Interploidy crosses in roses: use of triploids

Interspecific crosses between diploid rose species and tetraploid cultivars yield triploids. Using such triploids as pollen parents and tetraploid plants as seed parents resulted in relatively high seed set. Although efficiency was lower, reciprocal crosses with the triploid plant as a seed parent also yielded some seedlings. Screening of the progeny showed that seedlings obtained after a cross between a tetraploid seed parent and a triploid pollen donor are mostly tetraploid. In the reciprocal cross, both triploids and tetraploid seedlings are found. These results indicate that triploid rose plants form both haploid and diploid pollen and egg cells. However, in pollen production, the diploid fraction seems to have a competitive advantage over the haploid. Molecular marker (AFLP) data show that markers can be passed on from the diploid species to a tetraploid F2 generation via a triploid F1.