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Malus sieversii is a remnant of the tertiary species and is also believed to be progenitor of cultivated apple(M. domestica), which is rich in genetic diversity. M. sieversii is mainly distributed in Tianshan Mountains in Central Asia and in China is mainly distributed in the Ily State, Xinjiang Autonomous Region. Recently, M. sieversii is suffering serious destruction and is sharply decrasing in area. In this study, trees in 2 M. sieversii populations(i.e., Gongliu and Xinyuan populations) were used as materials and genetic diversity of M. sieversii were discussed by measuring chemical components such as sugar, acid, mineral elements and phenolic compounds. The aim of this study was to provide basic information for character variation and genetic diversity in M. sieversii and to supply scientific theory for elite seedlings and protection, conservation and utilization of M. sieversii. The main results were as follows:1. The sugar components of 88 seedlings in M. sieversii was studied. The results showed that the main sugar components in M. sieversii were fructose, glucose and sucrose, which was in consistent with cultivated apple. However, the content of each sugar component exists extremely significant diffenence, variation coefficent were between 26.41%~44.71%, which reveals rich genetic diversity.2. The mean sugar contents of 88 seedlings in M. sieversii was compared with M. domestica, the results showed that in M. domestica fructose content was the highest, then was glucose, sucrose was the lowest, and the ratio of fructose, glucose, sucrose was 2.8:1.4:1, which was in consistent with the previous research in Starkrimson and Fuji. Although the content of fructose in M. sieversii was highest, glucose was lower than sucrose, the ratio of fructose, glucose, sucrose was 6.6: 1: 3.6. The content of total sugar between M. sieversii and M. domestica had extremely significant diffenence which was caused by the contents of glucose and sucrose.3. The organic acid was detected by capillary electroproresis technology and the resulted showed that the main organic acid in M. sieversii was malic acid. The content of malic acid existed extensive variation and the variation range was between 2.66~23.62 mg.g-1, variation coefficient was 37.00%. 4. The results showed that the mean contents of malic acid of 88 seedlings in M. sieversii was 12.95mg.g-1 which was 3.5 times of M. domestica and represented extremely significant diffenence.5. The results indicated that variation coefficient of mineral elements(Ca, Mg, Fe, Cu, Mnand Zn) in M. sieversii was between 23.97%~73.20% and was rich in genetic diversity. In the 6 kinds of mineral elements, content of Ca was the highest, the mean of 88 seedlings in M. sieversii was 7.61 mg/100g, the maxium was 18.13 mg/100g and variation coefficient was 40.45%, which revealed large potiential for high Ca elite seedlings.6. The mean content of mineral elements of 88 seedlings in M. sieversii was compared with M. domestica(Fuji, Golden delicious, Starkrimson). The results showed that the mean content of Ca and Mg in M. sieversii was 7.61 mg/100g and 4.33 mg/100g respectively, which were 3.1 times and 1.4 times of the mean content in M. domestica(Fuji, Golden Delicious, Starkrimson) and represented extremely significant difference and significant difference. Howere, the content of Fe, Mn, Cu, Zn in M. sieversii and M. domestica was identical without sognificant diffenence.7. Gallic acid, chlorogenic acid,ρ-hydroxybenzoic, catechin, epicatechin, vanillin, ferulic acid, benzoic, phloridzin, quercetin, cinnamic acid and phloretin were identified in 30 seedlings of M. sieversii. Chlorogenic acid,ρ-hydroxybenzoic, catechin, epicatechin, vanillin, ferulic acid and phloridzin can be detected in all 30 seedlings, while gallic acid, benzoic, quercetin, cinnamic acid and phloretin were detected in some seedlings and the segregation ratio were 16:14, 27:3, 22:8, 28:2 and 26:4, respectively. The contents of phenolic compounds in M. sieversii existed significant difference and the coefficient variation was between 65.06%~329.22%, which revealed rich genetic diversity. The content of proanthocyanidin in M. sieversii between 903.13~4708.21μg/g, variation coefficient was 36.12% , which represented rich genetic diversity as well.8. The results suggested the identity in main phenolic compounds between the two species. However, proanthocyanidin in M. sieversii was the highest(aking up 35.03% in total phenolic compounds), then was epicatechin, phloridzin and chlorogenic acid (taking up 15.50%, 12.76% and 10.10% in total phenolic compounds, respectively) which made up the main phenolic compounds in M. sieversii. The main phenolic compounds in M. domestica were epicatechin, proanthocyanidin and chlorogenic acid. The results were consistent with the previous research in new Starkrimson.9. The results indicated that the total phenolic compounds, proanthocyanidin, epicatechin, phloridzin, chlorogenic acid and catechin had extremely significant difference between the two species and variation coefficient was between 36.12%~91.31%. The contents in M. sieversii were 5.1 times, 8.0 times, 3.2 times, 13.0 times, 3.1 times and 34.1 times of M. domestica, respectively, which represented high phenolic compounds traits. Gallic acid, benzoic, quercetin, cinnamic acid and phloretin had extensive segration ratio and variation coefficient was higher than 110.78%. The results implyed abundant genetic diversity in the varieties of phenolic composition in M. sieversii, which revealed large potential for the selecting of different phenolics elite seedlings.
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