Forest Pathology最新文献

Current season needle necrosis (CSNN) is a conifer foliar disease and a particular problem for Christmas tree plantations, as it causes necrosis and premature foliage shedding, resulting in significant economic and aesthetic devaluation. In September 2022, CSNN symptoms were detected on 10-year-old Abies grandis trees at a plantation located in Southern Sweden. Field surveys were employed to assess the extent of damage, and the causal agent of damage was identified via isolation and tissue culturing, microscopy, molecular diagnostics and pathogenicity testing. DNA sequencing and phylogenetic analysis of obtained cultures identified Sydowia polyspora as the potential causal agent of the observed CSNN symptoms. The pathogenicity of S. polyspora was confirmed through seedling inoculation and successful re-isolation from induced necroses. Field surveys indicated a high incidence (98%) of CSNN, with severity levels typically affecting up to 50% of the crown. To our knowledge, this is the first documented occurrence of CSNN on A. grandis in Sweden. Extreme weather conditions, that is, drought and high precipitation, may exacerbate CSNN development, increasing tree susceptibility to S. polyspora infections. These findings underscore the increasing threat of weak or latent pathogens like S. polyspora to trees under changing climatic conditions, emphasising the need for proactive management strategies, including shielding and resistance breeding.

Fusiform rust, caused by Cronartium quercuum f. sp. fusiforme (Cqf), is the most severe disease of planted southern pines in the south-eastern United States. Despite the critical role pathogen genomics play in disease outcomes, the population structure and genetic variability of Cqf remain poorly characterised. To address this gap, we generated a high-quality chromosome-scale genome assembly of Cqf and leveraged this resource to perform the population genomic analyses of 274 haploid pycniospore samples derived from controlled inoculations with geographically diverse aeciospore collections. The assembled Cqf genome (87.03 Mbp across 19 contigs) displayed high completeness (BUSCO: 91.1%) and structural continuity (Scaffold N50: 5.4 Mbp), establishing a robust reference for population-genetic analysis. PCA, DAPC and ADMIXTURE revealed a pronounced east–west structure indicating five genetically distinct metapopulations (Western Gulf, Upper Central Gulf, Lower Central Gulf, Lower Atlantic Coast/Eastern Piedmont, Mid-Atlantic Coast). AMOVA revealed that high levels of variation exist in Cqf, with the greatest proportion of genetic variation occurring in local populations (85.5%) with moderate differentiation among regional metapopulations (Φ = 0.117). Sliding-window F_ST analyses highlighted the genomic regions of elevated differentiation, including loci encoding candidate secreted effector proteins. Genetic diversity metrics revealed evidence of non-random mating in some regions. These results refine the understanding of Cqf population structure, confirm the relevance of USDA Resistance Screening Center geographic zones and provide novel genomic resources to support breeding for durable fusiform rust resistance in southern pines.

Brown spot needle blight (BSNB), caused by the fungus Lecanosticta acicola, is a widely distributed foliar disease of pines that causes needle necrosis, premature defoliation, and growth loss in both natural forests and commercial plantations. Although L. acicola has been reported from more than 50 pine species worldwide, recent large-scale outbreaks on native loblolly (Pinus taeda) and eastern white pine (P. strobus) in North America highlight emerging management challenges within the pathogen's presumed native range. Here, we synthesise current knowledge of L. acicola taxonomy, biology, pathogenicity, and global distribution, with particular emphasis on how recent North American epidemics fit into the broader invasion history and what they reveal about host–pathogen–environment interactions. We review how taxonomic instability and cryptic diversity complicate species delimitation and surveillance, and evaluate diagnostic and monitoring approaches spanning field sampling, microscopy, culture-based isolation, spore trapping, species-specific PCR and LAMP assays, and the emerging roles of environmental DNA and remote sensing. We then assess control and management options, including fungicides where permitted, silvicultural and hygiene practices, and resistance breeding in pine improvement programs, and place these in the context of projected climate-driven range expansion and ecosystem impacts. Finally, we highlight key research and policy priorities, including coordinated long-term monitoring, genomics-informed resistance screening, and international collaboration and data standards, that are needed to support integrated management strategies and mitigate the growing threat of BSNB to pine-dominated forests in North America and globally.

