Abstract: ObjectiveThe regulation mechanism of sucrose phosphate synthetase(SPS) on sucrose accumulation and yield in disease-free sugarcane seedlings was analyzed in order to provide reference for improvement of sugarcane yield and sucrose content.MethodOrdinary seedlings(CK) and disease-free seedlings of sugarcane cultivar ROC22 were used. The materials,including young leaves,mature leaves,young stems and mature stems,were sampled in mixed manner during seedling stage,tillering stage,elongation stage and mature stage. The expression levels of SPS genes of different types(SPSA,SPSB,SPSC,SPSD1 and SPSD2)at various developmental stages in different tissues were analyzed with real time fluorescence quantitative PCR(qPCR)method.ResultDifferent SPS genes were expressed in all sugarcane tissues of disease-free seedlings. The expressions of SPSD1 and SPSD2 were different in young leaves and mature leaves,and the expressions were also obviously different from those in CK. Expressions of SPSA,SPSB,SPSD1 and SPSD2 in 1st-3rd internodes of disease-free seedlings were higher than control. In the 9th-23th internodes at elongation stage,the expression of SPSA in disease-free seedlings was lower than control,but the expression of SPSB in disease-freeseedlings was higher than control and the expressions of SPSD1 and SPSD2 was not significantly different from that in control. Overall,the expressions of SPSA,SPSB,SPSD1 and SPSD2 in disease-free seedlings became closer to those in CK as internodes became more mature.ConclusionAlthough different SPS genes are differentially expressed in tissues of disease-free sugarcane seedlings at different developmental stages,the differential expressions are various. It is predicted that disease-free treatment is able to increase SPS genes expression in leaves and young internodes to improve the sucrose content and sugarcane yield.