Differences in Leaf Chemistry and Glandular Trichome Density between Wild Southwestern American Hop () and Commercial Hop Cultivars.

The female flowers ("cones") of the hop plant ( L.) produce compounds that contribute to the flavor and other properties of beer. Hop leaves and cones produce many of the same compounds, which also confer agronomic traits such as insect and disease resistance. Targeted and untargeted ultraperformance liquid chromatography-quadrupole time-of-flight-mass spectrometry with Waters MS technology (UPLC-QTof-MS) metabolomics were used to compare leaf phytochemical compositions of greenhouse-grown southwestern American wild (A. Nelson and Cockerell) Rydb. against a group of commercial hop cultivars consisting of both pure European L. and European-North American hybrids. Principal component analysis showed a clear distinction in chemical profiles between the two groups. leaves had a significantly higher content of total α acids ( = 4.4 × 10), total bitter acids ( = 2.6 × 10), cohumulone ( = 1.0 × 10), humulone + adhumulone ( = 9.1 × 10), and the prenylflavonoids xanthohumol ( = 0.013) and desmethylxanthohumol ( = 0.029) as well as significantly higher densities of glandular trichomes ( = 1.3 × 10), the biosynthetic site of those compounds. Most flavonol glycosides measured were also significantly more abundant in ( = 1.5 × 10 to 0.0027), whereas phenolic acids were consistently, but generally nonsignificantly ( > 0.05), more abundant in the cultivars. The higher bitter acid, prenylflavonoid, and flavonol glycoside content of leaves may help to confer more favorable insect and disease-resistance properties.