Leaf Mustard (Brassica juncea) Germplasm Resources Showed Diverse Characteristics in Agro-Morphological Traits and Glucosinolate Levels.

Leaf mustard, characterized by its purple/red/green leaves with a green/white midrib, is known for its thick, tender, and spicy leaves with a unique taste and flavor. There were only a few studies reported on leaf mustard for its morphological and biochemical traits from Korea. A total of 355 leaf mustard accessions stored at the GenBank of the National Agrobiodiversity Center were evaluated for 25 agro-morphological traits and seven intact glucosinolates (GSLs). The accessions showed a wide variation in terms of most of the traits. The quantitative agro-morphological traits varied from 16.0 (leaf length) to 48.7% (petiole width) of the coefficient of variation (CV). The highest variation was observed in glucoiberin (299.5%, CV), while the total GSL showed a CV of 66.1%. Sinigrin, followed by gluconapin and gluconasturtiin, was the most abundant GSL, accounting for as high as 75% of the total GSLs, while glucobrassicanapin and glucoiberin were the least abundant, contributing 0.7% and 0.1% on average, respectively. Sinigrin had a positive significant correlation with all GSLs but gluconasturtiin, while glucobarbarin and gluconasturtiin were highly positively correlated to each other, but least correlated with other GSLs. The leaf length was negatively correlated with sinigrin and glucoiberin. The width of the petiole showed a positive correlation with gluconapin, glucobrassicanapin, and glucobrassicin, while the length of the petiole had a negative correlation with sinigrin, glucobrassicanapin, glucoiberin, glucobrassicin, and the total GSLs. A higher width of the midrib was associated with higher contents of gluconapin, glucobrassicanapin, and glucobrassicin. A PCA analysis based on the agro-morphological traits showed that the first and second principal components accounted for 65.2% of the overall variability. Accessions that form a head tend to exhibit a longer leaf length, a larger plant weight, a thicker midrib, and higher widths of the midrib, petiole, and leaf. The GSLs showed inconsistent inter-and intra-leaf variation. Accessions that identified for various traits in their performance, such as, for example, Yeosu66 and IT259487 (highest total glucosinolates) and IT228984 (highest plant weight), would be promising lines for developing new varieties.

Construction of a core collection of native Perilla germplasm collected from South Korea based on SSR markers and morphological characteristics.

The leaves and seed oil of Perilla crop (Perilla frutescens L.) have attracted interest as health foods in East Asia. This crop has been traditionally cultivated and used for a long time as a folk plant, especially in Korea. In our study, the 22 SSR markers and eight morphological traits were used to assess the genetic diversity and population structure, to select a core collection of 400 Perilla accessions conserved in the RDA-Genebank of South Korea. A total of 173 alleles were detected and the number of alleles per locus ranged from 4 to 15 (average = 7.9). Gene diversity and polymorphic information content ranged from 0.138 to 0.868 (average = 0.567) and 0.134 to 0.853 (average = 0.522), respectively. The 400 accessions were not clearly distinguished geographically by STRUCTURE and UPGMA analyses. A core collection (44 accessions) was selected from the entire collection by using PowerCore. The core collection accounted for 11.0% of the entire Perilla collection, including 100% of the number of alleles maintained in the whole collection and with similar or greater Shannon-Weaver and Nei diversity indices than the whole collection. The core collection selected by SSR markers was evenly distributed in three clusters on a scatter plot by eight morphological traits. The first core collection of Perilla accessions was constructed, and it maintained allelic richness. Further modification of the core collection is expected with the continuous addition of new accessions of the two cultivated types of Perilla crop and their weedy types.

Nutritional Metabolites of Red Pigmented Lettuce (Lactuca sativa) Germplasm and Correlations with Selected Phenotypic Characters.

Lettuce is an important dietary source of bioactive phytochemicals. Screening and identification of the health beneficial metabolites and evaluating the relationships with phenotypic characters can help consumers adjust their preferences for lettuce plant types. Thus, we explored the major health-beneficial individual metabolites and antioxidant potential of 113 red pigmented lettuce leaf samples. A UV-Vis spectrophotometer and UPLC-DAD-QTOF/MS (TQ/MS) instruments were used for the identification and quantification of metabolites and antioxidant activity accordingly. The metabolites were quantified against their corresponding external standards. The contents of metabolites varied significantly among lettuce samples. Cyanidin 3-O-(6″-O-malonyl)glucoside (4.7~5013.6 µg/g DW), 2,3-di-O-caffeoyltartaric acid (337.1~19,957.2 µg/g DW), and quercetin 3-O-(6″-O-malonyl)glucoside (45.4~31,121.0 µg/g DW) were the most dominant in red pigmented lettuce samples among anthocyanins, hydroxycinnamoyl derivatives, and flavonols, respectively. Lettuces with dark and very dark red pigmented leaves, circular leaf shape, a strong degree of leaf undulation, and highly dense leaf incisions were found to have high levels of flavonoids and hydroxycinnamoyl derivatives. Principal component analysis was used to investigate similarities and/or differences between samples, and the partial least square discriminant analysis classified them into known groups. The key variables that contributed highly were determined. Our report provides critical data on the bioactive constituents of red pigmented lettuce to breeders developing varieties with enhanced bioactive compounds and to nutraceutical companies developing nutrient dense foods and pharmaceutical formulations.

