Fungi that destroyed a Populus tremula stand in Lagow Lubuski

The decay of a 20-year-old stand of Populus tremula growing on old agricultural waste land was observed from 1975 to 1981. There were 16 species of pathogenic and saprophytic fungi found on dying and dead trees, of which Heterobasidion annosum (Fr.) Bref. and Cytospora chrysosperma Fr. were the most frequent. The circumstances of combined action of both fungi in the disease process are discussed.     

First report of Cryptosphaeria pullmanensis as causal agent of Cryptosphaeria canker of Populus nigra in Iran

A diatrypaceous fungus was isolated consistently from cankers on Populus nigra trees showing dieback symptoms in Kohgiluyeh Boyer‐Ahmad, Zanjan and Esfahan provinces in Iran. Morphological characteristics and phylogenetic analyses of the ITS region of the rDNA identified the taxon as Cryptosphaeria pullmanensis. Pathogenicity tests conducted in potted 3‐month‐old cuttings of P. nigra confirmed Koch's postulates and revealed that C. pullmanensis caused canker on this host. This is the first report of C. pullmanensis causing a canker disease on P. nigra in Iran.     

Characterization and pathogenicity of six Cytospora strains causing stem canker of wild apple in the Tianshan Forest,China

Cytospora species are capable of causing destructive cankers of stems belonging to a wide range of woody plant species. In severe cases, cankers may lead to dieback of twigs and branches. Little is known about the Cytospora species causing canker disease of wild apple (Malus sieversii) trees in the Wild Fruit Forest Reserve in Tianshan Forest, Xinjiang Uygur Autonomous Region, China. In this study, six Cytospora isolates belonging to two species were isolated from cankerous lesions of wild apple twigs. Based on multi‐locus phylogenetic analysis using three DNA markers (ITS, tef1‐α and tub2) and morphological characterization, these isolates were identified as Cytospora mali and Cytospora parasitica. Temperature trials (15, 20, 25 and 30°C) showed that the optimal growth temperature for six isolates was 25°C. At a variety of temperatures, C. mali isolates tended to grow faster than isolates of C. parasitica, with the C. mali isolate, EGI1 performing better than others with regard to growth rate. Morphological observations showed that these species exhibited a single locule without conceptacles, and the conidia length was 3–5 μm. In vitro inoculation trials of twigs and leaves of M. sieversii seedlings revealed that the C. mali isolates were highly virulent phytopathogenic fungi, whereas the C. parasitica isolates were less virulent. The isolate EGI1 was the most virulent isolate among the six isolates. This paper presents the first report of pathogenic Cytospora spp. of the M. sieversii Tianshan Wild Fruit Forest Reserve of Yili, Xinjiang in China. It will aid in the understanding of how apple tree cankers are induced and provide disease management guidelines for M. sieversii forest conservation.     

Neofusicoccum parvum associated with pomegranate branch canker in Iran

Pomegranate (Punica granatum) is native to Iran and neighbouring countries and is negatively affected by a wide range of diseases. Canker and dieback diseases caused by Cytospora punicae and members of the family Botryosphaeriaceae are the main trunk diseases on pomegranate. In summer 2017, progressive dieback of branches on some young pomegranate trees was observed in orchards of the Gorgan Region (Golestan province, Northeast Iran). Fungal colonies with similar colony colour were isolated from symptomatic tissues. The identity of the causal agent was determined as Neofusicoccum parvum, based on a polyphasic taxonomic approach including morphological features of conidiomata and phylogenetic inference based on the ITS‐rDNA region and translation elongation factor 1 alpha (tef1‐α) gene. Koch's postulates were fulfilled using an excised shoot method. This study provides the first report on the occurrence of N. parvum as a cause of branch canker on pomegranate in Iran.     

Fungi in leaves,twigs and stem bark of Populus tremula from northern Spain

Fungal species were recorded from Populus tremula leaves, twigs and bark (trunk) at eight sites in the northern region of Spain, with the aim of evaluating the effect of sampling site, sampling tissue and isolation method on the frequency and species distribution of the fungi recovered from necrotic and healthy tissues. Two different isolation methods were used: the first consisted of finding fruitbodies on plant tissues after incubating them in wet and warm conditions, and the second included growing mycelia from plant fragments plated on potato dextrose agar (PDA). A total of 48 fungal species were isolated from 960 plant fragments. Cytospora chrysosperma, previously reported to be a pathogen of poplar, was recovered very frequently and was recorded as much in healthy as in dead or dying tissues. Cladosporium maculicola, Elsinoe veneta, Alternaria alternata, Aureobasidium pullulans and Pollaccia radiosa were also frequently isolated. The isolation frequencies from necrotic and healthy plant tissues were significantly different between sites and isolation methods. The incubation in moist chambers revealed significantly more fungal isolates and a higher species richness (38 species) than isolations on PDA. However, 16% of the fungal species were exclusively recorded from cultures. Therefore, a combination of several isolation methods is recommended for surveys of fungal communities associated with trees.     

