The alpha acids content of Czech hops from the 2025 harvest was evaluated using pre-harvest forecasts, harvest forecasts and final analytical data obtained from more than 3,300 commercial and farm samples processed by three independent laboratories. Weather conditions during the 2025 growing season differed from those in 2024, mainly because of lower summer temperatures and lower precipitation totals during April-September, while September rainfall was high but had only a limited effect on harvest results. In the Saaz variety, the final alpha acids content reached 3.52% w/w in the & Zcaron;atec region, 3.33% w/w in the & Uacute;& scaron;t & ecaron;k region, and 3.23% w/w in the Tr & scaron;ice region, i.e. values higher than those recorded in the preceding three crop years and closer to the long-term typical range for this variety. Among the Czech hybrid varieties, the highest alpha acids contents were observed in Agnus, Vital, and Rubin, while Sl & aacute;dek, Premiant, Kazbek, Saaz Late, Saaz Special, and Saaz Shine also showed commercially relevant levels. The total production of alpha acids in the Czech Republic in 2025 was estimated at 297.8 t, with Saaz accounting for 59% of total alpha acid production despite occupying 82.1% of the harvested area. The results confirmed the dominant role of weather conditions, but also highlighted the effects of stand age, planting material and local environmental conditions on the final alpha acids content.

The alpha acids content of the 2024 hop crop in the Czech Republic was evaluated using a pre-harvest forecast, a harvest forecast and a reality. The alpha-acids value in the Saaz variety was 2.72% w/w, in the Žatec (2.87% w/w) and Tršice (2.47% w/w) hop growing regions the content was well below the long-term averages, and in the Úštěk region (3.38% w/w) it was in line with the average. In Žatec and Úštěk, the alpha acids of the most widely cultivated hybrid varieties Sládek (7.5 and 6.7% w/w) and Premiant (7.5 and 8.5% w/w) were significantly higher than in Tršice (Sládek 4.8% w/w, Premiant 6.0% w/w). The values of the varieties Saaz Late and Saaz Special were below the average, while Kazbek (6.49% w/w) showed a good tolerance to weather conditions and the alpha acids content slightly above the average. The bitter varieties Agnus, Rubín and Vital with alpha acids content of 11–13% w/w give very stable alpha acids values over the long term, with 2024 corresponding to previous vintages. The harvest forecasts for alpha acids this year were in a very good agreement with reality. The year 2024 was relatively rich in water, but the distribution of rainfall over time was not optimal. Average monthly temperatures during the growing season were 1–2 °C above long-term averages, and the year as a whole was very warm. The Czech Republic's hop harvest (total of 6494 tonnes, yield 1.34 t/ha) was average in 2024. The total alpha acids production from the 2024 harvest was average at 242.5 t. The Saaz hops (82.1 % of the harvested area) accounted for 55% of the total. Bitter hop varieties cope better with adverse weather conditions than aromatic varieties.

Biometric parameters of hop plants were studied over a three-year period on the Czech variety Premiant grown in the Žatec (Saaz) hop-growing region under an organic farming regime. Initially, only bine leaves developed, with lateral leaves emerging during the third growing month (June). Their leaf area at the time of harvest was larger than the bine leaves. The moment when the area size of both leaf categories was the same, designated as the breaking point (BP), was determined in the interval 181–195 DOY (day of year). The leaf area (LA) measured using infrared imaging and gravimetric methods yielded comparable results, with correlation coefficients of 0.93 and 0.96, respectively. The total leaf area of one hop plant (LA) with four trained bines, which developed dynamically during ontogeny, was 10.45 m2 (2019), 6.65 m2 (2020), and 12.04 m2 (2021) in the harvest period. With a spacing of 3 m × 1 m, the corresponding Leaf Area Index (LAI) values were 3.5, 2.2 and 4.0 in the harvest season. Therefore, they are comparable to other crops such as maize or sorghum. Regression equations were calculated to determine the dry biomass of bine and lateral leaves depending on DOY. Correlations between the dry mass of leaves and the size of the leaf area for both bine and lateral leaves were also evaluated. This work also contains data on the mass proportions of the main plant organs (bine, leaves, cones).

