Title : Development of Virginia mountain mint as a potential commercial crop in the southern USA
Abstract:
Mountain mint (Pycnanthemum species) is a mint-flavored herb with a diverse range of essential oil profiles, offering potential for commercial applications similar to those of the Mentha genus. North Alabama has favorable weather conditions for cultivating mountain mint, particularly Virginia mountain mint (Pycnanthemum virginianum), provided suitable varieties and production technology are available. This research aimed to assess the adaptability, leaf biomass production, essential oil content, and composition of Virginia mountain mint (VMM) by evaluating four VMM varieties over a two-year period in North Alabama. Thirty-day-old greenhouse-grown plants of the four varieties were transplanted into raised beds in the experimental plots organized in a randomized complete block design with three replications in 2020. After three harvests at 135 (H1), 155 (H2), and 170 (H3) days after planting (DAP), the plants were left to overwinter and regrow in 2021. In Year 2 (2021), all four varieties sprouted in late March and were evaluated for regrowth, biomass production, essential oil content, and composition at two harvest times: 128 and 228 days after regrowth (DAG). Essential oils were extracted through hydrodistillation using continuous dichloromethane extraction and were analyzed using gas chromatographic techniques. In Year 1 (2020), the total fresh above-ground biomass (AGB) ranged from 125 g/g/ g/plant for M4 to 809 g/g/ g/plant for M3. Varieties M1 and M2 produced 699 g and 561 g of fresh biomass per plant, respectively. In Year 2, the percentage of fresh AGB increased by 82%, 66.5%, 21.9%, and 226.9% for M1, M2, M3, and M4, respectively, compared to Year 1. At the first harvest in Year 1, the essential oil (EO) content of M1 was 1.15%, higher than that of M2 (0.91%), M3 (0.76%), and M4 (1.03%). At the first harvest in Year 2, the EO content of M1 and M3 increased to 4.91% and 1.85%, respectively, while the EO content of M2 and M4 decreased to 0.53% and 0.79%, respectively. In Year 1, the concentration of isomenthone increased significantly throughout the season, rising from 19.93% at H1 to 69.31% at H3 in M1, and from 18.1% at H1 to 65.83% at H3 in M3. However, it increased only slightly in M2 and M4. The thymol concentration decreased slightly but not significantly in all four varieties, with M2 and M4 showing notably higher thymol levels compared to M1 and M3. Overall, varieties M1 and M3, with their higher whole-plant and leaf biomass and greater EO content, were the best performers. This study demonstrated that mountain mint has potential for commercial production in North Alabama, enabling farmers to maximize yield and minimize production costs, thereby increasing net profits by cultivating this crop over multiple seasons.
