Korean Sweet Potato Research Articles

Genetic diversity assessment and genome-wide association study reveal candidate genes associated with component traits in sweet potato (Ipomoea batatas (L.) Lam)

The Korean sweet potatoes were bred by various cultivars introduced from Japanese, American, Porto Rico, China, and Burundi. This issue enriched their genetic diversity but also resulted in a mixture of cultivars. For genotyping, we collected and sequenced 66 sweet potato germplasms from different localities around Korea, including 36 modern cultivars, 5 local cultivars, and 25 foreign cultivars. This identified 447.6 million trimmed reads and 324.8 million mapping reads and provided 39,424 single nucleotide polymorphisms (SNPs) markers. Phylogenetic clustering and population structure analysis distinctly classified these germplasms into 5 genetic groups, group 1, group 2, group 3, group 4, and group 5, containing 20, 15, 10, 7, and 14 accessions, respectively. Sixty-three significant SNPs were selected by genome-wide association for sugar composition-related traits (fructose, glucose, and total sugars), total starch, amylose content, and total carotenoid of the storage root. A total of 37 candidate genes encompassing these significant SNPs were identified, among which, 7 genes were annotated to involve in sugar and starch metabolism, including galactose metabolism (itf04g30630), starch and sucrose metabolism (itf03g13270, itf15g09320), carbohydrate metabolism (itf14g10250), carbohydrate and amino acid metabolism (itf12g19270), and amino sugar and nucleotide sugar metabolism (itf03g21950, itf15g04880). This results indicated that sugar and starch are important characteristics to determine the genetic diversity of sweet potatoes. These findings not only illustrate the importance of component traits to genotyping sweet potatoes but also explain an important reason resulting in genetic diversity of sweet potato.

Identification and quantification of hydroxybenzoyl and hydroxycinnamoyl derivatives from Korean sweet potato cultivars by UPLC-DAD-QToF/MS

A total of thirty-four hydroxybenzoyl and hydroxycinnamoyl derivatives were identified and quantified from the tuberous roots of Korean sweet potato (Ipomoea batatas L.) cultivars based on ultra performance liquid chromatography with diode array detection and quadrupole time of flight/mass spectrometry (UPLC-DAD-QToF/MS). From three colored cultivars (purple, yellow and white), caffeic acid (CA), 5-O-caffeoylquinic acid (5-CQA, chlorogenic acid) and 3,5-di-O-caffeoylquinic acid (3,5-diCQA, isochlorogenic acid A) were confirmed as major components, and also three classes of hydroxycinnamoylquinic acid derivatives were tentatively identified for the first time from their tuberous roots: two diferuloylquinic acids (diFQAs: 3,5-diFQA, 4,5-diFQA), three dicaffeoyl-feruloylquinic acids (diC,FQAs: 3 F,4,5-diCQA, 3,5-diC,4 FQA, 3,4-diC,5FQA), two diferuloyl-caffeoylquinic acids (diF,CQAs: 3,4-diF,5CQA, 3C,4,5-diFQA). In particular, the novel p-hydroxybenzoylquinic acids (pHbQAs: 3-pHbQA, 4-pHbQA, 5-pHbQA) and vanilloylquinic acids (VQAs: 3-VQA, 4-VQA, 5-VQA) were only presented as the predominant components in purple sweet potato. In total content (mg/100 g, dry weight) of 34 derivatives, all cultivars showed the significant differences according to their tuberous sites and mainly di-hydroxycinnamoyl derivatives, were found to be higher in the peels (yellow, 211.0 > purple, 147.0 > white, 97.1) than inner parts (purple, 83.8 > yellow, 26.3 > white, 12.7). Furthermore, it is considered that the profile of these derivatives is closely related to the corresponding acylated anthocyanins and can be a fundamental report in selection and breeding of superior varieties which are expected to possess higher antioxidant activities.

