Investigation of Scion and Rootstock Incompatibility in Some Asian (Pyrus serotina Rehd) and European (Pyrus communis L.) Pears

In pear trees, most of the features concerning vegetative and reproductive growth are affected by rootstock, so to establish modern and standard orchards for European pear (P. communis L.) and Asian pear (P. serotina Rehd.) in the country, the selection of suitable rootstock is important. To achieve desirable rootstock for Asian pear cultivars in Iranian climate conditions and also investigate rootstock and scion interaction and graft incompatibility mechanism in pear, the current research was designed and performed on grafted four-year-old trees during the 2014-2016 growth seasons. The factorial experiment in a randomized complete block design with the first factor including pear rootstocks including European pear seedling rootstock, quince ‎(Cydonia oblonga L.) ‎seedling rootstock, hawthorn ‎(Crataegus atrosanguinea) ‎seedling rootstock and clonal rootstock of ʻQuince A’‎ and the second factor consisted of two European pear cultivars including ʻBeurre Bosc’ and ʻWilliams Duchess’ and one Asian pear cultivar ʻKS10’ were used.‎ ‎Also, the scion growth length and starch accumulation were investigated at the top and bottom of the graft union and isozyme patterns in different interactions were analyzed between rootstock and scion. The results of scion growth length indicated the highest and lowest growth of scion in the pear seedling rootstock and hawthorn rootstock, respectively. Also, the starch accumulation amount at the top and bottom of the graft union confirmed the graft incompatibility in the interaction of ʻQuince A’ and quince rootstock with ʻBeurre Bosc’ and ʻKS10’ ‎cultivars‎. The investigation of the isozyme pattern indicated complete incompatibility of hawthorn rootstock with the studied cultivars.