2018 ASHS Annual Conference

Hibiscus syriacus is a woody ornamental shrub in the Malvaceae family and is commonly found throughout much of the U.S. due to its broad adaptability and variability of ornamental characteristics. Although H. syriacus is a very popular ornamental plant, little is known about its pattern of inheritance of ornamental traits such as flower color and petaloid stamens. Hibiscus syriacus has been identified as tetraploid based on its chromosome number (2n = 4x = 80); however, relatively little additional cytology or genetics information is available. In this study, a hexaploid (6x = 120) cultivar ‘Pink Giant’ was used to cross with tetraploid (4x) cultivars, and to create putative pentaploids (5x). Fluorescent in situ hybridization (FISH) was used to determine 45S and 5S rDNA loci numbers of 4x, 6x, and putative pentaploids. For the 4x and 6x cultivars, 4 and 6 signals of 45S rDNA were observed; however, only 2 and 3 signals of 5S rDNA were detected. Furthermore, the signal numbers of these putative pentaploids varied among siblings. The segregation patterns of rDNA signals in H. syriacus appeared to be random among the putative pentaploids and signals for each rDNA site ranged between the values of the two parents. Both the 5S rDNA loci numbers and the random segregation loci of putative pentaploids indicated that the H. syriacus genome presented with disomic segregation. In addition, the variation in rDNA loci number indicated that the putative pentaploids were actually aneuploids. This information is valuable for targeted H. syriacus breeding in that it will allow prediction of segregation patterns of ornamental traits.