Sunday, April 21, 2013

The mystique of the Navel Orange

The mystique of the Navel Orange

October 9, 2028

Weekly Report Posted: November 28, 2012 22:11

Navel oranges are characterized by the growth of a second fruit at the apex, which protrudes slightly and resembles a human navel. They are primarily grown for human consumption for various reasons: their thicker skin make them easier to peel, they are less juicy and their bitterness – a result of the high concentrations of limonin and other limonoids – renders them less suitable for juice. The widespread distribution and long growing season have made navel oranges very popular. In the United States, they are available from November to April, with peak supplies in January, February and March.

According to a 1917 study by Palemon Dorsett, Archibald Dixon Shamel and Wilson Popenoe of the United States Department of Agriculture (USDA), a single mutation in a Selecta orange tree planted on the grounds of a monastery near Bahia in Brazil probably yielded the first navel orange between 1810 and 1820.Nevertheless, a researcher at the University of California, Riverside, suggested that the parent variety was more likely the Portuguese navel orange (Umbigo), described by Antoine Risso and Pierre Antoine Poiteau in their book Histoire naturelle des orangers ("Natural History of Orange Trees", 1818–1822). The mutation caused the orange to develop a second fruit at its base, opposite the stem, as a conjoined twin in a set of smaller segments embedded within the peel of the primary orange. It was introduced in Australia in 1824 and in Florida in 1835. In 1870, twelve cuttings of the original tree were transplanted to Riverside, California, where they became known as "Washington". This cultivar was very successful, and rapidly spread to other countries. Because the mutation left the fruit seedless and, therefore, sterile, the only method to cultivate navel oranges was to graft cuttings on to other varieties of citrus tree. The California Citrus State Historic Park preserves this history in Riverside, as does the Orcutt Ranch Horticulture Center in Los Angeles County, California.

Today, navel oranges continue to be propagated through cutting and grafting. This does not allow for the usual selective breeding methodologies, and so all navel oranges can be considered fruits from that single nearly two-hundred-year-old tree: they have exactly the same genetic make-up as the original tree and are, therefore, clones. This case is similar to that of the common yellow seedless banana, the Cavendish. On rare occasions, however, further mutations can lead to new varieties.

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