Abstract
In this paper, I review recent advances in research on Japanese pear rootstocks. Several clones of Pyrus betulaefolia and P. calleryana seedlings have been identified based on their ability to induce dwarfing scion growth, and their use in the future as dwarfing rootstock is anticipated. Among the various rootstock species, P. betulaefolia exhibits good adaptability to different environmental conditions, with high tolerance to drought, cold, and salt. This is due, in part, to P. betulaefolia’s superior ability to regulate osmotic potential and ability to maintain a high degree of unsaturation in fatty acids in biological membranes during cold hardening. P. calleryana exhibits not only a relatively high drought tolerance but also the highest flood tolerance. This tolerance depends on the ability of P. calleryana to shift to alcohol fermentation under anaerobic conditions and to expel the ethanol thus generated. These two rootstock species are highly effective in preventing fruit-hardening disorders. While P. betulaefolia exhibits high salt tolerance among native Asian Pyrus species, it is exceeded in this respect by two native Mediterranean species, P. amygdaliformis and P. elaeagrifolia, with a mechanism to inhibit the transport of salts from the roots to above-ground plant parts. Furthermore, P. xerophila exhibits superior Fe3+-chelate reductase activity in roots, endowing the species with tolerance to alkaline soils.
