| Establishing good-breeding for licorice(Glycyrrhiza uralensis Fisch.) is an important way to improve and control yield and quality. Using or creating variation, and fixing down the favorable genes through the artificial selection, may realize the breeding of the new varieties. Among them, the selection and evaluation are the main parts of the breeding. Selection is not only an independent breeding method itself, but also an indispensable segment of all other sorts of breeding approaches. Meanwhile, the multi-purpose of licorice determines its diversity of breeding objectives. Therefore, it is very necessary to make appropriate evaluation method according to multi-objective breeding of licorice. Consequently, this paper aimed at analysing three aspects, including selection index of elite germplasm, evaluation index of elite germplasm of licorice according to multi-objective breeding and pollination biology characteristics, which is to lay the foundation for the good-breeding of licorice seeds. For that purpose, the main quantitative traits of various cultivated licorice genotypes (provenance and variation types) were investigated at four locations in 2010 and 2011. The main results were as follows:1. Genetic variation and relationship between the quantitative traits of cultivated licorice was analyzed, and selection index system for target traits was established It can provide the germplasm for the selection of elite types, for abundant genetic variation existed in cultivated licorice population. Among them, the coefficients of variation (CV) of taproot length (TRL), lateral root number (LRN) and root fresh weight (RFW) were above 20%, the CVs of liquiritin (LQ), Isoliquiritin (ILQ) and liquiritigenin (LQG) were above 30%. Persons correlation between traits showed that most of phenotypic traits had significant(p< 0.05) positive correlation with RFW, and among bioactive components traits had highly significant(p<0.01) positive correlation, and existed close relationship with TRL. Results of the path coefficient analyses showed that D20, root diameter (RD) and root length (RL) and TRL had the greatest positive direct effect on RFW and bioactive components traits respectively. For two-year licorice, its plant height (PH), TRL, LQ and ILQ not only had a higher genetic variation coefficient (GCV) and heritability, but also bigger relative genetic advance (RGA). However, the select potential of phenotypic traits was poor, compared with the bioactive component traits for the three-year licorice.It can realize effective indirectly selection for objective traits of licorice by certain phenotypic trait and their combination. Among them, the highest relative value of correlative genetic advance (CGA) for RFW in 2a and 3a were predicated indirectly by combined PH with RL and D20 with LRN, respectively. And its relative value increased by 40%than that of RFW. For principal bioactive component traits (PC1), the highest relative value of combination with tillering number (TL), TRL and RL by selection index was increased by 148%; nevertheless, selection index of single phenotypic trait was not effective.2. Germplasm (Genotype) and environment had different effects on the main quantitative traits of licorice, which also had close relations with climate factorsThe differences among various genotypes and different environment for most evaluated traits were significantly (p<0.05) through Duncan's multiple range tests. The quantitative traits of licorice were influenced significant (p<0.05) by genotype (G) and environment (E), and stalk diameter (SD), TN and glycyrrhizin (GL) were influenced significantly by genotype and environment interreaction (GEI) in all both two years. Meanwhile, genotypes have lager effect on TN, TRL, taperingness (TR) than environment, and environment have larger effect on RD, D20 and LRN than genotype, respectively. And genotype and environment have similar effect on the other traits. In addition, LQ and ILQ were influenced more by genotype than by environment, in contrast LOQ and isoliquiritigenin (ILQG) were influenced more by environment than by gennotype, and GL were influenced by both genotype and environment. Biplot of the principal component analysis of RFW and bioactive component traits of licorice showed that, germplasm from G2 (WNT-01) and G3 (JX-01) were elite, and the environment in E4 (Jiuquan) was favorable for the accumulation of bioactive component. Moreover, E2 (Chifeng) and E3 (Hangjinqi) were favorable for the RFW and accumulation of bioactive component in 2010 and 2011, respectively.Stepwise regression analysis (SRA) of 15 quantitative traits and nine geographical climate factors showed that sunshine duration had the greatest effect on quantitative traits, followed by rainfall, the average monthly temperature