Assessment of Ploidy Level and Genetic Relationships Among Selected Hemerocallis Hybrids

The market for daylily hybrids (Hemerocallis) demands plants with high quality, including diversity of colors, shape, size and number of flowers. In Southern Brazil, a breeding program has been developed in the city of Joinville, state of Santa Catarina focusing in the landscape market, aiming at plants with medium height and high number of flowers. Thirty crosses were performed among 13 daylilies cultivars selected for the plant characteristics mentioned above. However, some crosses did not produce seeds or seed production was very low. We raised two hypotheses to explain such results; 1) the different ploidy between the parents and 2) the genetic proximity of the parents due to the narrow genetic variability and consequently genetic inbreeding. To verify these hypotheses, the present study aimed at examining the ploidy level and the genetic relationships among selected daylily hybrids using chromosome and genetic analyses. Chromosome counting revealed a diploid chromosome number ranging from 20 to 24, with most cultivars showing ploidy of 22. This result indicates that ploidy level did not affect seed formation.  Genetic analysis was performed using RAPD (Random Amplification of Polymorphic DNA) markers, whereby nine primers out of fifteen were screened and selected. From a total of 122 bands obtained, 103 were polymorphic in at least one cultivar and 19 were monomorphic in all cultivars. The genetic similarity coefficient ranged from 0.35 to 0.65 and affected seed formation. The UPGMA cluster analysis showed cultivars grouping according to morphological traits, such as flower shape and nectary gland color. These results demonstrated the existence of genetic proximity among cultivars.