Deep learning-based elaiosome detection in milk thistle seed for efficient high-throughput phenotyping.

Milk thistle, Silybum marianum (L.), is a well-known medicinal plant used for the treatment of liver diseases due to its high content of silymarin. The seeds contain elaiosome, a fleshy structure attached to the seeds, which is believed to be a rich source of many metabolites including silymarin. Segmentation of elaiosomes using only image analysis is difficult, and this makes it impossible to quantify the elaiosome phenotypes. This study proposes a new approach for semi-automated detection and segmentation of elaiosomes in milk thistle seed using the Detectron2 deep learning algorithm. One hundred manually labeled images were used to train the initial elaiosome detection model. This model was used to predict elaiosome from new datasets, and the precise predictions were manually selected and used as new labeled images for retraining the model. Such semi-automatic image labeling, i.e., using the prediction results of the previous stage for retraining the model, allowed the production of sufficient labeled data for retraining. Finally, a total of 6,000 labeled images were used to train Detectron2 for elaiosome detection and attained a promising result. The results demonstrate the effectiveness of Detectron2 in detecting milk thistle seed elaiosomes with an accuracy of 99.9%. The proposed method automatically detects and segments elaiosome from the milk thistle seed. The predicted mask images of elaiosome were used to analyze its area as one of the seed phenotypic traits along with other seed morphological traits by image-based high-throughput phenotyping in ImageJ. Enabling high-throughput phenotyping of elaiosome and other seed morphological traits will be useful for breeding milk thistle cultivars with desirable traits.

Chromosome-level genome assembly of milk thistle (Silybum marianum (L.) Gaertn.).

Silybum marianum (L.) Gaertn., commonly known as milk thistle, is a medicinal plant belonging to the Asteraceae family. This plant has been recognized for its medicinal properties for over 2,000 years. However, the genome of this plant remains largely undiscovered, having no reference genome at a chromosomal level. Here, we assembled the chromosome-level genome of S. marianum, allowing for the annotation of 53,552 genes and the identification of transposable elements comprising 58% of the genome. The genome assembly from this study showed 99.1% completeness as determined by BUSCO assessment, while the previous assembly (ASM154182v1) showed 36.7%. Functional annotation of the predicted genes showed 50,329 genes (94% of total genes) with known protein functions in public databases. Comparative genome analysis among Asteraceae plants revealed a striking conservation of collinearity between S. marianum and C. cardunculus. The genomic information generated from this study will be a valuable resource for milk thistle breeding and for use by the larger research community.

Characteristics of Phenolic Compounds in Peucedanum japonicum According to Various Stem and Seed Colors.

Total polyphenol and total flavonoid assays were performed to characterize the relationships between the color of Peucedanum japonicum (PJ) seed coat and stem and the content of phytochemical compounds. The samples were divided into two groups based on their stem and seed coat color, with each group containing 23 samples. The stem color group was subdivided into green, light red, and red, whereas the seed coat color group was divided into light brown, brown, and dark brown. In the stem color group, the light red stems exhibited the highest content of phytochemical compounds, with levels over 10% higher than those of the stems of the other colors. Moreover, among the top ten samples with the highest total polyphenol content, eight samples were light red, and the light red group also exhibited the highest total flavonoid content among the examined color groups. In terms of the seed coat color, the plants grown from dark brown seeds exhibited the highest contents of both total polyphenols and total flavonoids. In conclusion, PJ plants with dark brown seeds and light red stems contained the highest levels of phytochemical compounds. Collectively, our findings provide a valuable basis for future seed selection of PJ for pharmaceutical purposes.

A Genomic Evaluation of Six Selected Inbred Lines of the Naturalized Plants of Milk Thistle (Silybum marianum L. Gaertn.) in Korea.

Milk thistle (Silybum marianum) belongs to the Asteraceae family and is a medicinal plant native to the Mediterranean Basin. Silymarin in achene is a widely used herbal product for chronic liver disease. There is growing interest in natural medicine using milk thistle in Korea, but the raw material completely relies on imports. Despite its economic importance, phenotypic evaluations of native resources of milk thistle in Korea have not been carried out. In addition, genomic research and molecular marker development are very limited in milk thistle. In this study, we evaluated 220 milk thistle resources consisting of 172 accessions collected from the domestic market, and 48 accessions isolated from 6 accessions distributed by the National Agrobiodiversity Center in Korea. Six plant characteristics (height, seed weight, number of flowers, seed weight per flower, spine length, and color at harvest) were measured, and six samples (M01-M06) were selected to represent the genetic diversity of the population for genomic research. To develop PCR-based and co-dominant insertion/deletion (InDel) markers, we performed genome-wide InDel detection by comparing the whole-genome resequencing data of the six selected accessions with the reference genome sequence (GCA_001541825). As a result, 177 InDel markers with high distinguishability and reproducibility were selected from the 30,845 InDel variants. Unknowingly imported alien plant resources could easily be genetically mixed, and jeopardized seed purity can cause continuous difficulties in the development of high value-added agricultural platforms utilizing natural products. The selected plant materials and 177 validated InDel markers developed via whole-genome resequencing analysis could be valuable resources for breeding, conservation, and ecological studies of natives to Korea, along with acceleration of Silybum marianum industrialization.