Identification of hop cultivars using high resolution melt curve analysis

Hops Session
William A Deutschman, Westminster College, Salt Lake City, UT, USA
Co-author(s): Julie Kilpatrick and Brian Avery, Westminster College, Salt Lake City, UT, USA

ABSTRACT: It is important for hop breeders, growers, and brewers to be able to accurately distinguish hop varieties. Here, we report the use of high resolution melting (HRM) of DNA fragments to identify and differentiate DNA microsatellite sequences from various hop strains. HRM is a PCR based technique that allows for the identification and differentiation of closely related DNA sequences that may differ in sequence by as little as a single base. HRM monitors the fluorescence of a dye that binds specifically to double stranded DNA and therefore can precisely measure the fraction of a sample that is annealed at any given temperature. HRM analysis is then based on the melting temperature profile of a PCR product, which depends both on the length and specific DNA sequence of that product. Thus, different products that are identical or nearly identical in length and cannot be distinguished by gel-based analyses can be easily discriminated using HRM. We performed HRM on 10 commercial hop cultivars and 3 native hop samples from northern Utah. Multiple primer pairs were used to amplify different microsatellite regions in order to assess the discriminatory power of each microsatellite region. Our results show that the HRM technique can differentiate between microsatellite alleles that were previously scored as being identical using gel-based detection methods. Thus, HRM shows great promise as a fast technique with stronger resolving power than traditional methods for identification or verification of hop cultivars. The goal of our work is to take advantage of the benefits of HRM to establish a broader DNA based scheme for cultivar identification that will be of use to hop breeders, growers, and brewers.

William Deutschman earned his Ph.D. degree in chemistry in 2001 at the Institute of Molecular Biology at the University of Oregon. From 2001 to 2006, he taught biochemistry at Plattsburgh State University in Plattsburgh, NY. In 2006, he moved to Westminster College in Salt Lake City, where he currently teaches chemistry, biochemistry, and brewing science, while also pursuing research projects with undergraduate students in the areas of brewing and fermentation science.