Forest Pathology最新文献

In Europe, Pinus sylvestris and Picea abies are the most common coniferous tree species used in commercial forestry, which rely on high-quality reproductive material for successful reforestation. Clear-cut harvested forest sites are often replanted using tree seedlings, which are produced in forest nurseries using seeds from seed orchards. However, incidences of fungal diseases in seedling production show that a better knowledge of seedborne fungi, including fungal pathogens, is needed to manage diseases in forest nurseries. This study aimed to assess seedborne fungal communities associated with commercial seeds of P. abies, P. sylvestris and Larix sp. seeds originated from geographically separated regions in Sweden, Belarus, Finland and Poland. Fungal communities were obtained first from the seed surface and then from the seed tissue. These were analysed using high-throughput sequencing of the ITS2 rDNA region. The results showed that fungal diversity and community composition differed between the seed surface and the seed tissue. Picea abies accommodated a higher fungal diversity than P. sylvestris. In addition, a strong host affinity of the fungal community composition on the seed surface and a weaker association in the seed tissue was found. Fungal communities on P. abies and P. sylvestris seed surface differed significantly between geographical regions, whereas no regional differences were found in the seed tissue. The seedborne fungal communities included a high proportion of plant pathogens, among which the most abundant were Sydowia polyspora (13.3%), Phoma herbarum (11.2%) and Sirococcus conigenus (3.8%). In conclusion, the results showed (a) characteristic fungal diversity and community composition between the seed surface and the seed tissue; (b) a host-specific fungal community composition on the seed surface and in the seed tissue; (c) regional difference in fungal communities on P. abies and P. sylvestris seed surface, thus the movement of seeds between different regions can contribute to the spread of fungal diseases; and (d) the presence of a high incidence of seedborne fungal pathogens which suggest a potential need of preventative or control measures to reduce the occurrence of these fungi on the seed surface.

Areca ipot, a Philippine endemic species, is categorized as endangered primarily due to habitat loss. A severe outbreak of a new leaf spot disease was observed on A. ipot seedlings in a nursery. Morphological and molecular features of isolates from diseased samples were identified as Neopestalotiopsis sp. and Calonectria sp. The pathogenicity of the isolates was confirmed by fulfilling Koch's postulates. This is the first report of Neopestalotiopsis sp. and Calonectria sp. causing leaf spot on A. ipot in the Philippines.

When monitoring the health status of various woody host plants in urban areas in Serbia, symptoms indicative of Cryphonectria-like infection were recorded on European hornbeam (Carpinus betulus) trees in the natural monument ‘Arboretum of the Faculty of Forestry in Belgrade’. One tree was affected by crown dieback while another one showed dieback of branches. Bark lesions were found on stems which contained numerous stromata with fruiting bodies and orange tendrils. Conidiomata were recorded solely in the infected tissue, producing hyaline, aseptate and bacilloid-shaped conidia with dimensions of 3.4 ± 0.46 × 1.2 ± 0.12 μm. In the isolation tests, all plated bark pieces were positive, and 25 isolates were obtained. Colonies on different agar media were white in the beginning, turning into orange-red colour during ageing. Optimum temperature for growth was 25°C and no growth was recorded at 30°C. A GenBank blast search and a phylogenetic analysis of ITS rDNA sequences of five representative isolates revealed their identity as Cryphonectria carpinicola. To our knowledge, this is the first report of C. carpinicola on hornbeam trees in Serbia, and implications of this finding are discussed.

Serpula himantioides is a widely distributed wood rot fungus that causes heart rot in various tree species. In Japan, heart rot associated with S. himantioides occurs in Chamaecyparis pisifera; however, its distribution within living trees and changes in its abundance as decay progresses remain unclear. In this study, we used a real-time polymerase chain reaction (real-time PCR) assay to specifically detect and quantify S. himantioides in wood. This allowed us to determine the distribution of S. himantioides in living C. pisifera and to monitor changes in its abundance as decay progressed. In addition, the mode of decay progression was characterized using nonhierarchical clustering. Serpula himantioides was detected from both decayed and undecayed heartwood and at sites as high as 12 m in the trunk, suggesting that it was widely distributed in the heartwood. The clustering analysis grouped samples into three clusters corresponding to the incipient, intermediate and advanced stages of decay. The abundance of S. himantioides increased from the incipient stage to the intermediate stage of decay and decreased at the advanced stage. The results quantitatively showed that intermediate stage decay moved up the trunk and replaced the part corresponding to the incipient stage as decay progressed. These results will be useful for devising methods for the early detection of heart rot caused by S. himantioides and to understand the progress of decay caused by wood rot fungi in living trees.