Root-knot nematodes (RKN, Meloidogyne spp.) are among the most important plant pathogenic organisms, causing significant damage, with a wide geographical distribution and being difficult to control. The ability of these nematodes to parasitize native trees from Brazilian biomes is little understood. This study evaluated the host status of 24 native tree species to M. incognita and M. javanica under greenhouse conditions. Overall, 62.5% of the species evaluated (15 out of 24) were classified as susceptible (reproduction factor, RF > 1.0) to M. javanica, whereas 70.8% (17 out of 24) were susceptible to M. incognita. The highest RF values for both nematodes were recorded in Enterolobium contortisiliquum, Handroanthus albus and Senna macranthera, while Cedrela fissilis showed high susceptibility only to M. incognita. Six species were resistant to M. javanica and five to M. incognita, with four species (Campomanesia guazumifolia, Erythrina falcata, Inga edulis and Parapiptadenia rigida) exhibiting resistance to both nematodes. In addition, four species were immune to M. javanica and two to M. incognita, with Apuleia leiocarpa and Myrcianthes pungens being the only species immune to both RKN species. Many of the most susceptible trees are widely distributed in the Cerrado, Brazil's leading grain- and fibre-producing region, indicating potential refuges for RKN near agricultural landscapes. This study provides the first comprehensive evaluation of native Brazilian trees as RKN hosts, filling a major knowledge gap and offering novel insights for sustainable nematode management, forest restoration and biotechnological exploration.

The increasing global demand for products derived from Eucalyptus spp. has stimulated its production in Brazil. However, productivity has declined in recent years due to several factors, with Ceratocystis wilt being one of the most significant. Conventional detection methods rely on visual assessment, histological sections and/or molecular analyses—procedures that are time-consuming and impractical for large-scale monitoring. Proximal or remote sensing based on VIS–NIR–SWIR spectroscopy (400–2500 nm) has been proposed as a non-destructive alternative for characterising plant biochemical and biophysical properties, yet its use for detecting Ceratocystis wilt in Eucalyptus spp. remains underexplored. Here, we evaluated whether leaf reflectance measurements in the VIS–NIR–SWIR range, acquired with a proximal non-imaging sensor, can be used to detect the disease in asymptomatic cuttings (vegetatively propagated plants). For that a greenhouse experiment was established with two Eucalyptus clones, one susceptible and another resistant. Plants were visually assessed and tested via the ‘carrot bait’ method for disease incidence, and spectral measurements collected four times between 12 and 60 h after inoculation. Observations for inoculated plants were compared with those from non-inoculated controls (total n = 77). Classification models trained with Partial Least Squares Discriminant Analysis (PLS-DA), Random Forest with Recursive Feature Elimination (RF + RFE) and Support Vector Machine with Genetic Algorithm (SVM + GA) achieved balanced accuracy of 0.63 ± 0.11, 0.75 ± 0.11 and 0.75 ± 0.13, respectively. Features selected via RFE and GA, or identified as highly important in the PLS-DA, RF + RFE and SVM + GA models, were predominantly located in the visible, NIR and especially the SWIR regions. This distribution is consistent with absorption features associated with leaf water, cellulose, starch and lignin (near 1100–1200 and 2300 nm), as well as proteins (near 1700, 2200 and 2300 nm). Spectra from the apical canopy layer generally provided better classification performance than those from the basal or middle canopy sections. Despite the relatively small dataset and limited number of clones, our results demonstrate the potential of proximal spectroscopy for detecting Ceratocystis wilt in asymptomatic Eucalyptus plants.