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1.
Thirty‐eight isolates of Rhizoctonia spp. were isolated from Scots pine (Pinus sylvestris) seedlings with damping‐off symptoms, originating from two forest nurseries in central‐west Poland (Wronczyn and Jarocin) and from diseased seedlings grown in soil from Wronczyn nursery. Majority of these isolates (79%) had multinucleate cells and were identified as Rhizoctonia solani. The remaining isolates were recognized as binucleate Rhizoctonia spp. R. solani isolates were characterized using hyphal anastomosis and were divided into five anastomosis groups (AG). The most prevalent was AG5 (37% of isolates), followed by AG2‐1 (30%) and 27% of the isolates were identified as AG4. Groups AG1‐IB and AG2‐2 were only represented by single isolates. The virulence recorded as mortality (in percentage) was comparatively high for binucleate and multinucleate isolates of Rhizoctonia spp. Sequence analysis of the polymerase chain reaction (PCR)‐amplified internal transcribed spacer (ITS) rDNA region was used for phylogenetic analysis. The dendrogram showed that isolates were distinctly separated based on their AG types and there was no relationship between pathogenicity on Scots pine seedlings and the AG to which the isolates belong to. The results are discussed with respect to pathogenic potential of the various AG groups.  相似文献   

2.
Sissoo (Dalbergia sissoo), commonly known as shisham, is amongst the finest woods of South Asia, but ‘wilt’ disease has caused a rapid decline in this species. The cause of the disease remains uncertain. The aim of this study is to identify the causal agent of the disease and characterize isolates made from diseased trees, based on genomic data and variations in virulence. Samples of infected roots, stems and the ooze exuded from infected trees were obtained from plants showing symptoms in different geographical regions of India for the isolation of microorganisms. Isolates were used to inoculate healthy plants. Based on the morphological characteristics, genus‐ and species‐specific PCR, and in silico analysis of 5.8S rDNA‐ITS regions, of the 38 fungal isolates, 24 and 14 were identified as Fusarium solani and Fusarium sp., respectively. In a pathotyping study, eighteen F. solani isolates, isolated from roots and stem parts of symptomatic plants, induced typical wilt symptoms when inoculated through soil and roots on D. sissoo seedlings of 1–15 months in age. The population of F. solani was the highest in infected roots and the lowest in parts of stems, gradually decreasing with height, and was isolated constantly up to approximately 40% height of the seedling. F. solani isolates used in inoculations were successfully re‐isolated from the rhizosphere, infected roots and wilted stems, as confirmed using isolate‐specific DNA fingerprints. Molecular phylogenies based on rDNA‐ITS sequences showed that the 38 isolates fell into 2 groups. Group I comprised of F. solani isolates from D. sissoo and F. solani sequences in the NCBI GenBank database, whereas group II included Fusarium isolates other than F. solani. These results are helpful in developing integrated control measures for this highly variable pathogen and to establish a base for future population studies.  相似文献   

3.
Melia dubia, a multipurpose tree species, is gaining importance to meet the demand supply gap of timber, plywood and pulpwood . In June 2016, a serious outbreak of wilt disease was observed in M. dubia seedlings planted in the Central Nursery of Forest Research Institute (FRI), Dehradun, India. The disease led to the destruction of one hundred thousand (100,000) seedlings. Earlier in June 2012, serious wilting of M. dubia seedlings was observed in Haryana, India. The pathogen was identified as Fusarium solani following standard laboratory procedures and sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal DNA (rDNA). The pathogenicity of three isolates has been proved under greenhouse conditions. This is the first report of F. solani causing wilt of M. dubia.  相似文献   

4.
In this study the phylogeographic variation among isolates of the Sirococcus conigenus P group and the phylogenetic relationships of S. conigenus with Sirococcus clavigignenti‐juglandacearum and other species previously placed in the genus Sirococcus were investigated. A collection of 33 isolates originating from Picea, Pinus and Larix in Europe, North America and Bhutan were characterized by sequence analyses of the internal transcribed spacer (ITS) region (including ITS1, 5.8S ribosomal DNA, ITS2) of the nuclear rDNA and a portion of the β‐tubulin gene. In phylogenetic analyses most isolates from pine, spruce and larch formed a distinct clade, representing the P group of S. conigenus, which was separated from the T group of this pathogen. Four isolates from Picea in Europe and Canada formed a third clade within S. conigenus and these isolates are referred to as the S group. The P group consisted of five distinct ITS haplotypes, which partly differed in their optimum growth temperature and their growth rates at 25°C on malt extract agar. Nested clade analysis resolved the five haplotypes into three distinct clades and revealed significant genetic/geographic associations for some of the haplotypes. Parsimony analysis of the small subunit (18S) ribosomal DNA sequences confirmed the phylogenetic affinities between S. conigenus and S. clavigignenti‐juglandacearum. In contrast, Godronia cassandrae and Hormococcus conorum, which formerly had been placed in the genus Sirococcus, were found to be only distantly related to S. conigenus and S. clavigignenti‐juglandacearum.  相似文献   

