Rapid Propagation of Three Herbal Species in a Newly Developed Temporary Immersion System

[ Objeelive] This study aimed to develop a rapid propagation method in a novel temporary immersion bioreactor system （TIS） for herbal plantlets com- pared with solid culture method. [ Method ] Three herbal species, including Dendrobium candidum Wall. Ex IJndl （D. candidum）, Anoectochilus roxburghii （Wall.）Lindl. （A. roxburghii） and Lilium davidii var. unicolor （L. davidii）, were used and tested by TIS against solid culture method. [Result] When the two culture methods were compared, the multiplication rate of D. candidum in TIS was found to be 1 ： 24.71, which was 6.55 times to those of solid culture. The multiplication rate of A. roxburghii was higher than those of the solid culture, but the plantlets was poorer than those of solid culture at the last phase in bioreactor culture, under the culture condition tested. The multiplication rate in TIS ofL. davidii was 1：17.23 whilst the rate was only 1：4.45 on solid culture, resulting larger bulbs than those in the solid culture. [ Conclusion] The TIS designed in our study could provide a potential mean for industrial production of plandets. However, the parameters vary greatly among different species, and it is to be optimized according to plant species.

The chromosome-level reference genome assembly for Dendrobium officinale and its utility of functional genomics research and molecular breeding study

Dendrobium officinale,an important medicinal plant of the genus Dendrobium in Orchidaceae family,has been used as traditional Chinese medicine(TCM)for nearly thousands of years.Here,we report the first chromosome-level reference genome of D.officinale,based on Pac Bio long-reads,Illumina short-reads and HiC data.The high-quality assembled genome is 1.23 Gb long,with contig N50 of 1.44 Mb.A total of 93.53%genome sequences were assembled into 19 pseudochromosomes with a super scaffold N50 of 63.07 Mb.Through comparative genomic analysis,we explored the expanded gene families of D.officinale,and also their impact on environmental adaptation and biosynthesis of secondary metabolites.We further performed detailed transcriptional analysis of D.officinale,and identified the candidate genes involved in the biosynthesis of three main active ingredients,including polysaccharides,alkaloids and flavonoids.In addition,the MODIFYING WALL LIGNIN-1(MWL1)gene,which inferred from Genome-Wide Association Studies(GWAS)based on the resequencing date from D.officinale and five related species and their morphologic features,may contribute to the plant production(yield of stems)of D.officinale.Therefore,the high-quality reference genome reported in this study could benefits functional genomics research and molecular breeding of D.officinale.