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1.
Pinewood nematode (PWN), Bursaphelenchus xylophilus, the causal agent of pine wilt disease (PWD), was detected in Spain in 2008. This gives rise to serious concern, as the disease has caused severe environmental and economic losses in Portugal and in Asian countries. We studied interspecific variation in susceptibility to pine wilt disease and differences in constitutive chemical compounds in the xylem tissue of the seven pine species -P. canariensis, P. halepensis, P. pinaster, P. pinea, P. sylvestris, P. radiata and P. taeda. Two-year-old trees were inoculated with B. xylophilus. Water potential and nematode densities were measured for each species on specific dates; whereas, wilting symptoms were recorded weekly until the end of the assay. Chemical compounds in the xylem were determined prior to inoculation. Three different resistance groups can be established in terms of the pine species susceptibility to PWN: non- to slightly-susceptible (P. canariensis, P. halepensis, P. taeda and P. pinea), susceptible (P. pinaster and P. radiata), and highly-susceptible (P. sylvestris). Nematodes migrated downward to the roots in all seven species. Constitutive xylem nitrogen, total polyphenols, and marginally phosphorus were negatively correlated with mortality caused by PWN. The most susceptible species, Pinus sylvestris, presented high levels of constitutive lipid-soluble substances and low levels of manganese, pointing to a possible relation between these components and PWN susceptibility. The results suggest P. sylvestris, P. pinaster and P. radiata forests could be severely damaged by PWN in Spain and highlight how constitutive chemical compounds such as nitrogen might play a role in resistance mechanisms against PWN.  相似文献   

2.
The response of three soft scales: the pyriform scale —Protopulvinaria pyriformis (Cockerell), the mango shield scale —Protopulvinaria mangiferae (Green), and the capparis soft scale —Coccus capparidis (Green), to paiasitization by the parasiteMetaphycus swirskii Annecke & Mynhardt (Hymenoptera:Encyrtidae), was studied. Although the parasite was able to complete its development in any of these three host species, different rates of mortality of parasite immatures were recorded in the various hosts. Parasite mortality inP. pyriformis was due to egg encapsulation only and was higher in the field than under laboratory conditions (53.1%vs. 27.7%, respectively). InP. mangiferae a total of 55.4% mortality was observed, while inC. capparidis it reached only 14.0%, rendering the latter the most suitable of the three soft scales tested, for successful development ofM. swirskii.  相似文献   

3.
Laboratory and nursery experiments were conducted to identify the causal agent of a needle blight of Pinus wallichiana, a species native to the Western Himalayas. The pathogen was identified as Myrothecium verrucaria, on the basis of morphological, cultural and molecular characterization. BLAST analysis of ITS sequences of the pathogen revealed maximum sequence identity of 99% with M. verrucaria. The sequence is the first of this fungus from P. wallichiana. Phylogenetic analysis grouped all M. verrucaria isolates in a single clade; M. roridum and M. inundatum clustered in separate clades. The pathogen grew optimally at 25 ± 1 °C on oat meal agar, pH 5.5. Inoculation experiments with M. verrucaria demonstrated pathogenicity on Pinus halepensis, Cedrus deodara and Cryptomeria japonica, in addition to Pinus wallichiana.  相似文献   

