content and particular suitability for cultivation in the Elbe-Saale region

6.4 Development of healthy, high-performance hops with high alpha acid content and particular suitability for cultivation in the ElbeSaale region

Initial Situation

The Elbe-Saale hop growing region covers 1,550 ha, which amounts to 7.6% of the total German hop growing area. The region thus makes a significant contribution to Germany's role in the world hop markets. Bitter and high alpha varieties dominate in the region. For the past 25 years, the main variety there has been the robust, high alpha Hallertauer Magnum. Yet, in more recent times, the share of the cultivation area devoted to Magnum has decreased from 65% to 39.8%, while the range of other varieties has expanded noticeably. Part of the reason for the decline of Magnum is its alpha acid yield of only 280 kg/ha. This is no longer competitive with yields of the Hüll-bred high alpha variety Herkules, which can produce more than 500 kg/ha of alpha acids. However, simply switching from Magnum to Herkules has not been successful in the Elbe-Saale region, because, in that region, Herkules is highly susceptible to crown rot.

Objectives

This project is designed to breed and test new, powerful and robust hop strains that can be cultivated economically under the special growing conditions of the Elbe-Saale region. The new plants must have a high alpha acid content and broad resistance especially to rot-causing pathogens. Furthermore, the plants must excel in climate adaptation and nutrient efficiency. The latter trait is particularly important within the context of the new Fertilizer Ordinance. This task was assigned to the Hüll Hop Research Center of the Bavarian State Research Center for Agriculture because of its world-renowned breeding expertise. The agriculture ministries of the three hop-growing states of Thuringia, Saxony-Anhalt and Saxony support this work financially.

Implementation and method

Crossings

- Targeted crossings with pre-selected Hüll breeding material - Mildew resistance testing in the greenhouse and laboratory (see 6.5) - Seedling testing (single plants) in the greenhouse - Cultivation tests with reduced use of pesticides and fertilizers o 3-year cultivation test in Hüll o 4-year extended tests at two trial locations in the Hallertau - Series of cultivation trials on commercial farms in the Hallertau and the Elbe-Saale region - Chemical analyses of cone compounds (IPZ 5d) - Organoleptic assessment of flavors - Virus testing using DASELISA (Double Antibody Sandwich Enzyme Linked Immunosorbent Assay) technology (IPZ 5b) - Tests for Verticillium infestation using the real-time PCR (Maurer et al., 2013; Seigner et al., 2017) - Pathogen elimination via meristem culture

Series of cultivation trials with Hüll high alpha strains in the Elbe-Saale region

Promising breeding lines from the LfL's high alpha breeding program have been tested under real world conditions in the Elbe-Saale cultivation area since 2014 and 2018. - Berthold farms in Monstab, Thuringia - Agricultural cooperative Querfurt, Saxony-Anhalt - Hopfen Estate, Saxony

Results Crossings

Since the start of the project in 2016, more than 200 targeted crosses with specially selected parents from Hüll breeding materials have been created to implement the goals of the project. In July 2020 alone, more than forty crosses were created.

Seedling preselection

At the start of this breeding program in the spring of 2020, more than 57,000 seedlings were tested for fungus resistance in the greenhouse in Hüll. Starting in May 2020, more than 1,900 seedlings that were pre-tested for disease resistance became available for further assessment „vegetation hall“ to determine their vigor and resistance under natural infection conditions as well as their stability when exposed to high winds. This work will last until the fall. In addition, the plants‘ gender was identified so that the prerequisites for cone development could be assessed in female individuals.

3-year seedling test

As is done every year, female seedlings from previous-year crosses, which had received a positive assessment in the vegetation hall, were planted in the test garden in Hüll, in the spring of 2020. Male individuals will prove their potential in the test garden for “boys” in Freising.

Promising seedling candidates from previous years are currently undergoing the 3-year seedling test in Hüll. With minimal plant protection and reduced fertilizer application over the entire vegetation period, only the most robust and, therefore, the most promising seedlings were selected on the basis of roughly 40 pertinent criteria. Of the 2017/2018/2019 vintages, 71 seedlings were harvested in the fall. The cone samples of the respective candidates were chemically analyzed in Hüll by IPZ 5d.

4-year test

Seventeen promising seedlings from individual plants that proved to be impressive after two to three years were selected for two sequential cultivation tests at two locations (in Hüll and Stadelhof), in 2020. Before the selected plants were propagated, they were tested for virus and Verticillium infections. Virus testing was carried out in the laboratory of the Plant Protection Working Group in Hop Cultivation (IPZ 5b), in Hüll. The results were negative. The absence of Verticillium was confirmed by the breeding team's genome analysis team in Freising using the highly sensitive real-time PCR technique. In order to achieve faster breeding progress, the tests in 2017 to 2019 were performed almost exclusively on seedlings from the Hüll high alpha breeding programs that were active before the start of the project. There are currently 54 breeding lines in trials in Hüll and Stadelhof. For the project, 41 candidates from the tests in 2017, 2018, and 2019 were harvested in 2020.

