The role of polyploidy in improving seed traits, growth kinetics, and embryo development in Cuminum cyminum L.

Cumin (Cuminum cyminum L.) is an annual herbaceous plant from the Apiaceae family, renowned for its medicinal and culinary applications as the second most popular spice globally after black pepper. Germination is a critical stage in the life cycle of plants, particularly for medicinal plants, as it determines successful establishment and productivity. This study explores the impact of ploidy levels (diploid and tetraploid) and genotype interactions on germination traits, seed morphology and early seedling growth in five selected cumin genotypes (YAR1, KBA4, SKD6, SIV8 and NKM9). Induction of tetraploidy significantly influenced germination percentage, rate, seed vigour index, and morphological traits. Notably, diploid genotypes exhibited higher germination percentages, while tetraploid SKD6 displayed the highest germination speed and seedling biomass, demonstrating genotype-specific ploidy effects. For the first time, root growth kinetics were analyzed, revealing distinct growth patterns between diploid and tetraploid seeds. Morphometric evaluations showed that tetraploid seeds and embryos were significantly larger, attributed to the ‘gigas effect’, which enhances storage reserves and seed vigour. However, challenges such as embryo-less seeds and variability in genotype responses to ploidy manipulation were observed. These findings underscore the importance of targeted breeding strategies that optimize genotype-ploidy interactions to improve seed quality, germination performance and early growth in cumin. By advancing our understanding of polyploidy’s role in shaping key agronomic traits, this study provides a foundation for sustainable cultivation practices and enhanced productivity of medicinal plants.