4.
The invasive small cypress bark beetle, Phloeosinus aubei (Coleoptera, Curculionidae, Scolytinae) has two flights in Central-Europe, however, it was unclear, whether this corresponds to two reproductive periods, when nuptial chambers are formed and galleries initiated. The aim of this study was to clarify the life-cycle of P. aubei in Hungary, representing populations in the range of invasion, and to compare preferences towards some popular cultivars of Thuja and Juniper ornamental trees. In order to reveal which is the pioneering gender, and to confirm females’ preferences between healthy and broken trunks behavioral tests were conducted. Results showed that adults prepare hibernation tunnels from August until October. Sex ratio of overwintering adults was nearly equal. The significantly highest number of hibernation tunnels was found on Thuja plicata Atrovirens (mean±S.E.: 6.0±0.7/tree), followed by T. occidentalis Smaragd (2.2±0.8), Juniperus chinensis Spartan (1.6±0.6), and J. scopulorum Blue Arrow (0.2±0.2). Nuptial chambers were made from April until June, by singly females, never by males. Females chose broken, drying trunks over healthy ones. Adults of the next generation emerged from the galleries from August until October. By October adults emerged from 94% of the galleries, and larvae were found only in 6% of the galleries. These results showed that the autumn flight of P. aubei is linked to making hibernation tunnels, while the spring flight to producing nuptial chambers. The latter corresponds to a single reproductive period per year. Control measures against adults should be timed to these two specific periods of the season.  相似文献   

5.
Sweet cherry is a major commercial crop in Turkey, the most important producer of the fruit worldwide. Sweet cherry decline was observed in an orchard in Ankara province of Turkey. Affected young trees exhibited reduced tree vigor, yellowing and wilting of leaves, and dieback symptoms resulted in tree death. A Phytophthora sp. was consistently isolated from necroses that appeared on taproots and crowns. The pathogen was identified as Phytophthora cryptogea based on several morphological features and DNA sequence of the internal transcribed spacer (ITS) region. P. cryptogea was pathogenic on excised shoots and 1-year-old cherry rootstocks. This is the first report of P. cryptogea causing disease of sweet cherry in Turkey.  相似文献   

6.
Leptographium qinlingensis is an ophiostomatoid fungal pathogen associated with a forest pest Dendroctonus armandi, which causes enormous deaths of its host trees Pinus armandi. The objective of this research was to isolate and characterise some toxic metabolites from cultures of the pathogen. Three toxins, 6-methoxymethyleugenin (compound 1), maculosin (cyclo(L-Pro-L-Tyr), compound 5) and cerevisterol (compound 12), together with 11 other compounds, have been isolated from the ethyl acetate extracts of the cultures of L. qinlingensis by several chromatographic methods. Their structures were characterized on the basis of spectroscopic analyses including ESIMS, 1H-NMR, and 13C-NMR, in comparison with those reported in the literature. Phytotoxic test showed that these three compounds were active in vitro against both aseptic Pinus armandi seedlings and field P. armandi seedlings. The present investigation demonstrated that three toxic metabolites including 6-methoxymethyleugenin, maculosin and cerevisterol, which were biosynthesized by L. qinlingensis isolated from the insect Dendroctonus armandi on Pinus armandi tree, could be phytotoxic to P. armandi seedlings.  相似文献   

7.
Vespa orientalis F. (Hymenoptera: Vespidae), a major pest of apiculture, indirectly disrupts pollination of fruit and vegetable crops, and constitutes a public health menace. Control methods are imperfect, labor-intensive, and entail the use of medically and environmentally dangerous chemicals. A parasitic wasp,Sphecophaga vesparum Curtis (Hymenoptera: Vespidae), has been found to attack a large proportion (up to 100%) of observedV. orientalis nests in southern Israel. Within these nests, 2.5–95.1% of host cells were parasitized by three to seven individuals. Heavily parasitized nests showed considerable reductions in the proportion of queen cells.  相似文献   