Sossah, F., L, et al. (2024). A critical review on bacterial black spot of mango caused by Xanthomonas citri pv. Mangiferaetndicae: Current status and direction for future research. Forest Pathology. 2024;54:e12860

Name of author number 6 on the above titled article was wrongly spelt. It was supposed to be FRED KORMLA ABLORMETI.

We apologize for this error.

Plant pathogens in the genus Phytophthora are a severe threat to forest plantations, ecosystems and tree nurseries. Especially in forests and natural ecosystems, there is a lack of effective measures to control and manage these pathogens. In this study, we conducted a systematic mapping review to collate evidence regarding the control and management of forest Phytophthora in different production settings and ecosystems. The study aimed to reveal possible knowledge gaps, thus guiding future research priorities. We extracted information from nine databases, limiting the search to studies published during the time period from January 2010 to December 2022. The articles were shared between three reviewers who classified the reports using a set of inclusion/exclusion criteria. A total of 561 articles were included and mapped in a database using pre-defined coding, and critically appraised for relevance and reliability. The analysis showed that biological or bio-based measures were the most studied interventions, followed by genetics or breeding programmes, whereas chemical and silvicultural management approaches were less studied. Most of the studies were conducted in Europe, North America, Australia and New Zealand. Phytophthora cinnamomi has been the most studied species followed by P. ramorum. We discuss the current knowledge gaps in the implementation of existing research, likely due to a lack of holistic understanding of the processes over time and space, and suggest future research that is needed to manage Phytophthora in forest ecosystems.

The occurrence of black crust, a disease previously considered secondary, has become a cause for concern due to early leaf fall in rubber trees (Hevea brasiliensis). This study aimed to identify sources of resistance to black crust in 21 clones of rubber trees in a clonal garden. To achieve this, the disease severity was evaluated through eight assessments conducted over a 2-year period. In each evaluation, 15 leaflets from three different parts of the plant (bottom, middle third and crown) were randomly collected, resulting in a total of 45 leaflets per plant. These leaflets were then taken to the laboratory, and the software Leaf Doctor was used to measure the percentage of leaf area exhibiting symptoms of black crust. The results were analysed using the Scott-Knott test at a 5% probability level. The clones with the highest infected leaf area observed during the evaluations were IAC300, IAC418, IAC503, PB311 and RRIM600. Clone IAC511 did not show any symptoms of the disease in any of the evaluations. Clones IAC301, IAC411, IAC501, IAC507 and IRCA111 exhibited low percentages of affected leaf areas. Additionally, this study revealed the progression of the disease over the evaluation period. The infection initially starts on the youngest leaves (crown) in March and subsequently intensifies in the middle third of the plant, corresponding to the youngest leaf previously infected in the crown. Furthermore, environmental data collected in the experimental area over the 2-year evaluation period indicated that the disease manifests with greater severity when the average temperatures fall below 25°C after periods of heavy rainfall, followed by dry periods with low relative humidity. The data presented in this study significantly contribute to the management of this disease in the field by identifying clones where the disease manifests with lower severity.

Tectona grandis is a vital hardwood tree species with substantial industrial and economic importance. From 2020 to 2021, an unusual leaf blight disease was observed in T. grandis saplings planted in the Nursery of the Central Agroforestry Research Institute (CAFRI), Jhansi, India. Disease incidence was recorded as 50%–70% with 40%–82% severity over two consecutive years on over 1000 saplings. The leaf blight disease was extensive, leading to defoliation of young leaves and mortality of teak saplings in the nursery. The pathogen was identified as Alternaria alternata following standard laboratory procedures and sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal RNA (rRNA). The pathogenicity of two isolates, A. alternata TgAa1 and TgAa2, was proven under greenhouse conditions. Phylogenetic analysis revealed the close association of TgAa1 and TgAa2 with other pathogenic A. alternata strains in the NCBI database. A. alternata is considered a severe foliar pathogen, known to cause leaf spot and leaf blight diseases in many annual and perennial plant species. Correct diagnosis and prevention are emphasized to contain the spread of teak leaf blight to other regions in India. This is the first report of A. alternata causing Tectona grandis leaf blight in the Bundelkhand region of India.

