Contribution to the Origin of the Grapefruit, Citrus paradisi (Rutaceae)

Some of the sources of confusion that contributed to the mystery of the origin of grapefruit, or pomelo, Citrus paradisi Macf., have now been identified. Results of current research in genetic markers, and conventional and chemotaxonomic considerations, strongly support the earlier proposal that the grapefruit originated from a cross between a pummelo, Citrus grandis (L.) Osbeck, and sweet orange, Citrus sinensis (L.) Osbeck. We also conclude that C. sinensis was the pollen parent. In 1828, botanist James Macfadyen said: genus citrus is so generally diffused, and its species have so long been submitted to the investigations of science, that it may appear strange if we assert that many points connected with its history still remain to be elucidated. He is credited with the botanical naming of the grapefruit, or pomelo, as Citrus paradisi Macf. However, it is surprising that the origin of such a relatively recent taxonomic addition to the genus would still remain buried in mystery. It is generally accepted by current researchers that most citrus biotypes are of Asian origin; the grapefruit, however, is believed to have originated as a chance seedling on the island of Barbados in the Caribbean. Christopher Columbus brought the first citrus biotypes-sour orange (C. aurantium), lemon (C. limon), and citron (C. medica) to the island of Hispanola (Haiti and Dominican Republic) on his second voyage in 1493. The Spanishand Portuguese-speaking territories in the New World subsequently cultivated sweet orange (C. sinensis), sour orange, lemon, citron, and lime (C. aurantifolia), the sweet orange and lime having been introduced later, in the 17th century. The Englishand Dutch-speaking territories appeared to have undertaken the additional cultivation of Citrus grandis (L.) Osbeck-pummelo-which was indigenous to the Malaysian Archipelago where they traded. In 1684, Hans Sloane visited Barbados for 10 days and identified the sweet orange and pummelo (Shaddock tree) as being present there (Sloane 1696), however, he made no reference to the grapefruit. In 1707 he described the origin of the name and the introduction of the Shaddock: seed of this was first brought to Barbados by one Captain Shaddock, Commander of an East India ship, who touched at that island in his passage to England and left its seed there. In 1750, Griffith Hughes, rector of St. Lucy's parish of Barbados, wrote ten books on the natural history of Barbados. In Book V, he described the following 14 Citrus biotypes: the Shaddock tree, a lesser Shaddock tree, a wild Shaddock tree, the sour orange tree, the China orange