6.3
Crossbreeding with the Tettnanger landrace
Objectives The local variety Tettnanger with its fine, spicy hop aroma is still very popular with brewers who value classic beer aromas. However, because of the Tettenanger variety’s lower yield per ha, rather unstable alpha acid levels, early flowering as a result of rising temperatures (Mozny et al., 2009), and lower disease resistance, the cultivation of this terroir variety is becoming more and more difficult for growers, especially from an economic perspective. During the last decade, there have been purely selective breeding attempts within the natural variability of this landrace, but they did not produce clear improvements. This was the reason for the start of a crossbreeding program in 2011. The goal was to develop a variety that would be very similar to the original by exhibiting its typical aroma expressions, but with significantly improved yields, greater resistance to fungi, and the ability to adapt to climate change, especially by not flowering too early during stretches of higher temperatures. In addition, a modern variety must optimize its nutrient uptake efficiency, which is also required by the new Fertilizer Ordinance. To achieve all these objectives and improvements in a single cross with Tettnanger as the mother while maintaining the Tettnanger aroma, was obviously not easy. Method ― ― ― ―
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Classic crosses with Tettnanger and preselected Hüll aroma lines Mildew resistance testing in the greenhouse and laboratory (see 6.5) Seedling tests (single plants) in the greenhouse Cultivation trials with reduced use of pesticides and fertilizers o Three-year cultivation test in Hüll o Four years of repeated confirmation trials at two locations in the Hallertau and in Tettnang Chemical analysis of cone compounds (IPZ 5d) Organoleptic flavor assessments by the breeding team and with the support of the GfH expert committee Virus testing using DASELISA (Double Antibody Sandwich Enzyme Linked Immunosorbent Assay) technology (IPZ 5b und IPS 2c, Seigner et al., 2014) Tests for Verticillium infestation using real-time PCR technique (Maurer et al., 2013; Seigner et al., 2017; see 6.7).. Pathogen elimination via meristem culture (Seigner et al., 2017; see 6.8.)
Result
Seedling testing Since 2010, a total of 41 targeted crosses have been produced. More than 1,600 seedlings raised in a greenhouse were pre-selected for disease resistance and then planted in the breeding garden in Hüll, where they were tested over a three-year period. Thanks to the minimal use of pesticides and the reduced use of nitrogen in the cultivation tests with seedlings and plants in the breeding gardens, the most robust, resistant and nutrientefficient candidates were selected.
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