Comparison Of Quality Of Citrus Grandis(L.) Osbeck. ’Guanximiyou’ And Its Bud Mutation Varieties And Effect Of ABA On Its Quality

Citrus grandis cv.‘Guanximiyou’is one of the excellent pummelo varieties cultivarted in Sichuan,and has produced mumerous varieties in field cultivations.Citrus grandis cv.‘Sanhongmiyou’,‘Hongroumiyou’,‘Hongmianmiyou’and‘Huangjinmiyou’are four new varieties mutated from‘Guanximiyou’.Our long-term field observations and investigations indicated that Guanximiyou and its bud mutates has good plant growth potential and results in Sichuan.However,the average annual temperatures in most of Sichuan’s planting areas were much lower（below 17℃）than provenance in Pinghe County,Fujian Province.which led to the light color of fruit peel as well as high acid content and low sugar accumulation in fruits.Therefore,in order to investigate the quality characteristics of pummelo fruits in Sichuan and improve the fruit quality,this study analyzed the fruit quality and bioactive substance characteristics of five mainly cultivated‘Guanximiyou’lines in Sichuan,Establish a comprehensive evaluation system of‘Guanximiyou’fruit quality based on principal component analysis（PCA）and cluster analysis methods.Taking Guanximiyou as a benchmark,the composition and content of sugar and acid components,phenols and carotenoids of the fruits of four bud varieties（‘Hongroumiyou’,‘Sanhongmiyou’,‘Hongmianmiyou’and‘Huangjinmiyou’）were detected with HPLC,and antioxidant capacity of fruits was also estimated/compared between strains with DPPH,FRAP,and ABTS methods.Subsequently,principal component analysis（PCA）and cluster analysis were used to assess.On the other hand,we also used exogenous abscisic acid（ABA）to treat‘Sanhongmiyou’fruits at three fruit coloring periods（120,140 and 165 DAF）to study the effects of exogenous abscisic acid（ABA）with different concentrations and different treatment dates on the basic quality,peel color performance,and saccharic acid of‘Sanhongmiyou’fruits to explore the most suitable ABA concentration and date.The main results are listed as follows.ⅰ.Six sugar-acid components,six phenolic substances,and four types of carotene were detected in five cultivars.Citric acid and sucrose are the main organic acids and soluble sugars in‘Guanximiyou’;gallic acid and naringin are the main phenolic acids and flavonoids in‘Guanximiyou’;lycopene is the main coloring of‘Hongroumiyou’β-carotene is the main coloring of‘Huangjinmiyou’.Among the five cultivars,‘Sanhongmiyou’had the best color performance and contained the highest amount of phenols,especially the flavonoid content(13.34 mg·g^-1)that was 1.6 times the control’s.It also showed strongest antioxidant capacity.ⅱ.Based on principal component analysis and cluster analysis method,20 fruit quality indicators were evaluated for soluble sugar,organic acid,carotenoid,phenolic substance and antioxidant capacity of Guanximiyou and its four bud varieties,and five varieties from high to low are:Sanhongmiyou、Huangjinmiyou、Hongroumiyou、Hongmianmiyou、Guanximiyouⅲ.Five different concentrations(0,0.5,2.5,5,7.5mmol·L^-1)of ABA at three stages（120 d,140 d and 165 d after flowering）of fruit coloring to Sanhongmiyou,The results showed that treatment with 2.5 mmol·L^-1ABA at 165 d after flowering could significantly increase the accumulation of peel lycopene,increase the soluble sugar content of pulp and reduce the content of organic acids,and promote the synthesis of endogenous ABA.