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United States Department of Agriculture

Agricultural Research Service

Plum Pox FAQ - More information for the plum orchard industry

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More information for the plum orchard industry—

I have an organic plum orchard. How do I keep pollen from HoneySweet from reaching my trees?

HoneySweet pollen can fertilize other European plum trees but not Japanese plums or other stone fruits such as peach or apricot. To find out how far HoneySweet plum pollen will travel to other European plum trees, over 12,000 seeds from non-genetically European plum trees were evaluated over 11 years at distances from 230 to more than 3,500 feet from a HoneySweet planting. Only 39 of the more than 12,000 seeds were found to have received HoneySweet pollen, and most were from the trees closest to the HoneySweet planting. In the published study, beyond about 1300 feet there was almost no spread of HoneySweet pollen to non GE plum trees. These results showed that plantings of HoneySweet plum can coexist with plantings of non-genetically engineered plums without cross contamination. (More information about pollination and crossbreeding.)

The inserted genes in "HoneySweet" would be found in only about half of the pollen grains of "HoneySweet". If a pollen grain carrying the inserted genes did fertilize a non-GE plum tree, the pollen grain would fertilize the ovule that forms a seed. It is important to understand that the flesh of the plum fruit is exclusively derived from the non-GE tree maternal tree. The cells of the fruit flesh and skin are genetically identical to the cells of the maternal (non-GE) tree. So even in the rare instance of cross pollination between a GE "HoneySweet" and a receptive organically or conventionally grown non-GE tree, the resulting edible portion of the plum fruit (i.e., flesh and skin) would contain no GE DNA in its cells.

Although the plum stone, or pit, resulting from the cross pollination described above could contain GE DNA, plum trees are not normally propagated from seeds. Rather, they are clonally propagated from another tree of the desired variety usually by grafting. A twig from such a tree is grafted onto an existing plum rootstock. The plum seed is not normally used for producing new plum trees nor are plum seeds used as food. The seed is bitter due to the presence amygdalin, so people naturally refrain from eating it. Moreover, amygdalin, upon digestion, produces cyanide.

Clearly, cross pollination cannot change the genetic background of the tree receiving pollen from a "HoneySweet" tree. The biology of plum fruit development and the method used for plum propagation ensure that in the unlikely event of a cross pollination from pollen of "HoneySweet" and an organically or conventionally non-GE produced tree, the edible portion of the fruit and the tree itself will not be genetically altered.

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Last Modified: 8/24/2015
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