Mechanisms of differential responses to drought stress in polyploid of Malus toringo (Siebold) Siebold ex de Vriese
Liu, C (Liu, Cheng) [1] ; Zhang, ZJ (Zhang, Zhijun) [1] ; Li, WT (Li, Wentong) [1] ; Fu, LQ (Fu, Lanqi) [1] ; Ma, FW (Ma, Fengwang) [1] ; Li, C (Li, Chao)
PLANTA
DOI:10.1007/s00425-025-04911-x
Abstract
Main conclusionPolyploidization enhances drought tolerance in A11 of Malus toringo. In polyploid A11 leaves, drought stress elevates soluble sugars and induces moderate ABA synthesis while sustaining photosynthesis to enhance drought tolerance.AbstractMalus toringo (Siebold) Siebold ex de Vriese, an apple rootstock, is known for its salt-alkali resistance and post-grafting vigor but has poor drought tolerance. Despite increased interest in polyploid rootstocks due to their improved drought tolerance, research on the drought resilience of polyploid M. toringo is lacking. In this study, we explored the mechanisms underlying drought stress responses in polyploid M. toringo strains by grafting diploid A12, triploid D13, and tetraploids A11 and A13 seedlings onto two-year-old Malus hupehensis rootstocks. The experimental findings revealed that the A11 and D13 plants are more drought resistant than the A12 plants, while the A13 plants exhibited lower drought tolerance. Under drought stress conditions, they displayed higher net photosynthetic rates and antioxidant enzyme activity than the A12 plants and had a higher leaf wax content. Transcriptomics analysis revealed that many differentially expressed genes between the significantly more drought-tolerant tetraploid A11 and its diploid control A12 were related to stress-related metabolic pathways. Notably, in the starch and sucrose metabolic pathways, the starch and sucrose levels in the A11 plants were significantly lower, while the glucose, fructose, and sorbitol content was higher, indicating enhanced osmoregulation. Concurrently, the downregulation in the sucrose phosphate synthase gene (MdSPS1) was accompanied by the upregulation in that of the sucrose invertase gene (MdNINV1). In conclusion, the polyploid A11 and D13 plants were more drought resistant than the diploid A12 plants, providing new insights for exploring apple rootstock germplasms with superior drought tolerance.