Verticillium tolerance – a crucial selection criterion in the development of hop cultivars Based on the knowledge gained with respect to wilt tolerance in hop breeding lines from the different breeding programmes when they are trialled in the next few years on the two field selection plots, in future resistance to the Verticillium fungus, especially to the lethal species, will be an important selection criterion in the development of new hops. However, every hop grower must know that problems of contamination with Verticillium cannot be solved simply by growing a wilt tolerant cultivar in the plot in question. Quite the converse in fact; heightened tolerance in a hop cultivar will eventually lead to the selection of forms of fungus with even more aggressive means of attack from among the Verticillium strains already present in the hop yard, creating what are known as super virulent species as a means to secure survival of the fungus. The fact that Ariana has been infected for the first time with more virulent strains of Verticillium (see above), in a commercial plot where there had previously been problems with wilt on the cultivar Saphir, points to the selection scenario outlined above and the emergence of super virulent strains. Outlook Managing Verticillium wilt in the German hop growing regions is a long-term undertaking. Both the research and guidance contributed by the LfL and the implementation of preventive horticultural measures by hop growers are of crucial importance in the concerted effort to combat Verticillium in hop cultivation. References Down, G., Barbara, D., Radišek, S. (2007): Verticillium albo-atrum and V. dahliae on hop. Bulletin OEPP/EPPO Bulletin 37, 528–535. Inderbitzin, P. and Subbarao, K.V. (2014): Verticillium Systematics and Evolution: How Confusion Impedes Verticillium Wilt Management and How to Resolve It. Phytopathology 104 (6), 564-574. http://dx.doi.org/10.1094/PHYTO-11-13-0315-IA Guček, T., Stajner, N., Radišek, S. (2015): Quantification and detection of Verticillium albo-atrum in hop (Humulus lupulus) with real-time PCR. Hop Bulletin 22, 26-39. Kindsmiller, S. (2015): Auswertung einer vierjährigen Versuchsserie zum Einfluss verschiedener Düngemaßnahmen auf die Verticilliumwelke im Hopfen. Bachelorarbeit, Hochschule Weihenstephan-Triesdorf, Fakultät Land- und Ernährungswirtschaft, Studiengang Landwirtschaft. Maurer, K.A., Radišek, S., Berg, G., Seefelder, S. (2013): Real-time PCR assay to detect Verticillium alboatrum and V. dahliae in hops: development and comparison with a standard PCR method. Journal of Plant Diseases and Protection, 120 (3), 105–114. Maurer, K.A. (2014): New strategies to control Verticillium wilt in hops. Dissertation, Technische Universität Graz, 1-82. Maurer, K.A., Berg, G., Seefelder, S. (2014): Untersuchungen zur Verticillium-Welke im Hopfenanbaugebiet Hallertau. Gesunde Pflanze, 66, 53-61. Radišek, S., Jakše, J., Simonic, A. and Javornik, B. (2003): Characterization of Verticillium albo-atrum field isolates using pathogenicity data and AFLP analysis. Plant Disease 87, 633–638 Radišek, S., Jakše, J. and Javornik, B. (2004): Development of pathotype specific SCAR markers for the detection of Verticillium albo-atrum isolates from hop. Plant Disease 88, 1115–1122. Radišek, S., Jakše, J., Javornik, B. (2006): Genetic variability and virulence among Verticillium albo-atrum isolates from hop. European Journal of Plant Pathology 116: 301-314. Seefelder, S., Seigner, E., Niedermeier, E., Radišek, S. & Javornik. B. (2009): Genotyping of Verticillium pathotypes in the Hallertau: Basic findings to assess the risk of Verticillium infections. In: Seigner E. (Ed.) 2009: IHGC International Hop Growers’ Convention of the Scientific Commission, Leon, Spain, 74-76. Talboys, P.W. (1987): Verticillium wilt in English hops: retrospect and prospect. Can. Journal of Plant Pathology 9, 68-77.
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