Effect of lime concentration on pear's rootstock/scion combinations

The aim of the research was the determination of the tolerance of different pear grafting combinations to various levels o lime concentration in calcareous soils. The experiment was carried out under pot conditions for a two-year period (2015-2016). Two factors including combination of rootstocks/scions (3 × 3) and levels of lime concentration were employed to evaluate leaf responses including total iron (Fe), available Fe, chlorophyll (Chl) (a, b, total), and chlorophyll fluorescence attributes (F0, Fm, Fv/Fm) as well as annual growth and internode length of current shoots. Results showed that soil lime significantly reduced tree growth but conversely intensified iron chlorosis. Also, contrary to our expectations, the Pyrodwarf/Pyrus communis L. (Dargazi) combination displayed more tolerance to high lime concentrations, whereas the OH × F/Williams Duchesse combination did not exhibit suitable tolerance. As a pear rootstock native to Iran, Dargazi seedling rootstock in combination with different scions was found to have relatively better growth under low lime concentrations, but its response under high lime was not as favourable as expected. Cultivar Dargazi combined with different rootstocks showed a better response to high lime stress compared to other scions, while cultivar Williams Duchesse exhibited lower tolerance to high lime concentration when combined with different pear rootstocks.