The pan-plastome of Hemerocallis citrina reveals new insights into the genetic diversity and cultivation history of an economically important food plant.

BACKGROUND: Hemerocallis citrina Baroni (Huang hua cai in Chinese) is a perennial herbaceous plant grown for its flower buds that are eaten fresh or dried and is known as the vegetarian three treasures. The nuclear genome of H. citrina has been reported, but the intraspecific variation of the plastome (plastid genome) has not yet been studied. Therefore, the panplastome of this species collected from diverse locations is reported here for the first time. RESULTS: In this study, 65 H. citrina samples were resequenced, de novo assembled, and aligned with the published plastome of H. citrina to resolve the H. citrina panplastome. The sizes of the 65 newly assembled complete plastomes of H. citrina ranged from 156,048 bp to 156,263 bp, and the total GC content ranged from 37.31 to 37.34%. The structure of the complete plastomes showed a typical tetrameric structure, including a large single copy (LSC), a small single copy (SSC), and a pair of inverted repeat regions (IRA and IRB). Many nucleotide variants were identified between plastomes, among which the variants in the intergenic spacer region were the most abundant, with the highest number of variants concentrated in the LSC region. Based on the phylogenetic tree constructed using the ML method, population structure analysis, and principal component analysis (PCA), the panplastome data were subdivided into five genetic clusters. The C5 genetic cluster was mostly represented by samples from Qidong, Hunan Province, while samples from Shanxi and Shaanxi Provinces were classified into the C4 genetic cluster. The greatest genetic diversity was found in the C1 genetic cluster, and the greatest genetic distance between any two clusters was found between the C4 and C5 clusters. CONCLUSION: The resolution of the panplastome and the analysis of the population structure of H. citrina plastomes provide important data for future breeding projects and germplasm preservation.

[Effects of inter-row economic crop planting on soil moisture in a rain-fed jujube orchard in loess hilly region, China].

Soil moisture variation in dryland sloping jujube. orchard was investigated after introducing two economic crops, i.e., feed Brassica napus (JR) and Hemerocallis fulva (JH) planted between jujube rows. Jujube tree without inter-row crop was set as control (CK). The results showed that mean soil moisture for JR and JH in the 0-180 cm soil layer increased by 6.2% and 10.1% compared with CK, respectively. Soil moisture changed mainly in the 0-60 cm soil layer in growth stage of Jujube trees. Soil moisture in JR and JH treatments significantly increased in the 0-60 cm soil layer, which could meet the demand in water resource of jujube plantation. The water consumption of jujube trees also mainly concentrated in the 0-60 cm soil layer. There was a significant decay exponential relationship between the soil moisture in the 0-20 cm layer and the drought duration after rainfall. During the 18-day dry period after rain, the soil moisture contents of JR and JH were apparently higher than that of CK. In conclusion, the jujube-crop intercropping system improved the soil moisture condition. It was an effective measure to overcome the seasonal drought in jujube orchards on the loess hilly region.