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Dutch elm disease (DED) still occurs in Poland. Previous studies confirmed occurring O. ulmi and two subspecies of O. novo-ulmi: subsp. novo-ulmi and subsp. amerciana. In this study the population of Ophiostoma occurred in Poland was investigated. The disease incidence was investigated on elms growing in 39 locations. The pathogen’s mycelium was isolated from elm branches and twigs collected from 22 plots. The disease symptoms were noted in 5% to 35% trees. Fungi were identified based on the PCR amplification of the ITS 1/2 rDNA together with phylogenetic analysis of this region. Ophiostoma novo-ulmi was the only agent caused DED on Ulmus glabra, U. minor and U. laevis. There were no genetic diversity of O. novo-ulmi Polish population in analyzed ITS region. All kind of specific symptoms and disease intensity occurred independently on elm species and host age. Ulmus minor was infested most sever among the three elms species.
In central Europe, the endangered Rosalia longicorn Rosalia alpina (L.) has rarely been observed to develop in the wood of elms Ulmus sp.; however, this beetle has recently expanded into habitats formed by elms. The factors driving these changes are unknown in detail, but a potential one is the increasing amount of breeding material, namely, dead elm wood. Dutch elm disease, caused by the fungi Ophiostoma ulmi and O. novo-ulmi, by killing off elm trees, has created a supply of dead wood. The aim of this work was to assess the potential role of Dutch elm disease in the formation of habitats suitable for the endangered Rosalia longicorn. The health of four elm stands (Carpathians, SE Poland) was analysed and the pathogen responsible for elm death were determined by DNA sequence comparison. O. novo-ulmi — the causative agent of Dutch elm disease — was isolated from weakened and dying trees at all studied localities. In total, 30% of the elm trees were dead, 34% showed signs of dieback or were moribund, while some 36% showed no signs of dieback (N = 120). The presence of the Rosalia longicorn was recorded at all four studied localities. The use of elms as a host plant was long-term; dead trees served as a breeding material through the past 11 years. Our results indicate that O. novo-ulmi is playing an important part in the death of elms in Rosalia longicorn localities. Dutch elm disease, due to its wide distribution, may shape suitable habitats for Rosalia longicorn within the species' range. While the chronic nature of the disease contributes to the slow and inexorable death of these trees, it may at the same time be a factor promoting the long-term stability of Rosalia longicorn habitats.
Three elm species are native to Poland: wych elm (Scots elm) (Ulmus glabra Huds.), field elm (U. minor Mill.), and European white elm (fluttering elm) (U. laevis Pall.). The epidemic of Dutch elm disease (DED) has led to a decrease in the popularity of elm cultivation. An analysis of forestry data was the first step in the assessment of elm resources. The area of forest stands where elms are dominant has more than doubled since 1978. Lowland alluvial forests rank first in regards to the number of elm localities per unit area of a given forest site type. While this site type is clearly preferred by elms, the majority of elm trees are actually scattered among sites of oak-hornbeam or closely related forests (of the alliance Carpinion betuli). Field research revealed a clear dominance of U. laevis, a species which in the past was predominantly located out of woodland and rarely cultivated. Data analysis indicated that all trees greater than 70 cm in diameter belonged to this species. Data from plots surveyed directly also suggest that the three elm species have slightly different habitat preferences. U. laevis prefers riparian habitats, although the major part of its resources is now on potential sites of oak-hornbeam or closely related forests. U. minor even more often than U. laevis occurs at less humid sites (mostly potential sites of oak-hornbeam or closely related forests), while U. glabra prefers moist slopes. In general, it appears that the impact of DED in the last 20–30 years has been smaller than in the preceding period, however, the disappearance of the disease has not been established. Undoubtedly, U. laevis is the elm species that is least impacted by DED
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