Genetic Variation of Native Perilla Germplasms Collected from South Korea Using Simple Sequence Repeat (SSR) Markers and Morphological Characteristics.

Using morphological characteristics and simple sequence repeat (SSR) markers, we evaluated the morphological variation and genetic diversity of 200 Perilla accessions collected from the five regions of South Korea and another region. In morphological characteristics analysis, particularly leaf color, stem color, degree of pubescence, and leaf size have been found to help distinguish the morphological features of native Perilla accessions cultivated in South Korea. Twenty SSR primer sets confirmed a total of 137 alleles in the 200 Perilla accessions. The number of alleles per locus ranged from 3 to 13, with an average number of alleles per locus of 6.85. The average genetic diversity (GD) was 0.649, with a range of 0.290-0.828. From analysis of SSR markers, accessions from the Jeolla-do and Gyeongsang-do regions showed comparatively high genetic diversity values compared with those from other regions in South Korea. In the unweighted pair group method with arithmetic mean (UPGMA) analysis, the 200 Perilla accessions were found to cluster into three main groups and an outgroup with 42% genetic similarity, and did not show a clear geographic structure from the five regions of South Korea. Therefore, it is believed that landrace Perilla seeds are frequently exchanged by farmers through various routes between the five regions of South Korea. The results of this study are expected to provide interesting information on the conservation of these genetic resources and selection of useful resources for the development of varieties for seeds and leafy vegetables of cultivated Perilla frutescens var. frutescens in South Korea.

Glucosinolate Content in Brassica Genetic Resources and Their Distribution Pattern within and between Inner, Middle, and Outer Leaves.

Glucosinolates (GSLs) are sulfur-containing secondary metabolites naturally occurring in Brassica species. The purpose of this study was to identify the GSLs, determine their content, and study their accumulation patterns within and between leaves of kimchi cabbage (Brassica rapa L.) cultivars. GSLs were analyzed using UPLC-MS/MS in negative electron-spray ionization (ESI-) and multiple reaction monitoring (MRM) mode. The total GSL content determined in this study ranged from 621.15 to 42434.21 µmolkg-1 DW. Aliphatic GSLs predominated, representing from 4.44% to 96.20% of the total GSL content among the entire samples. Glucobrassicanapin (GBN) contributed the greatest proportion while other GSLs such as glucoerucin (ERU) and glucotropaeolin (TRO) were found in relatively low concentrations. Principal component analysis (PCA) yielded three principal components (PCs) with eigenvalues ≥ 1, altogether representing 74.83% of the total variation across the entire dataset. Three kimchi cabbage (S/No. 20, 4, and 2), one leaf mustard (S/No. 26), and one turnip (S/No. 8) genetic resources were well distinguished from other samples. The GSL content varied significantly among the different positions (outer, middle, and inner) of the leaves and sections (top, middle, bottom, green/red, and white) within the leaves. In most of the samples, higher GSL content was observed in the proximal half and white sections and the middle layers of the leaves. GSLs are regarded as allelochemicals; hence, the data related to the patterns of GSLs within the leaf and between leaves at a different position could be useful to understand the defense mechanism of Brassica plants. The observed variability could be useful for breeders to develop Brassica cultivars with high GSL content or specific profiles of GSLs.

Fruit Morphology, Citrulline, and Arginine Levels in Diverse Watermelon (Citrullus lanatus) Germplasm Collections.

Watermelon (Citrullus lanatus) is a non-seasonal, economically important, cucurbit cultivated throughout the world, with Asia as a continent contributing the most. As part of the effort to diversify watermelon genetic resources in the already cultivated group, this study was devoted to providing baseline data on morphological quality traits and health-beneficial phytonutrients of watermelon germplasm collections, thereby promoting watermelon research and cultivation programs. To this end, we reported morphological traits, citrulline, and arginine levels of watermelon genetic resources obtained from the gene bank of Agrobiodiversity Center, Republic of Korea, and discussed the relationships between each. Diverse characteristics were observed among many of the traits, but most of the genetic resources (>90%) were either red or pink-fleshed. Korean originated fruits contained intermediate levels of soluble solid content (SSC) while the USA, Russian, Tajikistan, Turkmenistan, Taiwan, and Uruguay originated fruits had generally the highest levels of soluble solids. The citrulline and arginine contents determined using the High Performance Liquid Chromatography (HPLC) method ranged from 6.9 to 52.1 mg/g (average, 27.3 mg/g) and 1.8 to 21.3 mg/g (average, 9.8 mg/g), respectively. The citrulline content determined using the Citrulline Assay Kit ranged from 6.5 to 42.8 mg/g (average, 27.0 mg/g). Resources with high citrulline and arginine levels contained low SSC, whereas red- and pink-colored flesh samples had less citrulline compared to yellow and orange.

