Response Of Fruit Quality Of Different Table Grape Varieties To Exogenous Selenium Fertilizer

Table grape is a fruit well suited for consumption as fresh-cut product.Selenium（Se）is an essential trace elements in human nutrition,but Se deficiency is still a serious nutritional and health problem worldwide.Spraying Se fertilizer is a new practice for high-quality production in tree fruit cultivation,and an effective method of developing Se-enriched fruit.With Se-enriched fruit is becoming more and more popular among consumers,study how to improve Se content and fruit quality of grape berries,is not only especially important for human health,but also can provide important theoretical and practical basis for the high quality and efficient cultivation and production of table grape.This study was based on field experiment,conducted in Guanzhong region of Shaanxi province,cultivated in greenhouse and open field,selected European and American hybrid species and Eurasian species multiple table grape varieties as the experimental materials,accompanied by spraying Se fertilizer on the leaves during the growth and development of grapes.It had been further and systematical researched on following contents,including the variation of fruit quality on different varieties table grape under Se fertilizer treatments,the antagonism of Se and heavy metals in grape berries,response of fruit quality to exogenous Se fertilizer under different cultivation microclimates,the metabolism mechanism of sugar accumulation in grape berries under Se fertilizer treatment.Accordingly,providing scientific guidance for high-quality Se-enriched table grape future extensive cultivation.The main results were as follows:（1）Comparative research indicated that spraying 3 times with organic Se concentration of 120 mg·L^-1 of amino acid-chelated Se-enriched foliar fertilizer treatment was a suitable choice for the production of high-quality Se-enriched grapes.Organic Se fertilizer application enhanced the Se content in grape.Comprehensive evaluation analysis showed:whether Hutai No.8 or Crimson seedless,spraying Se fertilizer that organic Se concentration of 200 mg·L^-1 and 150mg·L^-1 was not conducive to the improvement of comprehensive fruit quality,however,spraying 3 times with organic Se concentration of 120 mg·L^-1 had the better comprehensive fruit quality than that of 1 or 2 times.（2）Se fertilizer could increase Se content of grape from different varieties,significantly improved the nutrition quality,reduce the accumulation of heavy metals,especially for European and American hybrid species,which is more suitable for producing high-quality Se-enriched grapes.Se content of grape was increased by foliar Se fertilizer,as well as Se content in grape of European and American hybrid species was higher than that of Eurasian species.Se fertilizer application increased the Vc,soluble protein,soluble solid nutrition quality,and reduced the organic acid for both Eurasian species and European and American hybrid species,while it had less effect on resveratrol and proanthocyanidin content of Eurasian species.Spraying Se fertilizer significantly increased K and Ca nutrients content in grape,at the same time reduced accumulation of heavy metals Pb,Cr,Cd,As,Ni.（3）Spraying Se fertilizer in greenhouse is an appropriate cultivation and management method to produce the high-quality Se-enriched grape.In greenhouse,spraying Se fertilizer was conducive to improving fruit appearance traits.Se content of grape berries was increased by Se fertilizer application,and spraying Se fertilizer was an effective measure to improve fruit quality for both Hutai No.8 and Summer Black.The fruit health care values of Hutai No.8 were superior to that of Summer Black,and the fruit health care values of Hutai No.8 in greenhouse were better than that in open field.Comprehensive analysis of fruit quality showed that,the fruit quality of Hutai No.8 and Summer Black grape under the condition of greenhouse cultivation of spraying Se fertilizer were optimal,followed by spraying Se fertilizer in open field,and the fruit quality of control in greenhouse was better than that of control in open field.（4）The high sugars accumulation of grape under Se fertilizer treatments mainly comes from the higher AI enzyme activity of berries,higher photosynthetic rate in leaves and enhanced plant resistance of Se fertilizer treatments,glucose and fructose were the primary sugars in berries.Foliar Se fertilizer not only could increase Se content in fruit,but also could promote grape growth and sugar accumulation,improving internal quality.At maturity in 2016 and 2017,the total soluble sugar content of berries in the Se fertilizer-treated group was significantly higher than that of control;glucose and fructose were the primary sugars in grape,with a trace amount of sucrose.During the accumulation of sugar in grape berries,AI activity in the peel was higher than that of pulp,and AI played an important role in the process of sugar accumulation in berries.To a certain extent,Se fertilizer application promoted the increasing of CAT,SOD and POD activity in leaves,and decreased the content of MDA,further enhanced the resistance of grape plants.Therefore,high AI activity in berries and high photosynthetic rate could explain the mechanism by which Se fertilizer affected sugar accumulation in grape.In conclusion,the effective and reasonable exogenous Se fertilizer application could increase Se content in grape,improve the appearance traits and nutritional health care values of the fruit,increase nutrient elements K and Ca content in grape,effectively reduce the accumulation of heavy metals in grape,enhance the plant resistance.In addition,the comprehensive fruit quality under Se fertilizer treated in greenhouse was optimum.High AI activity in berries and high photosynthetic rate could explain the mechanism by which Se fertilizer affected sugar accumulation in grape.Accordingly providing scientific guidance for foliar Se fertilizer application in high-quality Se-enriched grapes production and cultivation.