5.
The pathogenic fungus Heterobasidion annosum was identified in the rhizome of a couch grass (Elymus repens) using genetic markers. The couch grass grew in the proximity of a Scots pine stand that was visibly affected by the pathogen. The rDNA analysis showed 100% sequence similarity between two H. annosum sequences of ITS1 and ITS2 obtained from fruiting bodies found on the couch grass rhizome and on the stem of the Scots pine. These results indicate a close relationship between the two isolates of H. annosum and that they are derived from a common ancestor. The results show that H. annosum mycelia can infect couch grass rhizomes and subsequently produce fruiting bodies. It also suggests that the known modes of infection of tree roots by this pathogen in coniferous stands should take into account couch grass rhizomes in the dispersal of the disease in afforested post‐agricultural soils.  相似文献   

6.
Biscogniauxia nummularia is known for its association with beech (Fagus sylvatica), on which it occurs as a saprotroph and a pathogen causing strip cankers following water stress. This fungus has also been reported as a dominant endophytic species in plants of the sedge Carex brevicollis growing in the understory of beech forests and adjacent grasslands in Sierra de Urbasa (Navarre, Spain). In this area, stromata of B. nummularia were observed in dead and living wood of beech trees at several locations where plants of C. brevicollis also contained the fungus as an endophyte. Pure cultures obtained from stromata of B. nummularia on F. sylvatica trees were compared to endophytic isolates from symptomless C. brevicollis. Culture morphology and micromorphology as well as rDNA sequences of the internal transcribed spacer (ITS) regions were identical, suggesting that B. nummularia from beech can also live endophytically in C. brevicollis. It is unknown whether the endophytic strains of Carex might have a role as an inoculum source for the infection of beech trees, or whether they represent a dead end in the life cycle of the fungus.  相似文献   

7.
Pseudodidymella fagi is a leaf blotch pathogen of Fagus crenata in Japan. This pathogen is now reported for the first time on F. sylvatica in Switzerland and Germany. Species identity was verified by morphological assessment of the asexual and sexual morphs and by comparing the internal transcribed spacer (ITS) sequence of the type material from Japan and of freshly collected samples from Europe. ITS sequences proofed to be completely identical. The asexual morph Pycnopleiospora of Ps. fagi is formed on necrotic leaf spots during summer and autumn. In early spring, its sexual morph is formed in the litter of F. sylvatica. The connection between sexual and asexual morphs was verified by sequencing the ITS region of single conidium and ascospore isolates. The pathogenicity of Ps. fagi on F. sylvatica was tested by inoculations on detached leaves in vitro and Koch's postulates were fulfilled. The second pathogen we report in central Europe for the first time is Petrakia deviata, which causes a leaf blotch disease of field maple (Acer campestre). This species was collected only once in the central Caucasus region in 1929 and was never found again after its first discovery. Now it was rediscovered in two different locations in Switzerland on field maple (A. campestre) and on the new host Norway maple (A. platanoides). Species identity was verified by morphology and by comparison with the ITS sequence of the holotype specimen and freshly collected samples. Phylogenetic analysis based on ITS sequences suggested that Ps. fagi and P. deviata are closely related to each other. Whether these species were simply overlooked so far, profit from climate change, or represent newly introduced invasive species remains to be studied. Moreover, deeper phylogenetic analysis using multiple sequence markers should be conducted to verify species identities.  相似文献   