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.

In the new millennium, a lot of hop flavour cultivars with a unique "varietal aroma" have been bred and widely used for a dry hopping of beers. Seven flavour hop cultivars were also registered in the Czech Republic in recent years. Essential oils, depending on their concentrations, combinations and threshold levels, are responsible for diverse aroma and flavours of hop cultivars in dry cones and beers. In this study, we evaluated qualitative essential oils parameters and sensory aroma profiles in dry cones of 7 Czech and 23 world flavour hop cultivars by multivariate principal component analysis (PCA), which divides cultivars to quadrants. The Czech flavour cultivars Juno and Jupiter were placed in the first quadrant, influenced by higher geranyl acetate and methyl-4-8-decadienoate contents. The Kazbek, Ceres, Eris, Pluto and Saturn cultivars were grouped in the second quadrant, influenced by higher 2-MeBu-isobutyrate and geranyl isobutyrate contents, in essential oils analyses. However, in sensory aroma analyses, the Jupiter cultivar was placed in the first quadrant due to its woody aroma, whereas the Juno and Pluto cultivars were placed in the second quadrant due to their floral and grassy aromas. The Saturn cultivar was placed in the third quadrant due to a fruity aroma and the Kazbek, Ceres and Eris cultivars were grouped in the fourth quadrant due to their citrusy aroma. 7 Czech and 11 world flavour hop cultivars were also compared by sensory aroma analyses in dry hopping brewing tests. There was no correlation found between cultivar sensory aroma profiles in dry cones and beers, and differences and discrepancies in flavours for all of them. We proved that Czech hop flavour cultivars provided original sensory aroma profiles in beers and that they are useful for breweries in different beer styles.

Hops are an essential raw material for beer production and the Czech Republic is not only a traditional hop grower but also participates in the breeding of varieties that are important on a global scale, mainly in terms of quality. The presented study deals with the evaluation of selected varieties grown in conventional and organic management over 4 years (2020–2023). The main contribution of this paper lies in the fact that remote sensing data of hop gardens were obtained by UAV during the growing seasons for four consecutive years and were subsequently used to explain the development of hop stands with respect to their yield and production quality. Hop fields were scanned using a UAV with a multispectral camera and the vegetation indices NDVI, GNDVI, NDRE, CIR and SAVI were derived. These indices were used as indirect indicators for determining vitality, health and structure for predicting yield and quality parameters (alpha acid content in hop cones). Based on statistical analysis it was concluded that in terms of yield assessment, spectral indices can explain hop yields up to 61%, with better results being achieved in the later stages of growth development. However, spectral indices are only able to explain a maximum of 18% of qualitative parameters. On the contrary, the maximum was reached in the early stages of stand development. UAV scanning monitors the canopies of hop stands with high resolution, similar to vineyards. Indices evaluating chlorophyll content appeared to be more suitable for affecting differences between hop stands.

A four-year study compared the secondary metabolite profile of two flavour hops, the widely used Cascade and the new Czech variety Kazbek. The average alpha-acids and total essential oil of Kazbek and Cascade grown in Europe did not differ, while alpha-acids were 20 % higher in Cascade grown in the USA. Cluster analysis of essential oil composition distinguished the varieties, the markers being mainly farnesene derivatives. US-Cascade had higher terpenoids (geraniol, geranial) and lower fatty acid methyl esters than EU-Cascade. Both varieties have high and comparable levels of geraniol esters (230-360 mg/kg total) and low levels of free geraniol. The sulphur-containing volatile profile of US-Cascade and EU-Cascade hops differed significantly, probably as a result of treatment with different pesticides. The profile of hop-associated essential oils and aroma components of the single-variety experimental beers Kazbek and Cascade was similar for both whirlpool-hopped and additionally dry-hopped beers. Citrus and fruit notes were the dominant descriptors. Two independent sensory panels did not clearly distinguish or prefer beers hopped with Cascade and Kazbek hops, demonstrating the possibility of alternating between the two varieties in brewing. A new finding is that genetically distant hop varieties can provide similar sensory profiles in late- and dry-hopped beers.

