Physiological and biochemical changes in the graft site after in vitro grafting in grape

Abstract: 【Objective】In this study,the survival rates of different combinations of in vitro grafted grapeswere investigated. The relationships of physiological and biochemical parameters including the activitiesof superoxide dismutase(SOD),catalase(CAT),peroxidase(POD) and polyphenol oxidase(PPO),andthe contents of gibberellin(GA3),tannin and fructose in the graft site to graft affinity were studied. Thepurpose of this study was to obtain an understanding of physiological and biochemical aspects related tograft affinity.【Methods】The plantlets of‘Shuangyou'and‘Beta'grape were used as rootstocks,and‘Pi-not Noir',‘Cabernet Sauvignon'and‘Red Globe'as scions. Healthy plantlets were chosen for cleftgrafting. Each group contained 90 grafted plantlets. 14 days after grafting,stem segments 1.5 cm aboveand below the grafting sites were cut into pieces and stored in liquid nitrogen for later use. The activitiesof SOD,CAT,POD and PPO and the contents of GA3,tannin and fructose were measured. The survivalrate was used to indicate the graft affinity. Correlations of the above physiological parameters to grafting af-finity were analyzed.【Results】The group of‘Beta'/‘Red Globe'(rootstock/scion) had the highest surviv-al rate(88.89%),and the lowest survival rate was found in the group of‘Beta'/‘Pinot Noir'(64.44%). Inall the groups,the enzyme activity of SOD varied greatly in the late period of healing process. The groupof‘Beta'/‘Red Globe'had the greatest variation(1 107.8 U·g^-1·min^-1 FW),and the lowest change range was 157.4 U·g^-1·min^-1 found in the group of‘Beta'/‘ Pinot Noir'. The activity of POD maintainedstable during 14 to 28 d after grafting but changed greatly during 28-35 d. Among them,the group‘Be-ta'/‘Red Globe'changed most greatly with a range of 78.7 U·g^-1·min^-1,while the group of‘Beta'/‘Pi-not Noir'had the lowest change range(53.0 U·g^-1·min^-1). There was no defined pattern for CAT activityduring the healing process,and hence the change pattern might be species-specific. CAT activity in allgroups changed significantly from 14 to 21 d after grafting,and the group of‘Beta'/‘Red Globe'changed with a greatest range(71.09 U·g^-1·min^-1). The activity of PPO maintained basically stable in theearly days after grafting,and had decreased significantly by day 35. The group of‘Beta'/‘Red Globe'changed most widely in a range of 27.1 U·g^-1·min^-1. The content of GA3 changed greatly from day 14 today 28. The greatest change in GA₃ was 11.44 μg·g^-1 found in the group of‘Beta'/‘Red Globe'and thelowest change was 10.16 μg·g^-1 in the group of‘Shuangyou'/‘Cabernet Sauvignon'. Tannin contentshowed a sharp rise in plantlets with‘Shuangyou'as rootstock but a sharp decline in those grafted onto‘Beta'during 14-21 d after grafting,suggesting change pattern of tannin differed according to rootstockspecies. During this period,tannin content in the group of‘Beta'/‘Red Globe'showed the largest de-cline,which was 26.66 μg·g^-1. At day 35,fructose content in all the groups reached the lowest level butincreased gradually later except for‘Shuangyou'/‘Pinot Noir'. From day 14 to day 35,the group of‘ Be-ta'/‘Red Globe'had the greatest change range(38.4 mg·g^-1).【Conclusion】According to the graft surviv-al rates in different graft combinations and the changes in various physiological and biochemical parame-ters in graft site,the graft affinity in a descending order was‘Beta'/‘Red Globe'>‘Shuangyou'/‘RedGlobe'>‘Beta'/‘Cabernet Sauvignon'>‘Shuangyou'/‘Cabernet Sauvignon'>‘Shuangyou'/‘Caber-net Sauvignon'>‘Shuangyou'/‘Pinot Noir'>‘Beta'/‘Pinot Noir'. The enzyme activities of SOD,POD,CAT and PPO and the contents of GA3 and tannin were significantly correlated with affinity,butnot for fructose content.