Table 7_Phenotypic plasticity vs. local genetic adaptation: essential oil diversity of natural immortelle (Helichrysum italicum (Roth.) G.Don) populations along eastern Adriatic coast.docx

The essential oil of Helichrysum italicum (Roth) G.Don, commonly known as immortelle, is produced in Mediterranean countries to meet the increasing demand of the cosmetic and pharmaceutical industries. This study focused on the analysis of secondary metabolites, specifically essential oils, extracted from plants grown from the seeds of natural immortelle populations collected along the eastern Adriatic coast and cultivated ex situ under uniform conditions. Field trials were conducted to determine whether the observed variability was due to phenotypic plasticity or local genetic adaptation. Eighteen natural immortelle populations were sampled, hydrodistilled and their essential oil composition determined by gas chromatography-mass spectrometry. A total of 84 compounds were identified. Eighteen essential oil compounds were present in concentrations greater than 5% in at least one sample of 18 populations. The populations differed significantly in nine essential oil compounds: Limonene, linalool, nerol, neryl acetate, trans-caryophyllene, neryl propionate, ar-curcumene, β-selinene and δ-selinene and the differences were attributed to genetic adaptation to the native environment. Three chemotypes were identified within which the populations were grouped. Results showed a significant and strong correlation between biochemical and bioclimatic distance, with 22.4% of biochemical differentiation between populations explained by bioclimatic distance. Correlations between the 18 main compounds and the bioclimatic variables of the populations’ native environment revealed that BIO14 Precipitation of driest month and BIO15 Precipitation seasonality, were the most informative. These results can serve as a first step for future selection of immortelle populations with desirable adaptations to obtain commercial cultivars that ensure high quality immortelle essential oil.

俗称永久花（immortelle）的意大利蜡菊（Helichrysum italicum (Roth) G.Don）精油，目前在地中海国家规模化生产，以满足化妆品与制药行业日益增长的市场需求。本研究聚焦于次生代谢产物（特指精油）的分析，这些代谢产物提取自沿亚得里亚海东部沿岸采集的天然永久花种群种子培育出的植株，并在统一可控条件下进行异地栽培。研究开展田间试验，以探明观测到的性状变异究竟源于表型可塑性，还是本地遗传适应。本研究共采集18个天然永久花种群样本，通过水蒸馏法提取精油，并采用气相色谱-质谱联用法（gas chromatography-mass spectrometry，GC-MS）测定其精油成分，共鉴定出84种化合物。在18个种群的至少一个样本中，有18种精油成分的含量超过5%。18个种群在9种精油成分上存在显著差异，分别为柠檬烯（Limonene）、芳樟醇（linalool）、橙花醇（nerol）、乙酸橙花酯（neryl acetate）、反式-石竹烯（trans-caryophyllene）、丙酸橙花酯（neryl propionate）、莪术烯（ar-curcumene）、β-芹子烯（β-selinene）和δ-芹子烯（δ-selinene），且该差异被归因于种群对原生境的遗传适应。研究共鉴定出3种化学型，所有种群均被归入相应的化学型中。结果显示，生化距离与生物气候距离之间存在显著且强相关的关系，种群间22.4%的生化分化可由生物气候距离予以解释。通过对18种主要成分与种群原生境的生物气候变量进行相关性分析，结果表明最具解释力的变量为BIO14 最干月降水量（Precipitation of driest month）与BIO15 降水季节性（Precipitation seasonality）。本研究结果可为未来筛选具有优良适应性状的永久花种群提供参考依据，进而培育出可保障优质永久花精油产出的商业化栽培品种。