2017 ASHS Annual Conference

During preliminary experiments involving production of basil for fresh and oil production, it was noted that the quantity of essential oil varied from cultivar to cultivar. Therefore, investigations were undertaken to determine if there was a relationship between the presence/absence of oil trichomes on the adaxial and abaxial leaf surfaces of pesto and specialty basils and the quantity of oil produced. To ascertain this for each cultivar, the second pair of fully expanded leaves from a terminal whorl was selected. On the abaxial side, a clear grid of 25-mm squares was overlaid on either side of and along the midvein. Using a dissecting microscope with a magnification of 3.5 times, two rows of the centermost seven squares on one side of the midvein were observed for trichomes and photographed. The procedure was then replicated on the adaxial side, and for the second leaf selected for a total of 2 leaves per observation per plant. Trichomes were then counted within each 25 mm square. Additionally, 100 g of dried basil leaves were crushed and distilled for essential oil content. Initial observations indicate that oil content within and between cultivars varied widely. For example, the leaves from the pesto basil, ‘Dolly’, produced from <0.1 to 0.35 ml as compared to leaves from the specialty basil, ‘Mrs. Burns’ Lemon’, which produced from 0.5 to 1.5 ml per 100 g. Trichome numbers also varied according to cultivar. For example, ‘Dolly’ leaves had 0-3 trichomes over each of the squares on the adaxial surface and 2-12 trichomes on the abaxial surface. Leaves of ‘Lime’, a specialty basil, had 11-22 trichomes on the adaxial and 23-37 trichomes per each 25 mm square on the abaxial. Additional data for 6 other cultivars on trichome presence and oil quantity will be presented and implications for commercial production will be discussed.