Forest Pathology最新文献

Plants of the genus Myrciaria are commonly cultivated in the northern region of Brazil for fruit production. Symptoms of leaf spot in camu-camu (Myrciaria dubia) trees are frequently observed. The objective of this study was to identify the etiological agent associated with anthracnose in camu-camu using the concept of morphological and phylogenetic analyses. Leaves with symptoms of anthracnose were collected from camu-camu plants in the state of Roraima, Brazil. Morphological identification; sequencing analysis of CAL, GAPDH, CHS-1 and TUB2 gene regions; a pathogenicity test and reisolation of the fungus from symptomatic artificially inoculated plants confirmed C. theobromicola as the causal agent of the disease. This is the first record of C. theobromicola causing anthracnose in camu-camu in Brazil.

Bursaphelenchus mucronatus Mamiya & Enda, 1979 is a wood nematode widely distributed over Palearctic coniferous forests. It has two subspecies, that is, B. mucronatus mucronatus and B. mucronatus kolymensis, which present molecularly different East Asian and European genotypes, respectively. The European subspecies is found mainly in Europe and Siberia, while the East Asian subspecies occupies mostly Eastern regions of Asia. However, local isolates of both subspecies have been occasionally reported from various localities in Europe and Asia. Our field isolation and molecular (DNA ITS-RFLP) identification of 21 recently collected populations of B. mucronatus revealed only 4 isolates representing clearly East Asian or European genotypes, while the remaining 17 isolates showed intermediate genotypes with electrophoretic band characters of both the above types. Further individual crossbreeding, in vitro, of nematodes representing European, East Asian, and intermediate genotypes provided experimental evidence for the process of intraspecific hybridization between both subspecies, spontaneously taking place in the forest. Such a widening of the B. mucronatus genetic variation may have its effect on a range of reported in the literature direct interactions between this native, nonpathogenic nematode species and the genetically similar, causative agent of the pine wilt disease B. xylophilus which can colonize the same host trees, use the same insect vectors, compete, and crossbreed inter-specifically.

The chestnut gall wasp (CGW) Dryocosmus kuriphilus is a serious pest of chestnuts (Castanea sativa) in many chestnut growing areas in Turkey. Out of 200 galls randomly collected from four different areas of Yalova and Giresun provinces, 116 showed necrosis, while 84 were asymptomatic. Fungi associated with the necrotic and asymptomatic galls were determined based on morphology and DNA sequencing. Gnomoniopsis smithogilvyi, Colletotrichum acutatum, Penicillium glabrum, Botrysphaeria dothidea, Trichoderma atroviridea, and Botrytis cinerea were found on 49, 11, 10, 8, 7, and 1 necrotic galls, respectively. On the other hand, G. smithogilvyi, Fusarium proliferatum, Aureobasidium sp., C. godetiae, Rhizopus stolonifer, P. glabrum, C. acutatum, Cladosporium sp., Alternaria spp., and Aspergillus sp. were hosted by 37, 35, 15, 14, 12, 8, 6, 3, 1, and 1 asymptomatic galls, respectively. Seven fungi, G. smithogilvyi, C. acutatum, F. proliferatum, B. dothidea, Cryphonectria parasitica, Diplodina castanea, and Penicillium sp. were isolated from 31, 6, 4, 1, 1, 1, and 1 of the dead larvae of D. kuriphilus, respectively. Two fungi, F. proliferatum and Penicillium sp., were isolated from the adults of Torymus sinensis, a parasitoid of CGW. Pathogenicity of G. smithogilvyi, C. acutatum, and F. proliferatum detected from dead larvae of D. kuriphilus and galls was tested on young chestnut saplings: the former two produced necrosis while the third one did not.

Leaf chlorosis and root browning with root rot were observed on mature Cinnamomum camphora (Linn) Presl between 2021 and 2023 in Hangzhou, Zhejiang province, China. Three strains of fungi consistently isolated from the diseased roots were selected for identification and pathogenicity test. They were identified as Fusarium decemcellulare Brick based on the morphology and phylogenetic analysis using combined sequence data. The pathogenicity of the strains was verified by inoculating on C. camphora seedings in pots. Fusarium decemcellulare was reisolated from the artificially inoculated roots of C. camphora seedings. To our knowledge, this is the first report that F. decemcellulare causes root rot on C. camphora worldwide and its potential threat should be monitored.

Wood-decay fungi are major contributors to damage wood and logs, resulting in substantial economic losses. This study assessed the decay caused by Trametes flavida and Daldinia eschscholtzii on Gmelina arborea, Samanea saman, Albizia lebbeck, Acacia auriculiformis and Swietenia mahagoni. Both fungi demonstrated their ability to decay wood. However, the extent of damage varied significantly among the tested hardwood species. Findings showed that Trametes flavida caused greater wood mass and density loss than Daldinia eschscholtzii. Among the tested hardwood species, G. arborea was found to be more susceptible to the decay fungi, followed by S. saman, A. lebbeck, A. auriculiformis and S. mahagoni, respectively. The study will encourage the scientific management of timber and logs in sawmill depots to minimize the decay of wood and incurred economic loss.

