Saving the Florida Orange by Altering its DNA


Sun, Aug 4th, 2013 21:00 by capnasty NEWS

There is a disease called citrus greening, caused by a bacterium carried by insects, that's making the Florida oranges grow stunted: small and half green, rather than plump and orange. Everything that has been done to control the disease, from pesticides to trying to find a tree that's immune, has failed. The only way to save it, growers believe, is to "alter the orange’s DNA — with a gene from a different species."

Because oranges themselves are hybrids and most seeds are clones of the mother, new varieties cannot easily be produced by crossbreeding — unlike, say, apples, which breeders have remixed into favorites like Fuji and Gala. But the vast majority of oranges in commercial groves are the product of a type of genetic merging that predates the Romans, in which a slender shoot of a favored fruit variety is grafted onto the sturdier roots of other species: lemon, for instance, or sour orange. And a seedless midseason orange recently adopted by Florida growers emerged after breeders bombarded a seedy variety with radiation to disrupt its DNA, a technique for accelerating evolution that has yielded new varieties in dozens of crops, including barley and rice.

Its proponents argue that genetic engineering is one in a continuum of ways humans shape food crops, each of which carries risks: even conventional crossbreeding has occasionally produced toxic varieties of some vegetables. Because making a G.M.O. typically involves adding one or a few genes, each containing instructions for a protein whose function is known, they argue, it is more predictable than traditional methods that involve randomly mixing or mutating many genes of unknown function.

But because it also usually involves taking DNA from the species where it evolved and putting it in another to which it may be only distantly related — or turning off genes already present — critics of the technology say it represents a new and potentially more hazardous degree of tinkering whose risks are not yet fully understood.



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