8.
The genus Puccinia represents rust infections, which are responsible for great productivity losses in crops of commercial and ornamental plants worldwide. This work is aimed at determining the occurrence of Puccinia spp. spores in Madeira Island in order to infer the exposure risks from a phytopathological point of view. A phytopathological analysis was performed in 203 local plant samples between January 2003 and December 2012. During the same period the airborne concentrations of rust spores were monitored following well-established guidelines. Aerobiological data was compared with meteorological records. Based on macro and microscopic analyses, five species of rusts were identified: P. horiana, P. buxi, P. porri, P. pelargonii-zonalis, and P. sorghi, and they were found mostly in spring and summer. A total of 20 samples out of 203 analysed plants (9.8%), were infected with Puccinia spores, i.e., P. horiana (5.9%), P. buxi (1.47%), P. porri and P. pelargonii-zonalis (0.98%), and P. sorghi (0.5%). During the studied period Puccinia spores attained an annual average concentration of 126 spores m?3 and most of them were recorded between March and October. Meteorological factors were determinant in fluctuations in spore concentration. Relative humidity was the parameter that favoured the biggest release and dispersal of the rust spores, whereas rainfall revealed a significant negative effect. Rusts do not represent an important plant pathogen in Madeira Island, as shown by the low infection frequencies and levels of airborne spore concentrations.  相似文献   

9.
Fusarium oxysporum f. sp. melongenae (Fomg), causal agent of Fusarium wilt of eggplant, is a serious pathogen in open fields and greenhouses. Inter-simple sequence repeat (ISSR) banding profiles, sequence analyses of inter-transcribed-spacer (ITS), translation elongation factor 1-alpha (TEF-1α), and actin (actA) DNA regions were employed in this study to determine genetic diversity and population structure of Fomg isolates obtained from Turkey. For ISSR study, (ACTG)5, (GACAC)3, (GACA)4, (GATA)4, HVH(TG)7 and (CA)8RG primers were selected from a set of 16. Discriminative ability of the primers revealed with various indices including polymorphic information content (PIC), and mean PIC value was calculated as 0.26. The ISSR data revealed 31 loci belonging to 202 Fomg isolates and 14 of them were found to be polymorphic. The isolates on neighbor joining ISSR tree were grouped into two major clusters which separated Fomg and outgroup isolates. Population structure was investigated based on bayesian modeling and results indicated five subpopulations (K = 5, ?K = 205.42). Mean genetic and geographical distances among sampling locations revealed only a weak and insignificant correlation (r = 0.583, P = 0.06). Phylogenetic analyses were carried out with ITS, TEF-1α and actA DNA regions with a selected subset of 30 Fomg, along with one non-host and one outgroup isolates. Since ITS region were not able to provide a meaningful separation, TEF-1α and actA sequences of each organism were concatenated individually to build a dendrogram. The clustering tree successfully separated the Fomg, non-host and outgroup isolates in which all Fomg were located on the same branch, forming a monophyletic group in the dendrogram.  相似文献   

10.
Bacterial pathogens of onion (Allium cepa) plants and their undetected presence in seed can cause substantial losses to onion producers. In this study, 23 Pseudomonas syringae strains were isolated from five onion plants and 18 onion seeds. The symptoms on leaves and seed stalks were irregular lesions with necrotic centres and water soaked margins. The aim of the study was to characterize these P. syringae strains using Biolog GN III carbon source utilization, multilocus sequence typing (MLST) based on partial sequences of four housekeeping genes (cts, gapA, gyrB and rpoD), and to determine whether or not the strains were pathogenic on onion (cv. Granex 33), chive (Allium schoenoprasum cv. Grasiue), leek (Allium porrum cv. Giant Italian) and spring onion (Allium fistulosum cv. Salotte) plants. Both Biolog analysis and MLST analysis separated onion strains into two clusters, one supporting the existence of a new pathovar of P. syringae, and the other corresponding to P. syringae pv. porri. Pseudomonas syringae strains belonging to the new pathovar we pathogenic only on onion plants of the Allium spp. tested. The results of this study revealed that bacterial blight of onion in South Africa is caused by two pathovars of P. syringae sensu lato, namely, the newly described pathovar, allii, and P. syringae pv. porri. The symptoms caused by these two pathovars in the field were indistinguishable.  相似文献   

