Optimization Of Adventitious Shoots Regeneration System Using Immature Embryos Of Maize Inbred Lines Ye478 And TY4 As Explants

Maize immature embryo is the most common explant in maize tissue culture.It is important to optimize the tissue culture system of maize immature embryos for high-efficiency genetic transformation of maize immature embryos.The shoot regeneration efficiency of tissue culture system may be affected by some factors,for example,the type of culture medium,hormone type and hormone concentration.Both Ye478 and TY4 are two elite maize inbred lines.The embryonic callus could be easily induced from their immature embryos,while it is difficult to regenerate green seedlings.In this study,the immature embryos of two inbred lines were cultured on three available media?N6 medium,modified N6 medium and MS medium?for 14 days,respectively.The callus induction frequency of type II was recorded and analyzed.The results showed that the optimal medium for inbred line Ye478 was N6 medium and the optimal medium for inbred line TY4 was MS medium.Based on this,exogenous hormone Dicamba with different concentration(0 mg·L^-1,1 mg·L^-1,2 mg·L^-1 and 3 mg·L^-1)were added into the callus induction medium.The embryogenic callus induction rate was counted and analyzed for determine the optimal hormone concentration.The results revealed that the optimal concentration of Dicamba for inbred Ye478 was 3 mg·L^-1 and the optimal of Dicamba concentration for inbred TY4 was 2 mg·L^-1.And then,exogenous hormone Zeatin with different concentration(0 mg·L^-1,3 mg·L^-1,5 mg·L^-1 and 7 mg·L^-1)were added into the shoot regeneration medium.The efficiency of shoot regeneration was counted and analyzed for determine the optimal hormone concentration.The results revealed that the optimal concentration of Zeatin for inbred Ye478 was 5 mg·L^-1 and the optimal of Zeatin concentration for inbred TY4 was 3 mg·L^-1.More importantly,under our optimal tissue culture system,the time of shoots regeneration could be shorten about two weeks.Taken together,we optimize the tissue culture systems of two inbred lines Ye478 and TY4 by comparing three different based mediums and screening the optimal concentration of exogenous hormones Dicamba and Zeatin in different culture stages,which is very helpful for the construction of high-efficency genetic transformation of these two elite inbred lines in the near future.