ISOPEROXIDASE VARIABILITY IN PEAR ROOTSTO CKS (PYRUS-CALLERYANA DCNE AND P-BETULAEFOLIA-BUNGE)

Shoot bark peroxidases of Pyrus calleryana Dcne and P. betulaefolia Bu nge rootstocks were compared by polyacrylamide gel electrophoresis. Se ven bands were detected in each one of the species. Three electrophore tic patterns were found in P. calleryana, which were differentiated by presence, absence or presence of two bands (R.M. values = 0.77 and 0. 82). The presence of bands of R.M. 0.49 and 0.5 1, or bands of R.M. 0. 54 and 0.56 or of these four bands allowed to distinguish three patter ns in P. betulaefolia. Isoperoxidase analysis of clone XII indicates t he occurrence of probable interspecific hybridization, due to the pres ence of common bands to both species. Variability found emphasizes the need of rootstock selection and identification to establish uniform p ear orchards.