Yield Performance and Oil Chemotype Variation of <i>Coriandrum sativum</i> L. Genotypes under Different Sowing Dates in a Mediterranean Climate

Coriander is a multipurpose medicinal and aromatic plant whose economic value is determined by seed yield and chemical profile of its essential and fixed oils. In the Mediterranean basin, a climate change hotspot, optimizing the cropping calendar is vital to mitigate environmental stress. This study aimed to evaluate the genotype-by-environment interaction regarding yield components and phytochemical characteristics of six coriander genotypes (Erba, Gamze, Irak, Kudret, Mardin, and Pelmus) across four sowing dates (November 01, November 15, March 01, and March 15) in the eastern Mediterranean region of Turkey. A split-plot field experiment was conducted over two consecutive growing seasons (2020–2020 and 2021–2022) in Adana. Agronomic traits were recorded, and chemical compositions of essential oils and seed oils were determined using GC-MS. The sowing date significantly influenced productivity; early autumn sowing (Nov 01) achieved the maximum seed yield (3134.63 kg/ha), while spring sowings (March) resulted in a substantial reduction of approximately 70% due to a shortened vegetative period. Genotype G1 (Erba) emerged as the most productive cultivar (2463.65 kg/ha). The essential oil content ranged from 0.52 to 1.03%, with linalool as the predominant constituent (47.44–74.96%). While early November sowings maximized the linalool content, spring sowings favored the accumulation of aliphatic aldehydes (n-decanal and 2-dodecenal). Fixed oil analysis revealed a dominance of petroselinic acid (69.93–85.82%), which exhibited a strong negative correlation with linoleic acid. PCA effectively distinguished the superior agronomic and monoterpenol-rich profiles of autumn-sown genotypes from aldehyde-rich spring sowings. To maximize both the seed yield and high-quality essential oil content in Mediterranean climates, cultivation of the “Erba” genotype during the early autumn window (early November) is highly recommended.