| In this study,representative peach varieties with different color types were used as test materials,including Jingxiang peach,Crisp peach,Okubo peach and Jinxiu yellow peach.Based on the separation of sugar components by high performance liquid chromatography(HPLC)and the analysis of the changes of sugar metabolism,the changes of pigment and related substances in peach peel at different stages were systematically studied.The changes of pigment content,related enzyme activities and sugar metabolism in four peach cultivars were determined to reveal the relationship between pigment and related enzyme in four peach cultivars at different growth and development stages,as well as the difference of peel color among peach cultivars.The effects of POD,PPO,SOD,PAL and CHI enzyme activities on the color of peach peel were discussed,which could provide reference for improving the quality and color of peach fruit.The main results and conclusions are as follows:1.The anthocyanin content,chlorophyll content and carotenoid content in pericarp of four peach varieties were different with different varieties.The content of anthocyanin,chlorophyll and carotenoid in the peel of four peach varieties were different.The a/b ratio of Crisp peach,Okubo peach and Jinxiu yellow peach increased to 5.3,6.1 and 4.9 respectively.The results showed that the color difference of the peel and anthocyanin of the peel of the peach were significantly different.The color difference of the peach peel and anthocyanin of the peel developed with the fruit growth(115d-175d after flower),the color difference L value decreased from 75.1 to 73.3,and the color difference a/b value increased from 1.6 to 2.7.55 in days after anthesis,the anthocyanin content of four peach cultivars increased to the peak value,and the peak value of crisp peach was 21.36 μg·g-1.The peak value was 7.22 μg·g-1.There was no significant correlation between chlorophyll and carotenoid content in the pericarp of Jingxiang peach.At maturity,chlorophyll and carotenoid content in the pericarp of Jingxiang peach decreased to 3,39 μg·g-1 and 0.01μg·g-1.2.The changes of sugar metabolism of four peach varieties varied with varieties.The highest sucrose content was 22.65 mg/g in Jingxiang peach,and the lowest was 15.71 mg/g in Okubo;Among the four peach varieties,Jingxiang peach had the highest glucose content(31.45 mg/g)and Okubo had the lowest glucose content(24.41 mg/g);The fructose content of Jingxiang peach was 52.67 mg/g,and Jinxiu yellow peach was the lowest(40.14 mg/g);The content of sorbitol in Jinxiu yellow peach was the lowest,which was 0.33 mg/g;The highest content of total sugar in Jingxiang peach was 64.63 mg/g,and the lowest was Jinxiu yellow peach,55.29 mg/g.The results showed that the accumulation of sugar had a significant effect on the growth and development of peach fruit.The content of sucrose and fructose in Jingxiang peach was significantly higher than that in Cuimi peach,Okubo peach and jinxiuhuang peach.3.The contents of POD、PPO、SOD、PAL and CHI in four peach cultivars increased first and then decreased,but the peak time was different.The POD activity,SOD activity and PAL activity in the pericarp of Jingxiang peach were significantly lower than those of the other three varieties,which were 1.99 u·g-1·min-1,0.10 u·g-1·min-1 and 0.147 u·g-1FW-1,respectively.The PPO activity and ChI activity of Jingxiang peach were 3.69 D·g·1·min-1 and 0.191 u·g-1FW-1,respectively.The analysis of main factors of pericarp coloration showed that Pericarp Pigment was significantly correlated with flesh sugar content,anthocyanin content,chlorophyll content,POD and SOD,while carotenoids were significantly negatively correlated with POD,SOD and PAL.4.There was a significant correlation between fructose,pericarp pigment and related enzymes:(1)The L value of color difference was negatively correlated with sucrose,glucose and fructose,and positively correlated with sorbitol(0.988*).The a/b value was not significantly negatively correlated with related enzymes,but negatively correlated with sorbitol content;(2)Carotenoids and chlorophyll contents were negatively correlated with sugar components,and positively correlated with sorbitol content(0.984*,0.976*),carotenoids were significantly correlated with PPO and CHI(0.962*,0.986*),chlorophyll was significantly correlated with PPO and CHI(0.970*,0.976*);(3)Cyanidin-3-galactoside,Cyanidin-3-arabinoside in pericarp were significantly different from total sugar in fruit.Cyanidin was significantly positively correlated with each sugar component(0.771),but the correlation value of Hengyang honey peach anthocyanin was low(0.467).The results showed that there were significant differences in fruit sugar,Pericarp Pigment and their metabolism among four different peach varieties,which further proved the synergistic effects of POD,PPO,SOD,PAL and CHI enzymes on fruit sugar metabolism and anthocyanin biosynthesis.In conclusion,studying the regulation of fruit sugar metabolism and pericarp enzyme activity of different peach varieties is one of the ways to improve fruit quality,which can significantly improve fruit appearance quality.Among them,the significant difference in peel color between Jingxiang peach green peel and other peach varieties at maturity is due to the interaction of chlorophyll and PPO activity and POD activity in peel related enzymes. |
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