Occasionally a single limb of a citrus tree produces unusual fruit that looks or tastes different than fruit on the rest of the tree. This is caused by a spontaneous mutation in the cell lines of the limb, which causes a natural modification in gene expression, and is known as a budsport. Many traits such as color and texture of the rind, color and flavor of the fruit, maturity date, season of flowering, and seediness can be altered as a result of a mutation.
Most citrus cultivars arise this way. A classic example is the navel orange, which we know of as being seedless and having a small conjoined twin (the navel) at it's base. This unusual fruit was discovered nearly 200 years ago from a sweet orange tree in Brazil that did not have these traits. In the late 1800's budwood from this tree was sent to the US, propagated onto rootstocks, and widely planted in California. Since then, clonal propagations of this 'Parent' navel have resulted in more budsports, and there are now more than 60 navel orange cultivars in the Citrus Variety Collection at UC Riverside. A popular 'Parent' navel budsport is the 'Cara Cara' navel, with pink flesh and an earlier ripening date, and from the 'Cara Cara' came the 'Variegated Cara Cara', with pink flesh and a striped rind.
Citrus Clonal Protection Program Staff Research Associate Rock Christiano firstname.lastname@example.org welcomes growers and individuals who have, or think they have, discovered a budsport to learn about how to develop it into a novel citrus variety. The choice of what to name it is usually left to the grower who discovered it! More information is available at http://ccpp.ucr.edu/
These photos show fruit on a limb of 'Frost Owari' satsuma which is distinctly different than the fruit on the rest of the tree. This budsport limb, recently photographed near Exeter CA, produced fruit that is smoother in rind texture, more vibrant in color, higher in °Brix, and lower in acidity than the rest of the fruit on the tree. The fruit on that limb is maturing sooner than the rest of the tree and could potentially produce a new 'Early Owari' variety.