Mulching with plastic film improved the root quality of summer-sown sweet potato (Ipomoea batatas (L). Lam.) in northern China

The root quality of sweet potato cultivated during the summer season is poor in northern China; thus, this study was conducted to determine whether root quality could be improved through mulching with plastic film (MPF). The effect of MPF on root starch and its composition, the activity of starch synthesis enzymes, and other quality-related parameters were investigated in two purple flesh sweet potato cultivars, Jishu 18 and Ayamurasaki (Aya). The results indicated that root dry matter, anthocyanin content, adenosine triphosphate (ATP), and starch content were higher in both cultivars under the MPF treatment than those under the control treatment. The root adenosine diphosphate glucose pyrophosphorylase/uridine diphosphate glucose pyrophosphorylase (ADPGPPase/UDPGPPase) activity and adenosine triphosphatease (ATPase) activity were increased using MPF. However, under the MPF treatment, the amylose content, soluble sugar content, and granule-bound synthase (GBSS) activity increased in Jishu 18 but decreased in Aya, and the amylopectin content, protein content, and soluble starch synthase (SSS) activity decreased in Jishu 18 but increased in Aya. Therefore, MPF seems benifit to improve the quality of sweet potato, but the effects of this treatment condition may be dependent on the cultivar.