Flax (Linum usitatissimum L.) is a significant marketable crop for seed, oil, fiber, and pharmaceutical products. The latest study transpired to assess the morphological, biochemical, and yield traits with inter-simple sequence repeat (ISSR) markers to determine the genetic diversity among flaxseeds of Sakha-1, Sakha-2, Sakha-3, Sakha-5, Sakha-6, Giza-12, and Amon genotypes under sandy soil conditions. Results indicated that all flax varieties varied significantly (P > 0.05) in most studied characteristics. Sakha-6 exceeded all genotypes in seed yield (0.888 t ha^-1), straw yield (6.093 t ha^-1), oil yield (0.302 t ha^-1), and biological yield (6.981 t ha^-1). These increases were due to the rise in different biochemical contents of carotenoids (0.601 mg), proline (34.81 mg), free amino acids (396.85 mg), oil (35.46%), phenolic (189.61 mg), and total carbohydrates (32.07%), which reflected on seed yield plant^-1 (0.509 g). Flax genotypes showed high genetic variations; eight of the 15 ISSR primers employed resulted in 74 bands, with 35 as polymorphic. The average percentage polymorphism of the amplified loci ranged from 16.67% to 50%, the average number of polymorphic bands per primer was 4.38, and the average number of amplified bands per primer was 9.25. The marker index for ISSR values ranged from 0.08 to 2.40 for UBC-846 and UBC-825, respectively. The similarity between genotypes ranged from 0.58 to 0.90. Three markers showed significant regression association with the six traits.

Keywords: Flax (L. usitatissimum L.), genotypes, genetic variability, biochemical, physiological, and yield traits, ISSR markers, cluster analysis

Key findings: Seven flax (L. usitatissimum L.) genotypes incurred morphological, biochemical, and ISSR markers evaluation. The flax genotypes varied significantly in all studied traits. They showed a high level of genetic variations, with the genotypes divided into two main clusters and a dendrogram created using the similarity matrix produced by UPGMA.