Expression profiles of 18 SsDREB genes under drought and cold stresses. a A heat map illustrating of gene expression levels of the 18 SsDREB genes under normal, drought and cold conditions. b The expression levels based on FPKM for SsDREB1F, SsDREB1L, SsDREB2D, and SsDREB2F under normal and drought conditions. F172, GT31, and GZ18 are three sugarcane cultivars. F172 is a strong drought tolerance cultivar, GT31 is a middle drought tolerance cultivar, and GZ18 is a drought sensitivity cultivar. A: the tissues under normal conditions; B: mild drought stress; BCK: the control group of mild drought stress; C: moderate drought stress; CCK: the control group of moderate drought stress; RC: re-watering after moderate drought stress treatment; D: severe drought stress; DCK: the control group of severe drought stress; RD: re-watering after severe drought stress treatment. HL, HC, LL and LC are S. spontaneum accessions with different polyploidy levels under cold stress treatment. HL: hyperploid clone 15–28 under cold stress; HC: hyperploid clone 15–28 under normal condition; LL: hypoploid clone 12–23 under cold stress; LC: hypoploid clone 12–23 under normal condition .