Effect of Exogenous Glycine Betaine on the Germination of Tomato Seeds under Cold Stress

Cold stress is known to influence tomato growth, development, and yield. In this study, we analyzed the germination of tomato seeds treated with exogenous glycine betaine (GB) at a low temperature (14 degrees C). The results showed that cold stress inhibited tomato seed germination, and pretreatment with exogenous GB reduced this inhibition and enhanced the germination rate (GR), germination index (GI), and viability of tomato seeds at low temperatures. Analysis of gene expression and metabolism revealed that GB positively regulated endogenous hormone gibberellin (GA) content and negatively regulated abscisic acid (ABA) content, while GB reduced the starch content in the seeds by up-regulating the amylase gene expression. Gene expression analysis showed that the key genes (SlSOD, SlPOD, and SlchlAPX) involved in reactive oxygen species (ROS) scavenging systems were up-regulated in GB-pretreated tomato seeds compared with the control. At the same time, levels of malondialdehyde and hydrogen peroxide were significantly lower, while the proline content and peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) levels were elevated compared with those in the control. These results demonstrate that exogenous GB as a positive regulator effectively alleviated the inhibition of tomato seed germination under cold stress by different signal pathways.

Automated summary

Cold stress inhibits tomato seed germination, but pretreatment with exogenous glycine betaine (GB) alleviates this inhibition and enhances the germination rate and viability of tomato seeds at low temperatures. GB positively regulates gibberellin content and negatively regulates abscisic acid content, while up-regulating the expression of the amylase gene to reduce starch content in the seeds. GB also up-regulates genes involved in reactive oxygen species scavenging systems, leading to lower levels of malondialdehyde and hydrogen peroxide and elevated levels of proline, peroxidase, superoxide dismutase, and catalase.