Evaluation of genetic diversity and drought tolerance among thirtythree dichondra ( Dichondra repens) genotypes

Dichondra (Dichondra repens) is an important ground cover plant and is also used as a herbal medicine in China. Objectives of this study were to evaluate phenotypic and genetic diversities among 33 genotypes by using 18 simple sequence repeat (SSR) markers and to further identify the drought tolerance of these germplasms based on five physiological parameters. Results showed that natural variations in phenotypes including plant height, leaf area, leaf thickness, and petiole length were observed among 33 genotypes under well-watered conditions. All 18 SSR primer pairs were found to be polymorphic and significant genetic variation was found in these genotypes. In addition, there were obvious differences in leaf relative water content (RWC), electrolyte leakage (EL), chlorophyll (Chl) content, photochemical efficiency (Fv/Fm), and performance index on absorption basis (PIABS) among 33 genotypes in response to a prolonged period of drought stress (46 d). Drought tolerance of 33 genotypes was then ranked by using subordinate function value analysis (SFVA) and the most drought-tolerant or-sensitive genotypes were identified as Dr5 or Dr29, respectively. Principal component analysis (PCA) further classified 33 genotypes into group I (drought-tolerant), group II (drought- sensitive), and group III (medium types). Current findings showed that 18 selected SSR primers could be potentially used to analyze genetic diversity and varietal identification in dichondra species. Drought-tolerant wild dichondra resources provide a rich genetic base for breeding of new cultivars.