Effect Of Abscisic Acid On The Ripening And Softening Of Raspberry(Rubus Idaeus L.)and Its Relationship With Ethylene

Raspberry is a small berry rich in various nutrients,its fruit is extremely soft after maturity and it is not resistant to storage.ABA,as a plant hormone,plays an vital effect on controlling fruit ripening.In this study,‘Heritage' raspberry was used as the experimental material.Fruits at different maturity stages were collected,and fruits at white stage were treat ed by exogenous ABA and its inhibitors.In order to reveal the possible effect of ABA on regulating ripening and softening of raspberry from physiological and molecular aspects,physiological parameters related to raspberry ripening,as well as ABA accumulation,the transcript level of ABA metabolism key enzyme genes Ri NCED1,Ri CYP707A1 and Ri BG1 and ethylene biosynthesis key enzyme genes Ri ACS1 and Ri ACO1 in the fruit with the receptacle,drupelets,receptacle and seeds of raspberry were determined.The main findings were as follows:(1)The ABA content in the fruit with the receptacle,drupelets,receptacle and seeds of raspberry from the white stage to the overripe stage rose in the early stage,then declined,which reached the highest at ripe stage,the ABA content in which stage was the highest in receptacle,followed by seeds,drupelets,the lowest in the fruit with the receptacle.It was accompanied by a decrease in fruit firmness,chlorophyll and titratable acid content,an increase in anthocyanin and soluble sugar content,and degradation of cell wall cellulose an d protopectin during the natural ripening of raspberry fruit.(2)The increase of ABA content,anthocyanin and soluble sugar and the degradation of cell wall cellulose and protopectin of raspberry were promoted after exogenous ABA and ethrel treatment.However,fruit firmness,chlorophyll and titratable acid declined more quicker.And the promotion effect of ABA was more significant.1-MCP,fluridone and NDGA could inhibit the increase of ABA content and delay the changes of these physiological parameters,and the effect of NDGA+1-MCP treatment was more significant.(3)It was consistent between the expression patterns of Ri NCED1 and Ri BG1 and the ABA accumulation in the fruit with the receptacle,drupelet s,receptacle and seeds of raspberry from the white stage to the overripe stage,and interestingly it was inversely proportional between the expression level of Ri CYP707A1 and ABA accumulation,which indicating ABA biosynthesis metabolic enzymes and catabolic enzymes work together in the accumulation of ABA in raspb erry fruits.(4)With the treatment of ABA and ethrel,the expression of Ri NCED1 and Ri BG1 in the raspberry fruits were promoted.However,the expression of Ri NCED1 in the fruit with the receptacle,drupelets and seeds were inhabited,the expression of Ri NCED1 in the receptacle and the expression of Ri BG1 in the raspberry fruits were promoted with the treatment of fluridone.ABA+ 1-MCP treatment could promote the expression of Ri NCED1 and Ri BG1 genes in the raspberry fruits.1-MCP treatment could significantly inhibit the expression of Ri NCED1,Ri CYP707A1 and Ri BG1.NDGA+1-MCP treatment could inhibit the expression of Ri NCED1 in raspberry fruits and the expression of Ri BG1 in the fruit with the receptacle and drupelets of raspberry.(5)The expression of Ri ACS1 and Ri ACO1 in the fruit with the receptacle,drupelets,receptacle and seeds of raspberry declined at the early stage and then rose,which reached the lowest in the white stage and the highest in the overripe stage,yet the two genes expression in the receptacle were the lowest in the green stage,then decreased in the mottled stage after a brief rise in the white stage,and then rose to the maximum at the ripe stage and then decreased.(6)The transcript level of Ri ACS1 and Ri ACO1 in raspberry could be promoted significantly with the treatment of ABA.Fluriodne could inhibit the expression of Ri ACS1 and Ri ACO1 in the fruit with the receptacle,drupelets and seeds,and only temporarily inhibit the expressi on of Ri ACS1 and Ri ACO1 in the receptacle of raspberry.ABA+1-MCP treatment only promoted the expression of Ri ACS1 and Ri ACO1 in the fruit with the receptacle,drupelets and seeds,and inhibited the expression of Ri ACS1 but promoted the expression of Ri ACO1 in the receptacle of raspberry temporarily.The effect was opposite between the treatment NDGA+1-MCP and ABA+1-MCP.Ethrel treatment only temporarily promoted the expression of Ri ACS1 and Ri ACO1 in raspberry,and 1-MCP significantly inhibited the expression of Ri ACS1 and Ri ACO1.