| Northwest China has low rainfall, abundant light and large temperature difference between day and night, which is conductive to the synthesis organic matters in plant, especially for the sugar accumulation, but the temperature in this area often down to-15℃ in the winter, which belongs to the grape hilled overwintering cultivation area. In recent years, due to the effect of the frequently extreme low temperature and late spring frost, the wine grape often suffered serious freezing, which has seriously affected the development of wine grape planting and wine industry. The internal mechanism of grape frost resistance is affected by a number of factors, but the mechanism of cold resistance and physiological process of grape under low temperature is still a lack of system research. Some varieties of grape species have characteristics of strong resistance, such as the "Beta", the root can stand-20℃, which provide important resources and essential materials for the improvement of grape freezing resistance. Research materials for this study are provided by Gansu Agricultural University Institute of grape seeding resistance cultivation base. Four rootstock varieties "Beta", "SO4", "101-14" and "5BB" with strong frost resistance and two wine grape branches "Merlot" and "Pinot Noir" with weak frost resistance were used as materials, and the moisture content, sugar content, invertase(Inv) activity, sucrose synthase(SS) activity, sucrose phosphate synthase(SPS) activity, starch content, amylase(Amy) activity and starch phosphorylase(SP) activity is measured. In order to provide the technical data for the formation mechanism and improvement of grape frost resistance, this study analyze the relationship between changes of sucrose, starch content and the activities of related metabolic enzyme on different overwintering stage in grape branches, and the relationship between these changes and the grape frost resistance.1. From winter period December 21 th 2013 to late winter March 19 th, sucrose content in the branches of four varieties "SO4", "Beta", "Merlot" and "Pinot Noir" shows a ―medium-low-high" trend, and the average content increased from 47.03 mg·g-1DW in the early days to the 52.98 mg·g-1DW in the late winter. The lowest value appeared in February 13 th of mid-winter, which is 23.88 mg·g-1DW. SS and SPS kept high activity in different winter stage, which is the main enzyme in sucrose synthesis of grape branches, and the average value is 638.69 mg·g-1·h-1FW and 727.59 mg·g-1·h-1FW, respectively. The Inv activity increased in the mid-winter, but kept a low level in other winter period(15.82 mg·g-1·h-1FW), which showed a significant negative correlation with changes of sucrose content.2. From early winter period December 20 th in 2014 to March 19 th of late winter period, the change trend of sucrose content of "Beta", "101-14", "5BB" and "SO4" is basically as the same as last year, and the average content increase from 17.92 mg·g-1DW to 29.12 mg·g-1DW. It was the lowest on January 19 th, which is 14.22 mg·g-1DW. The change of SS activity and SPS activity is mainly similar in the whole winter period. From winter period December 20 th to February 23 th of mid-winter kept high activity, and the average activity reached 635.21 mg·g-1DW and 692.67 mg·g-1DW, respectively. But it both decreases at 32.68% in later winter period, which indicates that SS and SPS are the main enzymes for sucrose synthesis of grape branches. The Inv activity always maintains at a lower level from early winter period to mid-winter period, and increase obviously in later winter period. It manifests that Inv contributes to promoting the sucrose synthesis when SS and SPS activity reduces in later winter period.3. The change trend of starch content in grape branches is similar in the experiment in 2013 and 2014. It decreases gradually from early winter period December 20 th to March 23 th of the later winter period. In the two years, the highest average content of the experimental variety is 1.48 mg·g-1DW and 1.26 mg·g-1DW, and the lowest average content is 0.37 mg·g-1DW and 0.34 mg·g-1DW. The degree of reduction is 75.03% and 72.57%, respectively. Amy active change, increasing gradually from early winter period December 20 th to March 23 th of the later winter period, has significantly negative correlation with starch content. It shows that Amy is the major enzyme that breaks down starch. SP activity, which increases sometimes in several experimental varieties, always keeps at a low level. It has no obvious correlation with the starch decomposing.4. The sucrose content show a significant positive correlation with the freezing resistance of grape branches. From winter period December 21 th 2013 to late winter March 19 th, The sucrose content of "SO4" and "Beta" which with strong cold resistance was higher than the sucrose content of "Merlot" and "Pinot Noir". From winter period December 20 th 2014 to late winter March 19 th, there was no significant differences among the sucrose content of "SO4", "Beta", "Merlot" and "Pinot Noir" branches, which shows that a significant positive correlation between the sucrose content and the freezing resistance of grape branches. The branches with strong cold resistance contain a higher sucrose content.Above all, the sucrose content in different wine grape branches keep a higher level during wintering period, and shows a ―medium-low-high" trend. SPS and SS are main enzyme in sucrose synthesis of grape branches. There existed a strong positive linear relationship between sucrose content and the SPS activity, SS activity, respectively. Inv activity contributes to promoting sucrose synthesis, but there were no significant correlation with changes of sucrose content. The starch content maybe the material base for keep and increase the sucrose content. There existed a strong negative linear relationship between starch content and sucrose content of grape branches. The high sucrose content is beneficial to enhance the freezing resistance of grape branches. |
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