Phenotypic diversity analysis of Polygala tenuifolia Willd germplasm resources in China

Genet Resour Crop Evol https://doi.org/10.1007/s10722-023-01826-y RESEARCH ARTICLE Phenotypic diversity analysis of Polygala tenuifolia Willd germplasm resources in China Hongling Tian · Changjuan Wu · Lijun Zhang · Shuhong Guo · Yaoqin Wang · Shuaishuai Pei · Xianqiang Zuo · Qiubao Wang · Qiang Zhang Received: 7 March 2023 / Accepted: 4 December 2023 © The Author(s) 2024 Abstract Polygala tenuifolia Willd is a perennial herb in the family Polygalaceae and is used as an expectorant and stimulant in traditional Chinese medicine. There is a large demand for P. tenuifolia, while the good cultivars of P. tenuifolia are not enough. In this study, we collected 157 germplasm resources of P. tenuifolia from different regions in China, and 12 phenotypic traits of these samples were analyzed using correlation analysis, principal component analysis (PCA), and cluster analysis methods. The correlation analysis showed the associations between different traits, and the first four principal components contributed 62.63% of the total variation. They contained most of the information of five above-ground traits and eight root traits. Phylogenetic clustering divided materials divided into four taxa, with characteristics of high-yielding specific material, long-rooted specific material, multi-branching Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/s10722-023-01826-y. H. Tian (*) Center for Agricultural Genetic Resources Research, Shanxi Agricultural University, Jinzhong, China e-mail: C. Wu · L. Zhang · S. Guo · Y. Wang · S. Pei · X. Zuo · Q. Wang · Q. Zhang The Industrial Crop Institute, Shanxi Agricultural University/Shanxi Academy of Agriculture Sciences, Jinzhong, China specific material, and high plant height specific material, respectively. Our study provides the material and theoretical basis for the utilization of germplasm resources, parental selection, and varietal improvement of P. tenuifolia. Keywords Polygala tenuifolia · Phenotypic Diversity · Willd Germplasm · Parental selection · Varietal improvement Introduction Polygala tenuifolia Willd, also known as ‘Yuanzhi’ in Chinese, is a perennial herb in the family Polygalaceae and is widely distributed in China (Jin et al. 2014). In traditional Chinese medicine, P. tenuifolia is generally used as an expectorant and stimulant and is frequently applied in the treatment of forgetfulness, insomnia,P. tenuifolia and neurasthenia (Zhang et al. 2016). Previous studies on P. tenuifolia also showed that it has protective effects on the central nervous system and confirmed that the aerial parts of P. tenuifolia exhibit significant biological activities in ameliorating learning ability and memory impairments (Deng et al. 2020; Nguyen et al. 2020; Vinh et al. 2020; Zhao et al. 2020). The first record of P. tenuifolia appeared in the Compendium of Materia Medica as a treatment for amnesia in China (Cheng 2021). It is an important medicinal herb and is one of the 42 tertiary wild Vol.: (0123456789) 13 Genet Resour Crop Evol species under national priority protection in China. Shanxi province is the main production area of P. tenuifolia in China, accounting for 70% of the national production and including 90% of the national germplasm resources. The domestic history of the P. tenuifolia is short, with little domestication, and breeding is also lacking. With the accelerating pace of life, the number of people with insomnia and forgetfulness is gradually increasing, the demand for P. tenuifolia has been growing. However, the lack of good P. tenuifolia cultivars has severely restricted the development of its industry. Germplasm resources are the basis of plant breeding (Liu et al. 2020; Thudi et al. 2021). The investigation of agronomic and physiological traits of P. tenuifolia allows a comprehensive assessment of its various characteristics, quality and yield. At present, morphological markers are usually the simplest and most effective methods for the identification and evaluation of genetic resources (Chesnokov et al. 2020). The principal component analysis (PCA), correlation analysis and cluster analysis are the most widely used methods in morphological and genetic diversity research of genetic resources. They have been broadly used in soybean (Wang and Komatsu 2018), rice (Bhargavi et al. 2021), millet (Sharma et al. 2018), tomato (Zhou et al. 2015), among other plant cultigens, while few investigations have their focus on P. tenuifolia. Hence, we collected 157 germplasm resources of P. tenuifolia from different regions in China and analyzed their genetic diversity, estimated trait correlation, and did principal components and clustering based on 12 phenotypic traits. Our study provides the material and theoretical bases for the utilization of germplasm resources, parental selection and varietal improvement of P. tenuifolia in China. Materials and methods Experimental materials A total of 157 germplasm resources of P. tenuifolia from Shanxi, Hebei, Inner Mongolia, Henan, and Shaanxi were collected in this study (Table 1). Samples were provided by the Institute of Cash Crops, Shanxi Agricultural University, and purified over three generations (Fig. 1). Vol:. (1234567890) 13 Overview of experimental base The experiment was conducted at the experimental base of the Cash Crop Research Institute, Shanxi Agricultural University in Fenyang, China. Fenyang is located in Loess Plateau, with an average altitude of1414 m. The climate in Fenyang is temperate monsoon, with an annual average temperature of 9.7 °C, an average ground temperature of 12.6 °C, and annual average precipitation of 467.2 mm. The soil type of the experimental base belongs to a brown soil. Experimental design Polygala tenuifolia seeds were planted on 25th June 2016. The planting density was 3.5 kg/667m2, with an area of 3 m × 2 m, and three replications were set for each germplasm resource. The manual seed drill was a depth of 1.5 cm and a row spacing of 25 cm. Chicken manure 350 kg/667 m2 was added before planting, and no more fertilizer was used during the reproductive period. Weeding was performed for 4–5 times a year, and treatments for all regions were consistent. Seeds were harvested from 1–7 October 2019. Measurement indicators Plant traits, including the plant height, leaf shape, leaf color, and flower color, were recorded during the flowering stage in 2019. After harvesting the seeds in late July, three plants were randomly selected from each area to measure plant height. Root length, root thickness, and fresh weight were measured in October. When the moisture of roots dried to 20–24%, the bast was extracted manually, and the bast weight and wood core thickness were measured. After baking to a constant weight at 105 °C, the dry weight of the bast and wood core were measured. Qualitative traits were assigned different values (Fig. 2). For the leaf shape, thin and long was 1 (width ranging fr (...truncated)