A reliable assessment of all selection criteria, in particular reliable prognoses for yield, compounds, and disease resistance, especially against crown rot pathogens, will be possible only after the completion of the 4-year cultivation test in the Hallertau. Two high-yielding strains with high to very high alpha acid contents turned out to be promising candidates for serial cultivation on farms in the Elbe-Saale area.

Cultivation trials

One hop grower in the Elbe-Saale region is currently testing four high alpha breeding strains from the Hüll breeding program. The tests involve comparisons of these breeding strains with Hallertauer Magnum, Herkules, Polaris, and Ariana to determine their location-specific suitability for cultivation (see Table 6.2). The LfL, in conjunction with the Thuringian State Institute for Agriculture, participates in these cultivation experiments by providing scientific and technical assistance. In addition, two breeding lines are being tested for their locationspecific suitability on one farm each in Saxony and Saxony-Anhalt. Meaningful assessments of all high alpha breeding strains, especially in terms of their required resistance to crown rot, are expected to be available only in two to three years.

Large-scale cultivation trials with the 2011/071/19 high alpha strain

In the current series of trials on farms in Thuringia, Saxony and Saxony-Anhalt, as well as in the Hallertau, one promising high alpha strain has already emerged. It not only has a very high alpha acid content and a good yield potential,but it also shows stability under stress conditions. In addition, it meets the requirement of extensive disease resistance, especially against crown rot and powdery mildew. Even the results of brewing trials with this strain are promising. Therefore, the Society for Hop Research (GfH) approved this high-performance, high alpha strain (2011/071/019) for larger-scale testing on a hectare basis. In the summer of 2020, this hop was planted in the Hallertau on 5.4 ha. In 2021, this breeding line will also be tested on 0.5 ha in the Elbe-Saale region. This large-scale cultivation trial over two to three years generates reliable assessments of this strain‘s cultivation and resistance characteristics at various locations. In addition, there is a need to confirm its heat and drought tolerance in the Elbe-Saale region. Trials in the Hallertau thus far have been convincing.

Outlook

The new strains show promising signs already. However, as candidates, they still have to prove themselves in further trials on farms in the Elbe-Saale hop region. It was clear already from the start of this breeding work in 2016 that the breeding and testing tasks (see figure) in the series of trials in the Elbe-Saale regon could not be completed successfully during the first project phase (2016 to 2020). Thus, it is gratifying that funding for this promising breeding and selection work by the LfL will be available for another five years. The funds are contributed by the Thuringian Ministry of Infrastructure and Agriculture, the Ministry for the Environment, Agriculture and Energy of the State of Saxony-Anhalt. and the Saxon State Ministry for Energy, Climate Protection, Environment and Agriculture.

Economic significance of the project results

This project will develop healthy, high-performance, high alpha breeding lines that combine all the advantages of modern varieties with future potential. These include highly stable alpha acid yields, broad resistance to pathogens such as powdery mildew, downy mildew and crown rot, as well as high efficiency in the uptake of nitrogen. They make hop production more environmentally friendly; conserve resources by reducing the use of pesticides and fertilizers; and help to save production costs. In addition, these new breeds are selected for the special cultivation conditions in the Elbe-Saale region. Finally, they have proven to be well armed against increased periods of heat and drought stress from climate change. This means that these new varieties can increase the competitiveness of hop cultivation in the Elbe-Saale region and thus decisively strengthen the region’s position long-term on the world markets.

References

Seigner, E. and Lutz, A. (2020): Zukunftsweisende Züchtungskooperation zwischen Bayern und den Elbe-SaaleHopfenbauländern – Leistungsstarke, robuste Hüller Hochalphasorten für die Elbe-Saale- Hopfenpflanzer. Hopfenrundschau International, Jahresausgabe 2020/2021, 28-31. Seigner, E. and Lutz, A. (2020): Entwicklung von leistungsstarken, gesunden Hopfen mit hohen Alphasäuregehalten und besonderer Eignung für den Anbau im Elbe-Saale-Gebiet. 4. Sachbericht zum Forschungs- und Entwicklungsprojekt

strains with Hallertau Magnum, Herkules and the serial cultivation test of Hüll high alpha Table 6.2: Results of according to EBC 7.4 % lfr.  acid content in wt. 1 Saale grower; Polaris as reference varieties at an Elbe