Lettuce (Lactuca sativa L.) is one of the most important leafy vegetables in the world due to its health related benefits. Bitter sesquiterpene lactones (BSLs) are crucial secondary metabolites of lettuce which are useful in many physiological activities, and also has been used to relieve pain. This study was conducted to appraise the variability of phenotypic characteristics and the total content of BSLs in fifty lettuce germplasm. The germplasm collections exhibited wide variation in both qualitative and quantitative characters. The average plant weight was 333.3 g with a range from 60.0 to 700.0 g and the lactucin content was varied from 3.4 (IT265031) to 448.6 (IT300287) μg/g DW with an average concentration of 94.0 μg/g DW. Whereas lactucopicrin ranged from 6.8 (IT217859) to 2,714.9 (Superseonpung) μg/g DW with an average concentration of 805.8 μg/g DW. Total BSLs content was ranged from 19.6 (IT217859) to 2,821.9 (Superseonpung) μg/g DW with the average concentration of 899.8 μg/g DW. Significant (p≤0.05) differences in lactucin, lactucopicrin and total BSLs content were found among the germplasm collections. Leafy type lettuce germplasm collections originated from South Korea revealed the highest average total BSLs content (2,821.9 μg/g DW). Principal component analyses of lactucin and lactucopicrin generated based on leaf color and plant growth type yielded two principal components, PC1 and PC2, which accounted for 60.8 and 39.2 % of the total variance, respectively. Our study provides fundamental insights on phenotypic characteristics and the total content of lactucin and lactucopicrin of lettuce germplasm which may further help researchers and breeders to produce improved lettuce varieties.

Sesquiterpene lactones (SLs) are a group of over 500 compounds, characteristic of the Asteraceae. They are interesting from the chemical and chemotaxonomic point of view, and show antitumour, anti-leukaemic, anti-cardiovascular disease, reduction of inflammation, and anti-microbial activities. The SLs, free lactucin and lactucopicrin, content in 572 accessions of lettuce (Lactuca sp.) germplasm introduced from 30 countries were quantified using high-performance liquid chromatography. Variation range of free lactucin content exhibited trace ~ 235.3 μg from 1g of dried leaves and average was 41.2 ± 1.2 μg (Avr ± SE), variation range 55.0 ~ 3,041.0 μg and average 526.9 ± 17.5 μg in free lactucopicrin content, and variation range 66.3 ~ 3,188.5 μg and average 568.1 ± 18.1 μg in total free SLs content. Lactucopicrin occupied 92.7% of the total SLs content. Among the varietal types, crisphead type exhibited the highest average total free SLs content, next is leaf lettuce, and butterhead type lettuce exhibited the lowest that of content. German accessions exhibited the lowest average total free SLs content, Korean accessions exhibited the highest, and European origin accessions exhibited lower that of content. Red leaf color accessions having higher SLs content than that of green color. Seven accessions having more than 2,000 μg·g-1 dwt of total free SLs content and five accessions having less than 100 μg·g- 1dwt that of content. These accessions can be used as low SLs content cultivar breeding or high SLs content cultivar breeding sources as well as research materials for medical treatment such as, anti-tumour, anti-leukaemic, and antimicrobial activities, etc.

Inflorescence, stem, and leaf samples of lettuce grown in a greenhouse in spring and autumn seasons were assayed for sesquiterpene lactones (SLs) content by high performance liquid chromatography. The concentrations of SLs were significantly higher in the inflorescences followed by upper leaf and stem compared to the other plant parts in most of the samples. SLs content (sum of lactucin and lactucopicrin) in various tissues of lettuce cultivated in spring season varied from 5.7 to 22.5 fold ranging from 27.4 ㎍/g dry weight (DW) in the upper stem (cultivar “PI 176588”) as the lowest to as high as 2,292.0 ㎍/g DW in the inflorescence (cultivar “709849-1”). During autumn cultivation, the concentration of SLs varied from 2.0 to 14.4 fold ranging from as low of 32.4 ㎍/g DW in the lower stem (cultivar “PI176588”) to as high of 838.0 ㎍/g DW in the upper leaf (cultivar “Dambaesangchu”). Higher lactucin (1.2 to 5.6 fold) and lactucopicrin (1.1 to 3.9 fold) concentration was observed during spring compared to autumn cultivation in most of the samples. SLs content in various organs of lettuce increases from the basal plant part going upwards. As lactucin and lactucopicrin are the major SLs which affects the sensory property of lettuce, their quantitative variation in the lettuce cultivars is useful for breeding new varieties with better consumer acceptance.

