Primula, well known for its heterostyly, is the largest genus in the family Primulaceae with more than 500 species. The considerable species number has introduced a huge challenge for taxonomy. The phylogenetic relationships among Primula still maintain unresolved due to frequent hybridization and introgression between closely related species. In this study, we sequenced and assembled the complete chloroplast genomes of Primula wilsonii Dunn, which is a PSESP (plant species with extremely small populations), using Illumina sequencing and compared its genomic sequences with those of four related Primula species. The chloroplast genomes of Primula species were similar in the basic structure, gene order, and GC content. The detected 38 SSRs (simple sequence repeats) loci and 17 hypervariable regions had many similarities in P. wilsonii, P. anisodora, P. miyabeana, and P. poissonii, but showed a significant difference compared with those in P. secundiflora. Slight variations were observed among Primula chloroplast genomes, in consideration of the relatively stable patterns of IR (inverted repeats) contraction and expansion. Phylogenetic analysis based on chloroplast genomes and protein‐coding genes confirmed three major clades in Chinese Primula, but the infrageneric sections were not in accordance with morphological traits. The P. poissonii complex was confirmed here and P. anisodora was the most closely related species to P. wilsonii. Overall, the chloroplast genome sequences provided useful genetic and evolutionary information for phylogeny and population genetics on Chinese Primula species.

Rhamnus globosa Bunge is a small shrub that can be used in the treatment of swollen poison, because of the antimicrobial activity. Here, we constructed the complete chloroplast genome of the R. globosa using Illumina sequencing technology. The circular cp genome was 160,642 bp in size, and comprises a large single-copy (LSC) region of 88,889 bp, a small single-copy (SSC) region of 18,897 bp, and a pair of inverted repeats (IR) of 26,428 bp. The GC content was 37.14% overall, with 35.01%, 31.42%, and 42.75% for the LSC, SSC, and IR regions, respectively. The plastome comprised 129 unique genes including 81 protein-coding genes, 30 tRNAs, and 4 rRNAs. The ML phylogenetic analysis based on 44 chloroplast genomes in Rosales showed a strong sister relationship with Berchemia species.

Chinese lacquer tree (Toxicodendron vernicifluum) is an important commercial arbor species known for the production of raw lacquer. Here, we investigated the intraspecific chloroplast (cp) genome variability of T. vernicifluum using two available and five newly sequenced cp genomes. We found that each of the seven cp genomes encoded 87 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Phylogenetic analyses based on protein-coding genes indicated that the four individuals from western China formed a monophyletic group sister to the cluster containing the three individuals from eastern China. The cp genomes from western China exhibited a larger genome length and longer large single-copy (LSC), small single-copy (SSC), and inverted repeat (IR) regions than those from eastern China. A total of 466 single nucleotide polymorphisms (SNPs) and 141 insertion-deletion mutations were detected among the seven cp genomes, most of which were found between the eastern and western lineages. The two groups exhibited a similar number of microsatellites, long repeats, and tandem repeats. Notably, complementary repeat sequences were only found in the IRs of the individuals from eastern China, while reverse repeat sequences were only detected in the LSC of the individuals from western China. Eight intraspecific mutational hotspots were also identified, including six intergenic regions (trnF-ndhJ, rpl32-trnL, ccsA-ndhD, trnH-psbA, psbC-trnS, and trnL-trnF) and two gene regions (rpl32 and rps19). The genomic resources presented in this study will be useful for further studies on evolutionary patterns and resource protection of T. vernicifluum.

This experiment aimed to explore the effects of bioactive substances such as alginate (seaweed extract) (SW), potassium humate (humic acid) (HA), diethyl aminoethyl hexanoate (DA-6) and brassinolide (BR) on the germination and salt resistance of melon seeds, and to optimise their appropriate concentrations and ratios. The simulated salt stress environment was irrigated with a 100 mmol · L ⁻¹ NaCl solution. Treatment groups with different concentrations of SW, HA, DA-6 and BR were set up, and a completely blank control group (CK) was set up. The optimal concentrations were SW 1000 mg · L ⁻¹ , DA-6 10 mg · L ⁻¹ , HA 50 mg · L ⁻¹ and BR 0.2 mg · L ⁻¹ . Among them, SW treatment can maximise the germination index, with an average of 26.7. DA-6 had the best effect on promoting the growth of the radicle and the most significant promotive effect, with embryonic root length and hypocotyl length reaching 95.0 mm and 11.8 mm, respectively. HA can also effectively improve seed germination rate and vigour index, with mean values of 91.5% and 217.4%, respectively. BR can effectively improve the vigour index of seeds, reaching 241.6. All tested bioactive substances significantly improved the salt resistance of melon seeds, and among them, alginate showed the most significant effect compared with the control group. Not only did the main root length increase, but the number of lateral roots also significantly increased. When the concentration of SW reached 1000 mg · L ⁻¹ , vigour index and radicle length showed significant differences compared with the control, thereby enhancing its salt resistance.

Sorbus amabilis Cheng ex Yü, a small excellent ornamental tree species, is only distributed in Eastern China. In this study, we assembled and annotated the complete chloroplast (cp) genome of the species using the next-generation sequencing for the first time. The cp genome was 160,006 bp in size, consisting of two copies of invert repeat (IR) regions of 26,405 bp, one large single-copy (LSC) region of 87,870bp, and one small single-copy (SSC) region of 19,326 bp. The overall GC content of the genome was 36.55%. The genome was predicted to contain 128 genes, including 88 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Phylogenetic analysis of 25 chloroplast genomes in Rosaceae indicated that S. amabilis is most closely related to S. commixta. These findings may provide useful information to the phylogeny of the genus Sorbus.