MICROPROPAGATION OF 3 PYRUS ROOTSTOCKS

Explants of three rootstock selections Pyrus calleryana Dcne 'Oregon P ear Rootstock (OPR) 157', P. betulifolia Bunge 'OPR 260', and P. commu nis L. 'Old Home' x 'Farmingdale 230' ('OH x F 230' were initiated fro m forced branches of field-grown trees. 'OPR 260' and 'OH x F 230' sho ots cultured on Cheng medium with IBA proliferated better than those o n NAA. NAA and IBA at concentrations >0.5 mu M inhibited shoot multipl ication. Overall, the best micropropagation medium for 'OPR 260' and ' OH x F 230' was Cheng medium with 8 mu M BA and 0.5 mu M IBA. Shoot mu ltiplication of 'OPR 157' was best on 8 mu M BA and better on low NAA (0.5 CIM) Or no auxin than on IBA. 'OH x F 230' rooted easily >80%) wi th ah IBA and NAA treatments. The best rooting treatment (42.9%) for ' OPR 260' was 10 mu M IBA in darkness for 1 week; for 'OPR 157' (23.9%) , it was a 15-second dip in 10 mM NAA. Only rooted plantlets survived 4 weeks of greenhouse acclimatization. Chemical names used: Nb-benzyla denine (BA); indole-3-butyric acid (IBA); napthaleneacetic acid (NAA).