Background : Carotenoids are pigments that are found in plants, fruits, bacteria, and fungi. β -carotene and canthaxanthin are orange pigments among thousands of carotenoids that possess potent antioxidant activity. The objective of this study was to determine β-carotene and cantaxanthin in 55 Kimchi cabbage germplasm using liquid chromatography mass spectrometry (LC-MS) method. Method and Results : 55 Kimchi cabbage accessions were sown in plug trays in the end of August, 2016. All the tissue samples were freeze-dried for 1 week and ground into fine powder and stored at -20℃ until analysis. Crude carotenoids from freeze-dried materials (100 mg) were extracted using 1 ㎖ of 100% (v/v) hexane in 10 minutes by using sonication bath followed by centrifugation. The average β-carotene contents was 1.43 ㎎·㎏-1 and ranged from 0.76 (IT 120045) to 2.25 ㎎·㎏-1 (IT 100378). The average canthaxanthin content in the entire domain of sample was 0.59 ㎎·㎏-1 with a range between 0.36 (IT 32746) and 1.08 ㎎․㎏-1 (IT 100386). Canthaxanthin content was significantly positively correlated with β-carotene (r = 0.65**) and leaf length (r = 0.63**). However, canthaxanthin was negatively correlated with cotyledon color (r = -0.41**). Principal component analysis results of the first two components (PC1 and PC2) explained 44.53% of the point variability. Conclusion : The resources with the highest β-carotene and canthaxanthin content are IT 100378, 100386, 100391, and 110828. This study could be useful to select a potential sources of health beneficial carotenoids (β-carotene and canthaxanthin) in Kimchi cabbage germplasm in nutraceutical formulations and for further applications as a breeding material and other research activities.

Lettuce is an important annual leafy vegetable and bitterness is its potent flavor character. Lettuce germplasm differ their phenotypic characters and sesquiterpene lactones (SLs) contents which are important for consumer’s acceptance. This study was carried out to evaluate the phenotypic characters and SLs contents in one hundred lettuce germplasm in Jeonju, Korea. Twenty-three agro-morphological (16 qualitative and 7 quantitative) traits and two SLs (lactucin and lactucopicrin) contents were studied in these germplasm. Germplasm exhibited the variation in qualitative and quantitative characters. Average plant weight was 423.9 g with a range from 116.0 to 905.0 g. Lactucin content was varied from 19.7 (IT 294226) to 194.4 ㎍/g (IT 294298) with an average concentration of 84.7 ㎍/g. Lactucopicrin ranged from 82.5 (IT 300134) to 2228.6 ㎍/g (IT 294210) with an average concentration of 586.3 ㎍/g. Total SLs content was ranged from 120.1 (IT 300134) to 2286.6 (IT 294210) ㎍/g with the average concentration of 671.0 ㎍/g. Significant (p≤0.05) differences were found between crisp head and butter head germplasm for lactucin, lactucopicrin and total SLs content. Crisp head germplasm revealed the highest average lactucin (112.9 ㎍/g), lactucopicrin (734.8 ㎍/g) and total SLs content (847.7 ㎍/g). Crisp head and leafy type germplasm exhibited more total SLs content (847.7 and 744.7 ㎍/g, respectively) than cos (524.9 ㎍/g) and butter head type (519.4 ㎍/g). Principal component analyses of the quantitative traits indicated that the first principal component axis accounted more than 91% of the total variation. This study revealed the ample genetic variation in the agro-morphological traits and SLs contents to support the selection for improved lettuce varieties.