University of Tabriz Journal of Plant Physiology and Breeding 2008-5168 16 2 2026 05 31 Genetic diversity among Iranian Citrullus colocynthis accessions using morphological and phytochemical characteristics 87 104 21803 10.22034/jppb.2026.21803 EN Maedeh Fereshtian Department of Botany, Research Institute of Forests and Rangelands, Tehran, Iran. Forozandeh Soltani Department of Horticultural Science and Landscape Architecture, Faculty of Agriculture & Natural Resources, University of Tehran, Karaj, Iran. Journal Article 2025 11 15 <strong>Objective:</strong> Colocynth<em> </em>(<em>Citrullus colocynthis</em> L. Schrad.) is an important medicinal and oilseed species adapted to arid and semi-arid environments. This study aimed to characterize the morphological and phytochemical diversity among Iranian <em>C. colocynthis</em> accessions and identify superior genotypes with desirable yield and nutritional traits. <strong>Methods:</strong> Seventeen accessions, collected from different geographical regions of Iran, were evaluated under field conditions using a randomized complete block design with three replications. Morphological traits related to fruit and seed characteristics, along with phytochemical attributes- including fatty acid composition, total phenolic content, and carotenoid concentrations- were analyzed using several statistical methods, including analysis of variance, principal component analysis, and hierarchical clustering. Correlation coefficients among the morphological and phytochemical characteristics were also computed. <strong>Results: </strong>Significant variation was observed among the colocynth accessions for all of the evaluated traits, indicating substantial genetic diversity within the Iranian colocynth germplasm. The Jiroft, Khorasgan 5, Arak, and Orzoeeh accessions exhibited superior performance for fruit yield, and fruit number. Seed oil analysis revealed the predominance of unsaturated fatty acids, particularly linoleic acid, with the highest concentration detected in the Orzoeeh accession (73%), followed by Arak (72%), Hormozgan (72%), Jiroft (71%), and Khorasgan 5 (71%). Higher total phenolic content was observed in the Kerman and Yazd accessions, while the Ahvaz, Jiroft, and Arak accessions exhibited higher total carotenoid levels, suggesting a higher antioxidant potential and adaptation to environmental stress conditions. Principal component and cluster analyses confirmed the divergence among the colocynth accessions and differentiated them based on combined agronomic and phytochemical characteristics. <strong>Conclusion:</strong> This study represents one of the first evaluations integrating the morphological and phytochemical characteristics of Iranian colocynth germplasm. The results demonstrate substantial genetic diversity within Iranian colocynth germplasm for morphological and phytochemical characteristics. The high proportion of unsaturated fatty acids, particularly linoleic acid, further emphasizes the nutritional and pharmaceutical value of this germplasm. The identified superior accessions may serve as valuable genetic resources for breeding programs targeting drought tolerance, medicinal quality, antioxidant capacity, and seed oil improvement under arid climatic conditions. https://breeding.tabrizu.ac.ir/article_21803_1ab2079ce233adc91ae285a7f3412d9b.pdf