Plant regeneration from in vitro leaves of four commercial Pyrus species

An efficient shoot regeneration from in vitro leaf sections of Pyrus communis Bartlett, P. pyrifolia Shenbuzhi, P. bretschneideri Zaosu and P. ussuriensis Manyuanxiang was successfully developed for use in future transgenic studies. On the basis of regeneration frequency and average shoot numbers, optimal shoot regeneration was obtained on leaf sections of P. communis Bartlett when cultured on Murashige and Skoog complete medium containing 6.0 mg/l BA (6-benzyladenine) and 0.1 mg/l NAA (α-naphthaleneacetic acid), while Quoirin and Lepoivre complete medium supplemented with 1.0 mg/l TDZ [thidiazuron (N-phenyl-N1-1,2,3-thiadiazol-5-ylurea)] and 0.1 mg/l NAA was found best for P. pyrifolia Shenbuzhi, and Nitsch and Nitsch complete medium containing 3.0 mg/l TDZ and 0.1 mg/l NAA or 0.2 mg/l IAA was suitable forP. bretschneideri Zaosu or P. ussuriensis Manyuanxiang, respectively. After cutting the leaves into three sections perpendicular to the midrib and culturing under the equivalent conditions, regeneration occurred more frequently on basal sections than middle sections, and no shoots formed on apical sections. A ratio of NH+4-N/NO-3- N of 1:2~1:7 was found beneficial for shoot regeneration. 75.0-87.5% of proliferating shoots formed roots after 4 weeks of transfer to 1/4 strength of Murashige and Skoog complete medium supplemented with 2.5 mg/l IBA (indole-3-butryric acid) and 30.0 g/l sucrose. Regenerated plants were successfully established under greenhouse conditions.