The poor quality and low productivity of cultivated liquorice (Glycyrrhiza uralensis) continues to put pressure on wild plant populations. As arbuscular mycorrhizal fungi are known to support plant growth and in some cases even to enhance the accumulation of valuable molecules in the plant, the effect of Glomus mosseae on the growth and active ingredient contents was evaluated in liquorice plants grown under nutrient deficiency. We created a nutrient-deficient environment by mixing paddy soil, washed river sand, and pumice at a ratio of 1:5:1. Our results showed that the inoculation of pot-grown liquorice plants with G. mosseae significantly increased the shoot and root biomass (by 25 and 17 folds, respectively) and the contents of glycyrrhizic acid, liquiritin, isoliquiritin, and isoliquiritigenin in the main root (by 1.6, 4.8, 6.5, and 4.4 folds, respectively). Both isoliquiritin and isoliquiritigenin were detectable in the lateral roots of the plants inoculated with G. mosseae, but not in plants without G. mosseae inoculation. G. mosseae inoculation improved the features of the root system and increased photosynthetic efficiency of liquorice. The uptake of P and K by liquorice increased when G. mosseae was inoculated, leading to the depletion of these macronutrients in the soil; G. mosseae also improved the availability of Mg, Cu, Zn, and Mn. Based on these results, we concluded that the inoculation of liquorice plants with G. mosseae is beneficial, particularly for those grown in nutrient-deficient soil, and such positive effect is related to the improvement of the root system and an increased photosynthetic efficiency.

Background: As one of the largest genera in Apiaceae, Bupleurum L. is well known for its high medicinal value. The genus has frequently attracted the attention of evolutionary biologist and taxonomist for its distinctive characteristics in the Apiaceae family. Although some chloroplast genomes data have been now available, the changes in the structure of chloroplast genomes and selective pressure in the genus have not been fully understood. In addition, few of the species are endemic to Southwest China, a distribution and diversity center of Chinese Bupleurum. Endemic species are key components of biodiversity and ecosystems, and investigation of the chloroplast genomes features of endemic species in Bupleurum will be helpful to develop a better understanding of evolutionary process and phylogeny of the genus. In this study, we analyzed the sequences of whole chloroplast genomes of 4 Southwest China endemic Bupleurum species in comparison with the published data of 17 Bupleurum species to determine the evolutionary characteristics of the genus and the phylogenetic relationships of Asian Bupleurum. Results: The complete chloroplast genome sequences of the 4 endemic Bupleurum species are 155,025 bp to 155,323 bp in length including a SSC and a LSC region separated by a pair of IRs. Comparative analysis revealed an identical chloroplast gene content across the 21 Bupleurum species, including a total of 114 unique genes (30 tRNA genes, 4 rRNA genes and 80 protein-coding genes). Chloroplast genomes of the 21 Bupleurum species showed no rearrangements and a high sequence identity (96.4–99.2%). They also shared a similar tendency of SDRs and SSRs, but differed in number (59–83). In spite of their high conservation, they contained some mutational hotspots, which can be potentially exploited as high-resolution DNA barcodes for species discrimination. Selective pressure analysis showed that four genes were under positive selection. Phylogenetic analysis revealed that the 21 Bupleurum formed two major clades, which are likely to correspond to their geographical distribution. Conclusions: The chloroplast genome data of the four endemic Bupleurum species provide important insights into the characteristics and evolution of chloroplast genomes of this genu, and the phylogeny of Bupleurum.