Cross-breeding With Different Ploidy In Hemerocallis Spp.&Cvs

The daylily(Hemerocallis spp.) is important ornamental plant species in landscaping. Although cultivars number is increasing, the genetic diversity of daylily cultivars is rapidly decreasing. In order to expand the genetic diversity in daylily cultivars, interploidy crosses between diploid(2n=2x=22) and triploid(3n=3x=33)and between tetraploid(2n=4x=44) and triploid were performed to derive aneuploid and triploid. Two diploids with light color bloomed nocrurnally. Others bloomed diurnally. The major barrier to interploidy hybridization and how to overcome the barrier were discussed. Some filial generations were were subjected to verification of ploidy status by root tip chromosome counting. At the same time polyploid induction of dipoloid Hemerocallis was studied. Main results are as follows:1. The average seed-setting rate between diploids was26.62%, and between triploids and diploids was18.19%. The average seed-setting rate between tetraploids was14.27%. There were serious segregations between triploids and tetraploids and the average seed-setting rate was6.50%. It is hard to get seed from the cross between diploids and tetraploids the seed-setting rate was as low as2.23%. when parents had different ploidy types, abortion always happen.2. Germination trial of the seeds from H.lilioasphodelus X’Red Rum’ and H.lilioasphodelus X’ Childrens Festival’with4different treatments was carried for study the germination characteristic of Seed. The result showed that the seeds which were hidden in wet turf at5℃for2month had the highest germination rate, more than96%, and germinated fastest, sprout most orderliness. The key of seed germination is keeping the seeds moist.3.19hypothetically aneuploid genotypes were subjected to verification of ploidy status.12of them were confirmed aneuploids. The number of chromosomes of aneuploid from crossing between diploid and triploid was from23to25. There was only one plant derived from crossing between diploid and tetraploid, which had38chromosomes. Only one of7genotypes from crossing between diploid and tetraploid was triploid, others were diploid.4. By the examination of pollen viability, pollen germination on stigma and hybrid embryos paraffin section observation, finding that the barrier to interploidy hybridization had many reasons, including low pollen viability of polyploid daylily, pollen tube distorted and blocked, and postzygotic endosperm abortion.5. The polyploid induction result of the seeds of H. fulva×H. lilioasphodelus indicated that the treatment of0.05%colchicines for12h gained2plants with larger stomas, the mutation rate was40%. For’Si Yuehua’stem tip, the treatment of0.2%colchicines gained16plants with larger stomas, the mutation rate was53.3％.