Quality Properties of Makgeolli Brewed with Korean Sweet Potato Cultivars (Ipomoea batatas (L.) Lam)

Quality Properties of Makgeolli Brewed with Korean Sweet Potato Cultivars (Ipomoea batatas (L.) Lam)

Physicochemical and Bread-making Properties of Flours from Sweet Potatoes with Different Flesh Colours

Flour was prepared from Korean sweet potatoes (SPs) with different flesh colours (white, yellow/orange, and purple) and evaluated for physicochemical and pasting properties and their partial substitution for bread-making. SP tubers were soaked in sodium metabisulfite solution (anti-browning agent) and subjected to hot air drying, followed by grinding. SP flours with different colours showed variations in chemical compositions, especially amylose, dietary fibre, and starch contents. Yellow/orange-fleshed SP flour had the highest content of total carotenoid (5.26 mg/100 g) among all SP flours. The highest total anthocyanin content (59.92 mg/100 g) was reported for purple-fleshed SP flour. Water absorption index (WAI), water solubility index (WSI), and an oil absorption of purple-fleshed SP flour were 1.63 g/g, 25.59%, and 187.21%, respectively, and relatively higher than those of white or yellow/orange-fleshed SP flour. Wheat flour was substituted with SP flour in bread at 10-30% level. The increase in the proportion of SP flour resulted in a significant decrease in loaf volume, and maximum reduction in loaf volume was reported for the bread containing purple-fleshed SP flour. However, SP flour may serve as a substitute for wheat flour at levels up to 10% without causing any deteriorating effects on the overall bread quality. Therefore, coloured SP flour could be useful in the bread-making industry to improve the nutritional value of bread.

Phenolic compounds and antioxidant activity in sweet potato after heat treatment.

The ability of heat treatment with a soaking solvent to increase soluble phenolic compounds due to the liberation or breakdown of the cell matrix has been investigated in various plants. This study investigated the changes in phenolic compounds and antioxidant activities of 12 sweet potato cultivars after heat treatment with distilled water or prethanol A. The highest total polyphenol content (134.67 mg gallic acid equivalents/g extract residue) and flavonoid content (65.43 mg catechin equivalents/g extract residue) was observed in the 'Jami' (JM) cultivar after heat treatment with prethanol A. Higher polyphenol and flavonoid content was generally observed in the purple sweet potato cultivars. Salicylic acid was the major phenolic acid, followed by protocatechuic acid or chlorogenic acid in almost all untreated sweet potato cultivars. The salicylic acid, vanillic acid, gallic acid, and caffeic acid content of the sweet potatoes increased after the heat treatment, whereas the protocatechuic acid and chlorogenic acid content decreased. The highest 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azinobis(3-ethyl benzothiazoline)-6-sulfonic acid (ABTS) radical scavenging activity levels were observed in the JM cultivar subjected to heat treatment with prethanol A (48.15 and 80.00 mg TE/g extract residue, respectively). These results suggest that heat treatment with a soaking solvent is an efficient method to enhance the antioxidant characteristics of Korean sweet potato cultivars. © 2019 Society of Chemical Industry.

국내산 및 국외산 고구마의 영양성분 비교 분석

Recently, the importance of domestic sweet potato (Ipomoea batatas) varieties following the entry into force of the Nagoya Protocol has been highlighted. In this study, dietary fiber content, free sugars, constituent amino acids, inorganic components, vitamin contents and antioxidative activities were compared and analyzed using two domestic sweet potatoes (Hogammi, Danjami) and one foreign species (Beni-Haruka). The antioxidant activity and dietary fiber content of the Korean sweet potatoes were the highest, and vitamin content, amino acid composition and inorganic content were the highest among the three types of sweet potatoes. Sweet potatoes have a low calorie content and are full of sugar, and are in the spotlight as dietary foods. The most important thing when taking sweet potatoes is the sugar content and dietary fiber distribution. These results suggest that the Korean sweet potato species, which are superior to the foreign sweet potato varieties, Beni-Haruka, are considered to be a good variety and are useful for general food and processed food consumption.