Canker disease of willow and poplar caused by Cryptosphaeria pullmanensis recorded in China

A new canker disease of Salix alba and Populus alba has been observed in Xinjiang, China. Black circular spots on dead branches and stems are the symptoms of the disease. Sixty‐seven isolates recovered from Salix matsudana, S. alba and Populus alba were identified as Cryptosphaeria pullmanensis based on morphological features and multigene phylogeny. Pathogenicity tests were performed on S. alba and P. alba stems using the C. pullmanensis isolates. Cankers on and Cryptosphaeria pullmanensis of C. pullmanensis from the stems fulfilled Koch's postulates and confirmed C. pullmanensis as the causal agent of the canker disease. C. pullmanensis is characterized by its yellow stromatic tissue surrounded by a black conceptacle with regularly arranged multiple locules sharing common walls and hyaline, allantoid, aseptate conidia (mean size 7.42 × 1.72 μm). This is the first report of C. pullmanensis causing Cryptosphaeria canker in China, and S. alba and P. alba are new host records for C. pullmanensis.     

Teratosphaeria gauchensis associated with trunk,stem and foliar lesions of Eucalyptus globulus in Portugal

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.     

Development and use of new sensitive molecular tools for diagnosis and detection of Melampsora rusts on cultivated poplar

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.     

A new leaf disease on Populus euphratica in south‐western Iran

During the winter of 2012, a leaf spot disease was observed on Euphrates poplar (Populus euphratica) in the forest areas of Khuzestan province, south‐western Iran, causing significant damage in the Karun's riverside forests. Symptoms consisted of necrotic dark brown, circular to oval, 5‐ to 10‐mm spots on both surfaces of the leaves. A fungus having distinct dictyospores similar to those produced by Alternaria spp. was observed. The morphological characteristics, as well as the phylogenetic analysis of the internal transcribed spacer (ITS1‐5,8S‐ITS2) region, confirmed the identity of the strains belonging to the species Alternaria alternata. Pathogenicity tests were conducted on the alive leaves of P. euphratica on the young branches, as well as on the detached leaves in Petri dishes, through inoculation with spore suspension. Target spot symptoms similar to those observed in naturally infected leaves were developed on the inoculated leaves seven to 10 days after inoculation in both the inoculation procedures. A. alternata was consistently re‐isolated from the spots. Interestingly, similar symptoms were observed 7 days after detached leaf treatment with droplets of 15‐day‐old fungal culture filtrate, suggesting the production of pathotoxic compounds by the fungus. To our knowledge, this is the first report of A. alternata causing leaf spot on Euphrates poplar in Iran.     

Newly recognized bacteria involved in trunk scab and canker of white and hybrid poplars

In a 4‐year‐old collection of native Italian Populus alba, growing in the eastern Po valley, many trunks showed severe symptoms characterized by brown spots, similar to trunk scab and/or by cankers. Canker‐like growths, often with gall‐like‐formations in the earlier developmental phases were also found on some clones of P. trichocarpa and their hybrids, as well as on P. deltoides growing in several Northern Italian nurseries. Bacteria and fungi present in the affected tissues and potentially involved in the disease were examined. No fungi were detected, however, several species of bacteria were isolated and identified: Pseudomonas mendocina and Erwinia herbicola group, from the brown spots; Erwinia carotovora sub sp. carotovora and, occasionally, E. herbicola group, from cankers. Only E. carotovora sub sp. carotovora produced clear symptoms of canker when artificially inoculated on young plants of different poplar species. This is the first time this symptomology on poplar species has been clearly related to E. carotovora sub sp. carotovora.     

ITS-based comparison of endophytic mycota in twigs of native <Emphasis Type="Italic">Populus nigra</Emphasis> and cultivated <Emphasis Type="Italic">P. x euramericana</Emphasis> (cv. I-214) stands in Northern Spain

Context  

The European black poplar (Populus nigra) is considered one of the most seriously endangered indigenous tree species. However, the total area covered by monoclonal plantations of hybrid poplar is growing, because of the high profitability of these trees.     

