Determination of Tolerance and Sensitivity of Safflower Genotypes Based on Germination Indices and Comparison of Biochemical Contents Under Salt Stress

Abstract

Safflower germination and seedling growth stages are extremely sensitive to salinity. The study aimed to identify safflower genotypes' germination, seedling growth responses, and biochemical changes in tolerant and susceptible genotypes in response to salt stress. Total of 28 genotypes were subjected to salt (NaCl) treatments (0, 180, 240 mM), and germination percentage, mean germination time, seedling and root lengths, and vigor index of the genotypes were determined. The genotype, treatments, and interaction effects were significant for germination, seedling, and biochemical parameters. The genotypes' germination percentage, seedling length, root length, and vigor index decreased under salt stress. While the reduction in germination percentage of salt-tolerant genotypes was between 6-21%, it was between 46-65% in sensitive genotypes at 240 mM salt treatment. Five tolerant (Shufu, Sidwill, Finch, Yuyao, Oleic Leed) and sensitive (Huaxian, Linas, 4022, Oker, Rehbein) genotypes were chosen based on reductions in germination percentage and vigor index, and the proline, hydrogen peroxide, and malondialdehyde (MDA) contents of these genotypes were investigated. The proline content of the genotypes increased by 26 to 56 fold at 180 mM salt concentration. The hydrogen peroxide content of sensitive and tolerant genotypes increased at 180 mM salt treatment, but at 240 mM salt treatment, the hydrogen peroxide content of the sensitive genotypes continued to increase by 6-50%, hydrogen peroxide content decreased in tolerant genotypes by 10-30%. MDA contents increased in the sensitive and tolerant genotypes, but the level of increase was higher in sensitive genotypes (307-631%) than the tolerant genotypes (103-323%) at 240 mM salt treatment. The heatmap generated by means of sensitive and tolerant genotypes showed 28 coefficients and 5 of which were significant. These results show that changes in hydrogen peroxide and MDA contents are different between tolerant and sensitive genotypes. They could be useful selection criteria along with germination percentages for determining tolerant and susceptible safflower genotypes at the seedling stage.