238 Isoperoxidase and Protein Patterns in Compatible and Incompatible Pear/Quince Graft Combinations

Abstract

The similarity or differences of peroxidase isozymes in rootstocks and scions may influence their graft compatibility. This study was conducted to identify peroxidase isozymes and/or other proteins that may be used as markers to predict compatibility between pear and various quince clones. `Bartlett' (BT) and `Beurre Hardy' (BH) pear cultivars were budded on 13 selected quince clones and quince A (QA) rootstocks; BT and BH cultivars are known to be incompatible and compatible, respectively, with quince root stocks. Bark and cambial tissues were taken from unbudded rootstocks, scions, and 4 cm above and below the graft union for isozyme analysis. Samples were collected 1, 2, 3, and 12 months after grafting. In addition, samples from the graft unions were also analyzed 12 months after grafting. Isozyme separation was performed by starch gel electrophoresis. Many isozyme bands were commonly observed in the two scions; however, one anodal peroxidase was detected in BH but not in BT samples. This isozyme was also detected in QA and in all but four quince clones. Protein profiles of bark tissues from QA and three pear scions (BT, `Bosc', and P. crassane) were determined using SDS-PAGE. In general, protein profiles of the three pear cultivars appeared remarkably similar; however, P. crassane (a compatible pear cultivar on QA) had a 63 kDa protein, which was absent in BT and faintly observed in `Bosc' (intermediate compatibility). Our results suggest that these isoperoxidase and polypeptide could be associated with pear/quince graft compatibility.