Abstract: In this study, the morphological characters of Glycyrrhiza specimens from nine regions of Xinjiang and Gansu Provinces where natural hybrids occur were classified by numerical taxonomic study to identify the parent species and hybridization type in different geographic areas where hybrids occur. Following field investigation and specimen collection, data on morphological traits were measured and recorded. After the numerical data collection, principal component analysis was carried out to identify the most important traits for classification purposes, and 29 traits were evaluated by R-cluster. The parental species and their hybrids in the different areas of hybrid occurrence were classified by operational taxonomic unit scatter and Q clustering. Principal component analysis result shows that Among the first three principal components, degree of legume inflation, upper limit of foliolate , lower limit of foliolate, presence of legume glandular hair, compound leaf length, no. of seeds per pod, compound rachis length, leaflet margin morphology, infructescence length, infructescence length:width ratio, leaflet length:leaflet width ratio, and leaflet width all are above 0.7, meaning that these twelve characters play an important role in taxonomic study on Glycyrrhiza species. The 29 traits could be classified into 2 categories: the first, mainly comprising leaflet and inflorescence traits, and the second, mainly comprising legume and compound leaf traits. The correlation coefficient between scores of the two categories of traits was 1, indicating that these trait groupings occur in conjunction and have high relevance as taxonomic indicators. Glycyrrhiza accessions (n=344) were classified into groups as follows: A, Glycyrrhiza inflata; B, The hybrid of G. inflata and Glycyrrhiza uralensis; C, G. uralensis; D, Glycyrrhiza glabra; E, the hybrid of G. inflata and G. glabra. A variation of G. inflata includes plants from Alaer and Korla in Xinjiang, and Guazhou and Minqin in Gansu Provinces, which are gathered into one branch, as these populations of G. inflata are less genetically differentiated. Plants of group C from Minqin, Zhangye in Gansu and from Korla, Yanqi, and Bohu in Xinjiang, were divided into two branches, as intravarietal genetic differentiation had occurred. Group D representing G. glabra. includes G. glabra and Glycyrrhiza glabra var. glandulosa from Alaer, Xinjiang, as G. glabra var. glandulosa is a variety of G. glabra. Nine geographic areas where natural interspecific hybrids occur could be divided into three categories: Alar and Turpan in Xinjiang Province are interspecific hybridization areas of G. inflata and G. glabra; Yanqi and Korla in Xinjiang and Guazhou in Gansu are interspecific hybridization areas of G. inflata and G. uralensis; Shanshan in Xinjiang is a mixed hybridization area of G. inflata, G. glabra and G. uralensis. All hybrid specimens of Glycyrrhiza examined, have distinctive and different inter-species combinations of morphological features. This study laid the foundation of morphological taxonomy for the utilization of medicinal Glycyrrhiza germplasm resources and the formation ofhybrid species.

Key words: Glycyrrhiza, hybrid zones, morphological features, numerical taxonomy