Many of the most important modern commercial red raspberry cultivars derive from hybrids between R. idaeus and R. strigosus. Some botanists consider the Eurasian and American red raspberries to all belong to a single, circumboreal species, Rubus idaeus, with the European plants then classified as either R. idaeus subsp. idaeus or R. idaeus var. idaeus, and the native North American red raspberries classified as either R. idaeus subsp. strigosus, or R. idaeus var. strigosus. Recent breeding has resulted in cultivars that are thornless and more strongly upright, not needing staking.
The black raspberry, Rubus occidentalis, is also occasionally cultivated in the United States, providing both fresh and frozen fruit, as well as jams, preserves, and other products, all with that species’ distinctive, richer flavor.
Purple raspberries have been produced by horticultural hybridization of red and black raspberries, and have also been found in the wild in a few places (for example, in Vermont) where the American red and the black raspberries both grow naturally. The botanical name Rubus × neglectus applies to these naturally occurring plants, as well as horticulturally produced plants having the same parentage. Commercial production of purple-fruited raspberries is rare.
Both the red and the black raspberry species have albino-like pale-yellow natural or horticultural variants, resulting from presence of recessive genes that impede production of anthocyanin pigments. Fruits from such plants are called golden raspberries or yellow raspberries; despite their similar appearance, they retain the distinctive flavour of their respective species (red or black). Most pale-fruited raspberries commercially sold in the eastern United States are derivatives of red raspberries. Yellow-fruited variants of the black raspberry are sometimes grown in home gardens.
Red raspberries have also been crossed with various species in other subgenera of the genus Rubus, resulting in a number of hybrids, the first of which was the loganberry. Later notable hybrids include boysenberry (a multi-generation hybrid), and tayberry. Hybridization between the familiar cultivated red raspberries and a few Asiatic species of Rubus has also been achieved.
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