Mini shoot Scion Proliferation in vitro of the Precocious Walnut Cultivars

A technique for mass proliferating mini shoot scions in vitro of the prcocious walnut cultivars (Juglans regia) has been established. Tests on the proliferation were carried out and presented in this paper.The results showed that it was the suitable time to collect the shoot node explants in tree for in vitro culture when the shoots grew to form 8～10 nodes. The shoot tip and the fourth and fifth nodes under the shoot tip in the shoot had highest survival and germination rate after being sterilized and cultured in vitro. The proliferation rate and the quality of mini shoot scion was obviously influenced by th BA level in DKW medium,the temperature for culture and the proliferation subculture interval,and the best results were achieved when BA in the medium was 0.5～1.0 mg/L,changing temperature of 25±3 ℃ in day and 18±2 ℃ at night and 20 d interval of proliferation subculture.The treatment of cutting off the shoot tips (about 0.5 cm) of the deteriorated shoots clump could partly recover its growth vigor and inhibited its flowering in vitro.From our tests, a modified DKW medium was developed which could dismiss the deterioration phenomenon.After being applied in our lab,the modified DKW demonstrated a better medium for mass proliferation of the mini shoot scion of precocious walnut cultivars.