Physiological and Biochemical Variations in Different Pepper (Capsicum annuum var. conoides) Varieties under Salt Stress (PRJCA048714)
Soil salinization poses an increasingly severe threat to sustainable development in the cluster pepper (Capsicum annuum var. conoides) industry. To elucidate physiological responses and salt tolerance mechanisms, this study screened 63 cluster pepper accessions and selected salt-tolerant (P47) and salt-sensitive (P18) varieties for comparative analysis. Physiological profiling, transcriptomics, and metabolomics revealed that under salt stress, P47 exhibited: Higher chlorophyll and proline content: (1) Enhanced activities of POD, CAT, and SOD; (2) Lower relative leaf electrical conductivity, malondialdehyde content, and Na+/K+ ratio compared to P18.P47 demonstrated significantly lower Na+ accumulation in both shoots and roots, while effectively sequestering more Na+ in the root system. Ultrastructural analysis of pepper leaves revealed that under salt stress, the mesophyll cells of P18 exhibited severe damage, with disorganized palisade and spongy tissues, disrupted chloroplast membranes, and atrophied starch grains. In contrast, P47 maintained intact cellular architecture with well-ordered tissue arrangement. Integrated omics analysis identified differentially expressed metabolites enriched in phenylpropanoid biosynthesis and glycerophospholipid metabolism pathways. Key salt-responsive genes (SAUR, ARF7, TAT) were implicated in hormone signaling, tyrosine metabolism, and alkaloid biosynthesis. These findings provide insights into the molecular basis of salt tolerance in cluster pepper and establish targets for breeding resilient cultivars.