The research presented in the article was focused on determining the C-factor for hops for conventional cultivation (CT) and soil conservation technique, which is based on the presence of cover crops (CC) in the inter-rows. The values of the soil loss ratio, which are the basis for the calculation of the C-factor, are also presented. The research activities were carried out between 2016 and 2023 and a field rainfall simulator was used for the measurements. Rainfall simulations were conducted at three developmental stages of CC. The results show a high C-factor value for CT (0.73), which indicates insufficient erosion control efficiency. In contrast, a C-factor of 0.16 was determined for the cover crop technique. This means that cover crops in the inter-rows of hop gardens can effectively reduce the risk of water erosion. The values reported in the article can be used as input parameters in various erosion models and equations to refine the subsequent calculation.

BackgroundThis paper brings new information about the genome and phenotypic characteristics of Pantoea agglomerans strain DBM 3797, isolated from fresh Czech hop (Humulus lupulus) in the Saaz hop-growing region. Although P. agglomerans strains are frequently isolated from different materials, there are not usually thoroughly characterized even if they have versatile metabolism and those isolated from plants may have a considerable potential for application in agriculture as a support culture for plant growth.MethodsP. agglomerans DBM 3797 was cultured under aerobic and anaerobic conditions, its metabolites were analyzed by HPLC and it was tested for plant growth promotion abilities, such as phosphate solubilization, siderophore and indol-3-acetic acid productions. In addition, genomic DNA was extracted, sequenced and de novo assembly was performed. Further, genome annotation, pan-genome analysis and selected genome analyses, such as CRISPR arrays detection, antibiotic resistance and secondary metabolite genes identification were carried out.Results and discussionThe typical appearance characteristics of the strain include the formation of symplasmata in submerged liquid culture and the formation of pale yellow colonies on agar. The genetic information of the strain (in total 4.8 Mb) is divided between a chromosome and two plasmids. The strain lacks any CRISPR-Cas system but is equipped with four restriction-modification systems. The phenotypic analysis focused on growth under both aerobic and anaerobic conditions, as well as traits associated with plant growth promotion. At both levels (genomic and phenotypic), the production of siderophores, indoleacetic acid-derived growth promoters, gluconic acid, and enzyme activities related to the degradation of complex organic compounds were found. Extracellular gluconic acid production under aerobic conditions (up to 8 g/l) is probably the result of glucose oxidation by the membrane-bound pyrroloquinoline quinone-dependent enzyme glucose dehydrogenase. The strain has a number of properties potentially beneficial to the hop plant and its closest relatives include the strains also isolated from the aerial parts of plants, yet its safety profile needs to be addressed in follow-up research.

The most important weather factor for the hop growing season in 2023 was the rainy period in the last decade of July and the first decade of August, which replaced the previously warm and dry weather. Heavy rainfall with a total of 60–100 mm of water and temperatures in the range of 20–25 °C saved the annual hop harvest from the yield decline that occurred in 2022. However, the above-average harvest of nearly 7000 tonnes and a yield of 1.44 t/ha was achieved at the expense of the bitter compound content of most varieties. The alpha acid content of Saaz hops was well below 3.0% w/w in all hop-growing regions, one of the lowest levels for the last 10 years. It is even lower than the extremely hot and dry year 2022 and comparable to 2015. Lower levels of alpha acids were also found in Sládek (4.8–6.7% w/w), Premiant (6.9–7.9% w/w) and Saaz Special (4.3% w/w). The varieties Agnus, Rubín and Vital contained stable amounts of alpha acids in the range of 11–13% w/w, which is about the same as in previous years. The total production of alpha acids in Czech hops from the 2023 harvest was 253 tons, which is average in a longerterm comparison. Saaz hops accounted for only 55% of the total production, although they are grown on 83.3% of the harvest area.