11.
Phylogenetic analysis of Chinese isolates of the citrus Huanglongbing (HLB) bacterium based on the 16S rDNA and 16S/23S rDNA intergenic regions sequences was carried out. Nine HLB samples collected from different hosts with different symptoms in seven Chinese provinces, were subjected to PCR for amplifying and sequencing the 16S rDNA. The identity level among Chinese isolates was 98.5% to 100% and was the same with the Indian HLB isolate ‘Poona’ (GenBank accession number: L22532). By contrast, identity values were 97.5% to 97.8% with Candidatus Liberibacter africanus strain ‘Nelspruit’ (L22533), 96.3% to 97.3% with Ca. L. africanus subsp. ‘Capensis’ (AF137368), 95.3% to 96.5% with the Ca. Liberibacter sp. ‘LSg2’ (AY919312), and 94.9% to 96.0% with a strain of Ca. L. americanus from Brazil (São Paulo State; AY742824). A phylogenetic tree constructed with 16S rDNA sequences showed that all Chinese isolates belong to Ca. L. asiaticum. Analysis of the 16S/23S rDNA intergenic region was conducted on 18 HLB-diseased citrus samples with different symptoms, collected in seven provinces. These isolates showed no obvious variation and had an identity level >99.0% with one another. Sequence analysis of 16S/23S rDNA intergenic region and the relative phylogenetic tree showed that the Chinese isolates are very close to Ca. L. asiaticus, and distinct from Ca. L. africanus and Ca. L. americanus. These results suggest that the Chinese HLB isolates belong to the species Candidatus Liberibacter asiaticus. This is the first report on the classification of HLB isolates from China based on molecular investigations.  相似文献   

12.
In organic orchards disadvantages within the tree row weed management include tree damages, soil structure disturbance and humus erosion due to bare soil. As a solution to this problem the Sandwich system was developed at the Research Institute of Organic Agriculture (Frick, CH). Hereby the tree row is planted and strips right and left of the tree row are hoed mechanically. Grasses, legumes and grasses-legume mixtures were tested to identify suitable species for the tree row. Lolium perenne L., different Festuca species and subspecies, Poa pratensis L., Trifolium pratense L., Swiss and imported (i.e. European) ecotypes of Lotus corniculatus L. and Medicago lupulina L. were chosen. Additionally seedlings of Potentilla reptans L. and the allelopathic Hieracium pilosella L. were planted. Evenness, plant height and vegetation cover were monitored over one vegetation period. L. perenne turned out to be dominant; M. lupulina was more competitive as an imported ecotype whereas the reverse was shown for the Swiss ecotype of L. corniculatus in species-poor mixtures. The establishment of P. reptans was higher (nearly 100%) compared to H. pilosella. Both species showed the lowest height and due to these results future orchard tree row management research should focus on low-growing, stolon-building species.  相似文献   

13.
Information is presented on new occurrences of two homopteran pests,Matsucoccus josephi Bodenheimer et Harpaz (Matsucoccidae) andPineus pini (Macquart) (Adelgidae), in Israel, Jordan and southern Lebanon.M. josephi occurs in Israel in almost all natural relicts of Aleppo pine (Pinus halepensis). It infests all plantations of Aleppo pine, brutia pine (Pinus brutia ssp.brutia) and Eldar pine (P. brutia ssp.eldarica) north of 31°12′ lat. N. Heavy damage has been observed in the Judean Foothills, Judean Mts. and northern Samaria.M. josephi and its specific predator,Elatophilus hebraicus Pericart (Hemiptera: Anthocoridae), are recorded for the first time in Jordan and southern Lebanon. The scale was found in all visited Aleppo pine and brutia pine stands in Jordan and in natural and planted brutia pine in southeastern Lebanon. Damage byM. josephi in Jordan was observed only in young plantations of Aleppo pine; in Lebanon no signs of injury were recorded.P. pini was found for the first time in Jordan, where it causes severe damage to young stands of Aleppo pine and stone pine (Pinus pinea). Contribution from the Agricultural Research Organization. No. 1225-E, 1993 series.  相似文献   

