National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Micropropagation of common ash (Fraxinus excelsior L.)
Šedivá, Jana ; Havrdová, Ludmila ; Maršík, Petr
The aim of the methodology is to provide an optimized process of micropropagation of common ash, which can support the production of its elite genotypes with a higher degree of tolerance to the invasive fungal pathogen Hymenoscypus fraxineus causing our domestic species of ash (Fraxinus excelsior and F. angustifolia) so called necrosis of ashes (known in Europe as " ash dieback "). The methodology includes two integrated in vitro propagation techniques, which are based either on juvenile plant material (from seeds) or on adult trees using apical buds.
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Analysis of selected factors affecting occurrence of Chalara fraxinea in the environment.
Havrdová, Ludmila ; Šrůtka, Petr (advisor) ; Jaroslava, Jaroslava (referee)
Extensive investigation of ash dieback impact on different rural vegetation types (solitaires, scattered plantations, riparian stands, scree- and ash-alder alluvial forests) was performed in the Lusatian Mts. (the Czech Republic) between 2011 and 2013. The rate of ash dieback and 27 environmental variables were investigated in 80 research plots with a total of 1045 evaluated trees. The developed model (GLM) explained ca 27% of the disease variability. Particular models for each vegetation type importantly differed from each other and explained 28--46% of the disease variability. The variables that positively affected the disease impact included the host crown area, ash area and rate of ash in the stands, tree layer area, canopy closure, north aspect, shrub and herbaceous layer canopy, vertical heterogeneity and standard deviation of TPI. Tree height, the distance and damage of the nearest host as well as the water source distance, slope and its standard deviation affected it negatively. The coincidental attack of the trees by Armillaria sp. and Hylesinus fraxini positively affected the disease progress, whereas the presence of Nectria sp. and Aceria fraxinivorus conclusively decreased progress, most likely via the induction of secondary metabolites. The highly conclusive regression of ash dieback on the number of days with an air humidity of >95% between 6--11 a.m. in the main period of ascospore spread was identified. Because the air humidity near the ground was highly affected by local factors, a GLM model explaining the variability of air humidity with that of investigated factors was developed. This model explained 77% of the variability attributed to air humidity, local factors (TPI and SD of TPI, aspect, slope, altitude, distance from open water, tree and shrub layers canopy, tree stand height, etc.) greatly affected the disease impact related to air humidity. The landscape form was identified as a factor (most likely via air humidity) that affects the impact of the disease -- for example, the stands on mountain tops and slopes were less affected than the stands in valleys. The vegetation types highly differed in the disease extent. In general, the solitaires and scree forests were significantly less damaged than mixed ash-alder forests and riparian stands. The smaller stands were less affected than the more extended, the stands enclosed in canopy of other forests were less damaged than comparable vegetation in open landscapes and stands with higher humidity (riparian stands and mixed ash-alder forests) were more damaged than those without water. The outcome clearly supports the possibility of development and usefulness of appropriate forest and landscape management of the disease.

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