Abstract: Explants derived from shoot apices and mature embryos of elite barley cultivars were assayed for their callus induction and growth on culture media containing various concentrations of mannose as carbon sources.The results showed that a clear inhibiting effect on the leaf elongation and rooting of shoot apices in the concentration of 20 g/L mannose.For mature embryos,callus induction and growth rate were inhibited in the presence of 20 g/L or 25 g/L mannose,whereas 10 g/L or 15g/L treatment could effectively result in a reduction of callus formation and growth up to 50%.These results indicated that 20 g/L and 25 g/L mannose were required for inhibition of the explants derived from shoot apices and mature embryos,respectively,when mannose was used for positive selections of transgenic barley plants.In addition,it is more suitable to select during the initial induction and culture of barley explants.