Forest Pathology最新文献

Eucalyptus is one of the most widely grown industrial crops worldwide. This wide distribution comes with many diseases due to the wide exchange of germplasm, and Eucalyptus being a suitable host for indigenous pathogens. Eucalyptus plantations in Uganda are affected by stem canker diseases that have reduced productivity. Therefore, it is crucial to understand the prevalence and distribution of canker diseases among species and clones and regions in order to develop management strategies. A nationwide survey on Eucalyptus canker diseases was conducted in different regions, hereafter clusters, of Uganda. The most prevalent disease in all clusters was Botryosphaeria canker, mainly affecting Eucalyptus grandis, E. camaldulensis and the GU hybrid clone (E. grandis × E. urophylla). However, the most severe disease was Teratosphaeria canker, which affected 50% of the GC hybrid clone (E. grandis × E. camaldulensis). The incidence and severity were highest in the Western and Central Uganda clusters, respectively. The incidence and severity varied significantly with age, with 41% of trees less than 5 years in age being the most affected. Plantations with mixed species, mixed hybrid clones and mixed species with hybrids had the lowest disease incidence and severity compared to monocultures. The findings indicated that, although Botryosphaeria canker was the most prevalent of these diseases, Teratosphaeria canker caused more damage to Eucalyptus plantations in Uganda, with the highest severity recorded in monocultures and clusters characterised by high annual rainfall (1244–1356 mm per year). This information will help Eucalyptus growers carry out site-species matching and select appropriate combinations of species and clones for canker disease management and better yields.

Frangipani (Plumeria spp.: Apocynaceae) is a small ornamental tree native to Mexico, susceptible to significant diseases such as anthracnose and foliar blight in hot, dry environments. Understanding the diversity of pathogens responsible for these diseases is crucial for developing effective disease management strategies. This study aimed to identify the pathogens responsible for these diseases. In February 2020 and 2021, symptoms of anthracnose and foliar blight were observed on frangipani plants in recreational areas of Morelos and Sinaloa, Mexico. Isolations from diseased leaf tissue resulted in the recovery of 12 Colletotrichum isolates from P. rubra and 18 Alternaria isolates from P. obtusa. After morphotype grouping, a representative isolate from each group was identified by morphology and phylogenetic reconstruction (ITS, act, gapdh, rpb2 and tef1) as Colletotrichum karstii, Colletotrichum siamense, Alternaria destruens and Alternaria burnsii. For pathogenicity testing, a conidial suspension was sprayed onto the leaves of 90-day-old plants, while control plants were sprayed with sterile distilled water. All inoculated fungi were pathogenic, reproducing the characteristic symptoms of the disease, while control plants remained symptomless. The fungi recovered from symptomatic plants were morphologically identical to the inoculated fungi, fulfilling Koch's postulates. This is the first report of A. burnsii and A. destruens causing foliar blight in P. obtusa, and C. siamense and C. karstii causing anthracnose in P. rubra. These findings contribute valuable insights for developing effective disease management strategies.

Lecanosticta acicola, the causal agent of brown spot needle blight, is a known pine needle pathogen. During the past decades, it has spread in Northern Europe, including the Baltics, where it has mainly infected exotic pines. This study presents novel data on the occurrence of the pathogen on introduced, as well as on further spread of the pest to the native pine species in Latvia. In the autumn of 2022, infection of L. acicola was discovered on several young native Scots pine (Pinus sylvestris) stands throughout Latvia, and in a commercial nursery, thus signifying the transition to a native host with high potential for wider expansion. The transmission of the pathogen to the local pine populations could accelerate the spread of the pathogen and decrease the vitality of pines in the Baltics in the future. The fungus was identified by molecular PCR-based methods; conidia were found only on a few pines in surveyed stands, as symptom severity was still low (mostly latent infection). Nevertheless, the observed behaviour of the pathogen implies the establishment and presumed invasion in the native forest areas, and thus the emergence of additional forestry risks.

Due to the intense ash dieback in Europe, which begins with the appearance of leaf infection, this study presents the results of the research on the impact of a selected isolate Pseudomonas koreensis R4.45P on the development of Hymenoscyphus fraxineus in the rachises of Fraxinus excelsior. Preliminary in vitro testing of P. koreensis R4.45P showed a statistically significantly lower growth of H. fraxineus compared to control cultures that were not exposed to this bacterium. The results of the in planta test on F. excelsior seedlings showed a statistically significant decrease in dieback occurrence and the length of necrotic lesions caused by H. fraxineus in rachises treated with P. koreensis R4.45P compared to untreated rachises. Additionally, leaf mortality in F. excelsior seedlings treated with P. koreensis R4.45P was statistically significantly lower. This study is the first to show the possibility of application of antagonistic bacteria P. koreensis R4.45P to effectively slow the initial stage of H. fraxineus development.

Pine pitch canker (PPC) emerged as a significant problem in 1945 in Southeastern USA. The causal agent, Fusarium circinatum, has spread widely and now occurs in pine forests and plantations worldwide. Fusarium circinatum causes damping off, shoot and tip die-back, and the death of seedlings in nurseries. Infection of mature trees leads to excessive resin bleeding on branches and main stems, sunken cankers with bark remaining attached, and finally, tree death. Arguably, F. circinatum is the most important pathogen of pine seedlings in many areas of the world. At least 67 species of Pinus, 18 Pinus hybrids, and 6 other non-pine tree species are susceptible to PPC. The selection and development of tree germplasm resistant to pathogens is considered the most robust approach to reduce losses to diseases. Genetic variation in resistance to F. circinatum certainly exists, even in generally very susceptible hosts, such as P. radiata. Exploiting genetic resistance as a tool to manage PPC requires screening large numbers of tree genotypes and fine-tuning efficient phenotyping protocols. The greater the number of genetic lines and replications, the higher the selection differentials and accuracy of the genetic parameter estimates. Recent advances in physiological and molecular techniques exploring the plant-pathogen interaction have expanded our understanding of genetic resistance mechanisms in pines to PPC and represent an added-value tool to support phenotypic selection. This review provides an overview of current knowledge on the molecular, physiological, and genetic basis of resistance to F. circinatum in pines and considers possibilities to improve the resistance of pines against the pathogen through breeding and selection.