Vavilov said of Jaffa oranges:
The well-known brand ‘Shamudi’ arose apparently as a vegetative mutation as was demonstrated by a Dutch research worker, Oppenheimer. Jaffa oranges are distinguished by their smooth and thick skin and the large size of the juicy fruits and have therefore, in essence, no competitors. The market for them is absolutely secure and practically unlimited.
The history of the Shamouti orange is not quite that simple. Wikipedia is quite wrong when it cites Daniel Rogov as an authority for the statement that “the variety ‘originated in China and Cochinchina’”. Rogov’s article says clearly that “sweet oranges grow on an elegant tree, one with pleasantly scented blossoms, that originated in China and Cochin-China”. Note: Rogov is talking about the species (sensu latu) of sweet oranges, rather than the variety Shamouti. So, with that out of the way, where did the variety arise?
The most common explanation that one sees around is that Shamouti arose as a branch sport — a kind of mutation that can give rise to noticeably different properties in the fruit — of a local orange variety called Beledi some time around 1844 (or 1860) near the town of Jaffa. There’s an early record from the poet Lamartine visiting Palestine in 1832, but Aaron Aaronson calls attention to what he considers mistakes in Lamartine’s account and concludes:
This and other errors of observation cause me to doubt the value of the poet’s description from the point of view of the naturalist and agriculturist, although its value as literature is unquestioned.
Beledi is thin-skinned and has seeds. Shamouti is thick-skinned and generally almost seedless. The exact genetic differences between them, however, have not as far as I can discover been identified. It seems that Shamouti is what is called a periclinal chimera, that is a mixture of cells from the original Beledi and mutant Shamouti cells. A periclinal chimera arises when the mutation originally takes place in a cell very near the apex, or growing tip, of a plant shoot. These cells in the apical meristem are more or less the plant equivalent of embryo stem cells in animals. A mutation there will often be carried in all the cells of one of the plant’s tissue layers, with unmutated cells in other layers: a chimera. Then, depending on how the sport is propagated, some of the offspring could end up with only mutated cells. [1] In experiments, seeds from some Shamouti trees gave rise to only Beledi trees; the cells that formed the seeds were pure Beledi cells. Seeds from other trees gave rise only to Shamouti trees; they ere now composed entirely of Shamouti cells, homohistonts, if you hadn’t forgotten.
As for the seedlessness, that was studied a long time ago by Otto Frankel and one J.D. Oppenheim. [2] I can see only the abstract, but it seems to be saying that genuine Shamouti produces plenty of ovules and plenty of pollen, so something else is interfering with them getting together to produce seeds. Frankel’s is a name to conjure with. He and Vavilov must have met, but that will have to await more research. And while we’re on the subject of names, Balady [3] is an Arabic word, meaning endemic to an area, or, to put it more prosaically, the local orange, date, sugar cane, ginger, whatever. As for Shamouti, who knows? Luigi thinks it may be something to do with the Sun, which seems reasonable enough, but what we really need is an Arabic etymologist, in case you happen to know of one.
And finally, there’s an interesting account of the history of trade in Shamouti, or Jaffa, oranges in the book From Desert Sands to Golden Oranges, which stresses the robust nature of Jaffas. They survived camel trains and later truck journeys, hand-loading onto ships and a month or more in unrefrigerated cargo holds before arriving in northern Europe almost undamaged. They must indeed have seemed “absolutely secure” to Vavilov, but the recent history of Israeli citrus exports shows it to have been anything but.
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