The Breeders' Approach
The breeders conclude that there is evidence the variegation trait for their lilac should be passed on through the mother, since they found research that dealt specifically with lilacs. They design a reciprocal crossing pattern where the interesting plant (with variegated leaves) is used as the mother, bringing in pollen from other lilac plants (with normal green leaves), and also as the father, by carrying pollen from the variegated plant to fertilize the flowers of normal lilacs.
They do this because, even though they found research suggesting that most lilac species only show maternal inheritance of cytoplasmic DNA, each species can be different. And in order to be safe, they use the interesting variegated plant as both mother and father. If the trait is not passed on equally, if one of the reciprocal crosses has a disproportionate number of seedlings with the trait, then the trait should be controlled by organelle DNA. The results of their experiment will only be known after several seasons of crossing and growing seedlings, but an interesting new lilac cultivar is worth the wait!