Fusarium circinatum is an important fungal pathogen of Pinus species utilized in commercial forestry worldwide. In Colombia, it was first found on nursery plants and later in plantations associated with basal cankers on young trees. In this study, we explored the population diversity of the pathogen in Colombia by analyzing 136 isolates collected from diseased nursery plants (2005–2007) and plantation trees (2017 and 2020). These were sourced from different geographical regions and Pinus species. Genotyping was performed using 10 microsatellite markers, while mating types were identified with PCRs targeting the MAT1 locus. Using microsatellites, a total of 33 multilocus haplotypes were detected. Genetic diversity indices showed low levels of diversity in both the overall collection and in specific collection groupings. The data also suggested that a small number of isolates had unique origins in the country (p < .05), and relatively low levels of population differentiation were detected between the nursery and plantation collections. All the isolates were scored as having the MAT1-1 mating type, and no evidence for the random association among microsatellite alleles (p = .0001) was found. Overall, these data suggest that F. circinatum was introduced into Colombia a small number of times, likely on seed for nursery production. Furthermore, the data also indicate that the pathogen has spread from nurseries to the plantations via asexual reproduction and on asymptomatic plants. This has resulted in a highly clonal F. circinatum population in Colombia that has resulted from accidental introductions of the pathogen into a production nursery.

Both Ceratocystis lukuohia and C. huliohia have been associated with Rapid ʻŌhiʻa Death (ROD), an emerging threat to ʻōhiʻa (Metrosideros polymorpha), a keystone forest tree species. The vascular wilt disease caused by C. lukuohia has been recently described and is responsible for the widespread ROD epidemic on Hawai'i Island. However, the role of C. huliohia in ROD development and tree death is not clear. Artificial inoculation of field-grown ʻōhiʻa with C. huliohia and dissections of naturally infected, early symptomatic forest trees were conducted to confirm pathogenicity on field grown trees and the pattern of internal colonization. In two trials, crowns of trees with main stems inoculated with C. huliohia were visually healthy at the time of tree harvest after 43–55 days in the first trial, and after 91 days in the second trial. However, elliptical inner bark cankers underlain by reddish-brown xylem were associated with the inoculation points. Similar canker and stain symptoms were found on stems and branches of ʻōhiʻa (24–26 cm trunk diameter) naturally infected by C. huliohia. This xylem stain manifested as multiple distinct elliptical cankers or the coalescing of multiple cankers. The pathogen was commonly isolated from the perimeter of the stained outer sapwood and to a depth of 4 cm. The coalescence of multiple cankers was associated with the crown symptoms observed on the naturally infected forest trees that were dissected. Multiple C. huliohia infections that lead to coalescing cankers which subsequently girdle stems likely occurs over one or more years compared to the shorter time (e.g., months) required for C. lukuohia-caused death to occur.

Bacterial black spot (BBS) of mango, caused by the bacterium Xanthomonas citri pv. mangiferaeindicae, is an emerging disease affecting mango-producing areas in Asia, Africa, Oceania, and the Americas. The disease spreads primarily through wind-driven rain and farm implements, and its host range is limited, affecting mango, cashew, and pepper plants. BBS is characterized by dark, angular lesions with elevated borders on infected leaves and fruits in the lower and upper parts of the tree canopy. Infected plants display numerous tiny water-soaked black lesions on leaves, fruits, and stems. Early symptoms on leaves include tiny, veined, water-soaked patches with angular black dots and occasionally chlorotic spots. Managing BBS presents challenges, but various control measures have shown effectiveness in different regions. Integrated disease control measures, such as cultural methods and removing diseased plant parts, could further reduce BBS prevalence in the field. This paper reviews the detrimental effects associated with the disease, while also offering a concise overview of the existing body of research concerning BBS and its implications for mango cultivation.

Leaves of Schima superba with typical anthracnose symptoms were collected in July 2023 in Zhejiang Province, China. The fungi isolates were conducted from the margins of the lesions, and three isolates CA13, CA18 and CA27, were selected for identification and pathogenicity test. Based on morphological characteristics and phylogenetic analyses of the partial regions of internal transcribed spacer (ITS), actin (ACT), calmodulin (CAL), beta-tubulin (TUB2), and glyceraldehyde-3-phosphate-dehydrogenase sequences (GAPDH), the fungi were identified as Colletotrichum fructicola. Inoculation of the fungi on healthy S. superba leaves showed symptoms similar to those observed in the field, and the fungi were re-isolated from the lesions. To the best of our knowledge, this represents the first report of C. fructicola causing anthracnose on S. superba worldwide.

In the summer of 2023, small-leaved lime trees (Tilia cordata) in the capital city of Warsaw were found to be dying along transport routes. The stem fragments collected for analysis showed the presence of necrosis near larval galleries caused by Agrilus viridis (L.). After a detailed microbiological analysis of both the tissues taken directly from the necroses and from the larval galleries, the presence of five different bacteria was confirmed, including Gibsiella quercinecans, which is responsible for the phenomenon of oak stand dieback known as Acute Oak Dieback. The pathogenicity tests carried out confirmed that this bacterium is also capable of causing necrosis on lime trees. The fact that this bacterium was found in the larval galleries of the polyphagous A. viridis could also indicate that it was vectored into the lime tree from other species, for example, oaks. The results obtained are the first report on the occurrence of G. quercinecans on lime trees in Poland.