Edaphic and environmental factors shaping essential oil profiles and morphological variation in wild Carum carvi L. populations from northwestern Iran

Abstract

Wild caraway ( Carum carvi L.) populations in northwestern Iran remain largely uncharacterized despite their potential as high-value genetic resources for essential oil (EO) production. This study aimed to evaluate the morphological and EO composition diversity of eight wild populations from different ecological zones in the region, identify superior accessions, and clarify associations between soil, climatic, and plant characteristics in relation to EO yield and composition. Key morphological traits and soil physicochemical properties were recorded for each population, and EO composition was determined using hydrodistillation followed by GC-MS analysis. The data were analyzed using ANOVA, PCA, cluster and correlation analysis to assess population diversity and trait associations. Significant variation was observed among populations for most of the measured parameters ( p ≤ 0.05). Population P3 exhibited the most favorable performance, with the tallest plants (72.40 cm), the highest number of umbels per plant (19.80) and 1000-seed weight (6.63 g). The highest EO content was observed in P6 (4.10%), while P8 showed the lowest (1.75%). Soil analysis revealed variation in edaphic conditions across sampling sites, with populations P3 and P6 growing in soils with the highest organic matter (OM) (P3: 2.32%) and (P6: 2.28%) and nitrogen content (both 0.23%). GC-MS analysis identified eight major compounds; carvone (55.13–73.25%) and limonene (19.75–38.75%) were the dominant constituents. Population P1 showed the highest carvone proportion (73.25%), while P3 had the highest limonene concentration (38.75%). PCA explained 59.95% of total variance and differentiated populations along axes reflecting soil–plant interactions and chemical profiles. Cluster analysis resolved three distinct groups, with P2 and P3 forming a superior cluster characterized by robust morphological traits and favorable edaphic conditions. This study provides the first morphological and EO composition characterization of wild caraway germplasm from north-western Iran. As populations were sampled directly from natural habitats rather than evaluated under common-garden conditions, the observed differences likely reflect the combined influence of genetic background and local edaphic/climatic factors, and genotypic and environmental effects cannot be fully disentangled. Nevertheless, P6 and P3 emerge as priority accessions for high EO yield and superior biomass, respectively. These accessions could provide valuable parental lines that are awaiting validation through common-garden trials and molecular analyses.