comparison of the dwarfing effects of two hawthorn and quince rootstocks on several commercial pear cultivars

a principal obstacle facing intensive pear orchard establishment in iran is the absence of appropriate dwarfing or semi-dwarfing rootstocks, compatible with commercial cultivars, as well as showing adaptability with alkaline soils. this research aimed at an evaluation of the hawthorn seedlings (crataegus sp.) as a potential dwarfing rootstock for pear and a comparison of its dwarfing effects with clonal quince a and normal pear seedling rootstocks on several commercial and fire blight tolerant pears (2005-2010). the evaluated cultivars were spadona, dar gazi and harrow sweet, beside two moderately fire blight susceptible cultivars namely bartlett and shah miveh. results confirmed high dwarfing effects of crataegus and semi-dwarfing of quince a rootstocks on pear cultivars. reduced tree size on dwarfing rootstocks resulted from decrease in the tree height and its canopy expansion ended up to reduced tree vigor, but the rootstock type did not affect the length of the internodes. none of scion/rootstock combinations demonstrated incompatibility-dependent disorders including abnormal scion/rootstock growth rate. with respect to the low growth induced in the shoots of pear cultivars on crataegus rootstock, and difficulties in transplanting of this rootstock due to its weak root productivity, it seems that this species does not possess the potential to be used as an efficient dwarfing rootstock for commercial pear cultivars.