Textural character of sweet potato root of Korean cultivars in relation to chemical constituents and their properties.

A relationship between chemical constituents and physicochemical and textural properties of different Korean sweet potato (SP) cultivars were investigated in terms of the hardness of raw and cooked root, alcohol insoluble solid (AIS), starch and amylose content, amylase activities, and pasting properties. Correlation coefficients were analyzed and principal component analysis was performed. The hardness of cooked root was found to correlate with the hardness ratio of cooked/raw SP, AIS content (0.75**), starch content (0.64**), and peak viscosity of SP powder (0.56*). It was discovered that SP cultivars could be classified into mealy (Sincheonmi, Daeyumi, Sinyulmi), intermediate (Dahomi, Sinjami, Geonhwangmi, Yeonjami, Pungwonmi), and waxy (Juhwangmi, Sinhwangmi) types depending on the first principal component (PC1, 68%). Therefore, it was found that the texture types of SP cultivars could be predicted from hardness of cooked root and are in relation to AIS and starch contents, and peak viscosity of raw powder.

Difference of Storability According to the Curing Treatment in Korean Sweetpotato Varieties

Difference of Storability According to the Curing Treatment in Korean Sweetpotato Varieties

Virus Incidence of Sweet Potato in Korea from 2011 to 2014.

A nationwide survey was performed to investigate the current incidence of viral diseases in Korean sweet potatoes for germplasm and growing fields from 2011 to 2014. A total of 83.8% of the germplasm in Korea was infected with viruses in 2011. Commercial cultivars that were used to supply growing fields were infected at a rate of 62.1% in 2012. Among surveyed viruses, the incidence of five Potyvirus species that infect sweet potato decreased between 2012 and 2013, and then increased again in 2014. Representatively, the incidence of Sweet potato feathery mottle virus (SPFMV) was 87.0% in 2012, 20.7% in 2013 and then increased to 35.3% in 2014. Unlike RNA viruses, DNA viruses were shown to decrease continuously. The incidence of Sweet potato leaf curl virus (SPLCV) was 5.5% in 2003, 59.5% in 2011, and 47.4% in 2012. It then decreased continuously year by year to 33.2% in 2013, and then 25.6% in 2014. While the infection rate of each virus species showed a tendency to decline, the virus infection status was more variable in 2013 and 2014. Nevertheless, the high rate of single infections and mixed infection combinations were more variable than the survey results from 2012. As shown in the results from 2013, the most prevalent virus infection was a single infection at 27.6%, with the highest rate of infection belonging to sweet potato symptomless virus-1 (SPSMV-1) (12.9%). Compared to 2013, infection combinations were more varied in 2014, with a total of 122 kinds of mixed infection.

Characterization and development of EST-SSR markers in sweet potato (Ipomoea batatas (L.) Lam).

In this study, a cDNA library was constructed from the total RNA of sweet potato leaves. A total of 789 copies of the cDNA were cloned in Escherichia coli by employing the pGEM-T Easy vector. Sequencing was carried out by Solgent Co. (Korea). As many as 579 expressed sequence tag–simple sequence repeat (EST-SSR) markers were designed (73.38%) from the known cDNA nucleotide base sequences. The lengths of the developed EST-SSR markers ranged from 100 to 499 bp (average length 238 bp). Their motif sequence types were varied, with most being dinucleotides and pentanucleotides, and the most commonly found motifs were CAGAAT (29.0%) and TCT (2.8%). Based on these SSR-containing sequences, 619 pairs of high-quality SSR primers were designed using WebSat and Primer3web. The total number of primers designed was 144. Polymorphism was evident in 82 EST-SSR markers among 20 Korean sweet potato cultivars tested and in 90 EST-SSR markers in the two parents of a mapping population, Yeseumi and Annobeny. In this study, the hexaploid sweet potato (2n = 6x = 90) EST-SSR markers were developed in the absence of full-sequence data. Moreover, by acting as a molecular tag for particular traits, the EST-SSR marker can also simultaneously identify information about the corresponding gene. These EST-SSR markers will allow the molecular analysis of sweet potato to be done more efficiently. Thus, we can develop high-quality sweet potato while overcoming the challenges from climate change and other unfavorable conditions.

