The Evaluation Of Cold Resistance In Different Sweet Cherry Varieties

Sweet Cherry (Prunus avium L.) is praised as"titbit of fruit"because of its beautiful fruit, high quality, rich nutrient and ripen earliest in the north deciduous fruit trees in spring ,thus it also has the good name of '' the first branch of spring fruit". The fruit of Sweet cherry is expensive and, it is introduced and cultivated in many provinces of China. Low temperature is an important factor to limit the distribution and growth of plants. Especially in northern of China, which has a long cold winter, and has a big significant difference with the origin of Sweet Cherry. In the introduction and cultivation of sweet cherry, we found that the flowers,buds and branches of introduced Sweet Cherry varieties are usually injured by the low-temperature damage, and even death in winter. The cold physiology of Sweet Cherry is also rarely reported, the cold resistance of Sweet Cherry is discussed in this study in order to explore mechanisms and measures to improve cold tolerance, which is not only good for the introduction and cultivation of Sweet Cherry, but also enriched the cold resistance physiology theory of Sweet Cherry.Because there has greater cold resistance differences between the Sweet Cherry cultivars, with the result that Sweet Cherry cultivars in some regions also suffer cold damage to some different extent, and result in a great loss of production. There are of great significance to identify the cold resistance of different sweet cherry varieties ,that is good for the use of resources, rational planning and evaluation, the distribution of species, breeding resistant cultivar, promoting cold-resistance of varieties and so on.cold resistance mechanism and cold resistance in different months of dormancy as well as after low temperature stress were studied with one-year-old branches of Sweet Cherry in this paper, the change law were proved according to measuring the soluble protein content, proline content, MDA content, relative electrical conductivity, bound water / free water value, the evaporation rate of natural branches, branches to resume growth after low temperature stress and SOD, POD activity in different months of dormancy and different temperatures after low temperature stress. The data were used for synthetical evaluation with a view to provide a theoretical basis for the introduction and cultivation of Sweet Cherry. The main results are as follows:1. Physiological and biochemical indexes of different Sweet Cherry varieties were measured in the process of living through the winter, and get the order of cold resistance in accordance with comprehensive evaluation of test results The changes of various physiological and biochemical indexes only reflect its adaptation to low-temperature regulation, and did not show the phenomenon of chilling injury in morphological characteristics. Artificial drop of low-temperature experiment was done in order to further study the mechanism of cold resistance of Sweet Cherry. Artificial cooling is not only control the test conditions freely, but also make up for the complexity and levity of natural cooling to a certain extent, and different from the process of gradually cooling of natural cooling to reflect the physiological and ecological situation of different plants under low temperature stress. The artificial drop of low temperature test was carried out under the same conditions in this study, the results is not only of statistical significance, the order of relative cold resistance of different cultivars can be arranged, but also it is unanimously between the comprehensive evaluation of cold resistance and the evaluated results in the process of living through the winter among different Sweet Cherry varieties.2. The changes of physiological and biochemical indexes of different Sweet Cherry varieties are basically the same trend in the process of living through the winter. Relative electrical conductivity, activity of protective enzymes, soluble protein, proline, MDA content and the bound water / free water have the cut-off point in January, and the trend is dropping after rising, the changes of physiological and biochemical indicators were reflected more objectively when different varieties of Sweet Cherry adjust to adapt to low temperature stress.3. physiological and biochemical indexes of different Sweet Cherry varieties are basically the same trend in the process of artificial low-temperature. The cold resistance of Sweet Cherry was determined by relative conductivity, which better reflect the changes of cell membrane permeability and the extent of injury intuitively in different Sweet Cherry varieties. Relative electrical conductivity show a gradually growing trend as the temperature decreased, it showed that the effect of low temperature stress on the artificial branches of Sweet Cherry damage is not reversible (the relative electrical conductivity of different Sweet Cherry varieties showed the trend of increasing at first and then drop during the process of living through the winter, which indicated that the effect of natural low-temperature on membrane injury in branches of Sweet Cherry is reversible); MDA content also has the trend of decreasing after increasing at first, the content of MDA increased after low-temperature stress treatment, MDA content of Sweet Cherry varieties on zy-1 rootstocks decreased rapidly at -25℃in addition to LongGuan and Lapins decline rapidly at -30℃. That showed the low temperature at that time may have exceeded the maximum capacity of cells to resist. the MDA content of Sweet Cherry varieties on 90-1 rootstock were all declined rapidly at -30℃; SOD activity and soluble protein content had the trend of increased, drop and then increased, drop, SOD activity had the highest value at -20℃and then declined. Apart from the HongDeng on ZY-1 rootstock had the lowest value at -25℃, the other varieties were at -30℃, and then the SOD activity started to rise slowly, declined at -35℃; The content of proline lowered after rising at first with the gradually lower temperature of artificial cold treatment, but the change range was different from the temperature of reaching the highest value.4. physiological and biochemical indexes of different Sweet Cherry varieties are basically the same trend in the process of persisting low-temperature stress. Relative electrical conductivity,MDA content,the water evaporation rate of branches were increased. The activity of SOD decreased after went up at first. The content of praline and soluble protein in varieties of weaker cold resistance had the highest value at early time, furthermore the content were decreased with the delay of low temperature stress.5. The cold-resistance of plant are affected by many factors and the cold-resistant mechanism are more complex, the strength of cold resistance of Sweet Cherry in this study based on a number of indicators coupled with field observation in order to get a comprehensive evaluation of different Sweet Cherry varieties.The results of comprehensive evaluation: the order of the sweet cherry varieties on rootstock 90-1 during the processes of living through the winter and artificial low-temperature was: LongGuan> LongBao> HongMi>LongDan. the order of the sweet cherry varieties on rootstocks ZY-1 during the processes of living through the winter and artificial low-temperature was: LongGuan>Lapins>Van> BigarreauMoreall > HongDeng.