Response Mechanism Of Grape Bioactive Compounds And Quality To Regulated Deficit Irrigation And Cultivation Environment

Owing to the increasing demand for the natural antioxidants and high-quality fruits,biologically health-promoting active dietary components of fruits have started to gain widespread attention.Grape(Vitis vinifera L.)is one of the most popular fruits worldwide.It contains many beneficial secondary metabolites,which can be affected by viticulture management and various environmental factors.Water is the basis of all lives,it could directly affect the growth,development and quality of fruit.Numerous reports have focused on vegetable growth,controlling excess vigour in the open field.However,researches about bioactive compounds and related enzyme activities in grape leaves,berries and berries tissue in response to deficit irrigation under different protected cultivations were less.In this study,table grape variety‘Hutai No.8'was used as the test materials under two cultivation environments(greenhouse and rainshelter).Two irrigation levels(50-60%FC and75-90%FC)were set up to conduct deficit irrigation(full irrigation,FI;deficit irrigation,DI)based on phenological(from budburst to fruit set,DI1;from fruit set to full maturation,DI2;from budburst to anthesis,DI3;from anthesis to pea size,DI4;pea size to full maturation,DI5;from pea size to changing color,DI6;from changing color to maturation,DI7;from maturation to full maturation,DI8)during three years.We combined with field observation and laboratory analysis to investigate the bioactive compounds and related enzyme activities in grape leaves,berries and berries tissue in response to deficit irrigation.What's more,grape fruit quality,yield and water use efficiency were also analyzed.In order to explore the mechanism about effect of deficit irrigation on grape bioactive compounds metabolic.Furthermore,it is potentially beneficial for utilizing grape leaves and providing scientific water management technology for superior grapes production under protected condition.The main results are as follows:(1)Regulated deficit irrigation could promote the accumulation of grape bioactive compounds and the improvement of antioxidant activity,but its promotion effect is related to the cultivation environment.Deficit irrigation from maturation to full maturation were the best period to improve the bioactive compounds contents under greenhouse,and regulated deficit irrigation during this period could improve resveratrol(seed),proanthocyanidins(skin and homogenate),anthocyanins and total phenol content(pulp and homogenate)of multiple grape tissue.Deficit irrigation from changing color to maturation were the best period to improve the bioactive compounds under rainshelter,and regulated deficit irrigation during this period could improve resveratrol(seeds and pulp)and proanthocyanidins(leaves and homogenate),anthocyanins(pulp)and total phenol(leaves)of multiple grape tissue.Meanwhile,grape resveratrol and proanthocyanidins were characterized by positive direct effect on 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS·~+),1,1-diphenyl-2-picrylhydrazyl(DPPH)and Ferricion reducing antioxidant power(FRAP)antioxidant activity.The contents of bioactive compounds were grape phenological period and tissue dependence.Bioactive compounds accumulated the highest in grape seeds and the lowest in grape pulp under greenhouse and rainshelter.Grape homogenate is suit to eat,skin and seeds could be used for the extraction and processing of a large number of bioactive compounds in the commercial industry.(2)Regulated deficit irrigation could enhance enzyme activity related to the synthesis of bioactive compounds in grape leaves and fruit tissue,and benefit to the accumulation of L-phenylalanine,the content of bioactive compounds depends on the strength of the related enzyme activity.Deficit irrigation from maturation to full maturation were the best period to enhance enzyme activity under greenhouse,and regulated deficit irrigation during this period could improve PAL(skin),4CL activity(leaves,homogenate and skin),L-Phe content(leaves,homogenate and skin)and inhibit PPO activity(leaves)of the multiple grape tissue.Deficit irrigation from changing color to maturation were the best period to improve enhance enzyme activity under rainshelter,and regulated deficit irrigation during this period could improve PAL(leaves and pulp),C4H(leaves,seeds and pulp),4CL activity(seeds)and L-Phe content(leaves,skin and pulp)and inhibited PPO activity(leaves,homogenate and seeds)of the multiple grape tissue.Under both cultivation environments,grape PAL,C4H and 4CL activity showed the strongest in fruit seeds and the weakest in fruit pulp,while PPO showed the strongest in fruit pulp and the weakest in fruit seeds.There is no significant difference about L-Phe content among grape tissues,but L-Phe content is more in grape skins,which providing substrate for the synthesis of bioactive compounds.Related enzyme activities were grape phenological period and tissue dependence.Correlation analysis showed that resveratrol,proanthocyanidins and anthocyanins in grape seeds were very significant positive correlation with C4H and 4CL activity.The influence of PAL and 4CL showed directly positive effect on resveratrol and total phenol,respectively,4CL and L-Phe showed positive direct effect on proanthocyanidins,C4H and 4CL showed positive direct effect on anthocyanins;4CL was the key enzyme to enhance bioactive compounds content in response to regulated deficit irrigation.(3)Moderate deficit irrigation could improve grape quality and water use efficiency without affecting the yield.The content of titrable acid(TA)in grape fruits was decreased when deficit irrigation from budburst to full maturation.Deficit irrigation from fruit set to full maturation increased the content of soluble sugar(SS)and soluble solids(TSS)in grape homogenate,decreasing the content of TA,and increasing TSS/TA.Regulated deficit irrigation and cultivation environment have significant effects on TA,TSS/TA and vitamin C(VC)content in grape fruit homogenate and pulp.SS,TA,TSS,VC and SP contents of grape homogenate in FI treatment were higher than those in grape pulp,but TSS/TA in grape pulp was higher than that in grape homogenate.Grape TA content was low when deficit irrigation from pea size to full maturation,VC content and TSS content were high,made fruit had the best taste,but the water use efficiency was low.Deficit irrigation from budburst to full maturation water saving most,but the yield loss is serious and the water use efficiency was low,which should not be advocated in the actual production.Yield loss were happened when conducted deficit irrigation from anthesis to peasize,but yield and water use efficiency were the highest when full irrigation from budburst to full maturation.Deficit irrigation from maturation to full maturation made water saving more,and no reduction of yield.(4)Based on grape health-promoting quality,nutritional quality,yield and water use efficiency,fuzzy comprehensive evaluation result shows that grape comprehensive quality were optimal,comprehensive benefit is supreme when deficit irrigation from peasize to full maturation under greenhouse;The grape comprehensive quality were optimal when deficit irrigation from peasize to full maturation under rainshelter,but grape comprehensive benefit is supreme when deficit irrigation from budburst to anthesis under rainshelter.However,it is more effective to improve the comprehensive quality and comprehensive benefits of grape when deficit irrigation from maturation and full maturation under greenhouse and rainshelter.In summary,deficit irrigation from peasize to full maturation under greenhouse and rainshelter could promote bioactive compounds accumulation and improve the antioxidant activity of multiple grape tissue,enhancing enzyme activity related to the synthesis of bioactive compounds in grape leaves and fruit tissue,and it is benefit to the accumulation of L-phenylalanine,bioactive compounds contents dependent on the strength of the enzyme activity,meanwhile,it could improve grape quality and improve water use efficiency.However,it is more effective to adjust deficit irrigation from maturation to full maturation.