Viscum album (European mistletoe), a perennial, evergreen, hemiparasitic shrub, infects a wide range of woody species. It adversely affects the height and diameter of growth and it is associated with increased mortality of its hosts. There is no effective control methods against it. We have found a specific hyperparasitic fungus, which can completely destroy European mistletoe by infecting its branches, leaves and berries. Both morphological and molecular identification, based on ribosomal internal transcribed spacer sequences (rDNA-ITS), established its identity as Phaeobotryosphaeria visci. Our analysis also revealed unexpected ITS variability, as compared to the previous studies, that needs to be considered in identifying of this pathogen. Because of its efficient pathogenicity this fungus might be a good candidate for biological control of mistletoe.

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Bittersweet (Solanum dulcamara), a European native weed, is widespread across a variety of habitats and often occurs as a coloniser of open, disturbed, ephemeral environments or wetlands, although it is also found in mountain habitats and on forest edges. As recent studies have shown the potential utility of the species in plant breeding programs, we assembled a collection of bittersweet germplasm from natural populations found in Europe. This collection was analysed with conserved DNA-derived polymorphism (CDDP) and intron-targeting (IT) markers to assess genetic diversity found within and among the populations. We found that there is limited genetic variability within the collected S. dulcamara accessions, with a greater proportion of allelic variation distributed among populations and considerably greater population structure at higher regional levels. Although bittersweet is an outcrossing species, its population structure might be affected by its perennial selfcompatible nature, reducing genetic diversity within regional populations and enhancing inbreeding leading to high interpopulation or spatial differentiation. We found that populations have been separated by local selection of alleles, resulting in regional differentiation. This has been accompanied by concurrent loss of genetic diversity within populations, although this process has not affected species-level genetic diversity. Germplasm collecting strategies should be aimed at preserving overall genetic diversity in bittersweet nightshade by expanding sampling to southern Europe and to smaller regional geographic levels in northern and central Europe. Currently, the major defense against this pathogen is the use of fungicides. However, P. infestans has developed Ann Appl Biol 159 (2011) 141-153

We investigated patterns of nucleotide polymorphism in the internal transcribed spacer (ITS) region for Sphaeropsis visci, a hyperparasitic fungus that causes the leaf spot disease of the hemiparasite European mistletoe (Viscum album). Samples of S. visci were obtained from Hungary covering all major infected forest areas. For obtaining PCR products we used a fast and efficient direct PCR approach based on a high fidelity DNA polymerase. A total of 140 ITS sequences were subjected to an array of complementary sequence analyses, which included analyses of secondary structure stability, nucleotide polymorphism patterns, GC content, and presence of conserved motifs. Analysed sequences exhibited features of functional rRNAs. Overall, polymorphism was observed within less conserved motifs, such as loops and bulges, or, alternatively, as non-canonical G-U pairs within conserved regions of double stranded helices. The secondary structure of ITS2 provides new opportunities for obtaining further valuable information, which could be used in phylogenetic analyses, or at population level as demonstrated in our study. This is due to additional information provided by secondary structures and their models. The combined score matrix was used with the methods implemented in the programme 4SALE. Besides the pseudoprotein coding method of 4SALE, the molecular morphometric character coding also has potential for gaining further information for phylogenetic analyses based on the geometric features of the sub-structural elements of the ITS2 RNA transcript.

BALTAZÁR TIVADAR, PEJCHAL MILOŠ, VARGA ILDIKÓ: Evaluation of European mistletoe (Viscum album L.) infection in the Castle Park in Lednice.Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 6, pp. 1565-1574 This experiment focused on the evaluation of mistletoe infection (Viscum album L.) in main sections of the castle park in Lednice. The study evaluates the proportion of aff ected and unaff ected individuals of host taxa and the intensity of their infestation. For Acer campestre and Tilia cordata one-way ANOVA was used to detect the diff erence among the number of mistletoe bushes and tree age, development stage, vitality and location. For the modelling of mistletoe infection probability also the dependence on these and other continuous explanatory variables (height and crown volume) was used for logistic regression with binomial distribution. Our results show that number of mistletoe on trees within same taxa increases with the tree age and with the lower tree vitality, but there is large diff erence between the hosts. Due to the results of logistic regression, the same factors also have strong impact on the probability of mistletoe infection, e.g. tree age and tree vitality. In this case no large diff erences were found between the hosts.