Žatec (Czechia)

Downy mildew of hops represents a serious disease affecting hops production in all growing regions. Disease management is primarily based on the application of fungicides at regular intervals based on a short-term forecasting methodology that is essential for evaluating the occurrence of theoretical infections. To enable a more reliable assessment of the pathogen’s presence in a given area, spore traps capturing airborne Pseudoperonospora humuli sporangia can be utilized. The use of quantitative real-time PCR (qRT-PCR) for the detection of sporangia collected by these traps allows for the elimination of laborious and time-consuming microscopic counting. Among four tested P. humuli-specific nuclear DNA sequences, an effective qRT-PCR detection method was developed based on the c127233.5e3 sequence. This detection approach was used for the quantification of sporangia from volumetric spore trap samples collected in situ under field conditions at three selected localities in Bohemia and Moravia during the 2021–2022 period. The obtained results were compared with the short-term forecasting method of the downy mildew (HDM) weather index (I) based on meteorological data. The overall course of the HDM weather index (I) closely correlated with the occurrence of sporangia: after reaching the maximum HDM weather index (I) value, the highest sporangium detection was observed with a time delay of 1–2 weeks at all the monitored sites. The results corresponded well with data obtained from volumetric spore traps in Germany, and the qRT-PCR method proved to be fully comparable to light microscopy. The combination of volumetric spore traps and qRT-PCR can significantly improve the precision of short-term forecasting systems for P. humuli infection, thereby enabling more efficient fungicide application programs in hops protection and contributing to a better understanding of the pathogen’s dispersal dynamics.

In the present study, the effect of two different formulations (NCH1 and NCH2) of trans-anethole was examined against hop flea beetles, Psylliodes attenuatus in field conditions. Products were applied in different locations in the spring seasons of 2019–2021. In 2019, 0.5% and 1% concentrations of both formulations were used so that the effective field dose could be determined. Doses of 1% for both formulations were shown to be more efficient. In 2020, experiments with this dose were carried out in two localities in order to select a more suitable formulation of the product (NCH1 vs. NCH2). The NCH1 formulation was shown to be more effective. After application, there was a significant reduction in the number of flea beetles compared to the control (p < 0.0001). On the other hand, no significant difference was found between the non-treated plot and the NCH2 formulation. In the third year of the experiment (2021), it was found that the number of P. attenuatus on plants treated with NCH1 encapsulation was significantly lower than in the untreated control (p < 0.0001). Residues of trans-anethole degraded immediately; thus, the product is suitable for use in the summer to protect the hop cones before harvest.

Characterising the sensory profiles of beers made from new hop varieties is of considerable importance for their application in brewing. New Czech bitter varieties Boomerang and Gaia were tested in three-year pilot brews (200 l) of 12% single-hopped pale lager, produced in kettle and kettle+dry-hopped variants. The hop-derived aroma and bitterness profile of the beers was evaluated using a comprehensive descriptive method. Hop-related volatiles in beer were determined by GC/MS-MS method. Both of these bitter varieties showed a pleasant bitterness profile even in dry-hopped beers. The overall impression of the beers from the varieties tested was favourable, at the level of the control beer (Saaz). The profile of hop derived volatiles and aroma in beers from Gaia and Boomerang varieties were different. The results show the potential of Boomerang for both single kettle-hopped beers and dry-hopped lagers due to its interesting aroma profile (spicy, herbal, floral). The Gaia variety can be used in a similar way, with a preference for dry hopping to give a well-balanced hop-derived aroma profile. Both varieties have shown considerable potential for the production of new beer brands, and their drought tolerance may also help their widespread cultivation.

The course of weather conditions during the growing season, but also beyond it, decides the economics of hop cultivation every year. Ongoing climate changes manifested by more frequent occurrence of compound hot and dry waves affect hop cultivation not only in the Czech Republic, but in the entire region of Central Europe. The paper evaluates the harvest results (yields, alpha acid content) of four Czech hop varieties in the period 2019–2022 with a focus on the weather diametrically opposed vintages 2021 and 2022 on a specific agricultural farm in the Žatec (Saaz) hop-growing region. While the 2021 vintage was rich in precipitation in the decisive vegetation phase, the 2022 vintage was very dry and hot. The age of the plants significantly influenced the alpha acid content of the varieties Saaz, Sládek and Premiant independently of the vintage. Young growths of the Saaz variety contained at least 60% rel. more alpha acids than older growths (more than 5 years old), while the increase in the Sládek variety was 30–40% rel. and in the Premiant variety 20–25% rel. In the case of the variety Agnus, the age of the plants did not have a demonstrable effect on the content of alpha acids. In 2021 the yields of all varieties were negatively affected by the calamitous occurrence of downy mildew. In 2022, the rainfall deficit was so large that it could not be fully compensated even by the maximum use of drip irrigation. Of the evaluated varieties, the Agnus variety coped best with the different weather conditions of the assessed vintages. This shows that the cultivation of climate resistant varieties is one of the promising but time-consuming ways to face the expected climate changes. Other options include regular renewal of hop growths, consistent regionalization, i.e. planting hop in locations that are suitable for the given variety and efficient use of irrigation systems.

