Ploidy variation and karyotype analysis in Hemerocallis spp. (Xanthorrhoeaceae) and implications on daylily breeding

Daylily or Hemerocallis spp. (Xanthorrhoeaceae) is one of the most economically important flowering crops in the world. Ploidy level of 149 genotypes both local to China and introduced from the United States and New Zealand were assessed with an outcome of 79 diploids, 22 triploids and 48 tetraploids. A large proportion of introduced cultivars were tetraploid (42%), half were diploid and the rest, 8%, were triploid. Most Chinese cultivars were diploid; only one was tetraploid. Among the 29 wild genotypes collected from the Taihang Mountain range, 13 (45%) were triploid and 16 (55%) were diploid; no tetraploids were identified. For the 31 genotypes with known ploidy, 22 matched previous counts with the rest showing a lower ploidy. As different ploidy is common in daylily, we suggest that ploidy levels should be assessed in breeding programmes for specific breeding purposes. Karyotypes of three diploid, three triploid and two tetraploid genotypes were constructed and they were assigned to '3A', '2B' and '3B' categories based on Stebbins' karyotype classification.