Effects of genetically modified Burkholderia pyrrocinia JK‐SH007E1 on soil microbial community in poplar rhizosphere

It is important to assess the biosafety of genetically engineered bacteria before release into the environment. In a previous study, the genetically engineered bacterium Burkholderia pyrrocinia JK‐SH007E1 was developed, showing biological control activity against a poplar canker disease. In the present work, the potential effects of B. pyrrocinia JK‐SH007E1 on soil microbial diversity and population structure in the poplar rhizosphere were assessed. The micro‐ecological effects of JK‐SH007E1 on soil microbial communities were investigated using substrate utilization assays (Biolog EcoPlate), enzyme activity assays and 16S rRNA sequencing to research species diversity and population structure of soil microbial communities. The genetically engineered isolate JK‐SH007E1 improved the functional diversity, soil enzyme activities and alpha diversity of soil microbial communities. However, the positive effects after inoculation attenuated with time, except for soil enzyme activities. Treatments with JK‐SH007 or JK‐SH007E1 were not different in impacts on soil enzyme activity and functional diversity of soil microbial communities. The results demonstrated that inoculation of JK‐SH007E1 into the poplar rhizosphere posed little or no threat to soil microbial communities in the long term. This work provides an additional insight into the effects of genetically engineered JK‐SH007E1 on the environment during long‐term use as biological control against poplar canker diseases.     

Cultural and PCR‐based detection of Septoria musiva in inoculated hybrid poplar stems

The fungal pathogen Septoria musiva can be difficult to isolate from cankers that result from its colonization of poplar stems, and its persistence in these cankers has not been well studied. In order to compare cultural and polymerase chain reaction (PCR)‐based assays for detection of S. musiva in cankers, stems of susceptible hybrid poplar clone NC11505 were wounded and inoculated in August 2003. At 8, 16, 24 and 32 weeks after inoculation (October and December 2003, February and April 2004, respectively), 110 inoculated stems (plus controls) were harvested and a semiselective culture medium was used in attempts to detect the pathogen in bark and wood. Six chips of bark and six chips of underlying wood from one half of each canker were incubated on the semiselective medium for 2 weeks until pycnidia and conidia of S. musiva could be identified. The number of positive cankers and positive chips (out of six attempts per tissue per canker) was recorded. The remaining halves of cankers from subsets of 70 inoculated stems (plus controls) of those harvested in October 2003 and April 2004 were tested using a PCR‐based assay. Three chips of bark and three chips of underlying wood were ground, and DNA was extracted and then amplified using S. musiva‐specific primers designed from the internal transcribed spacer (ITS) region of nuclear rDNA repeats. The number of positive cankers and positive chips (out of three attempts per tissue per canker) was recorded. For both assays, the number of positive cankers and the number of positive chips per canker decreased with time. Using either assay, however, the pathogen was still detected from at least 49% of cankers at 32 weeks after inoculation.     

First report of Teratosphaeria zuluensis causing stem canker of Eucalyptus grandis in Uganda

Teratosphaeria stem canker is one of the most important diseases to have emerged on non‐native plantation‐grown Eucalyptus trees globally. In 2012, Eucalyptus grandis trees with typical Teratosphaeria stem canker symptoms were observed in Uganda. Multigene sequence analyses of isolates from these cankers led to the identification of T. gauchensis, previously recorded in Uganda, and T. zuluensis. This study represents the first report of T. zuluensis in Uganda. Furthermore, this is the first report of the co‐occurrence of T. zuluensis and T. gauchensis in a single area.     

Biochemical responses associated with induced resistance to Colletotrichum acutatum in Pinus radiata seedlings treated with methyl jasmonate and Trichoderma spp.

