35 localities are new P. mugo DNB stands. No DNB symptoms were observed in natural and naturally regenerated plantations. DNA was extracted from a total of 236 isolates and eight needle samples. Based on the ITS-rDNA comparisons and using species specific primers, both pathogenic Dothistroma species were detected: D. septosporum and D. pini. Isolates of D. septosporum had ITS sequences identical to D. septosporum from Europe and both mating types were identified with slight predominance of MAT2. The ratio of D. septosporum mating types varies significantly between sites, ranging from an equal proportion of each mating type to single mating type populations. D. pini ITS sequence grouped with D. pini from Ukraine, Russia and Switzerland and only MAT2 was found.  相似文献   

12.
The nematicidal effect of a formulated product containing extract from Quillaja saponaria was evaluated against the root-knot nematodes. The product QL Agri® 35 (QL) was tested to record the effect on second stage juveniles motility, egg hatch and also against field populations in greenhouse experiments contacted in three different locations of Greece. Convulsive movement of second stage juveniles of Meloidogyne incognita was recorded after exposure for 8 days at a series of doses, while the most paralyzed juveniles were counted at the dose of 8 mg l?1. There was also a gradual decrease in the number of juveniles emerging from egg masses of the same nematode species when the dose of Q. saponaria was increased from 0 to 8 mg l?1. In greenhouse experiments, the use of Q. saponaria could control root-knot nematodes and prevent nematodes increase in soil. The present study demonstrates that the use of Q. saponaria extract has the ability to control root-knot nematodes. Control given by Q. saponaria in field populations infecting cucumber was similar to that of cadusafos (Rugby®) and oxamyl (Vydate®) under the tested dosages and the specific conditions of the experiments.  相似文献   

13.
Due to its ability to transmit plant viruses, Paratrichodorus teres (Hooper in Nematologica, 7, 273–280, 1962) is recognized as an economically important trichodorid species. Morphological and molecular analyses (18S and 28S rDNA) were performed, and 10 new plant hosts are reported for Polish P. teres populations. Major morphological features and the measurements obtained for the investigated specimens were within the wide ranges indicated for this species. However, a more detailed comparative analysis of Polish and Iranian P. teres showed significant morphological differences, particularly, in the shape and the structure of the walls of pars proximalis vaginae and the shape of the rectum.Phylogenetic study based on the 18S rDNA data suggests positioning of the Polish P. teres sequences within a cluster of sequences originating from the Netherlands. A comparison of the 28S rDNA fragment from Polish populations with the only P. teres 28S rDNA sequence available (from Iran) in GenBank revealed a sequence variability of 9.3%. The variation across these two representatives was higher than in the case of many other pairs of Trichodoridae species. The results obtained on the Polish P. teres specimens are discussed in the framework of the species taxonomy and phylogenetic relationships.  相似文献   

14.
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15.
Crude ethanol extracts and six organic solvent fractions of 10 Thai medicinal plants were evaluated for their antifungal activity against Alternaria brassicicola in laboratory and under greenhouse conditions. The results showed that the ethanol extracts of Coscinium fenestratum, Piper betle, Syzygium aromaticus and Zingiber cassumunar displayed complete mycelial growth inhibition of A. brassicicola at a concentration of 0.1%. Meanwhile, the crude ethanol extract and methanol fraction obtained from the stems of C. fenestratum revealed the greatest inhibition against A. brassicicola at 10%, forming inhibition zones 2.55–2.58 cm in diameter. In the greenhouse experiments, crude ethanol extracts of C. fenestratum and P. betle at 1% significantly (P?<?0.05) reduced the disease incidence at up to 67%, indicating promising preventive and curative activities against A. brassicicola. This activity is similar to that of iprodione, a widely used commercial fungicide. Interestingly, Illicium verum extract showed a greater curative effect (58% disease reduction) than protective effect (47% disease reduction). Because the C. fenestratum extract showed the highest activity against the black spot pathogen both in vitro and under greenhouse conditions, its methanol fraction was further analyzed by spectroscopic techniques. We found that berberine is a key active substance inhibiting mycelial growth of A. brassicicola. The results of this study showed the potential of Thai medicinal plants as alternatives to the use of synthetic fungicides for controlling black spot in Chinese kale caused by A. brassicicola.  相似文献   

16.
In previous research, concentrated metabolites produced by bacteria of the genera Xenorhabdus and Photorhabdus (which are symbionts of entomopathogenic nematodes) were reported to be highly suppressive to fungal and oomycete plant pathogens. Conceivably, application of non-concentrated bacterial filtrates would be more economically feasible compared to using concentrated metabolites. We evaluated the potency of 10 % v/v cell-free supernatants of the bacteria X. bovienii, X. nematophila, X. cabanillasii, X. szentirmaii, P. temperata, P. luminescens (VS) and P. luminescens (K22) against Fusicladium carpophilum (peach scab), F. effusum (pecan scab), Monilinia fructicola (brown rot), Glomerella cingulata (anthracnose) and Armillaria tabescens (root rot). A bioactive compound derived from Photorhabdus bacteria, trans-cinnamic acid (TCA), was also compared with the bacterial filtrates. Fungal colony size based on manual measurements was compared for accuracy to measurements taken by image analysis. Supernatants of Xenorhabdus spp. exhibited stronger suppressive effects on spore germination and vegetative growth when compared with Photorhabdus spp. Overall, TCA was the most effective treatment; vegetative growth was completely inhibited by TCA (1.27 mg/ml). TCA treatments also suppressed spore germination of F. carpophylium and F. effussum by approximately 90 %. The efficacy of supernatants varied among Xenorhabdus species depending on the species tested, but X. szentirmaii filtrates tended to cause greater inhibition relative to the other bacteria supernatants. Manual measurement of colony diameter required at least two replicate estimates of the colony to avoid a type II error. Area measurements were slightly overestimated based on ruler measurements, but did not affect the outcome of the analysis. Supernatants of Xenorhabdus spp., Photorhabdus spp., or TCA, did not cause any phytotoxic effects when applied to various plant species in the greenhouse. Our results indicate the potential of using TCA or Xenorhabdus cell free supernatants as bio-fungicides. Such a product, based on bacterial culture supernatants, would be economically viable, marketable and easily applicable by the end-users in many situations.  相似文献   

