Predictive ability of hop (Humulus lupulus L.) grown in single hills on plot environments

Hop (Humulus lupulus L.) is a perennial, climbing plant species whose female strobiles or cones play a critical role in flavoring and bittering beer. The species is dioecious and outcrossing, and new cultivars are clonally propagated. The breeding timeline from cross to release is generally long, averaging between 13 and 15 years. We evaluated the predictive ability of various plant spacings and trellis configurations to see how predictive early-stage breeding environments were of later stages to see if accurate selections could be made earlier in the pipeline. We evaluated the performance of seven hop cultivars with varying end uses (high alpha, aroma, and dual purpose) in the seedling year in high-density, short-trellis plantings (0.46 and 0.61 m apart on a 2.4 m trellis), in established, low-density, single-hill nurseries (1.52 and 21.3 m apart on a 5.4 m trellis) and in plots representative of the commercial standard (1.07 m on a 5.4 m trellis). The trial was established in a single location in Prosser, WA, U.S., and was conducted for two years in 2022 and 2023. The experiment was established as a split-plot design in which the main plot factors, spacing, and trellis configurations, were randomized according to a randomized complete block design with four blocks. A variety of agronomic and cone-related traits were measured, including flowering time, percent up a string (vigor) lateral length, flowering pattern, harvest date, wet cone yield, dry matter at harvest, harvest index, alpha acid, beta acid, hop storage index (HSI), cone area, cone length, cone width, perimeter, and openness.

Methods
Flowering time, vigor, arm length, and flowering pattern were all collected by visual observations in the field. The remainder of traits were collected at harvest. Hop bines were pulled from the trellis, transported to a Wolf 170 hop picker where they were weighed, measured, and cones were separated. Ten cones were imaged using the HopBox, and the reaminder of the cones were dried and submitted for alpha, beta, and HSI measurements according to ASBC methods a local hop lab. The data were collected using tablets, and tracked throughout the harvest process using thermal printed tags and barcodes. All datasets were compiled using Program R.