Ploidy Variation in Hemerocallis spp.and the Implications on Daylily Breeding

摘要

Daylilies (Hemerocallis spp.) are widely cultivated as one of the most important flowers in addition to their reputed nutritional and medicinal effects in traditional Asian cuisine.Ploidy level of 149 established cultivars both local and introduced from America and New Zealand as well as wild genotypes collected from Taihang Mountain ranges were assessed.The results indicated 79 diploids,22 tripioids and 48 tetraploids.A large proportion of introduced cultivars are tetraploid (42％), half are diploid and the rest 8％ are tripioid.Most Chinese cultivars are diploid with only one tetraploid.Among the 29 wild genotypes collected from Taihang Mountain ranges, 13 (45％) were triploid and 16 (55％) were diploid with no tetraploid identified.This result suggests that triploidy is common in the wild and the triploids are probably originated from unreduced gametes because no tetraploid was identified.For the 31 genotypes with known pioidy, our assessment showed that 22 of them matched previous counts with the rest showing a lower ploidy.Analysis of variance indicated that triploids (0.9 cm) and tetraploids (1.0 cm)grow significantly thicker flower stems than diploids (0.6 cm) and they also grow wider leaves (3.5, 2.4 and 1.8 cm, respectively).There is no difference between triploids and tetraploids for the two traits.As different ploidy is common in daylily,we suggest that pioidy levels should be assessed in breeding programmes so that parents of different pioidy can be matched for specific breeding objectives with maximum outcome.