If you have only one clone having the trait, then you will outcross to a similar plant having as close as you can get to the trait you want, backcross these F1 to the parent with the trait, and then do sibling crosses or back crosses with these F2 progeny selecting toward the trait.

This was used to get white redbud seed. Cercis is self sterile, so a rare white flowering tree was outcrossed by pollinating with a magenta one, then one of these seedlings was backcrossed to the white parent. Any of these F2 plants with white flowers is now homozygous in the white gene. Crosses of them will give all white flowering trees.

Most traits are more complicated than albinoism, so more generations might be needed.

George

Thanks George.