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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Background The farmyard manure application maintains quality of arable soils, provides nutrients, mitigates climate change by soil carbon sequestration. Biochar and other complex carbon rich amendments may stabilize organic matter derived by composting and decelerate organic carbon mineralization. However, how the combined utilization of biochar, humic substances and manure effects on soil chemical and biological properties have been least explored, especially their effect on soil basal and substrate induced respirations are needed to be further explored. Therefore, the potential of biochar and Humac (a commercial humic substances product) in combination with manure to improve the soil properties and plant growth was investigated in this experiment using barley under a short-term (12 weeks) and maize under long-term (following 12 weeks, a total of 24 weeks) cultivation. Results In the early phase of cultivation (12 weeks) Humac- or biochar-enriched manures (M + H, M + B, respectively) enhanced the contents of nutrient elements (carbon + 5.6% and + 7%, nitrogen + 6.7% and − 5%, sulphur − 7.9% and + 18.4%), the activity of enzymes including (β-glucosidase + 32% and + 9.6%, phosphatase + 11% and 6.3%), and dry aboveground biomass (+ 21% and + 32%), compared to the control and manure-treated soil. However, these impacts of M + H and M + B manures were reduced under longer period, i.e., at the experiment end (24 weeks). After 24 weeks of cultivation, a decrease in absolute values of all determined enzyme activities indicated putative reduction of mineralization rate due to presumed higher recalcitrance of manure-derived organic matter, with Humac, biochar amendments. Increased stability of soil organic matter reduced microbial activity due to lower availability of nutrients. Possibly, the shortened period of manure maturation could help preserve a higher amount of less degraded organic matter in the enriched manures to counteract these observed features. Conclusions We summarized that the biochar and humic substances combined with manure have the potential to improve the soil characteristics, plant biomass and soil health indicators but the improvements faded away in a cultivation time-dependent manner. Further studies are required to explore the structure and functioning of microbial activities under long-term experimental conditions. Graphical abstract

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.

Objective: Biochar and a commercial humic acid-rich product, Humac (modified leonardite), represent soil amendments with the broad and beneficial effects on various soil properties. Their combination has been scarcely tested so far, although the positive impact of their interaction might be desirable. Materials and Methods: The dehydrogenase activity (DHA), microbial biomass carbon (Cmic), soil respiration (basal and substrate-induced), enzyme activities, total carbon (Ctot), and both shoot and root biomass yield were measured and compared in the short-term pot experiment with the lettuce seedlings. The following treatments were tested: the unamended soil (control), the Humac-amended soil (0.8 g·kg−1), the biochar-amended soil (low biochar 32 g·kg−1, high biochar 80 g·kg−1), and the soil-amended with biochar + Humac. Results: The effect of both amendments on the soil pH was insignificant. The highest average values of Ctot and Cmic were detected in high biochar treatment and the highest average values of basal and substrate-induced respiration (glucose, glucosamine, alanine) were detected in the low biochar treatment. The phosphatase activity and fresh and dry lettuce aboveground biomass were the highest in the low biochar + Humac treatment. Conclusions: Even though the combination of both biochar + Humac decreased the microbial activities in the amended soil (Cmic, DHA, enzymes, substrate-induced respiration) at the low biochar dose, they mitigated the detrimental effect of the high biochar dose on respiration (all the types) and the enzyme (phosphatase, arylsulphatase) activities. In contrast to the previously published research in this issue, the effects could not be attributed to the change of the soil pH.

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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 12 th day. All tested antibiotics are useful, except nystatin.

Different types of soil respond variably to biochar amendment. Soil structure and fertility are properties which strongly affect the impacts of biochar on soil fertility and microbial activity. A pot experiment with lettuce was conducted to verify whether biochar amendment is more beneficial in sandy soil than in clay soil. The nutrient content (carbon and nitrogen), microbial biomass carbon, soil respiration, metabolic quotient, and plant biomass yield were determined. The treatments were prepared by mixing silty clay loam (Haplic Luvisol) with a quartz sand in ratios of 0%, 20%, 40%, 60%, 80%, and 100% of sand; the same six treatments were prepared and amended with biochar (12 treatments in total). Soil carbon and nitrogen, microbial biomass carbon, and soil respiration were indirectly dependent on the descending sand ratio, whereas the metabolic quotient increased with the ascending sand ratio. The biochar’s effects were positive for total carbon, microbial biomass carbon, metabolic quotient, and plant biomass in the sand-rich treatments. The maximum biochar-derived benefit in crop yield was found in the 100% sand + biochar treatment, which exhibited 24-fold (AGB) and 11-fold (root biomass) increases compared to the unamended treatment. The biochar application on coarse soil types with lower fertility was proven to be favorable.