and mean temperature in July. Among them, the upground traits PH and SD were influenced most strongly by sunshine duration, and the root part traits RL, RD, and LRN were influenced by sunshine duration, temperature and rainfall simultaneously. And for bioactive component traits, GL was mainly influenced by sunshine duration, and LQ, LQG and ILQG were mainly influenced by sunshine duration and rainfall.3. The growth and photosynthetic performance for different variation types of cultivated licorice existed certain variation, and the relationships between those parameters were closeThere existed certain difference in growth characteristics for different variation types of cultivated licorice, and these differences were more significant especially among different locations of origin. For PH, the time of entering bloom prime stage, bloom luxuriant stage and bloom final stage was 28 d,47 d and 65 d after seedling, respectively. However, for SD, the time of entering bloom luxuriant stage and bloom final stage was 16 d and 50 d, respectively. Among these types, for SD and PH, the period between the earliest time and the latest time of entering the bloom luxuriant stage was 10d. The difference of PH in growth period mainly came from the difference among the origin location; Photosynthetic performance parameters existed great variation and there existed close relationship in different variation types of cultivated licorice. Person's correlation analysis among parameters showed that chlorophyll content (Chl) and specific leaf weight (SLW) can reflect photosynthetic performance of licorice to a certain extent. However, PH and SD only had significant(p<0.05) positive correlation with net photosynthetic rate (Pn) only in the early growth period.4. Different variation type of cultivated licorice was evaluated comprehensively, and corresponding evaluation index system was established according to different breeding objectivesThe information of target traits in licorice could be extracted preferably by means of principal components analysis (PCA), and then multi-characters of different objectives breeding of licorice could be converted into two to three independent comprehensive traits (PCs), which could explain different breeding objectives, and germplasm with various characteristics could be selected. Among them, V3, V1 and V6 performed better as "hiGL type", and V8, V7 and V3 performed better as both "yinpian type" and "extractum type". As "yinpian type", the comprehensive PCs score of V1 and V2 ranged the fourth and fifth as "yinpian type", respectively. The comprehensive PCs score of V9 and V10 ranged the fourth and fifth as "extractum type", respectively. Evaluation indexes system of licorice germplasm for different breeding objectives were constructed preliminarily, according to different traits extracted by PCs of different traits, including root strip (RL and TR), root yield (RFW) and bioactive component traits (LQ, LQG, GL, ILQ, ILQG, total flavonoids (TF) and total saponins (TS)). Among them, "extractum type" mainly considered comprehensive bioactive components, and also took the root yield into account; "hiGL type" mainly considered the total amount of GL (absolute amount); "yinpian type" mainly considered the root strip, and also gives consideration to the comprehensive bioactive components.5. Pollination biology characteristics was explored, and breeding technology of licorice was discussedThe breeding system of licorice was presumed to be selfing and outcrossing compatible, but outcrossing took the leading role, according to pollen-ovule ratio (P/O), outcrossing index (OCI) and artificial pollination. Thereby, we may realize breeding by using combination of many ways, according to the breeding characteristics of licorice. For mass selection breeding offspring, quarantine measures should be taken to avoid the pollen pollution. In addition, selfing could be taken by artificial pollination for selected materials of high generation to foster inbred lines. When the length of bud is 10-15 cm approximately, it was time for artificial pollination. Artificial pollination origin selfing and outcrossing were carried out in different periods, based on pollen vitality and stigma receptivity.In this paper, there are three characteristics and innovations:(1) In this paper, indirect selection index system between RFW and bioactive component traits was established by means of certain phenotypic traits and their combination.(2) The germplasm evaluation index system of "hiGL type","yinpian type"and" extractum type"was extablished from the point of multi-objective breeding.(3) This paper proved that selfing and outcrossing exist simultaneously in licorice natural population, and outcrossing dominates in it.
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