Identification, Nomenclature, Genome Sizes, and Ploidy Levels of Liriope and Ophiopogon Taxa

Abstract

Liriope Lour. and Ophiopogon Ker Gawl., collectively known as liriopogons, represent important evergreen groundcovers grown throughout the world for their ornamental features and medicinal qualities. As a result of the diversity of desirable traits and evidence of wide hybridization, there is considerable potential for breeding and improvement of liriopogons. However, confusion over taxonomy and proper identification and lack of information on ploidy levels and cytogenetics of individual clones and cultivars have constrained breeding efforts. Objectives of this study were to validate the identification and nomenclature and determine genome sizes and ploidy levels for an extensive reference collection of species and cultivars of liriopogons. Identification was accomplished using existing keys, nomenclature was corrected, and numerous accessions were reassigned based on morphology. Genome sizes were determined by flow cytometry. Ploidy levels for each species were confirmed by traditional cytology. Results confirmed a basic chromosome number of x = 18 for liriopogons with aneuploidy, polyploidy, and cytochimeras found in some cases. The Liriope examined included diploids (L. graminifolia, L. longipedicellata, L. minor, and some of the L. platyphylla), tetraploids (L. muscari and the remaining L. platyphylla), and hexaploids (L. exiliflora and L. spicata). The Ophiopogon studied included diploids (O. intermedius, O. jaburan, O. planiscapus, and O. umbraticola) and a tetraploid/hypotetraploid species (O. japonicus). Monoploid (1Cx) genome sizes varied by genus and species with 1Cx values ranging from 4.27 pg in L. exiliflora to 8.15 pg in O. jaburan. These results clarify nomenclature and taxonomy and provide specific information on genome sizes and ploidy levels of cultivated liriopogons. This information and associated reference collection will aid future taxonomic revisions and enhance efforts to develop new cultivars of liriopogons.