Czech bitter varieties were evaluated between 2010 and 2022. Hop varieties displayed an average content of alpha acids between 10.24% w/w (Agnus) and 13.73% w/w (Gaia). Variability below 15%, proved good stability of alpha acids content in all tested bittering hops. All varieties showed a decrease in the content of alpha acids over a period of 13 years of hop cultivation. The highest content of beta acids was determined in Gaia (7.30% w/w). In contrast, the lowest content of beta acids was found in Rubín (3.73% w/w). The new bitter genotypes Uran and 5304 had an average alpha acid content of 11.56% w/w and 10.82% w/w, respectively. Uran showed an average beta acid content of 5.47% w/w and for the genotype 5304 it was 3.61% w/w. In terms of the alpha/beta acids ratio, the hop varieties can be divided into three groups. The first group included the varieties with an alpha/beta acids ratio below 2, i.e. Vital, Boomerang and Gaia. While Agnus and Uran displayed an alpha/beta ratio slightly above 2. The highest alpha/beta ratio above 3 was found in Rubín and the 5303 genotype.

New hop varieties were evaluated in brewing tests in the years 2020 and 2021. The Saaz Comfort, Saaz Shine, Saaz Late and Saaz fine aroma hops were compared in lager style beers. Saaz Comfort has the best evaluation in terms of overall popularity. With a 95% probability, its evaluation is different from that of Saaz Shine. Saaz Comfort has a considerably different evaluation of bitterness than Saaz Late and Saaz Shine. The results show that fine aroma hop varieties have different characteristics and thus do not compete with each other. Kazbek and Cascade were compared in lager and ale beer styles. No significant difference was determined in the lager style. However, a significant difference between Kazbek and Cascade was established in ALE. Gaia has a considerably better evaluation in the lager style than in ALE. Gaia has the best evaluation of aroma and bitterness in lagers with dry hopping.

The specification of varietal profiles of secondary metabolites of hops in beer is rather important for hop growing and beer brewing. Chemical and sensory profiles of beers hopped with the varieties of Saaz Special and the traditional Saaz semiearly red bine hops (Saaz) were compared in three-year pilot brews (200 L). Single kettle hopped beers and single kettle + dry hopped beers were prepared. The overall sensory impression of the Saaz Special beers was comparable to Saaz hops. The profile of essential oils and hop aromas/flavours in the beer was partially different, but the hop aroma did not receive a worse rating than Saaz. The Saaz Special dry hopped beers were clearly distinguished from Saaz in triangle tests, but no preference was given to either variety. Based on the achieved results, the Saaz Special variety was listed among varieties recommended for the production of the beer with the Protected Geographical Indication of Czech Beer thanks to the achieved results.

The objective of this study was to evaluate integrated pest management (IPM) practices among hop growers in relation to downy mildew. Forty-eight hop samples, originating from the Saaz hop growing region (Czech Republic) and harvested in 2018 and 2019 seasons, were analyzed using HPLC-HR-MS/MS and AAS methods. Of all the samples analyzed, residues of Ametoctradin, Azoxystrobin, Boscalid, Dimethomorph, Mandipropamid, and Pyraclostrobin, and residues of copper-based fungicides were found at levels ranging from 0.02 to 32 mg/kg and from 7 to 404 mg Cu/kg, respectively. Hierarchical clustering analysis (HCA) was applied to categorize the samples according to the fungicide treatment schemes used to control fungal plant pathogens. The data showed that (1) there was not one universal fungicidal sequence commonly used by all hop growers, and (2) that the sum of pesticide residues varied by more than two orders of magnitude, depending on the fungicide treatment scheme. This study suggests a new approach for evaluating Integrated Pest Management (IMP) practices used in hop-yards on the basis of post-harvest recognition of various fungicidal sequences.

Four new aroma hop varieties – Saaz Brilliant, Saaz Comfort, Saaz Shine and Mimosa – were registered in the Czech Republic in 2019. All of the new hop varieties have significantly higher yields than the traditional Saaz aroma variety. Saaz Comfort has the significantly highest content of alpha acids (5.59%) whereas Mimosa has the significantly lowest content of alpha acids (1.90%). The Saaz Comfort and Saaz Brilliant varieties show a variability of alpha acid content below 20%. The other hop varieties, Saaz Shine and Mimosa, as well as Saaz, have a variability of alpha acid content above 25%. Mimosa has the significantly highest content of beta acids (6.07%). Mimosa shows the highest average cohumulone content (29.29% rel.) whereas Saaz Comfort has the lowest cohumulone content (18.04% rel.). Saaz Comfort and Saaz Shine have the highest average contents of hop essential oils (0.84% w. and 0.75% w., respectively). The Saaz, Saaz Shine and Saaz Brilliant varieties show the significantly highest farnesene contents (13.47% rel., 12.50% rel. and 12.38% rel., respectively), which are higher than those of Saaz Comfort and Mimosa.