Micropropagation of Three Pyrus Rootstocks

Explants of three rootstock selections Pyrus calleryana Dcne `Oregon Pear Rootstock (OPR) 157', P. betulifolia Bunge `OPR 260', and P. communis L. `Old Home' × `Farmingdale 230' (`OH × F 230') were initiated from forced branches of field-grown trees. `OPR 260' and `OH × F 230' shoots cultured on Cheng medium with IBA proliferated better than those on NAA. NAA and IBA at concentrations >0.5 μ m inhibited shoot multiplication. Overall, the best micropropagation medium for `OPR 260' and `OH × F 230' was Cheng medium with 8 μ m BA and 0.5 μ m IBA. Shoot multiplication of `OPR 157' was best on 8 μ m BA and better on low NAA (0.5 μ m ) or no auxin than on IBA. `OH × F 230' rooted easily (>80%) with all IBA and NAA treatments. The best rooting treatment (42.9%) for `OPR 260' was 10 μ m IBA in darkness for 1 week; for `OPR 157' (23.9%), it was a 15-second dip in 10 m m NAA. Only rooted plantlets survived 4 weeks of greenhouse acclimatization. Chemical names used: N 6 -benzyladenine (BA); indole-3-butyric acid (IBA); napthaleneacetic acid (NAA).