8.
Cherry laurel (Prunus laurocerasus) is a native plant species in Serbian forests, but is also widely used for ornamental plantings. Following two extremely wet summers in 2014 and 2015, in spring and summer of 2016 and 2017, numerous cherry laurel plants with symptoms indicative for Phytophthora diseases, like wilting and chlorosis of leaves, dieback and bleeding bark necroses, were recorded in a park in Belgrade and in two ornamental nurseries in central Serbia. From necrotic bark samples and rhizosphere soil, self‐sterile Phytophthora isolates with woolly colonies were obtained. Due to the production of ellipsoid and elongated, non‐papillate sporangia in water and of ornamented oogonia with two‐celled antheridia in mating tests with tester strains of both Phytophthora × cambivora and P. cryptogea, these isolates were identified as P. ×cambivora which was confirmed by ITS sequence analysis. Pathogenicity of P. ×cambivora from cherry laurel (PCCL) was tested by inoculating one‐year‐old seedlings of cherry laurel under the bark. P. ×cambivora from European beech (PCB), and isolates of P. cactorum (CAC), P. cryptogea (CRY), P. plurivora (PLU) and P. ×serendipita (SER) were included as comparison. Three and a half months after inoculation, nine of the twelve plants in PCB, three in PCCL and CAC and two in PLU declined with longitudinal necroses and chlorosis, wilting and premature shedding of leaves. These results demonstrate the ability of P. ×cambivora to infect and cause decline of cherry laurel plants. The particularly high aggressiveness of the P. ×cambivora isolate from beech shows that this pathogen poses a serious risk to cherry laurel in the rare natural communities of cherry laurel and beech in Serbia.  相似文献   

9.
Lophodermium piceae, the dominant needle endophyte of Norway spruce (Picea abies), is known to be extremely diverse. This work aimed to test the possible occurrence of cryptic species within the morphological species L. piceae. Genetic variation in 36 South Finnish L. piceae isolates originating from six localities was investigated by comparing DNA sequences of three genetic markers. One of the markers was the internal transcribed sequence (ITS) of the ribosomal DNA and the other two (LP1 and LP2) were based on sequence characterized amplified regions designed for L. piceae. The LP2 marker could be detected only from isolates of L. piceae but not from 20 other ascomycete species tested. This sequence, therefore, is considered as a species‐specific marker for L. piceae. For comparison, ITS sequences of isolates representing two other Lophodermium species, L. pinastri and L. seditiosum, were also investigated. In a neighbor‐joining analysis of ITS sequences all L. piceae isolates fell into one cluster, which was clearly separate from those of L. pinastri and L. seditiosum. Dendrograms of the three markers were incongruent indicating that the L. piceae population examined consisted of a single phylogenetic species. No geographical differentiation was observed. Our results confirm that L. piceae is a genetically highly diverse endophytic species.  相似文献   

10.
Wilt disease caused by Fusarium solani is a serious constraint to Dalbergia sissoo (shisham) plantations in northern India. In this study, the antagonistic potential of 40 bacterial isolates recovered from rhizophere soil of healthy shisham trees, and a well‐characterized Trichoderma species (Trichoderma virens) were tested for their possibility as biocontrol agents for F. solani. Two promising isolates (S1 and S15) were identified which inhibited pathogen growth, caused chitin degradation, produced siderophores and solubilized phosphate in vitro. Isolate S15 scored highest for hydrogen cyanide (HCN) production while isolate S1 was a non‐HCN producer. These two isolates were identified as Serratia marcescens (S1) and Pseudomonas azotoformans (S15) following sequence analysis of 16S rDNA. In dual culture assays, T. virens caused 80% inhibition of mycelial growth of the test fungus. The three selected antagonists when tested in planta in the glasshouse completely suppressed production of wilt symptoms on 12‐month‐old shisham plants. Further work is needed to ascertain the potential of these isolates to be used as biocontrol agents to manage shisham wilt under field conditions.  相似文献   

11.
In a recent survey of Eucalyptus clones in the Republic of Congo, Central Africa, a serious wilt and die-back disease of two different hybrid clones was observed. Affected trees ranged in age from approximately 6 months to 4 years. Isolations from symptomatic plant material consistently yielded a Ceratocystis species. On the basis of morphology and sequence data this fungus was identified as Ceratocystis fimbriata, a well-known wilt and canker pathogen of many economically important plants. The Eucalyptus isolates were compared with other Ceratocystis spp. based on sequence data generated from the ITS and 5.8S region of the rRNA operon. The results confirmed the identity of the Ceratocystis isolates from Eucalyptus as C. fimbriata and showed that they group with other C. fimbriata isolates from Brazil, South Africa and Europe. Inoculations on young Eucalyptus plants were conducted in the greenhouse and all three of the Congolese isolates tested, produced typical lesions in the bark and xylem. This study represents the first report of C. fimbriata as a pathogen of Eucalyptus in Africa. This is a serious new disease that will require considerable study in order to ensure that losses, caused by C. fimbriata, do not continue.  相似文献   

