Effects Of Different Shading Intensities On The Growth And Anthocyanin Synthesis Of Purple-fleshed Sweet Potatoes

Purple-fleshed sweet potato contains a lot of anthocyanins,which are loved by people for its functions such as scavenging free radicals,anti-tumor,anti-cancer,preventing diabetes,preventing high blood pressure and protecting eyesight.The synthesis of anthocyanins requires light induction in most plants.The present studies have mostly focused on the effect of light intensity on the characteristics of anthocyanin accumulation in the aboveground tissues of plants(flowers and fruits),while little is reported about the effect of light intensity on the accumulation of anthocyanins in the underground tissues of plants.In this experiment,purple-fleshed sweet potato violet was treated as the research object,and different degrees of shading treatments(natural light,20% shading,40%shading,60% shading and 80% shading)were performed in the tuberous root expansion stage(50-125 days after planting).The agronomic traits,yield,anthocyanins,soluble sugars and flavonoids contents were determined,and the activity of phenylalanine ammonia lyase(PAL),dihydroxyflavonol reductase(DFR)and anthocyanin synthase(ANS)in storage root were analyzed in order to understand the tolerance of purple-fleshed sweet potato to different light intensities under low-light conditions and the synthesis and accumulation characteristics of anthocyanins in purple-fleshed sweet potato under low-light stress.This study provides a theoretical basis for revealing the regulation of purple potato anthocyanin synthesis,and provides guidance for mining and cultivating shade-tolerant,high-anthocyanin and high-yielding purple potato germplasm resources,optimizing purple potato cultivation methods(intercropping,forest planting,etc.)and expanding cultivation areas.The main results of this test are as follows:1.Compared with the control without shading,mild shading(20% shading)had no effect on the growth and yield of purple-fleshed sweet potato,while moderate and severe shading(40%-80% shading)reduced the dry weight of the plant and increased the weight ratio(T/R value)of the aerial part to root,which led to a significant decrease in their yield.2.Compared with the control without shading,mild shading(20% shading)significantly increased the content of anthocyanins and soluble sugars purple-fleshed sweet potato,and moderate and severe shading(40%-80% shading)significantly decreased the content of anthocyanins and soluble sugars in purple-fleshed sweet potato,and as the degree of shading increases,the decrease is larger.Correlation analysis showed that the content of anthocyanins and soluble sugars in purple potato tubers were significantly positively correlated(P<0.001),indicating that the rapid accumulation of soluble sugars in purple potato tissues was an important factor in promoting the synthesis of anthocyanins.3.The key enzyme activities in the anthocyanin synthesis pathway of purple potato tubers responded differently to light intensity.PAL in purple potato tubers was not sensitive to light intensity,there was no significant difference between each shade treatment and the control.DFR is a light-induced enzyme,that is,the activity decreases with the increase of shading degree,and the decreasing range increases with the increase of shading degree,However,it is not completely consistent with the change trend of anthocyanins in purple sweet potato tubers,indicating that the effect of light conditions on anthocyanin synthesis in purple-fleshed sweet potato tubers is not completely changed through the changes of PAL activity and DFR activity;ANS activity varies under different light intensities.The change trend of anthocyanin content in purple potato tubers was basically the same.Correlation analysis showed that ANS activity in purple-fleshed sweet potato tubers under different light intensities was significantly positively correlated with anthocyanin content and soluble sugar content(P<0.001),indicating that ANS was involved in anthocyanin synthesis in purple potato under low light stress.One of the key enzymes of the pathway.In summary,mild shading(20% shading)significantly increased the content of soluble sugar,anthocyanins and flavonoids in purple potato tubers,and improved economic benefits on the premise that the yield of purple potato was not reduced.Therefore,the purple sweet potato has a certain shade tolerance,and under-forest planting and intercropping with less shade can be selected in the future planting.