Yield Performance and Phytochemical Stability of ‘Comet’ Hop Under Contrasting Light Supplementation Regimes in Subtropical Conditions

Abstract

This study evaluated the agronomic performance and phytochemical stability of the 'Comet' hop (<i>Humulus lupulus</i> L.) under contrasting photoperiod management regimes (with and without supplemental lighting) in subtropical conditions over two consecutive crop cycles (2024-2025). The experiment, conducted at the School of Agricultural Sciences (FCA/UNESP, Botucatu, Brazil), followed a split-plot factorial design with ten replications. Supplemental lighting (50 W, 6500 K LED floodlights) extended the photoperiod to 17 h during the vegetative stage. Morphometric, phenological, and phytochemical parameters were analyzed, including α- and β-acid contents and essential oil composition by GC-MS and GC-FID. Supplemental lighting significantly increased plant height (590.9 cm), number of lateral branches (70.1), cone length (3.49 cm), and dry cone mass (374.6 g plant^-1) while reducing the insertion height of the first cone (99.0 cm). α-Acid content increased from 9.35% to 11.92%, and essential oil content from 1.34% to 1.90%, while β-acid levels showed no significant variation. Chemical analysis identified 31 compounds, predominantly β-myrcene (65-74%) and sesquiterpenes such as (<i>E</i>)-caryophyllene, α-selinene, and β-selinene, exhibiting remarkable compositional stability across years and treatments. Photoperiod extension delayed floral induction, promoted biomass accumulation, and increased cone yield without altering the characteristic herbaceous-resinous aromatic profile. These findings validate supplemental lighting as a decisive strategy to optimize hop production in subtropical regions, ensuring phenological regularity, higher yield, and consistent chemical quality, thereby strengthening the viability of domestic hop cultivation in Brazil.