12.
Poplar rusts due to Melampsora larici‐populina (Mlp), M. allii‐populina (Map) and M. medusae f. sp. deltoidae (Mmd) are the most serious disease in Europe on cultivated poplars, that is, Populus × euramericana and P. × interamericana hybrids. These pathogenic species can be identified by the observation of morphological characteristics of urediniospores but this method is not appropriate for high‐throughput analysis and cannot be used on other spore stages, such as aeciospores or teliospores, that are morphologically similar. The aim of this study was to develop a rapid and sensitive molecular method based on PCR amplification that was able to specifically detect these species on various hosts for routine analysis. Three primer pairs ITS‐MLP‐F/ITS‐MLP‐R, ITS‐MAP‐F/ITS‐MAP‐R and ITS‐MMD‐F/ITS‐MMD‐R were designed within the internal transcribed spacer (ITS) sequences of ribosomal DNA to target Mlp, Map and Mmd, respectively, and their specificity were confirmed on a wide range of isolates and species. ITS‐MLP‐F/ITS‐MLP‐R and ITS‐MAP‐F/ITS‐MAP‐R primers proved to be highly specific to Mlp and Map, respectively, whereas ITS‐MMD‐F/ITS‐MMD‐R cross‐reacted with DNA from M. larici‐tremulae and M. pinitorqua. However, these species are not pathogenic on cultivated poplars that all belong to sections Aigeiros and Tacamahaca of the genus Populus. Specific Mmd primers proved to be very sensitive as a positive signal could be obtained with DNA extracts from 6 target urediniospores mixed with 800 000 urediniospores of Mlp. An internal amplification control (IAC) was included to discriminate false negative results due to the potential presence of inhibitory compounds in DNA extracts. ITS‐MMD‐F/ITS‐MMD‐R primers are therefore efficient for the detection of the quarantine pathogen Mmd on samples collected on poplar or larch and are fit for use in official tests. This new PCR assay has been used in routine for ten years, and Mmd has hitherto never been detected in commercial poplar nurseries in France.  相似文献   

13.
Ganoderma lucidum has been found to be a pathogen on a wide range of tree species in India. Because of large variations found in both macro‐ and microscopic characters, traditional identification and characterization methods are unreliable for this genus. We analysed nrDNA internal transcribed spacer (ITS) sequences of 52 isolates in the G. lucidum complex by the parsimony method, finding 17 lineages. The maximum parsimony analysis showed that the isolates of G. lucidum from the same host species had high similarity in ITS sequences, compared to isolates from other tree species. The result was also supported by high values of population differentiation parameters such as NST and FST values. Genetic analysis suggests the occurrence of host‐mediated genetic differentiation in G. lucidum isolates, which requires further investigation.  相似文献   

14.
Pseudodidymella fagi, described from infected leaves of Fagus crenata in Japan, has recently been spreading in Europe, where it causes leaf blotch of European beech Fagus sylvatica. In the years 2008–2016, an outbreak of P. fagi was observed on European beech in Switzerland, Germany and Austria, and it is reported here for the first time from Slovakia where it was detected in 2017. The identification of the pathogen is supported by the morphological analyses of material observed in vivo and in vitro and molecular analyses based on ITS sequences. Detailed morphological characterization of cultures based on European material, on F. sylvatica, is provided here for the first time.  相似文献   

15.
Taxus chinensis is a valuable tree with uses for timber, medicinal, ornamental and landscape purposes. Most importantly, it is a source of the anti‐cancer drug paclitaxel. In 2016, needle spot disease was observed on T. chinensis in Fujian Province of China. Five isolates of similar morphology were isolated from diseased samples. The pathogen was identified as Neopestalotiopsis clavispora based on morphological and cultural characteristics and confirmed by sequence analysis of the internal transcribed spacer region (ITS) and the large subunit ribosomal RNA gene (LSU). The pathogenicity of the isolates was confirmed by fulfilling Koch's postulates. To the best of our knowledge, this is the first report to indicate that the causal agent of needle spot disease on Chinese yew in China is N. clavispora.  相似文献   

16.
Teratosphaeria gauchensis and T. zuluensis both cause a stem canker of eucalypts that leads to serious damage in various parts of the world. Until recently, this disease was unknown in Portugal. Nevertheless, severe damage to Eucalyptus globulus has been observed in Portugal since 2006 when symptoms appeared as necrotic spots on young green stems and leaves, twig lesions, and dark oval‐shaped lesions on stems and trunks. The isolates from affected E. globulus tree plantations were identified using sequence data of the ITS1‐5.8S‐ITS2 and EF‐1α clusters, together with morphological characteristics. Based on these results, the causal organism was identified as T. gauchensis, which represents the first report of this pathogen from Portugal.  相似文献   

