Targeted generation of polyploids in Hydrangea macrophylla through cross-based breeding.

Background: Up to now, diploid and triploid cultivars were reported for the ornamental crop Hydrangea macrophylla. Especially, the origin of triploids and their crossing behaviors are unknown, but the underlying mechanisms are highly relevant for breeding polyploids.

Results: By screening a cultivar collection, we identified diploid, triploid, tetraploid and even aneuploid H.