14.
Nearly 5700 plants of 14 cultivated and 8 wildAllium species and varieties from the Netherlands and other parts of the world, were tested for infection with aphid-borne potyviruses by ELISA, electron microscope decoration tests and/or inoculation onto test plants. This resulted in the detection of two known viruses, viz. leek yellow stripe virus (LYSV) and onion yellow dwarf virus (OYDV), and the discovery and characterization of two new viruses, viz. shallot yellow stripe virus (SYSV) and Welsh onion yellow stripe virus (WoYSV), and of six strains of these viruses. ‘Garlic mosaic’, ‘barlic yellow streak’, ‘onion mosaic’, ‘shallot mosaic’, ‘shallot X’, and ‘shallot yellows’ viruses, incompletely described in the literature, are now reidentified as well-known viruses or as strains or mixtures of such viruses. ‘Garlic yellow stripe virus’ is also a complex containing a potyvirus possibly differing from the viruses found in this survey. The symptoms of the potyviruses studied varied widely and ranged from mild to severe chlorotic to yellow striping of leaves, and they are of little diagnostic importance.LYSV was found in vegetatively propagated pearl onion (A. ampeloprasum var.sectivum) from Europe and Asia. It has decreased in leek crops (A. ampeloprasum var.porrum) in the Netherlands since the 1970, apparently due to resistance in new cultivars. OYDV was common in onion (A. cepa var.cepa) from the former USSR and North Africa, and in European cultivars of shallot (A. cepa var.ascalonicum), with the exception of the highly resistant ‘Santé’, but was not detected during this survey in Asian shallot. European samples of ever-ready onion (A. cepa var.perutile), multiplier onion (A. cepa var.aggregatum) and tree onion (A. cepa var.viviparum) contained OYDV. It was also found in sand leek (A. scorodoprasum) from european gene collections. A strain of OYDV from onion and shallot in Morocco and Spain was virulent on onion and shallot cultivars resistant to common OYDV, as reported early for a similar isolate in the USA.Asian shallot appeared generally infected with the new SYSV, similar to OYDV in host range and symptoms but serologically distinct. It was not detected in onion and shallot from Europe or North Africa. A virulent strain of this virus caused striping in sap-inoculated garlic (A. sativum) and Formosan lily (Lilium formosanum). The new WoYSV, infecting Welsh onion in Indonesia and Japan, was earlier described in Japan as OYDV from rakkyo and Welsh onion. It appeared serologically closely related to SYSV and distantly to OYDV, but differed in its host range.Host-specific strains of LYSV and OYDV were detected in garlic, wild garlic (A. longicuspis), an unidentifiedAllium species (suffix-G), and great-headed garlic (A. ampeloprasum var.holmense) (suffix-GhG)., LYSV-G and OYDV-G infected on average 45% and 73%, respectively, of the garlic samples of worldwide origin. Symptoms of isolates of both strains varied in severity, implying the necessity of serological tests for disease diagnosis and health certification. LYSV-GhG was the cause of yellow striping in 93% of the great-headed garlic plants tested, mainly from the Mediterranean area. One sample was also infected with OYDV-GhG.Many samples from vegetatively propagated crops grown from non-certified planting stock contained a few plants free of potyviruses, implying the possibility to obtain healthy (and possibly resistant) selections of such cultivars avoiding meristem-tip culture. Cross-protection of garlic sets by a mild potyvirus isolate seems to be an alternative to the use of vulnerable virus-free sets.Generally, viruses and virus strains could not be transmitted to anyAllium species other than their natural host, except to the highly susceptible crow garlic (A. vineale). This species, and other predominantly vegetatively propagating wildAllium spp. (field garlic,A. oleraceum; ramsons,A. ursinum; sand leek), were found not to be reservoirs of viruses that might infectAllium crops in the netherlands. Streaking in vegetatively propagated wild leeks (A. ampeloprasum and closely related species) originating from the Mediterranean area and Asia was due to an undescribed miteborne virus. The survey confirmed that spread of potyviruses inAllium crops in the Netherlands is from planting sets, and from a neighbouring crop only if of the same species.  相似文献   