17.
Investigations on root and crown status of spruce and beech were carried out on selected trees in the ‘Werdenfelser Land’ area (Bavarian Alps, Southern Germany). In addition, the association of fine root pathogens of the genera Phytophthora and Pythium with the trees’ rhizosphere was studied. In a variety of stands representing various site conditions, soil and root samples were taken from 12 spruce (Picea abies) pairs and eight beech (Fagus sylvatica) pairs. Each pair consisted of a healthy and a declining tree as indicated by crown transparency. The root status was characterized using a set of parameters, and correlations between crown and fine root status were observed. In spruce, most parameters decreased significantly with increasing crown transparency, whereas in beech, correlations were less pronounced. The total number of lateral roots per cm small root (diameter 2–5 mm) was significantly lower in both species for declining trees compared to healthy trees. Pythium spp. were isolated from 15 of 24 soil samples taken from under spruce, and from eight of 16 samples from under beech. Phytophthora citricola was found in two beech stands only. Among the isolated species, Pythium anandrum, Pythium inflatum and Pythium acrogynum were identified according to morphological features. After polymerase chain reaction‐restriction fragment length polymorphism analysis, residual Pythium isolates were assigned to four different groups. No crown transparency‐dependent differences in isolation frequency were found. In soil infestation tests, all species tested caused root damage on both young spruce and beech plants, with P. citricola being the most aggressive pathogen. Additionally, Pythium‐infected beeches showed severe leaf chloroses and necroses. Due to their low isolation frequency, Phytophthora spp. are not considered to play a major role in the decline of spruce and beech in the investigated area. Pythium spp., however, were isolated frequently, showed pathogenicity towards the fine roots of spruce and beech, and are therefore considered to be at least contributing factors in the decline of Bavarian mountain forests.  相似文献   

18.
Decline phenomena of shrub species such as Quercus coccifera and Retama raetam have occurred throughout Tunisian forests since 2012. These evergreen shrubs have long been regarded for their medicinal and ecological interests. Therefore, their preservation as valuable forest resources is of great interest. However, information regarding aetiology of this disease is still scarce. Hence, the aim of this study was to identify and characterize the causal agents associated with disease symptoms in two Tunisian forests. Thirty-eight isolates were obtained from symptomatic Q. coccifera and R. raetam twigs. Morphological characterization and phylogenetic analysis of the internal transcribed spacer (ITS) region of the nuclear ribosomal RNA gene cluster and partial sequence of the translation elongation factor 1-alpha gene (tef1-α) allowed the identification of three Diplodia species namely Diplodia africana, D. seriata and D. pseudoseriata. Our findings revealed that the incidence of Diplodia species was significantly correlated to the altitude, the temperature and the rainfall. Pathogenicity test showed that all Diplodia isolates are pathogenic. However, D. africana revealed to be the most aggressive species toward R. raetam. These findings were the first record of D. seriata as fungal pathogen associated with Q. coccifera dieback and D. pseudoseriata and D. africana on R. raetam in Tunisia.  相似文献   

19.
This preliminary study identified the fungal endophytes of Sitka spruce (Picea sitchensis) in four Scottish plantations, analysed their recruitment possibilities and community structure across the sites, and identified the possible origins of the endophytes in this non‐native host. Although Sitka spruce is native to north‐western North America, it comprises a huge portion of Scottish forestry and is an economically vital timber tree. Needles from two age classes were collected and cultured for emerging endophyte isolates. Using a combination of morphological features and genetic sequencing of the nuclear ribosomal ITS regions of representative morphological types, 57 morphotypes were recorded which represented at least 15 different species, including a hypothesized sister species to the pathogen of Pseudotsuga menziesii in North America and Europe, Nothophaeocryptopus gaeumannii (previously P. gaeumannii) that was present at all sites tested. Diversity, recruitment, site, needle age and needle part effects are discussed. The phylogeny of Nothophaeocryptopus based on analysis of combined ITS and Tub2 sequence data is given in order to assess the relationship of the unknown endophyte to the Douglas fir pathogen N. gaeumannii.  相似文献   

20.
Bursaphelenchus fungivorus is reported for the first time in Portugal, identified as associated with Pinus pinaster bark and characterized on the basis of morphological and morphometrical characters for this species. Species identification was confirmed using restriction fragment length polymorphism analysis and sequencing of the internal transcribed spacer (ITS) regions of ribosomal DNA. Intraisolate genetic variability was detected among ITS sequences of the Portuguese B. fungivorus isolate. Phylogenetic analysis, obtained from multiple sequence alignment between ITS sequences of Bursaphelenchus species, revealed that the Portuguese B. fungivorus isolate clusters with other B. fungivorus isolates, forming a separate group close to B. seani highlighting a molecular proximity of these two species.  相似文献   

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