Differential Study On Starch Synthesis Of Sweet Potato In Three Types Of Environments In Chongqing

Starch is the main component in the storage roots of sweet potato,sugar was formed by photosynthesis in the leaves and transported to the storage roots to form starch.Starch synthesis is easily affected by environmental factors during the long growth period of sweet potato.Many previous studies have investigated the effects of environment on yield and quality of sweet potato.However,the effect of environment on the starch synthesis remains scarcely documented.Hence,this study selected 11sweet potato varieties（7 high-starch and 4 medium-starch varieties）that widely planted in Chongqing,and were conducted at three regions（Shiliu Township in Pengshui County,Huangjia Township in Pengshui County in 2020 and Hebao Township in Rongchang District in 2021）to determine photosynthetic characteristics of functional leaves,and key enzyme activities of starch synthesis,sucrose content,fresh potato yield,starch yield,starch content starch components of storage roots,then analyzed the effects of environment and genotype on each index,studied the relationship between each index and starch synthesis.The main results are as follows:1.Effects of environment and genotype on fresh potato yield,starch content and starch yield of sweet potato The effect of genetype was the main effect on fresh potato yield,starch content and starch yield,it reached a extremely significant level.The effect of environment on starch yield of high-starch and medium-starch sweet potato was respectively realized through the effect on fresh potato yield and starch content.The starch yield of highstarch sweet potato varieties was significantly higher than that of medium-starch varieties in three regions.The starch yield of Yushu 15 and Zhongshu 1performed well in three regions and they were suitable for promotion in several areas of Chongqing.Yushu 27 performed well in Hebao and Shiliu,Yushu 198 and Yushu 68performed well in Hebao and Huangjia;and Wanshu 9 performed well in Shiliu and Huangjia.2.Effects of environment and genotype on the activity of key enzymes for starch synthesis in storage roots of sweet potatoOn 90 days after transplanting,the effect of genetype was the main effect on the activity of key enzymes for starch synthesis.As the process of growth and development,the effect of environment became the main effect on the enzyme activity,and each variety responded differently to the environmental changes,there was a different trend in the change of enzyme activity during the growth period of each cultivar.Different environments mainly affected the content and composition of starch in dry power,while the starch content in storage roots was not significantly affected.The content of starch in dry power of Yushu 27,Yushu 15 and Yushu 198 performed well in all three regions.The amylose of Zhongshu 1 performed well in three regions,and the amylopectin of Yushu 27 performed well in three regions.3.Effects of environment and genotype on photosynthetic characteristics in functional leavesThe effect of genotype was the main effect affecting the relative chlorophyll content（SPAD）of high-starch varieties,while the effect of environment was the main effect affecting medium-starch sweet potato varieties.The effect of environment was the main effect affecting the net photosynthetic rate of medium-starch and high-starch sweet potato varieties.The net photosynthetic rate was higher in Hebao than Shiliu and Huangjia at light intensities of 0-500μmol/（m²·s）,and beyond this range,the net photosynthetic rate was higher in Huangjia or Shiliu than in Hebao.The net photosynthetic rate was higher in the Shiliu area than in the Hebao and Huangjia areas.The light response curve and CO₂ response curve showed a phenomenon,the photosynthetic potential of each sweet potato variety was high at high-altitude region.4.Effects of environment and genotype on sucrose content in storage roots of sweet potatoThe main effect affecting sucrose content is different in growth periods.Sucrose content decreased from 90 days to 120 days and increased from 120 days to 150 days.From 90 days to 150 days after transplanting,the sucrose content of high-starch varieties was always significantly lower than that of medium-starch varieties,and there was a extremely significant correlation between starch content and sucrose content in three growth periods.In conclusion,fresh potato yield,starch content and starch yield were mainly affected the effect of genetype,and the effect of different environments on starch synthesis were mainly realized by influencing photosynthetic properties of functional leaves and starch synthesis key enzyme activity of sweet potato storage roots.On 90days after transplanting,the effect of environment on various traits is still small,with the advancement of the growth periods,the effect of environment have gradually become the main effect which affect the changes of various factors in the process of starch synthesis.