15.
Colletotrichum leaf disease of Hever brasiliensis (rubber tree) caused by C. gloeosporioides is one of the major causes of declining rubber tree yields. Little is known about the fungal molecular characters that are important for pathogenicity on rubber tree and fungicide resistance. In this study, we cloned the CgPBS2 gene, the key component of the Hog1 pathway which controls various aspects of osmoregulation and fungicide resistance in various fungal pathogens, including the causal agent of Colletotrichum leaf disease of rubber tree. We characterized the function of the CgPBS2 gene by reverse genetics. Because the Hog1 pathway plays an important role in stress responses, we obtained a CgPBS2 gene deletion mutant by PEG-mediated transformation of protoplasts after reducing the concentration of sucrose in the screening medium from 1.0 M to 0.2 M. Then, the complemented transformants and GFP-labelled CgPBS2 gene transformants were selected directly under highly hyperosmotic medium (PDA?+?1.5 M sorbitol) without using other selectable gene markers. Phenotypic observations showed that the CgPBS2 protein was mainly localized in the conidial cytoplasm of the CgPBS2-GFP transformants. In addition, disruption of CgPBS2 led to sensitivity to hyperosmosis and high salt concentration as well as resistance to the fungicide fludioxonil. No obvious difference in virulence was observed between the null mutant and the wild-type strain. These results provide insights into the role of the CgPBS2 gene in osmotic stress, salt stress and fludioxonil resistance and suggest that osmotic stress sensitivity can be used as a selection marker.  相似文献   

16.
The development of insecticidal resistance in diamondback moth (DBM) Plutella xylostella has immediate implications for its management. In this study, we examined the mode of inheritance of Indoxacarb resistance in P. xylostella. The indoxacarb-resistant strain (Px-R) was obtained through continuous laboratory selection with increasing doses of indoxacarb in each generation. At the 14th generation of selection, the resistance ratio of Px-R strains was 238 over the susceptible strain (Px-S). The mode of inheritance to Indoxacarb in P. xylostella was examined performing standard reciprocal crosses between Px-R and Px-S and response of Px-R, Px-S and F1 hybrid progenies to Indoxacarb through leaf dip bioassay. The degree of dominance (D) and heritability (h) of F1 hybrid progeny ranged from ?0.001 to 0.0012 and 0.499 to 0.506, respectively. The Indoxacarb resistance was appeared to be autosomal and inherited as a semi-dominant trait. The Px-R strain of P. xylostella showed little cross resistance to cypermethrin and there was no cross resistance to other pesticides viz., chlorpyrifos, spinosad, karanjin, xentari (Bta-Cry1C) and MVP-II (Cry1Ac). Since the Indoxacarb resistance inherited as a semi-dominant trait in P. xylostella, the sub lethal doses and frequent use of indoxacarb should be avoided for the management of P. xylostella. Moreover, Px-R of P. xylostella showed positive cross resistance to synthetic pyrethroids (cypemethrin), therefore indoxacarb and synthetic pyrethroids should not be recommended together for management of P. xylostella.  相似文献   

17.
Pratylenchus zeae parasitizes various crops and damages the host roots, resulting in decreased yield and quality of the host plants. Alignments of mitochondrial DNA (mtDNA) Cytochrome Oxidase I (COΙ) sequences revealed the genetic variation among Pratylenchus species. The results indicated 0.2–2.4% intraspecific variations for mtDNA COI sequences among eight P. zeae populations, and 25.4–35.1% interspecific variations between P. zeae and other Pratylenchus species. Based on the mtDNA COΙ region, a loop-mediated isothermal amplification (LAMP) assay was developed for the rapid and specific detection of P. zeae. The optimal conditions for the LAMP assay were 64 °C for 40 min. The LAMP products were confirmed using conventional polymerase chain reaction (PCR), analysis with the restriction enzyme Bam HI and visual inspection by adding SYBR Green I to the products. The LAMP assay could detect P. zeae populations from different hosts and different geographical origins specifically. The LAMP assay was also sensitive, detecting 0.1 individual P. zeae, which was 10 times more sensitive than conventional PCR. This is the first report of the detection of Pratylenchus spp. using LAMP. In addition, the results also suggested that use of the COI gene might allow for good resolution at the Pratylenchus species level.  相似文献   

