The similarity or differences of peroxidase isozymes in rootstocks and scions may influence their graft compatibility. This study was conducted to identify peroxidase isozymes that may be used as markers to predict compatibility between pear (Pyrus communis L.) and various quince (Cydonia oblonga Mill.) clones. `Bartlett' (BT) and `Beurre Hardy' (BH) pear cultivars are known to form incompatible and compatible grafts, respectively, with quince rootstocks. The two pear scion cultivars were budded on `quince A' (QA), `quince BA-29', and 15 selected quince clones from Turkey. Bark and cambial tissues were taken from nonbudded rootstocks and scions, and 4 cm above and below the graft union for peroxidase isozyme analysis performed by starch gel electrophoresis. Isoperoxidase analyses were also performed on samples from the graft unions collected 12 months after grafting. Many isozyme bands were observed commonly in the two scions; however, one anodal peroxidase A was detected in BH (compatible scion) but not in BT (incompatible scion) samples. This isoperoxidase was also detected in QA, Quince BA-29, and nine of the Turkish quince clones. Another isoperoxidase, band B, was detected in BH but not in BT or any of the rootstocks. However, the compatible (BH/QA) and moderately compatible (BT/BA-29) graft union tissues contained bands A and B whereas incompatible graft union tissues (BT/QA) lacked both. Graft union samples involving BT and five Turkish quince clones (705, 609-2, 702, 804, and 806) had both `A' and `B' isoperoxidases while one or both of these bands were absent in nonbudded graft partners. Field observations of 3.5 year-old grafts of BT and Turkish quince clones revealed that the vegetative growth (vigor) of BT scion was significantly greater, when grafted on these five clones, than that in graft combinations with other clones. We suggest that matching of isoperoxidase `A' in quince rootstocks and BH pear scion may be associated with a compatible graft combination. Additionally, presence of isoperoxidases `A' and `B' in the graft union tissues may be used as an indicator to predict a compatible graft between BT and quince rootstocks.

Bayazit S., Imrak B., Küden A., Kemal Güngör M., 2011. RAPD analysis of genetic relatedness among selected quince (Cydonia oblonga Mill.) accessions from different parts of Turkey. Hort. Sci. (Prague), 38: 134-141.Quince (Cydonia oblonga Mill.) is a minor fruit crop, which is primarily used for marmalade, jam, sauce and as rootstocks for pears. Different cultivated and local quince genotypes are grown in almost all parts of Turkey for fruit usage. In this study, randomly amplified polymorphic DNA (RAPD) technology was used to study the genetic relationships among 13 quince accessions selected from different parts of Turkey. Thirty decamer primers were used and 14 of them did not produce any polymorphism. The remaining 16 primers ranged in their amplification fragments between one (P-402, P-437, OPA 10, OPA 16, OPA 18 and OPA-19) and five (OPA-06 and OPA-07). The size of fragments varied from 100 to 1500 bp. Similarity values among the studied genotypes ranged between 0.483 and 0.925. The resulting dendrogram clustered into two groups (0.69 similarity value) based on evaluation of genetic similarities and differences. The results suggest that RAPD analysis could be used to distinguish and determine genetic variation among quince accessions. Also, the obtained clustering based on RAPD markers agreed to some extent with the geographical origin of the studied set of quince accessions.

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