Rosa kordesii

Rosa kordesii, or Rosa × kordesii is a type of rose that arose naturally from hybridization followed by chromosome doubling. A hybrid between R. rugosa and R. wichurana was created called Rosa 'Max Graf', but it was diploid and nearly sterile, producing flowers but no fruit. This rose produced a few viable seeds as a result of self-pollination, and the seedlings that resulted were tetraploid instead of diploid, i.e., the chromosomes of both pollen and egg cells had been naturally duplicated. The tetraploid seedlings are amphidiploids. A selection with double deep pink flowers and repeat bloom, also called 'K01 AgCan' was released by W. Kordes' Söhne in 1951.

These tetraploid roses interbreed readily with one another, but not with their diploid ancestors. Under the biological species concept, a new species name Rosa kordesii was created for the tetraploid hybrid roses and their descendants.

Amphidiploid roses can also be created deliberately from diploid-diploid hybrids by using colchicine spray on the growing tips of the plants. That strategy gives few successes, however, because the plant tissue has various chromosome numbers in different cells. Amphidiploid roses including Rosa kordesii have been used to some degree in breeding programs in combination with naturally occurring tetraploid roses.