Coordinated Dhurrin Turnover Is Associated with HCN Potential and Salt Tolerance During Sorghum Seed Germination

Cyanogenic glycosides function as defense compounds and nitrogen reservoirs in sorghum, but their roles during seed germination under salt stress remain unclear. Here, two sorghum cultivars differing in salt tolerance were compared using physiological, biochemical, pharmacological and transcriptomic analyses to investigate the relationship between dhurrin metabolism and germination performance under salinity. Salt stress inhibited germination and early seedling growth in both cultivars, whereas the tolerant genotype SB19 maintained higher germination rates, earlier radicle emergence and stronger antioxidant capacity than the sensitive genotype SB08. SB19 exhibited lower dhurrin accumulation but more stable hydrogen cyanide potential (HCNp) and higher β-glucosidase activity during germination. HCNp stability was positively associated with germination performance and antioxidant enzyme activities, and negatively associated with reactive oxygen species accumulation. Pharmacological inhibition of alternative oxidase or cyanide detoxification reduced the salt tolerance advantage of SB19, while sodium thiosulfate partially alleviated the inhibitory effects of cyanide detoxification blockage. Transcriptomic and co-expression analyses further associated dhurrin turnover with redox regulation, membrane-related processes and stress-responsive regulatory networks. Collectively, these findings indicate that coordinated dhurrin turnover and HCNp homeostasis are associated with improved germination performance under salt stress in sorghum.