Investigation of rootstock/scion relationships in quince and pear by isozyme analysis

This study was conducted in identify PRX isozymes and other proteins that may be used as markers to predict the compatibility between pear and various quince rootstocks. For the PRX isozyme work, Bartlett (BT) and Beurre Hardy (BH) pear cultivars were budded on 15 selected quince clones, quince A (QA) and BA-29 rootstocks. BT and BH cultivars are known to be incompatible and compatible, respectively, with quince rootstocks. 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, 4, 8, 12 weeks after grafting. In addition, samples from the graft unions were also analyzed 12 months after grafting. Starch gel electrophoresis (SGE) was used for PRX isozyme analyses, acidic (anodal) and basic (cathodal) PRX separations were performed by polyacrylamide gel electrophoresis (PAGE). In the total protein work, bark tissues of current shoots of Passe Crassane (PC), B. Hardy (BH), Beurre Bosc (BS) and Bartlett (BT) pear scions budded on QA and pear seedling rootstocks were taken. Total protein profiles were determined using SDS-PAGE. In SGE, only anodal PRX was considered because of the fuzzy bands on the cathodic part of the gels. Comparasion of PRX profiles in SGE of 2 pear sicion and 17 rootstocks, many isozyme bands were commonly observed. However, two anodal PRX bands [Rf = 0.88 (A) and Rf = 0.68 (B)] were detected importantly. Band A was present in BH (a compatible pear scion), absent in BT (an incompatible pear scion) and present in QA, BA-29 and 9 of the quince clones. Band B was observed only in BH scion. Ill EOKÛMAflTASYON IJIERKEgJIsozyme profiles of graft union appeared as though isozymes of individual graft partners have been combined. However, some exceptions were observed for band A and B. Isoperoxidases A and B were not present in some graft union samples even though they were present in unbudded individual graft partners. Conversely, these isozymes were present in some graft union samples despite their absence in one or both graft partners. Isoperoxidase bands observed in the graft union samples were darker than those in unbudded graft partners. Isoperoxidase bands observed in the graft union samples were darker than in unbudded graft partners. In addition, comparison of compatible (BH/QA), moderately compatible (BT/BA-29) and incompatible (BT/QA) graft combinations indicated that more isoperoxidase bands were present in compatible and moderately compatible graft union samples than in incompatible one. Comparison of graft union samples for band A and B, both bands were detected in all the combination of BII. In graft combinations of BT, both bands were detected only in BT/BA-29 and 5 graft combinations of BT/quince clones, where as BT/QA (incompatible comb.) union neither had band A nor B. Therefore, these clones were detected as promising quince rootstocks that might compatible with BT. In SGE, there was not seen any difference among the PRX profiles of samples collected from 4 cm. above and below the union in the 4 periods for all of the combinations. Basic PRX profiles of scions and rootstocks were clearly resolved in PAGE. However, acidic PRX profiles in PAGE were remarkably similar with that were in SGE. Only one basic isoperoxidase band (Rf = 0.91 was commonly observed in BH scion and all of the rootstocks where as BT did not contain this band. Consequently, results of isozymes showed that electrophoretic detection of incompatibility using isoperoxidase analysis of graft union could be used in pear/quince graft combination. Protein profiles of bark tissues from 4 pear scion and QA rootstock appeared remarkably similar in general, however PC and BH (compatible pear cultivars on QA and BS (intermediate compatible) had a 63 kDa protein, which was absent in BT (an incompatible cultivar on QA). Even though, scion grafted on QA had more total protein than had grafted on pear seedling rootstock, there was not any relationship between total protein amount and graft incompatibility. In conclusion, our data indicated that 2 anodic, 1 cathodic isoperoxidases and one polypeptide could be associated with pear/quince graft incompatibility. Field observations of this experiments that are underway, would approve of the conclusion from this study. Key Words : pear/quince grafting, graft incompatibility, isozymes, peroxidase (PRX), protein IV