A review of recent Pyrus, Cydonia and Amelanchier rootstock selections for high-density pear plantings

The principal pear production regions around the world depend on rootstock clones from Pyrus sp. (pear) or Cydonia oblonga (quince). Pyrus rootstocks are generally too vigorous and non-precocious for many pear cultivars. In the US, performance of pear scions on the P. communis rootstocks 'Old Home' x 'Farmingdale 87' and Pyro 2-33 produce trees similar to 70% of seedling pear and may be managed at relatively high densities (similar to 2,000 trees ha(-1)), albeit with intensive horticultural intervention, especially when combined with high-vigor scion cultivars. Pyrus rootstocks are cold hardy, compatible and, depending on the genotype, resistant to pear decline and fire blight. Quince rootstocks are highly precocious and size controlling, conferring a range of vigor from very dwarfing to semi-dwarfing to accommodate moderate to high-density plantings. Most commercial quince rootstocks lack adequate cold hardiness for northern regions, though 'Eline' and several selections from international sources may be sufficiently hardy. 'Eline' and EMH have performed well in international field evaluations. Additional limitations of quince, depending on the genotype, are fire blight susceptibility and lack of tolerance to calcareous soils. Incompatibility with some pear cultivars can be ameliorated with an interstem. Relatively recently, selections of Amelanchier sp. were developed from intra- and interspecific hybridization with selection pressure toward dwarfing, productivity, pear decline resistance, and tolerance of alkaline soils. These selections appear compatible with 'Doyenne du Comice' and 'Beurre Hardy' but may require an interstem with other cultivars. Amelanchier rootstocks are cold hardy, dwarfing and precocious with high yield efficiency and produce large fruit. However, excessive size control conferred by Amelanchier may require vigor-inducing horticultural techniques (fertilization, pruning, crop load management, etc.) to maintain balance between canopy volume and the excessive fruiting. The purpose of this review is to describe new selections and performance data for pear rootstocks from three genera.