Genotype-Specific responses to salinity in chrysanthemum: Evaluation and mechanistic insights from salt-tolerant germplasm Chrysanthemum yantaiense

• Chrysanthemum yantaiense was proved to be an excellent material for improving salt tolerance in chrysanthemums. • A number of highly salt-tolerant strains have been screened to provide intermediate breeding resources for the production of salt-tolerant chrysanthemums. • The spatiotemporal physiological response of two offspring (i.e., YS-58 and YS-123) with contrasting salt tolerance was investigated under salt stress. • The salt-tolerant chrysanthemum (YS-58) accumulated less Na + in its leaves, had relatively stable soluble sugar content, higher proline content, stronger SOD activity and more stable K + in roots and stems. Chrysanthemum, a valuable ornamental flower, has limited salinity tolerance, which restricts its cultivation in salt-stressed conditions. In this study, we investigated the salt tolerance of a population derived from the salt-tolerant germplasm Chrysanthemum yantaiense . The parents and 91 offspring were subjected to 300 mM NaCl concentrations for 30 days. Based on the observed changes in growth and the degree of damage caused by salt stress, 15 high-resistant, 52 moderate-resistant, and 16 low-resistant strains were identified. Two offspring (i.e., YS-58 and YS-123) with contrasting salt tolerance were subjected to 15 days of salt stress, with phenotypic, physiological, and biochemical responses assessed at 5, 10, and 15 days. YS-58 demonstrated greater resilience, maintaining higher shoot fresh weight by day 10, and exhibiting significantly less growth impairment in both aboveground and belowground by day 15 compared to YS-123. Under salt stress, YS-58 accumulated lower Na⁺ levels in leaves, while sustaining higher K⁺ content in roots and stems. Additionally, YS-58 showed elevated proline levels, reduced soluble sugar content, and decreased malondialdehyde (MDA) accumulation, along with enhanced superoxide dismutase (SOD) activity relative to YS-123. Understanding these mechanisms will provide insights into how chrysanthemums survive under saline conditions, potentially enabling large-scale cultivation in saline soils.