Identification and quantification of selected metabolites in differently pigmented leaves of lettuce (Lactuca sativa L.) cultivars harvested at mature and bolting stages.

BACKGROUND: Identification and screening of cultivars rich in bioactive phytoconstituents can be potentially useful to make nutrient-dense dishes and in medicinal formulations. In this study, we have identified, characterized and quantified caffeoylquinic acids, dicaffeoylquinic acid, dicaffeoyltartaric acid, kaempferol conjugates, quercetin malonylglucoside, sesquiterpene lactones, and cyanidin in 22 lettuce cultivars at mature and bolting stages using UPLC-PDA-Q-TOF-HDMS, UPLC, and HPLC. RESULTS: The composition and contents of the studied metabolites and antioxidant activity varied significantly and depend on leaf color, cultivar type and stage of maturity. The main phenolic acid components of lettuce were quinic and tartaric acid derivatives, whereas kaempferol derivatives were the dominant flavonoids. The sum of the content of phenolic acids ranged from 18.3 to 54.6 mg/100 g DW and 15.5 to 54.6 mg/100 g DW, whereas the sum of the contents of flavonoids ranged from 9.2 to 25.9 mg/100 g DW and 14.9 to 83.0 mg/100 g DW in mature and bolting stage cultivars, respectively. The content of cyanidin, lactucin, lactucopicrin, and ABTS radical antioxidant activity were in the range of 0.3 to 9.7 (mature stage) and 0.5 to 10.2 mg/g DW (bolting stage), 1.8 to 41.9 (mature stage) and 9.7 to 213.0 (bolting stage) µg/g DW, 9.9 to 344.8 (mature stage) and 169.2 to 3888.2 (bolting stage) µg/g DW, and 12.1 to 29.0 (mature stage) and 15.7 to 30.3 (bolting stage) mg TE/g DW, respectively. The principal component analysis (PCA) showed that the green and red pigmented lettuce cultivars were grouped to the negative and positive sides of PC1, respectively, while the green/red pigmented cultivars were distributed throughout the four quadrants of the PCA plots with no prominent grouping. The loading plot showed that phenolic acids, flavonoids, and cyanidin are the most potent contributors to the radical scavenging activity of lettuce extracts. CONCLUSIONS: Lettuce at the bolting stage accumulate relatively high amount of sesquiterpene lactones (SLs), quercetin malonylglucoside (QMG), methylkaempferol glucuronide (MKGR), kaempferol malonylglucoside (KMG), and 3-O-caffeoylquinic acid (3-CQA) compared to the mature stage. Higher amount of phytoconstituents were found to be accumulated in the red pigmented lettuce leaves compared to the green lettuce leaves. In addition, the contents of most of the metabolites in lettuce seem to increase with age of the leaves. The presence of the two bitter SLs, lactucin and lactucopicrin, in significantly high amount in lettuce leaves at bolting stage could diminish consumer acceptance. However, alternatively, these leaves could be utilized by nutraceutical companies working to recover these compounds.

Evaluation of Resistance to Ralstonia solanacearum in Tomato Genetic Resources at Seedling Stage.

Bacterial wilt of tomatoes caused by Ralstonia solanacearum is a devastating disease that limits the production of tomato in Korea. The best way to control this disease is using genetically resistant tomato plant. The resistance degree to R. solanacearum was evaluated for 285 tomato accessions conserved in the National Agrobiodiversity Center of Rural Development Administration. These accessions of tomato were originated from 23 countries. Disease severity of tomato accessions was investigated from 7 days to 14 days at an interval of 7 days after inoculation of R. solanacearum under greenhouse conditions. A total of 279 accessions of tomato germplasm were susceptible to R. solanacearum, resulting in wilt and death in 70 to 90% of these plants. Two tomato accessions were moderately resistant to R. solanacearum. Only four accessions showed high resistance against R. solanacearum. No distinct symptom of bacterial wilt appeared on the resistant tomato germplasms for up to 14 days after inoculation of R. solanacearum. Microscopy of resistant tomato stems infected with R. solanacearum revealed limited bacterial spread with thickening of pit membrane and gum production. Therefore, these four resistant tomato germplasms could be used in tomato breeding program against bacterial wilt.