Effects Of Water Stress On The Contents Of Organic Acids And Methoxypyrazines In The Berries Of Cabernet Sauvignon

To explore the effects of different water stress on the content of organic acids and methoxypyrazine,9-year-old Cabernet Sauvignon were used as materials in this study.Three treatments were set on grapevines from the berry setting to veraison,which are mild(-0.2MPa>h2-0.4MPa),moderate(-0.4MPa>W62-0.6MPa)and severe(≤-0.6MPa).From the complete veraison to maturation(120d after anthesis),the treatments of grapevines were treated with mild,moderate and severe stress for each treatment again.The treatment of mild-mild water stress was used as control group.High-performance liquid chromatography(HPLC)and gas chromatography-hydrogen flame ionization detector(GC-FID)were used to determine the contents of major organic acids and methoxypyrazine during the development of grape berries.The results are as follows:1.Different water stress had a great effect on fruit quality.T4 treatment was beneficial to increase the content of soluble solids in Cabernet Sauvignon grape.The content of reducing sugar in T5 and T7 treated fruits was higher than CK.Except for T6 and T8,the content of tannin in other treatments was higher than CK.The content of total phenol and anthocyanin were higher than CK.Among them,T5 treatment had the best effect.The content of reducing sugar,tannin,total phenol and total anthocyanin in grape fruit increased by 6%,21%,7%and 31%,compared with CK.2.Different water stress had a great influence on the synthesis and degradation of organic acids during the fruit ripening.The decrease of organic acid content during fruit ripening was mainly due to the degradation of malic acid.Pre-veraison was an important period of organic acid synthesis.Tartaric acid and citric acid were continuously synthesized and accumulated after veraison,while the malic acid was gradually reduced by respiration.3.Mild-treatment is beneficial to the synthesis of organic acids in pre-veraison,while the severe-treatment inhibits organic acid synthesis.Among them,CK treatment is beneficial to the accumulation and retention of major acids,T5 and T6 treatments keep the contents of titratable acid in a moderate level.4.Under water stress treatment,the content of methoxypyrazine(MPs)increased firstly and then decreased in fruit ripening in per berry.Pre-veraison was an important period of MPs synthesis.After veraison,the MPs began to degrade,and the degradation rate of different pyrazines were different.5.Severe water stress could inhibit the synthesis of MPs in pre-veraison.SEMP and IBMP are the main sources of grape green pepper taste.To reduce the content of MPs,T5 and T7 were the best choices.In conclusion,T5 treatment not only helps to improve the quality of grape fruit,but also makes the content of main organic acid and methoxypyrazine be in a moderate level,Therefore the best treatment was using moderate water stress from berry-setting to veraison,and then from veraison to maturation by using severe-water stress.