Anthocyanidin in plants,an important pigment,is of great interest to researchers,consumers,and commercial entities due to its physiological functions.Anthocyanin content and mRNA levels of anthocynin biosynthesis genes were investigated in storage root of different purple-fleshed sweet potatoes (PFSP) genotypes to understand the regulation mechanism of anthocyanin under weak light conditions.Anthocyanin content,its amount of accumulation,and the expression of CHS,DFR,F3H,GT,and ANS genes in the PFSP storage root under weak light conditions were studied.The results demonstrated that the anthocyanin content of the treatments was decreased and was obviously lower than that of the control until 30 days after shading in Ayamurasaki,while it was lower than that of the control from the beginning of shading in Jishu 18.Their accumulation rates of both treatmeants were lower than its control before 10-20 d of shading in Jishu 18,while those of Ayamurasaki werent in their treatments.This indicated that Jishu18 is more sensitive to light as compared to Ayamuraska.Under the different weak light conditions,mRNA levels for ibCHS,ibF3H,ibDFR,and ibANS were obviously decreased,while the expression of ibGT was increased.These results indicated that anthocyanin content was regulated by light at the mRNA levels and the enzymatic level in sweet potato.Therefore,the development dynamic response to anthocyanin content varied in different genotypes of PFSP,and mRNA levels of anthocyanin biosynthesis were inhibited under the weak light condition.