Study On Propagation Technique And Rooting Physiology Of Sugar-free Tissue Culture Seedling Of Kiwifruit

Kiwifruit industry in China has entered a stage of rapid development,many new technologies are applied to practical production.Plant tissue culture technology has been successfully applied in the breeding of kiwifruit seedlings.However,there are some problems such as easy pollution,poor rooting effect and difficult transplanting,which need to be improved.In this study,a new plant micropropagation technology--sugar-free tissue culture propagation technology was used to solve the above problems,the technology has not yet formed an application system in the field of kiwifruitIn this study,Actinidia chinensis cv.‘Qihong’and Actinidia deliciosa cv.‘Yuxiang’were used as materials.The sugar-free tissue culture propagation system of kiwifruit was constructed from the aspects of explants sampling time,disinfection method,growth regulator ratio,substrate water content,substrate material,CO₂concentration and ventilation mode,and transplanting substrate.By analyzing the changes of endogenous hormones and related enzyme activity during rooting,the rooting mechanism of kiwifruit asexual reproduction was explored.The technique of sugar-free tissue culture of kiwifruit was established.which has important theoretical and practical significance for promoting the development of kiwifruit seedling industry.The main results are as follows:（1）The optimal time for stem explants of‘Qihong’and‘Yuxiang’was from April to May.The best disinfection methods were respectively:75%alcohol 15 s+1%Na Cl O 6 min;75%alcohol 30 s+1%Na Cl O 4 min.The optimum medium for proliferation and propagation were respectively:2 mg·L^-16-BA+0.3 mg·L^-1NAA;2 mg·L^-16-BA+0.3 mg·L^-1NAA+0.5mg·L^-1GA₃.The optimal medium for enhancing seedling growth were respectively:4 mg·L^-16-BA+0.5 mg·L^-1NAA+1 mg·L^-1GA₃;4 mg·L^-16-BA+1 mg·L^-1GA₃.（2）In the rooting process of sugar-free tissue culture,the optimal substrate for‘Qihong’and‘Yuxiang’was vermiculite with 80%water content.The optimal CO₂ environment were respectively:800μmol·mol^-1 15 min forced ventilation;1200μmol·mol^-1 15 min forced ventilation.The optimum growth regulators were respectively:0.3 mg·L^-1NAA+0.8 mg·L^-1IBA;0.8 mg·L^-1 IBA.The suitable transplanting substrates for sugar-free tissue culture root seedlings were respectively:Peat soil:Vermiculite=1:1;Peat soil:Perlite=1:1（3）Compared with sugar tissue culture,the root development of‘Yuxiang’and‘Qihong’in sugar-free tissue culture developed better,and the total root length,total root surface area,root tip number and branch number were 120.88/109.07 cm,15.10/18.36 cm²,87.00/82.60and 206.80/202.40,respectively,which were significantly higher than those of the control.（4）During the rooting process,the IAA content of‘Yuxiang’and‘Qihong’showed a“V”shape change.Sugar-free tissue culture can significantly increase the peak value of IAA,reduce the valley value of IAA,which was conducive to the formation of adventitious roots and the elongation of adventitious roots.ABA content of‘Qihong’and‘Yuxiang’in sugar-free tissue culture increased significantly,which was beneficial to root elongation.The GA₃content of‘Qihong’and‘Yuxing’in sugar-free tissue culture showed a trend of low in the early stage and high in the late stage.（5）In the early stage of rooting culture,sugar-free tissue culture can significantly increase the POD activity of‘Qihong’and‘Yuxiang’.The activity of‘Yuxiang’PPO in sugar-free tissue culture was high in the early stage and low in the late stage.IAAO activity of‘Qihong’and‘Yuxiang’in sugar-free culture was significantly higher than that in control sugar tissue culture on the 7th day.In summary,sugar-free tissue culture technology can significantly improve the rooting effect of kiwifruit tissue culture seedlings,with many advantages.Further research can be carried out to improve the technical system,so as to bring new ideas for kiwifruit seedling breeding.