Tivadar Baltazár

Leaf-spot disease on European mistletoe (Viscum album) caused by Phaeobotryosphaeria visci: a potential candidate for biological control.

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.

Changes in the Distribution of European Mistletoe (Viscum album) in Hungary During the Last Hundred Years

The hemiparasitic European mistletoe (Viscum album) from the family Viscaceae (Santalaceae s.l.) is able to infest more than 380 woody taxa in Europe. At the beginning of the 20th century, less than 10 % of Hungary was infested. The distribution area was centralized in the Transdanubian Mountains, and no mass occurrence was noticed elsewhere. Since then, the infested area has almost tripled, and heavily infested forests can be observed in numerous parts of Hungary, especially in the northeast area of the Hungarian Great Plain. However, the central region of the Hungarian Great Plain is still uninfested. In the North Hungarian Mountains, where the presence of potential hosts is very frequent, mistletoe is still quite rare. The most infested macroregion of Hungary is Western Transdanubia, the only region where all three different subspecies can be found. No significant changes have been observed in the proportions of the most common hosts in the last 90 years, with poplars (Populus spp.) and black locust (Robinia pseudoacacia) still being the most frequently infested species. Silver maple (Acer saccharinum) is now a heavily infested host in city parks, while the abundance of infested apple (Malus spp.) and pear (Pyrus spp.) trees has decreased with the transformation of cultivation techniques. In infested areas, nine to twelve of the most common 18 host species can be found, while only five to eight species can be observed in uninfested areas. The increased mistletoe occurrence can be attributed to several factors, including human impact, larger forest area and a growing number of breeding pairs of the mistle thrush (Turdus viscivorus).

A fehér fagyöngy (Viscum album L.) által fertőzött gazdafák vizuális értékelésének lehetőségei

The article discusses the process of mistletoe infection rating from visual evaluation to statistical analysis of the collected data. Besides, it also deals with the most common rating systems and possibilities of their usage. Outstanding it describes also those statistical models which are the most suitable not only characterizing of the current state of mistletoe infection intensity. Furthermore, it also allows modeling the future distribution of infection. The research methodology is extremely time-consuming and labor-intensive which may increase by the size of study area. However, its implementation requires only small financial investment. Nevertheless, the exact mistletoe infection evaluation in case of all host individuals is only possible (and recommendable) in parks or other urban green areas, because these potential host species are most endangered due to the urban air contamination and by other damaging factors than trees in forest belt.

OPTIMISATION OF GROWING CONDITIONS OF EUROPEAN MISTLETOE HYPERPARASITIC FUNGUS (PHAEOBOTRYOSPHAERIA VISCI): EFFECT OF DIFFERENT MEDIA AND ANTIBIOTICS / OPTIMALIZÁCIA RASTOVÝCH PODMIENOK PHAEOBOTRYOSPHAERIA VISCI, HYPERPARAZITICKEJ HUBY IMELA BIELEHO: VPLYV RÔZNYCH ŽIVNÝCH MÉDIÍ A ANTIBIOTÍK

Abstract European mistletoe (Viscum album) is an evergreen, perennial, hemiparasitic shrub, which is able to infect more than 450 woody species. Besides mechanical pruning, a hyperparasitic fungus (Phaeobotryosphaeria visci) could be a successful candidate to develop an effective biocontrol agent against mistletoe. It was necessary to find antibiotics which make the isolation easier and do not effect mycelia growth negatively under strain. Furthermore, we wanted to define a medium for optimal growth under in vitro laboratory conditions. Three different media (potato-dextrose agar, modified oatmeal agar, ¼ PDA + V8 agar) and four antibiotics (kanamycin, ampicillin, rifampicin, nystatin) were tested. Oatmeal agar and potato-dextrose agar are optimal to maintain the fungal strains, the colony diameter was 9 cm on the 12th day. All tested antibiotics are useful, except nystatin. Súhrn Imelo biele (Viscum album) je vždyzelený viacročný poloparazitický ker schopný napadnúť vyše 450 druhov drevín. Okrem mechanickej redukcie imela existuje možnosť vyvinúť proti nemu účinný biologický kontrolný prostriedok použitím hyperparazitickej huby (Phaeobotryosphaeria visci). Na zavedenie tejto metódy bolo nevyh- nutné identifikovať antibiotiká, ktoré umožnia jednoduchú izoláciu huby a nebudú mať negatívny vplyv na rast mycélia. Chceli sme tiež nájsť živné médium, ktoré by umožňovalo optimálny rast v laboratórnych podmienkach in vitro. Testovali sme tri druhy živných médií (zemiakovo-dextrózový agar, modifikovaný ovsený agar a ¼ PDA+V8 agar) a štyri druhy antibiotík (kanamycín, ampicilín, rifampicín a nystatín). Modifikovaný ovsený agar a zemiakovo-dextrózový agar zabezpečili optimálny rast, stredná hodnota priemeru kolónií na dvanásty deň dosiahla 9 cm. Všetky testované antibiotiká s výnimkou nystatínu boli na zvolený účel vhodné.