18.
Phytoplasma suspected symptoms of little leaf, flat stem, witches’ broom and leaf yellowing were recorded on the four legume species, cowpea (Vigna unguiculata (L.) Walp.), pigeon pea (Cajanus cajan (L.) Millsp.), lentil (Lens culinaris Medikus) and mung bean (Vigna radiata (L.) Wilczek) in the states of Delhi, Uttar Pradesh (UP) and Kerala from 2014 to 2016. DNA specific fragments of approximately 1.3 kb were amplified from symptomatic samples of cowpea, pigeon pea, lentil and mung bean in nested PCR assays by using two sets of universal phytoplasma nested specific primers P1/P7 followed by 3Far/3Rev. No DNA amplifications were observed in any of the non-symptomatic legume samples with same primer pairs. Pair wise sequence comparison, phylogeny and virtual RFLP analysis of 16S rDNA sequences of the four legume species confirmed the association of four different groups and subgroups of phytoplasmas in the present study. The mung bean witches’ broom at Delhi was identified to be associated with strain related to ‘Ca. P. aurantifolia’ (16SrII-D), pigeon pea little leaf at Faizabad, UP with strain related to ‘Ca. P. phoenicium’ (16SrIX-C), lentil witches’ broom at Faizabad, UP with ‘Ca. P. trifolii’ (16SrVI-D) and cow pea flat stem disease at Kerala with ‘Ca. P. cynodontis’ (16SrXIV-A). Association of ‘Ca. P. cynodontis' (16SrXIV-A) infecting cowpea, ‘Ca. P. trifolii’ (16SrVI-D) in lentil and phytoplasmas strain related to ‘Ca. P. phoenicium’ (16SrIX-C) infecting pigeon pea are the new reports to the world.  相似文献   

19.
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   

20.
Bayberry (Myrica rubra) is a fruit tree native to the subtropical regions of China. It produces fruit with a unique taste and pharmacological characteristics, thus making it a widely cultivated tree commercially in many regions of China, including Zhejiang, Fujian, Guizhou, Sichuan and Yunnan Provinces. Recently, a twig blight disease occurred on the fruit tree and caused destructive damage of plantings in the Zhejiang Province. However, the etiology of the disease was unclear. This study was carried out to identify the causal agent(s) of the blight disease on bayberry. Fungal isolates were obtained from blighted twig samples collected from bayberry fields in Xianju, Rui’an, and Huangyan of Zhejiang Province. The majority (87.9 %) of the 257 fungal isolates were identified as Pestalotiopsis spp. based on their conidial morphology. DNA sequences of the internal transcribed spacer (ITS) region of the ribosomal RNA gene and the β-tubulin gene were obtained from six representative strains (XJ27, XJ42, RA2-1, YS26, YS44 and RA1-2) of the Pestalotiopsis spp. Phylogenetic analysis showed that three of the strains (XJ27, XJ42, and RA2-1) grouped with P. versicolor (Speg.) Steyaert while the other three strains (YS26, YS44 and RA1-2) grouped with P. microspora (Speg.) Batista & Peres. Pathogenicity tests in the greenhouse showed that all these six isolates of Pestalotiopsis spp. caused twig blight disease symptoms on bayberry plants, which were the same as observed in naturally infected plants in the field. Our results clearly indicated that P. versicolor and P. microspora were the major pathogens causing the twig blight disease on bayberry in southern China.  相似文献   

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