17.
Zonate leaf spot (Gloeocercospora sorghi) is a common disease in Sorghum bicolor producing areas of the U.S., but little is known about its biology, virulence and severity on S. bicolor, Zea mays, and related crop grassweeds. Greenhouse studies were conducted to determine and compare the virulence and severity of G. sorghi on 10 commercially available sorghum hybrids, four Z. mays hybrids and selected grassweed species including Sorghum bicolor (grain sorghum and shattercane biotypes) and Sorghum halepense (Johnsongrass), two of the most problematic arable weeds. Plants from the respective species were inoculated with a local G. sorghi isolate and maintained in a dew-chamber at 24 °C for 24 h and then incubated under greenhouse conditions for 4 weeks. Plants were observed for lesion expression and rated using a modified Horsfall-Barrett scale (0–10). The first symptoms of infection were visible within 24 h following inoculation on shattercane and S. bicolor hybrids. Symptoms consisted of small, non-diagnostic purple lesions on the leaves. Results showed that S. bicolor, S. halepense and shattercane were susceptible to G. sorghi. All other species tested in this study were not infected. More particularly, disease severity, increased from a rating of 3 to 10 on sorghum and from 2 to 7 on S. halepense between 2 and 23 days after inoculation, respectively. However, disease severity on shattercane increased rapidly from 3.5 to 10 between 2 and 8 days after inoculation, respectively. Among the sorghum hybrids tested, FFR-322 appeared to be the most resistant to G. sorghi while Pioneer 83G66 appeared to be the most susceptible. Z. mays hybrids were not infected by the fungus used in this study. G. sorghi could be used effectively to manage shattercane and S. halepense infestations occurring in Z. mays and S. bicolor fields consisting of specific G. sorghi-resistant hybrids.  相似文献   

18.
The most harmful hymenopteran pests of Pinus sylvestris L. are conifer sawflies from the family Diprionidae, including the widespread Diprion pini (L.). Natural enemies of this pest are still poorly known in many European areas where attacks occur. We studied the egg parasitoids of D. pini at four sites in two mountainous areas of Spain: the Sierra de Francia (western Spain) and the Sierra de Albarracín (eastern Spain). At all sites, the dominant egg parasitoid was Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae), whereas other three chalcidoid species were rare. All these species were previously recorded in association with D. pini, but we report here their first record in Spain. Neochrysocharis formosa attacked up to 32.3% of egg clusters of D. pini in the Sierra de Albarracín and 18.5% in the Sierra de Francia. In the attacked egg clusters, this species parasitized up to 35% of eggs in the Sierra de Albarracín and 23.7% in the Sierra de Francia, with a marked female-biased sex ratio. Contrary to the clustered pattern of parasitism observed for N. formosa while attacking other gregarious diprionids, the oviposition in egg clusters of D. pini followed a random pattern, probably due to the froth roof (spumous coating) that covers its eggs and interferes with the egg-searching behavior of females. Indeed, other parasitoid species of D. pini have been reported to behave similarly.  相似文献   

19.
The taxonomic assignment of Japanese potato blackleg isolates of Dickeya spp. has not been confirmed after the changes in their former name, Erwinia chrysanthemi. Therefore, we investigated and identified 23 representative isolates of Dickeya spp. from symptomatic stems of potatoes in Japan, with biochemical tests and phylogenetic sequence analysis using recA, dnaX, rpoD, gyrB, and 16S rDNA sequences. Results of our biochemical tests showed that all isolates can be assigned to phenon 5 and biovar 1, which are associated with D. dianthicola. Based on the recA, dnaX, rpoD, gyrB, and 16S rDNA sequences, all isolates are in the same clade with D. dianthicola and were clearly distinguished from D. chrysanthemi, D. dadantii, D. dadantii subsp. dieffenbachiae, D. solani, D. zeae, and D. paradisiaca. Therefore, we conclude that Dickeya spp. isolated from potatoes with blackleg symptoms in Japan are D. dianthicola.  相似文献   

20.
Bois noir (BN) is the most widespread European grapevine yellows disease caused by ‘Candidatus Phytoplasma solani’. Although our knowledge of the mechanisms of interactions of this pathogenic bacteria with host is largely unknown, the plant-pathogen system of BN is commonly used as a model system for studying grapevine yellows diseases. We applied here a conceptual model of general plant pathology – a disease triangle for describing interactions among the host plant, the pathogen and the environment. We generated a proof-of-concept statistical model for disease triangle using original experimental data and different statistical and data mining approaches for a selected system of ‘Ca. P. solani’ infection of cv. ‘Chardonnay’ grapevine plants. We monitored individual plants from a single vineyard over a period of six years. Phytoplasma content, the expression of 21 selected grapevine genes and environmental conditions were recorded and related to disease severity. Our model predicts that in described conditions BN is a function of the expression of grapevine gene VvDMR6, summer rainfall and abundance of ‘Ca. P. solani’. The greatest impact among elements of the disease triangle is attributed to the pathogen, and is independent of the pathogen titer. We showed that this first de facto representation of the disease triangle is useful for showing disease dynamics over several years and could be applied to other plant-pathogen systems. The overall results of this study will contribute to understanding of ‘Ca. P. solani’ biology and its interactions with grapevine host.  相似文献   

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