Hop (Humulus lupulus L.) is an important commercial crop known for the biosynthesis of valuable specialized secondary metabolites in glandular trichomes (lupulin glands), which are used for the brewing industry. To achieve burgeoning market demands is the essentiality of comprehensive understanding of the mechanisms of biosynthesis of secondary metabolites in hop. Over the past year, several studies using structural biology and functional genomics approaches have shown that Mediator (MED) serves as an integrative hub for RNAP II-mediated transcriptional regulation of various physiological and cellular processes, including involvement of MED5a and MED5b in hyperaccumulation of phenylpropanoid in A. thaliana. In the present work, an unprecedented attempt was made to generate Hlmed5a/med5b double loci mutant lines in hop using a CRISPR/Cas9-based genome editing system. The Hlmed5a/med5b double loci mutant lines showed reduced expression of structural genes of the flavonoid, humulone, and terpenoid biosynthetic pathways, which was more pronounced in the lupulin gland compared to leaf tissue and was consistent with their reduced accumulation. Phenotypic and anatomical observations revealed that Hlmed5a/med5b double loci mutant line exhibited robust growth, earlier flowering, earlier cone maturity, reduced cone size, variations in floral structure patterns, and distorted lupulin glands without any remarkable changes in leaf morphology, intensity of leaf color, and chlorophyll content. Comparative transcriptome analysis of leaf and lupulin gland tissues indicates that the expression of enzymatic genes related to secondary metabolite biosynthesis, phytohormone biosynthesis, floral organs, flowering time, and trichome development, including other genes related to starch and sucrose metabolism and defense mechanisms, were differentially modulated in the Hlmed5a/med5b lines. The combined results from functional and transcriptomic analyses illuminates the pivotal function of HlMED5a and HlMED5b in homeostasis of secondary meatbolites accumulation in hop.

Hop is widely used in beer brewing and as a medicinal product. The present study comprehensively analyzed the main molecular determinants of the antibacterial activity of hop extracts. Minimum inhibitory concentrations (MIC) against Bacillus subtilis between 31.25 and 250 mu g/mL were found in the ethanolic extracts of five hop varieties for beer brewing, but not in the tea hop sample. Activity-guided fractionation revealed the highest antibacterial activity for lupulone and adlupulone (MIC 0.98 mu g/mL). Metabolome profiling and subsequent multistep statistical analysis detected 33 metabolites out of 1826 features to be associated with the antibacterial activity including humulone, adhumulone, colupulone, lupulone, and adlupulone. Xanthohumol, the three humulone- and three lupulone congeners were quantified in the hop extracts by a validated ultrahighperformance liquid chromatography-mass spectrometry method. Considering concentrations and MICs, colupulone and lupulone were identified as major contributors to the antibacterial activity of hop extract with the highest antibacterial activity values (concentration/MIC) of 1.59 and 2.56.

Hop ( Humulus lupulus ) biosynthesizes the highly economically valuable secondary metabolites, which include flavonoids, bitter acids, polyphenols and essential oils. These compounds have important pharmacological properties and are widely implicated in the brewing industry owing to bittering flavor, floral aroma and preservative activity. Our previous studies documented that ternary MYB-bHLH-WD40 (MBW) and binary WRKY1-WD40 (WW) protein complexes transcriptionally regulate the accumulation of bitter acid (BA) and prenylflavonoids (PF). In the present study, we investigated the regulatory functions of the R2R3-MYB repressor HlMYB7 transcription factor, which contains a conserved N-terminal domain along with the repressive motif EAR, in regulating the PF- and BA-biosynthetic pathway and their accumulation in hop. Constitutive expression of HlMYB7 resulted in transcriptional repression of structural genes involved in the terminal steps of biosynthesis of PF and BA, as well as stunted growth, delayed flowering, and reduced tolerance to viroid infection in hop. Furthermore, yeast two-hybrid and transient reporter assays revealed that HlMYB7 targets both PF and BA pathway genes and suppresses MBW and WW protein complexes. Heterologous expression of HlMYB7 leads to down-regulation of structural genes of flavonoid pathway in Arabidopsis thaliana , including a decrease in anthocyanin content in Nicotiana tabacum . The combined results from functional and transcriptomic analyses highlight the important role of HlMYB7 in fine-tuning and balancing the accumulation of secondary metabolites at the transcriptional level, thus offer a plausible target for metabolic engineering in hop.