The effect of Trichoderma (T. atrobrunneumFCC320 and T. atrovirideLU633) and/or methyl jasmonate (MJ) on resistance to terminal crook (Colletotrichum acutatum) and on seedling biochemistry was investigated in radiata pine (Pinus radiata) seedlings. Seedlings were germinated and grown in Trichoderma‐amended or non‐amended media for 3 months and then sprayed with 2.25 mM MJ 1 week before inoculation with C. acutatum. The incidence and severity of terminal crook in the seedlings treated with MJ and Trichoderma+MJ were lower than in Trichoderma‐treated and Trichoderma‐untreated seedlings. The MJ‐induced resistance response was concomitant with an increase in the concentrations of the monoterpenes α‐pinene, β‐pinene, β‐phellandrene, camphene and myrcene in needles, and also α‐pinene, β‐pinene and camphene in stems. The concentrations of α‐pinene, β‐pinene and camphene were elevated from at least 1 week until 4 weeks after MJ application, compared with those in non‐MJ counterparts. Trichoderma alone did not affect monoterpenes, but the concentrations of α‐pinene, β‐pinene and camphene were greater in needles of Trichoderma+MJ than in MJ‐treated seedlings after 28 days. Total phenolic concentration in needles and peroxidase activity in stems were twofold greater in MJ‐treated seedlings than in non‐MJ seedlings over the same period. None of the treatments affected the activity of peroxidase in needles. It is proposed that the accumulation of monoterpene and phenolics and the induction of peroxidases contribute, in part, to MJ‐induced resistance to terminal crook in radiata pine seedlings.     

Eutypella canker of maple: first report from Germany and situation in Austria

Eutypella canker of maple, caused by Eutypella parasitica (which is native to North America), is reported for the first time from Germany. From 2013 to 2015, this perennial canker disease was recorded on 105 maple trees in Munich. Six maple species were affected: Acer pseudoplatanus, A. campestre, A. platanoides, A. cappadocicum, A. heldreichii ssp. trautvetteri and A. hyrcanum. Occurrence on the latter three species represents new host records for E. parasitica. In Austria, Eutypella canker was newly discovered on two trees at a second locality in 2011, and it is now known to occur on seven A. pseudoplatanus trees at two localities, which are separated nearly 150 km. A. pseudoplatanus was the most frequent host of E. parasitica in Munich and Austria, which is in agreement with previous studies in Europe. The identity of the causative pathogen as E. parasitica was verified by ITS rDNA sequencing of fungal cultures obtained from cankers in Munich and at both Austrian localities. The presence of large and old cankers in both countries suggests that introduction of E. parasitica dates back a long time, probably several decades. The new records of Eutypella canker in Germany and Austria show that the disease is more widely distributed in central Europe than previously recognized.     

First report of botryosphaeriaceous fungi causing canker on Cedrela fissilis and leaf spots on Cariniana estrellensis in forest nursery in Brazil

Cariniana estrellensis and Cedrela fissilis are native forest species from Brazil that are widely used for arborization of parks and recuperation of degraded areas. The production of seedlings from these two forest trees in nurseries is severely affected by fungal diseases. Morphological identification, sequencing analysis of three gene regions (TEF+ACT+ITS or TEF+TUB2 + ITS) and pathogenicity tests confirmed that fungi belonging to Botryosphaeriales are the aetiological agent of the diseases. This is the first report of Phyllosticta capitalensis causing leaf spots on C. estrellensis and Botryosphaeria dothidea causing canker on C. fissilis in forest nurseries in Brazil.     

CONTROL TECHNIQUE OF BACTERIAL CANKER OF POPLAR

The poplar bacterial canker caused by Erwinia sp is a serious disease spreading inmost parts of Northeast China,where poplars are cultivalted.The disease seriously infects thosepoplars belonging to section Aigeiros or the intersection hybrids of section Tacamahaca and section Aigeiros and their clones.Five fine poplar cultivars resistant to the bacterial canker have been ob-tained by screening tests.They are Lz_2(Populus simonii×nigra var.italica),A_(15)(P.×sp.)613(P.×sp.),A_(102)and A_(98)(P.simonii×sp.)T following chemicals are obviously effective,such as:50％DT germicide ,40％ XF-136 and 10％ C.C.M.A.or 12.5％ ramphencol and 50,000 ppm/mlvalidamycin,with which the stems or roots can be watered.     

杨树烂皮病菌颉颃菌株的初步筛选与分子鉴定

对杨树烂皮病菌的平板对峙试验结果表明,6种颉颃真菌中木霉的抑菌率最高为51%,而颉颃细菌4个菌株的抑菌率均在60%左右,说明颉颃细菌的抑菌效果明显高于颉颃真菌;对B137等4株颉颃细菌的分子鉴定认为,1株为枯草芽孢杆菌(Bacillus subtilis),2株为解淀粉芽孢杆菌(Bacillus amyloliquefaciens),还有1株为苏云金杆菌(Bacillus thuringiensis,Bt);解淀粉芽孢杆菌和苏云金杆菌对杨树烂皮病菌有较好的颉颃效果。