Breeding for improvement of flowering attributes of winterhardy rosa kordesii Wulff hybrids

Summary The results from tetraploid hybrids of R. kordesii showed that flowering attributes can be improved by a suitable combination of modifying factors as was shown previously by investigations with diploid hybrids from R. rugosa. A longer flowering period than 7 weeks indicated always the ability for recurrent bloom in these investigations but a shorter flowering period did not always indicate non-recurrent bloom.The offspring from the cross of the recurrent R. kordesii with the non-recurrent seedling G12 segregated into non-recurrent and recurrent types in a ratio of 3:1 for a tetrasomic inheritance, assuming a duplex segregation and complete dominance.The flowering attributes could be improved without loss of a high level of winterhardiness.