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.

From the brewing and commercial point of view, the content of alpha acids is the most important quality parameter of hops, which is subject to significant annual fluctuations. The established system for evaluating the content of alpha acids in Czech hops consists of pre-harvest and harvest predictions and a detailed analysis of reality based on the analysis of all purchasing lots of raw hops. It is differentiated according to varieties and hop growing areas. This article presents the results of the 2022 harvest, discusses the influence of weather conditions, the age of hop gardens and virus-free seedlings on the harvest results, and the relationship of predictions to reality. The average content of alpha acids in the majority Saaz variety in the Saaz, Auscha and Tirschitz hop growing regions was 2.88, 2.80 and 2.63% by weight in the original respectively. In all areas, the alpha acid content has been significantly affected by the age of the hop growths. Hybrid varieties coped with adverse weather conditions much better than most aromatic hops. The total production of alpha acids in Czech hops from the harvest of 2022 was 182.9 tons, one of the lowest in the last 15 years. It is due to the concurrence of two factors: the low yield per hectare and the content of alpha acids in Saaz hops. The cause was, similarly to Germany, an extreme deficit of precipitation and high temperatures during the vegetation season.

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 & Zcaron;atec (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, Sladek 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 Sladek 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.

From the brewing and commercial point of view, the content of alpha acids is one of the most important quality parameter of hops, which is subject to significant annual fluctuations. The established system for evaluating the content of alpha acids in Czech hops consists of pre-harvest and harvest predictions and a detailed analysis of reality based on the analysis of all purchasing lots of raw hops. It is differentiated according to varieties and hop growing areas. This article presents the results of the 2021 harvest, discusses the influence of weather conditions, the age of hop gardens and virus-free seedlings on the harvest results, and the relationship of predictions to reality. The average content of alpha acids in the majority Saaz variety in the Žatec, Úštěk and Tršice areas was 4.45, 4.20 and 3.36% by weight in the original respectively. In all areas, the alpha acids content has been significantly affected by the age of the hop growths. The total production of alpha acids in hops harvested in the Czech Republic in 2021 was 414.5 tons. The harvest is the highest in the last 25 years; the result is due to the combination of two factors, both high yield per hectare and high alpha acids content.

Sulfur compounds of hop oils are important components of hop oils although their share is relatively very small, approximately 1 %. A collection of 30 sulfur-containing volatiles was detected by gas chromatographic analysis of hop oils which were isolated from the hops by steam distillation. Thioesters S-methylthio-hexanoate, S-methylthio-isovalerate, S-methylthio-butyrate have been identified as the dominant components. It was found out that the composition of sulfur compounds of hop oils, examined on a set of 14 Czech hop cultivars, is varietally characteristic. Statistical evaluation using multivariate statistical methods has shown that the spectrum of sulfur substances can be used to determine the variety authenticity for only a few cultivars (Boomerang, Kazbek, Gaia, Vital). For other varieties it is not sufficient to distinguish them reliably. The analysis of sulfur compounds of hop oils must therefore be considered as an auxiliary chemotaxonomic tool. To determine the identity of the variety with greater reliability, it is necessary to use other chemotaxonomic tools (terpenic and oxygenated substances of hop essential oils, bitter substances, prenylfavononoids and polyphenols). Genetic methods are also an important approach at determining and identifying the purity of hop varieties.