Clone Variation and Taxon Discrimination of Distylium Using ISSR Markers

Distylium is a popular ornamental plant in Asian countries and recently gains its popularity in eastern US with breeding effect of University of Georgia wood plant research program. Three new cultivars were recently marketed in the nursery industries and garden centers and confusion of new and existing cultivars caused the problem. To better understand the genetic relationships and identify the named cultivars, thirty-eight accessions of Distylium and one Sycopsis sinensis were collected and analyzed using ISSR markers. A total of 234 markers were generated from 15 primers and 195 markers (83.3%) were polymorphic markers. Both D. racemosum and D. myricoides were in the trade and majority of Distylium were derived from their hybrid. Seedling population from the hybrid had been evaluated for the last eight years and three cultivars were selected and released to the industry based on their performance and ISSR markers fully supported them as independent cultivars. ‘Emerald Height’ inherited much more genes from D. racemosum, while ‘Vintage Jade’ and ‘Blue Cascade’ were genetically closer to D. myricoides. Based on both morphological and DNA data, two clones should be further evaluated for their potential as two new cultivars. Three anonymous plants were identified as ‘Vintage Jade’. One seedling plant with a very slow growing rate and whitish to pinkish new foliage was similar to ‘Spring Frost’ and their ISSR markers were almost identical. The plant recently had new sprouts and restored its normal branch growth rate. Further studies should address this phenomenon on its gene expression.