Effect Of Exogenous ABA On Cold Resistance At Flowering And Young Fruit Stages Of Blueberry ’Northland’

As one of the"third-generation fruits"with great development potential,blueberry is often damaged by low temperature frost during the flowering and young fruit stages,which seriously restricts the healthy and stable development of its industry.Therefore,it is of great significance to study the techniques and methods to improve the cold resistance of blueberry to guide the actual production.In this experiment,the blueberry variety’Northland’was used as the experimental material to study the effects of different concentrations(10 mg·L^-1,15 mg·L^-1,20mg·L^-1,30 mg·L^-1,50 mg·L^-1)of exogenous ABA on the content of endogenous hormones（ABA,GA₃,IAA）in flowers and young fruits and various physiological indicators（soluble sugar,soluble protein,electrolyte exudation rate,malondialdehyde,proline content and catalase,superoxide dismutase,peroxidase activity）in flowers and young fruits under low temperature stress and the effect mechanism of exogenous ABA on cold resistance of blueberry,the main test results are as follows:1.Spraying different concentrations of ABA can increase the endogenous ABA content in blueberry buds,flowers and young fruits,while the contents of GA₃and IAA decrease.The increase of ABA content in buds and flowers is significantly higher than that in young fruits.When the spray concentration was 20 mg·L^-1,the effect was the most significant（P<0.05）.Compared with the control,the content of ABA increased by 230.4%,and the content of GA₃and IAA decreased by 68.4%and 46.7%,respectively.Overall,the ABA content in young fruit was significantly higher than that in buds and flowers.2.Under low temperature stress,the buds,flowers and young fruits sprayed with different concentrations of ABA,compared with the control,the electrolyte exudation rate and the accumulative content of malondialdehyde decreased to different degrees,and decreased first with the increase of ABA concentration.an upward trend.Among them,the spraying concentration of 20 mg·L^-1had the most significant decrease（P<0.05）.Electrolyte exudation rate and malondialdehyde of buds,flowers and young fruits were negatively correlated with stress temperature.Overall,the electrolyte exudation rate of young fruits was about twice as high as that of buds and flowers.3.Under low temperature stress,the content of proline,soluble protein and soluble sugar in buds,flowers and young fruits sprayed with different concentrations of ABA increased compared with the control,and increased first with the increase of ABA concentration.The trend of decline after spraying,among which the increase of spraying concentration of 20 mg·L^-1was the most significant（P<0.05）.In general,the size of soluble protein content is:flower>bud>young fruit,and the size of soluble sugar content is:flower>young fruit>bud.4.Under low temperature stress,the buds,flowers and young fruits sprayed with different concentrations of ABA,compared with the control,the enzymes of catalase（CAT）,superoxide dismutase（SOD）,peroxidase（POD）The activity of SOD increased in different degrees.The increase of SOD enzyme activity in young fruit was significantly higher than that in buds and flowers.Overall,the increase in POD activity was the most significant.With the increase of ABA concentration,it first increased and then decreased,and the spray concentration of 20mg·L^-1increased most significantly（P<0.05）.Buds and flowers were negatively correlated with stress temperature,while young fruits were positively correlated with stress temperature.Under the same low temperature stress,the activity of SOD enzyme in buds and flowers was about 2times that of young fruits,and the activity of POD enzyme in flowers was about 10 times that of buds and young fruits.5.The membership function method was used to comprehensively evaluate the cold resistance index,and it was concluded that under low temperature stress,spraying exogenous ABA with a concentration of 20 mg·L^-1could effectively alleviate the freezing injury at the flowering stage of blueberry and improve the cold resistance at the flowering stage.