Abstract: The hybrid tree[Broussonetia papyrifera （L.） Vent.]—Zhongke No. 1 was used as the experimental material, through the culture and expansion of the stem segments of the hybrid tree in vitro, the effects of different hormones on callus, shoot buds, strong seedlings and roots were studied. The results showed that the survival rate of explant material, stems of the buds with axillary buds, could reach 44%, after immersed in 75% ethanol solution for 40 s, then sterilized by 0.3% HgCl₂ for 15 min. The optimal medium for inducing callus is MS+IBA 0.5 mg/L+6-BA 2.0 mg/L+sucrose 25 g/L+agar 7.0 g/L, pH 5.6~5.8, the callus induction rate reached 90%. The optimal medium for inducing cluster buds was MS+IBA 1.5 mg/L+6-BA 2.0 mg/L+sucrose 25 g/L+agar 7.0 g/L,pH 5.6~5.8, the growth coefficient of cluster buds is 4.2, and the growth potential is good. The optimal medium for strong seedlings is MS+0.2 mg/L IBA+6-BA 1.5 mg/L+sucrose 25 g/L+agar 7.0 g/L, pH 5.6~5.8, average plant height is 4.8 cm. The optimal medium for rooting is 1/2 MS+IBA 0.8 mg/L+activated carbon 1.5 g/L+potato 50 g/L+sucrose 25 g/L+agar 7.0 g/L,pH 5.6~5.8, rooting rate is 100%. The best seedling transplanting substrate soil is a mixed substrate of peat∶perlite∶vermiculite=1∶1∶1. The seedlings grow best, with an average plant height of 7.3 cm.

Key words: hybrid Broussonetia papyrifera, tissue culture, callus, bush bud