Teratosphaeria nubilosa is the predominant causal agent of Teratosphaeria leaf disease (TLD) in experimental plantations of E. globulus in Brazil. It exhibits slow vegetative growth and lack of sporulation in in vitro culture, making it difficult to obtain enough ascospores for mass inoculation. This study aimed to establish an inoculation method based on ascospore ejection from naturally infected leaves and use it to assess the response to T. nubilosa of eucalypt species and interspecific hybrids. First, the optimal temperature and incubation time for ascospores ejection from naturally infected E. globulus leaves were determined in vitro. Then, these optimal conditions were used to assess the response of eight eucalypt genotypes to T. nubilosa inoculation using ejected ascospores. The infected leaves were placed above (T1), above and under (T2) or under (T3) the plants to be inoculated. Significant differences in disease incidence, disease severity and plant defoliation were observed among genotypes and inoculation treatments. Plants exhibited higher incidence, more severe symptoms and more defoliation when exposed to T2. E. globulus and E. globulus × E. nitens clones were the most susceptible whereas an E. benthamii clone was immune. The sources of resistance identified in this work can be used in hybridization programmes with E. globulus to obtain interspecific hybrids expressing resistance to T. nubilosa and retaining the desirable traits for planting in temperate climates. The inoculation method optimized in this work could be used for small and medium-scale screening of Eucalyptus spp. resistant to TLD. However, periodic validation of the species and genotype of the fungus associated with the naturally infected leaves used for inoculation and confirmation of the resistant phenotype of the selected eucalypt clones or progenies through experimental replications over time must be conducted.

Dieback of dwarf pine scrub (Pinus mugo subsp. mugo) shoots can limit the growth of this species in subalpine areas of the Carpathian Mountains. In July 2023, extensive shoot decline was observed in P. mugo patches in the West Tatra Mountains in southern Poland. Symptomatic shoots showed shoot tip dieback and red-brown needle discoloration. Internal symptoms included dark discoloration of the pith parenchyma and necrotic lesions in shoot periderms. In this study, we described the symptoms of P. mugo shoot dieback and surveyed the culturable fungi from asymptomatic and symptomatic P. mugo shoots, as well as the bases of needles growing from shoots. In addition, we conducted phylogenetic analyses to distinguish between potential cryptic species of Sydowia polyspora. The dwarf pine scrub shoots and needles were sampled from four patches in the Polish Tatra Mountains. In total, 128 distinct taxa were identified. Ascomycota was dominant, representing 96.6% of the isolates. Among the taxa identified, Sydowia polyspora crypt. sp. I, Lachnellula calyciformis, Mollisia sp. 8, Tympanis sp., Epicoccum mezzettii, E. nigrum, Infundichalara sp., Lophium mytilinum, Cytospora sp., Soosiella sp., Cladosporium westerdijkiae and Hendersonia pinicola were most frequently isolated. In most cases, tissue type and sample site significantly affected the abundance and composition of colonizing fungi. Only S. polyspora was found consistently in all sample types, suggesting that this fungus may be responsible for the shoot dieback of P. mugo. Phylogenetic analyses demonstrated that S. polyspora should be treated as a species complex containing at least four cryptic species (referred to as groups I–IV), that are highly host-specific to different conifer species. We also found several other well-known pathogens, namely Allantophomopsis pseudotsugae, Botrytis cinerea, Cytospora sp., Fusarium sp., Sirococcus conigenus and Tympanis sp., which may cause considerable damage to Pinus spp. shoots. Among them, only Cytospora sp., and Tympanis sp. were found often. This is the first comprehensive survey of the fungi associated with extensive shoot dieback of P. mugo in the Carpathian Mountains, and this research led to the discovery of numerous new fungal species associated with P. mugo.