Establishment And Application Of Evaluation Method Of Freezing Tolerance In Actinidia

To get freezing tolerance of kiwifruit,firstly,an accurate and effective method was established;secondly,using this method systematically evaluated freezing tolerance of kiwifruit germplasm.Dormant shoots of 9 genotypes that exhibited different freezing tolerance(FT)were subjected to low temperature stress(-5 ?,-10 ?,-15 ?,-20 ?,-25 ? and-30 ?),and the relative electrolyte leakage,the contents of cellular osmotic potential materials and the activity of antioxidant enzymes were measured.The optimum index was determined using correlation analysis between each index and the average membership among 9 genotypes under low temperatures.Then,16 species of kiwifruits including 51 genotypes were evaluated by relative electrolyte leakage.The results are as follows:1.The dormant shoots were used to measure REL(relative electrolyte leakage).Under both parameters contained 8 h at low temperature and soaked in the deionized water for 2 h,REL were so stable and accurate as to predict the LT50(lethal temperature 50)of the shoots of kiwifruit.The both parameters obtained by this experiment was useful to determine LT50 of kiwifruit.2.The relative electrolyte leakage of dormant shoots of 9 genotypes kiwifruit decreased with temperature,was in "S" trend;combining analysis REL and the Logistic equation calculate LT50(lethal temperature 50),LT50 ranging from-14.78 ? to-35.53 ? in different genotypes,and freezing tolerance pecking order was: ‘Changjiang-1' > ‘Mudanjiang-1' > ‘RB-4' > ‘Ruby star' >‘Zhongzhen-1' > ‘Zhejiang 15-10' > ‘Purpruea' > ‘Bruno' > ‘Hort16A'.3.According to the average membership function,the order of different kiwifruit genotypes in freezing tolerance weas: ‘Changjiang-1' > ‘Mudanjiang-1' > ‘RB-4' > ‘Zhongzhen-1' > ‘Ruby star' >‘Zhejiang 15-10' > ‘Purpruea' > ‘Bruno' > ‘Hort16A'.4.The results gainted from relative electrolyte leakage and comprehensive evaluation remained highly consistent.The coefficient between the LT50 and the average membership degree is 0.877,reaching significant level.Compared with average membership degree,the REL is appropriate to evaluate freezing tolerance.It is concluded that the freezing tolerance of kiwifruit also enhance with the increase of latitude of kiwifruit distribution.