Evaluation of Growth and Bearing of Several Commercial Pear (Pyrus communis) Cultivars on Semi-dwarfing Pyrodwarf Rootstock

Pear seedlings are the most predominant rootstocks for pear trees in Iran that are vigorous and show diversities. In addition, the use of semi-dwarfing clonal quince rootstocks is limited due to their susceptibilities to stresses. Based on these, Pyrodwarf pear rootstock could be considered as a new choice for intensive orchards, therefore, in this research growth and bearing of four important commercial pear cultivars including Beyrouti, Dargazi, Louise Bonne and Spadona cultivars were evaluated on this rootstock from 2012-2014. The orchard was established with 333 trees/hec and modified leader training form. The highest diametric growth of rootstocks, trunk diameters, tree heights, number of lateral shoots and annual growths were observed in the Spadona, Dargazi and Louise Bonne cultivars, respectively. All pear cultivars at the first year demonstrated higher diametric growth and lower height comparing to the standards of pear trees on the seedling rootstocks. In addition, cultivar Beyrouti with the lowest diameters of the stock and scion, and reduced 30% of growth was the most dwarf combination. All cultivars bloomed at the second years and had small quantities of fruit bearing at the subsequent year, but the highest bloom density and rate of spur/trunk surface area were observed in Dargazi, while the highest spur density along the branches observed in cultivar Beyrouti. According to the results, Pyrodwarf rootstock with dwarfing effects about 30%, early bloom initiation and bearing in the second and third years of cultivation could be considered as a promising choice for establishment of semi-dwarfing pear orchards.