The Study On Cold Resistance Of Six Different Fresh-enble Jujube Varieties

Jujube trees are widely planted in northern Shaanxi.With high economic and ecological value,it has become a competitive and characteristic industry in northern Shaanxi.However,due to the occurrence of constant low temperature and extreme ones in winter in northern Shaanxi,the freezing damage has been a major reason that restricts the healthy and sustainable development of the date industry.Cold resistance refers to the genetic characteristic formed in low temperature and it attaches great importance in the introduction and cultivation of fresh Jujube in northern Shaanxi.In this study,six different fresh Jujube varieties,including Liuyuexian,Jing60,Jin’ai3,Lingwu long date,Qingjian round date,and Zaocuiwang,were selected as the research objects and tested on their changes of physiological indexes under natural overwinter and low temperature stress.The conclusion on their cold resistance,using correlation analysis and membership function method is aimed to provide a theoretical basis for the selection and breeding of fresh Jujube varieties and large-scale planting in Yulin area,as well as a reference for the planting and supporting cultivation technology.1.The membrane permeability indexes of the six branches measured under natural cooling conditions showed an overall increase of the relative electrical conductivity,among which,the Jin60 was at a higher level on the whole while the Liuyuexian was at a lower level.The results of natural cooling and low temperature stress showed that the Mda content increased with the decrease of temperature,and that the Jinai3 was higher than that of other varieties.2.The protective enzyme activity of the six fresh Jujube showed an general trend of increasing first and decreasing later under low temperature stress.The POD activity of most Jujube changed significantly between-15℃ and-25℃,and inactive lower than-25℃,which indicates that POD is related to the cold resistance and dates with higher POD enzyme activity have a better adaptability to low temperature stress.3.The correlation coefficient matrix obtained through standardized processing of the physiological indexes showed a great difference between the six fresh Jujube.There was a significant positive correlation between soluble protein and proline,electrolyte permeability and MDA in most of them;there was a significant positive correlation between POD enzyme content and osmotic regulating substances;while SOD content was negatively correlated with proline content,soluble protein content,electrolyte permeability and MDA content;there was no significant difference between soluble sugar and the other indexes.Since the indexes are related to each other in some way,it is hard to determine the cold resistance of dates trees simply by one or two indexes alone.4.Through the membership function analysis and calculation,the cold resistance of the six Jujube ranks as follows: Zaocuiwang,Lingwu long dates,Liuyuexian,Qingjian round dates,Jin’ai3 and Jin60.In summary,Zaocuiwang and Lingwu long dates showed better cold resistance thus were more suitable for planting.