To identify known and novel miRNAs involved in the response and adaptation of sugar beet to short-term and long-term alkaline stress, miRNAs were identified by analysis of the deep sequencing of sRNA Overall design: Five-week-old sugar beet (Beta vulgaris L.) seedlings were treated with Hoagland solution, containing 75 mM mixed alkaline solution (Na2CO3:NaHCO3, 1:2) for 0 day (control, designated as C), 3 days (short-term treatment, designated as ST) and 7 days (long-term treatment, designated as LT). Fresh leaves from the same position of seedlings at different treatments were collected. Sample from each treatment represented a pool of more than 10 independent individuals. All the harvested leaves were immediately frozen in liquid nitrogen after collection and stored at -80 °C for RNA-seq.