Iranian Journal of Seed Research

Salinity is one of the most important factors limiting agricultural production. Cotton, as an oil-fiber plant, is one of the most important industrial plants and is sensitive to salinity, especially at germination and seedling stages. Therefore, in this study, 14 allotetraploid varieties of commercial and local cotton were selected. The study was carried out as factorial with a completely randomized design and three three replications, using the sandwich method. Germination tests were performed at three salinity levels of 0, 8 and 16 ds.m^-1. Afterwards, root and shoot length, fresh and dry weight of root and shoot, germination percentage, allometric coefficient, seedling water percentage and seed vigor index were measured and stress tolerance indices were calculated based on yield (seedling dry weight) in stress and non-stress conditions. Given these indices, all cultivars were aalyzed at two levels of 8 and 16ds.m^-1, using principal component analysis and biplot diagrams were drawn. Finally, the dendrogram classification of genotypes was plotted based on STI indices (stress tolerance index), SSI (stress susceptibility index), and the performance (dry weight plantlet) in stress and non-stress conditions. The result of variance analysis for genotype, salinity and salinity×genotype demonstrated that dry weight root, dry weight shoot, fresh weight root, stem length, vigor index seedling, allometric coefficient, dry weight seedling, and length seedling were significant in p-value 0.01, and fresh weight shoot, length root were significant in p-value 0.05. Clustering and the biplot of the genotypes based on STI and SSI indices at salinity levels of 8 and 16 ds.m^-1 indicated that the Sepid and Giza genotypes were tolerant and that the Kashmar genotype was sensitive to salt levels at germination stage.

Extended abstract
Introduction: Currently, in most countries around the world, cotton seeds are used in delinted form. The fuzzy cotton seed often lead to slower germination, increased susceptibility of seeds and seedlings to pests and diseases, and disrupts mechanized cotton planting. Delinted cotton seeds have numerous advantages, including the possibility of mechanized planting, reduced seed consumption per unit area, faster germination in the soil, and quicker emergence of seedlings in the field. Furthermore, delinted seeds are usually free from pathogenic agents, and the seed quality is improved with the availability of gravity separation and removal of broken, lightweight, and hollow seeds. One of the challenges faced by cotton seed delinting factories in Iran that employ acid-based methods is the reduction in the seed germination of the Delinted seeds, which poses a challenge to the continued operation of these factories.
Materials and methods: To investigate the reasons behind the reduction in the germination power of cotton seeds in the Delinting factory, this research was conducted to examine the physiological and mechanical characteristics of seeds at various stages of delinting in the factory. For this purpose, sampling was carried out in the Delinting factory in two replications. Traits such as seed vigor, germination percentage, ion leakage, seed density and volume, seed aging, level of abrasion and damage to the seed coat, and seed rupture force were studied. Finally, the data were analyzed using SAS, SPSS, and JMP software.
Results: The test results showed that seed sampling from both replications of the factory before centrifuge had the lowest germination percentage, leaf formation percentage, primary root length, primary stem length, dry weight of primary root, and dry weight of primary stem. These traits indicate that during the centrifugation stage, the seeds sustain significant mechanical damage, leading to a reduction in their physiological characteristics. As the percentage of breakage and ion leakage increases, the seed rupture force decreases non-linearly. Based on these findings, it can be concluded that acid contact with the cotton seed and the centrifugation process caused more mechanical damage to the seeds, leading to a significant reduction in seed rupture force.
Conclusion: The accuracy of operations at all stages of ginning significantly impacts seed quality, but investigations indicate that the centrifugation section, the temperature of the dryer cylinders, and the acid neutralization process require greater attention and monitoring. Therefore, it is necessary to adjust the duration or concentration of the acid used for delinting in the Delinting factory to match the seed condition, in order to minimize damage to the seeds.

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