Multi-Level Screening Identifies Salt-Tolerant Chrysanthemum Genotypes Through Physiological, Molecular, and Root Anatomical Responses

Salinity is a major abiotic stress limiting the productivity and ornamental value of chrysanthemum. In the present study, 10 chrysanthemum (Chrysanthemum morifolium) genotypes were evaluated for their salt-stress responses using an integrated framework encompassing biochemical, molecular, and anatomical analyses. Significant genotype-dependent variations were observed in antioxidant enzyme activities, lipid peroxidation, and physiological attributes under 100 mM NaCl stress. Bidhan Lalima and Bidhan Sabita exhibited superior salt tolerance, whereas Bidhan Jayanti and Silk Brocate were highly susceptible. Salt stress induced a marked increase in oxidative damage, with MDA content rising by ~1.5-2.5 fold, ranging from ~10.1 to 26.1 nmol g⁻¹ FW across genotypes. Tolerant genotypes such as Bidhan Lalima and Bidhan Sabita maintained lower MDA levels (~13.0-20.6 nmol g⁻¹ FW at 200 mM) compared to highly susceptible genotypes like Bidhan Jayanti and Silk Brocate (~20.5-28.5 nmol g⁻¹ FW). Antioxidant enzyme activities showed genotype-specific responses, with guaiacol peroxidase increasing up to ~2-4 fold and SOD activity ranging from ~0.20 to 0.64 Units mg⁻¹ protein under stress. Defense-related enzymes such as chitinase and β-glucanase also showed significant induction, reaching up to ~9.1 and ~2.5 Units mg⁻¹ min⁻¹, respectively. Gene expression profiling revealed differential regulation of key salt-responsive genes CmSOD, CmWRKY10, CmNCED3A, CmHSFA4, and CmHSP70 with tolerant genotypes showing enhanced expression of antioxidant- and ABA-related pathways. Root anatomical analysis highlighted distinct structural adaptations, including larger vascular areas and modified cortex and endodermal layers in tolerant genotypes, supporting improved water and nutrient transport under saline conditions. Collectively, this multi-tiered approach enabled reliable discrimination of salt-tolerant and susceptible genotypes and provided mechanistic insights into salt adaptation in chrysanthemum. The findings offer a robust foundation for breeding programs focused on developing salt-resilient cultivars for sustainable floriculture in salinity-affected regions.