Effect of Foliar Application of Methyl Jasmonate and Extracts of Juniper and Sagebrush on Essential Oil Yield and Composition of ‘Native’ Spearmint

Abstract

<jats:p>Spearmint (<jats:italic>Mentha spicata</jats:italic> L.) is a major essential oil crop in the United States. Developing means for increased biomass and oil yields and increased concentrations of carvone would be beneficial for the essential oil industry. A field experiment was conducted to study the effect of foliar application treatments [water (control), water + Tween20, sagebrush essential oil + Tween20, sagebrush water extract, juniper essential oil + Tween20, juniper water extract, and methyl jasmonate] on ‘Native’ spearmint essential oil content, shoot fresh weight, oil yield, and oil composition. The essential oil content was low in the water + Tween20 and in juniper essential oil (EO) + Tween20 treatments and high in the juniper water extract and in methyl jasmonate (MJ) treatments; however, neither of these were different from the water control or from the sagebrush EO + Tween20. Biomass fresh weight was lower in the sagebrush water extract (SWE) and in the juniper water extract (JWE) relative to the water control. The application of juniper EO + Tween20 reduced the concentration of carvone in the oil relative to the water control or to the water + Tween20 treatment. The sagebrush water extract, juniper EO + Tween20, juniper water extract, and MJ increased the concentrations of beta-caryophyllene relative to the water treatment. The concentration of trans-beta-farnesene was lower in the control water treatment and higher in all other treatments. Also, with the exception of sagebrush EO + Tween20, all treatments increased the concentration of germacrene D relative to the water control but not relative to water + Tween20. This study demonstrated that foliar application of sagebrush EO, sagebrush water extract, juniper EO, or juniper water extract to ‘Native’ spearmint may affect the essential oil profile of spearmint essential oil. Some of the treatments increased the concentrations of beta-caryophyllene, trans-beta-farnesene, and germacrene D in the essential oil; however, neither of the treatments increased the concentration of carvone, the main essential oil constituent of ‘Native’ spearmint oil.</jats:p>

Drying and Shade Effects on Spearmint Oil Yields and Composition

“…In this study the concentration of carvone varied from 51% to 52.8%, which was within the range reported previously for 'Native' spearmint grown in Wyoming (Zheljazkov et al, 2012(Zheljazkov et al, , 2013 and other regions in the United States (Murray et al, 1972;Zheljazkov et al, 2010aZheljazkov et al, , 2010b. For example, carvone concentration in the oil of the same cultivar of spearmint reported by Zheljazkov et al (2013) varied from 51.4% to 55.9%, whereas carvone concentration in Zheljazkov et al (2012) varied from 42.9% to 74.6%. Carvone concentration in this study was also comparable to literature reports from other countries (Bienvenu et al, 1999;Díaz-Maroto et al, 2003;Kizil and Toncer, 2006;Sokovic et al, 2009;Topalov, 1989).…”

“…Another example was beta-caryophyllene concentration: the concentration of betacaryophyllene in the study of Zheljazkov et al (2013) varied from 1.5% to 1.86%, whereas in this study, beta-caryophyllene varied from 1.71% to 2.26% depending on the drying period and drying condition.…”

“…Land preparation, planting, fertilization, and irrigation. Land preparation and transplanting were carried out as described earlier (Zheljazkov et al, 2012(Zheljazkov et al, , 2013. Raised beds were prepared with a press-pan-type bedshaper machine.…”

“…The production of 'Native' spearmint in the United States is concentrated in the midwest and northwestern states (NASS, 2009) and there has been an interest in expanding the production of 'Native' spearmint to other regions. Recent studies in Mississippi and Wyoming demonstrated that 'Native' spearmint can be grown in a wide range of environments outside the traditional spearmint production areas and produce desirable yields and oil composition (Zheljazkov et al, 2010a(Zheljazkov et al, , 2010b(Zheljazkov et al, , 2012(Zheljazkov et al, , 2013. Spearmint oil content in fresh herbage is 0.15% to 0.3% and depends on many factors.…”

“…Spearmint oil content in fresh herbage is 0.15% to 0.3% and depends on many factors. For example, in studies conducted in Wyoming, the oil content of fresh spearmint varied from 0.14% to 0.22% with carvone concentration in the oil ranging between 42% and 75% depending on the timing of harvesting after the first fall frosts (Zheljazkov et al, 2013). In studies conducted in Mississippi with the same cultivar of spearmint, the carvone concentration was 36% to 63% in the oil of freshly distilled biomass and 45% to 62% in the oil of dried biomass at different harvesting times (Zheljazkov et al, 2010b).…”