Forest Pathology最新文献

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.

Biscogniauxia species are opportunistic pathogens primarily associated with Quercus species dieback in the Mediterranean basin. Among these species, Biscogniauxia mediterranea stands out as the only species previously documented in Tunisia, affecting Quercus suber and Erica multiflora. This study unveils a novel finding, reporting the presence of Biscogniauxia rosacearum on Strawberry trees in Tunisia. The identification of B. rosacearum isolates was confirmed based on DNA sequence data (ITS, TUB2 and ACT) and morphological traits. Artificial inoculation trials on leaves confirmed the pathogenicity of the fungus towards Arbutus unedo. This finding emphasizes the significance of implementing proactive measures to effectively combat this pathogen because of the polyphagous nature of Biscogniauxia species that raises concerns about its potential spread within vulnerable hosts in Tunisian oak forests.

Fungi of the genus Cryphonectria are of special interest to tree pathologists because they cause bark disease in numerous species of the Fagaceae and Betulaceae. Despite this special attention, several Cryphonectria species were not recognized as such for a long time. This also affected the identity of eight isolates with outdated names that have been deposited in our laboratory since 1954. The present study reconstructs the history of the Cryphonectria cultures M282–M289 using primary bibliographic sources. To verify the species identity, all isolates were DNA barcoded and taxonomic affiliation was assessed using a phylogenetic approach. The taxonomic identity combined with the history of the isolates confirms that the chestnut blight epidemic (Cryphonectria parasitica) in Spain was caused by the planting of Asian chestnuts and that the first documented case of bark canker in 1940 was caused by Cryphonectria radicalis on Japanese chestnuts imported from France. The history of isolate M289 could be traced back to CBS 165.32, which proved to be the oldest preserved isolate of the rare Cryphonectria naterciae, confirming the presence of this fungus in Europe for at least 100 years. Based on the ITS barcoding of the 32-year-old type specimen, Cryphonectria decipiens must be reclassified as a later synonym of Cryphonectria radicalis. The reconstruction of the history of isolates M282–M289 takes us on a scientific journey from Italy to France, Spain and Portugal in the early twentieth century and offers new insights into the historical context of the invasion of Cryphonectria parasitica in Europe.

The European beech (Fagus sylvatica) is threatened by the foliar nematode Litylenchus crenatae subsp. mccannii (Lcm), the causal agent of beech leaf disease (BLD). Thus far, the majority of studies regarding BLD have focused on American beech (F. grandifolia). To better determine the impact of Lcm in buds of European beech, a total of 54 buds were collected from naturally symptomatic trees. Here, we characterized for the first time the bud scale morphology of two different cultivars of F. sylvatica infected with Lcm. Detailed observations of asymptomatic and symptomatic bud scales provided insight into the physical changes and arrangements of cells in the bud scale, shedding light on the dynamic processes occurring during Lcm infection. In addition, we evaluated the suitability of using the bud scale morphology for the early detection of BLD and Lcm in naturally infected buds. The distinct cellular arrangement of symptomatic bud scales cells (i.e., asymmetric pattern of enlarged cells) provides a rapid and visual, user-friendly methodology to prematurely diagnose BLD symptoms within the buds, as well as the detection of associated nematodes.

The author affiliations in the published version were incorrect and the corrected version is as follows.

Valeh abbasi¹, Heshmatollah Rahimian¹, Mohammad Ali Tajick-Ghanbari¹ and Ali Barzegar².

¹Department of Plant Protection, Faculty of Agronomy Sciences, Sari Agricultural Sciences and Natural Resources University (SANRU), Iran.

²Department of Basic Sciences, Sari Agricultural Sciences and Natural Resources University (SANRU), Iran.

We apologize for this error.

Hyrcanian forests comprise a long strip along the southern coast of the Caspian Sea in northern Iran. Oriental beech (Fagus orientalis) is one of the most valuable forest tree species in the Hyrcanian forests. Bark necrosis and bleeding spots of oriental beech were observed in Savadkuh forests in Mazandaran province during summer 2021. Ten samples were collected from symptomatic oriental beech trees. The bark canker symptoms included stem tissue necrosis, dark brown to black spots on the trunk, bleeding with dark exudates and dark lesions in the inner bark. Twenty-six strains of culturable bacteria were isolated from the samples which in culture were predominantly round, convex, smooth with entire margins on nutrient agar and a metallic green sheen pigment on eosin-methylene blue (EMB) agar. Fourteen strains induced necrosis and browning of the tissues around the inoculation sites on acorns after 2 weeks. Five representative strains also caused dieback in twigs of oriental beech 3 weeks after inoculation. These bacteria were Gram-negative, catalase positive and oxidase negative. All strains produced colonies with a green metallic sheen on EMB agar. Strains were negative in tests for starch and gelatine hydrolysis or production of levan. A phylogenetic tree based on concatenated sequences of gyrB and infB genes, of representative strains well as in each of the single gene-based phylogenetic trees, indicated that these strains clustered with Brenneria alni NCPPB 3934^T with high bootstrap values. To the best of our knowledge, this is the first report of B. alni associated with bark necrosis and bleeding spots on oriental beech.

In December 2022, a leaf spot and blight disease was observed in Eucalyptus plantations in northern India. Morphological features coupled with phylogenetic analysis of combined internal transcribed spacer (ITS), translation elongation factor 1-alpha (tef1) and β-tubulin (tub2) regions confirmed the association of Pseudoplagiostoma eucalypti with the disease symptoms. The pathogenicity of P. eucalypti was first proved on detached leaves of Eucalyptus camaldulensis and reconfirmed in glasshouse inoculation experiments. Finally, Koch's postulates were fulfilled by re-isolating the pathogen from the inoculated leaves. This pathogen was first described in 1995 from the leaves of Eucalyptus spp. collected from southern India, and this study confirms its first serious occurrence after more than two decades in northern India. In addition, this is the first report on the polyphasic characterization of P. eucalypti from India.