Optimization of citrus stem culture conditions in vitro and experiment of shoot-tip grafting

ObjectiveCitrus stem culture conditions in vitro was explored and the shoot-tip grafting(stem tip grafting in tube)was carried out which could provide reference for cultivating virus-free citrus culture seedling.MethodThe mature stems of Satsuma mandarin and Newhall navel orange were disinfected with different concentrations of HgCl2 and NaClO. The disinfection methods of citrus explants suitable for tissue culture,collecting season and hormone ratio were screened. The rootstock seed disinfection and the shoot-tip grafting were carried out to analyze germination status of grafted shoot-tips for the two varieties.ResultThe optimum disinfection method for S. mandarin explants was treated with 70% alcohol+1.0‰ HgCl2 for 6 min for 2 times. The optimum disinfection method for Newhall navel orange explants was 70% alcohol+15.0% NaClO solution for 2 times. The optimum citrus stem collecting period for culture in vitro was summer. Added 1.0 mg/L 6-benayl aminopuring(6-BA)and 0.1 mg/L naphthylacetic acid(NAA)in MS solid medium were beneficial to the germination of axillary buds for the two citrus varieties. The optimum disinfection method for rootstock seed was removing the inner and outer seed coat+70% alcohol+1.5% NaClO solution. The germination rate of the two varieties were low,which were 10.00% and 6.67% respectively,but citrus seedlings grew well after successful grafting.ConclusionThe mature stems with buds are harvested in summer and S. mandarin stems were disinfected with 70% alcohol+1.0‰ HgCl2 for 6 min for 2 times;and Newhall navel orange were treated with 70% alcohol+15.0% NaClO solution for 2 times. Then they are cultured in MS solid medium supplemented with 1.0 mg/L 6-BA+0.1 mg/L NAA. This method can achieve good culture effects. The citrus seedlings grafted with shoot-tip grow well. Therefore,this method can be used after improving the graft germination rate on this basis.