The easiest method to employ, is simply to breed back to one variety. For example, one would start with any male plant and pollinate Cascade. The seeds are then raised and any male plant is selected and its pollen used to pollinate a Cascade. The seeds from that breeding are then raised and another male is selected and used to pollinate a Cascade, and so on and so forth.
Its not necessary to test your male pollen donor. The object of the breeding program outlined above is to create a male line with a high percentage of Cascade genes. If you wish, you may select a male with particular growth characteristics that you deem valuable or desirable, for instance early flowering or high vigour. This is how a male plant of a particular variety is created.
After 7 generations, there remains less than 1% foreign genetic material in your breeding line -
X1 : 50%
X2 : 25%
X3 : 12.5%
X4 : 6.25 %
X5 : 3.125%
X6 : 1.5625%
X7 : 0.78125%
One thing that may happen with this method is that the male line may lose some vigour and become dwarfed. (Cue Yob!) This isn't an issue as this would normally be the breeding method employed to create a male of one variety to cross with the female of another variety. Hybrid vigour would return when the male is outcrossed.
Of course, when an outcross is performed, one can breed back to the male plant for more than one generation, selecting female plants from each generation if desired. And even when producing a male, it may be possible to select a female plant from the stock produced, etc.