Properties of Flavors and Tastes of Koguma-soju Prepared Using Korean Sweet Potato

Properties of Flavors and Tastes of Koguma-soju Prepared Using Korean Sweet Potato

Properties of Flavors and Tastes of Koguma-soju Prepared Using Korean Sweet Potato

Four types of koguma-soju, sweet potato-distilled liqior, were prepared using Korean sweet potato cultivar, namely Shingunmi, Jinhongmi, Daeyumi, and Hayanmi, The mono-terpene alcohol (MTA) concentrations and flavor properties of koguma-soju were analyzed. The general properties of the MTA concentrations were as follows; nerol concentration was the lowest of the five MTAs with a range of approximately 14.2-15.8 ㎍/L, geraniol and citronellol concentrations were approximately 41.90-50.75 ㎍/L, linalool concentrations were 43.20 ㎍/L and 45.15 ㎍/L in Shingunmi and Jinhongmi koguuma-soju, respectively, and 93.2 ㎍/L and 96.05 ㎍/L in Daeyumi and Hayanmi koguma-soju, respectively, and the α-terpineol concentration was the highest of the five MTAs, with a range of 177.5-218 ㎍/L in the four types of koguma-soju. These results were different from the MTA concentrations in Imo-shochu, Japanese sweet potato-soju as the nenol concentration of Korean koguma-soju was lower than that of Imo-shochu, and the α-terpineol concentration was higher than that of Imo-shochu.BR Flavor evaluation tests revealed that the koguma-soju prepared from the Shingunmi variety had a floral, roasted flavor and rough, sweet, bitter taste, whereas the Jinhongmi-koguma-soju was characterized by a floral, fruity, soapy, brown sugar-like flavor and sweet, pungent taste. Green leaf-like, aldehyde-like flavor and astringent, dry taste were predominant in the Daeyumi koguma-soju, while the Hayanmi koguma-soju had either a vegetable-like, woody, citrus-like flavor and sour, body taste. This study suggested that koguma-soju prepared from different sweet potato cultivars have unique characteristic flavors because they contain different ratios of MTAs.

Molecular Characterization of Five Potyviruses Infecting Korean Sweet Potatoes Based on Analyses of Complete Genome Sequences.

Sweet potatoes (Ipomea batatas L.) are grown extensively, in tropical and temperate regions, and are important food crops worldwide. In Korea, potyviruses, including Sweet potato feathery mottle virus (SPFMV), Sweet potato virus C (SPVC), Sweet potato virus G (SPVG), Sweet potato virus 2 (SPV2), and Sweet potato latent virus (SPLV), have been detected in sweet potato fields at a high (~95%) incidence. In the present work, complete genome sequences of 18 isolates, representing the five potyviruses mentioned above, were compared with previously reported genome sequences. The complete genomes consisted of 10,081 to 10,830 nucleotides, excluding the poly-A tails. Their genomic organizations were typical of the Potyvirus genus, including one target open reading frame coding for a putative polyprotein. Based on phylogenetic analyses and sequence comparisons, the Korean SPFMV isolates belonged to the strains RC and O with >98% nucleotide sequence identity. Korean SPVC isolates had 99% identity to the Japanese isolate SPVC-Bungo and 70% identity to the SPFMV isolates. The Korean SPVG isolates showed 99% identity to the three previously reported SPVG isolates. Korean SPV2 isolates had 97% identity to the SPV2 GWB-2 isolate from the USA. Korean SPLV isolates had a relatively low (88%) nucleotide sequence identity with the Taiwanese SPLV-TW isolates, and they were phylogenetically distantly related to SPFMV isolates. Recombination analysis revealed that possible recombination events occurred in the P1, HC-Pro and NIa-NIb regions of SPFMV and SPLV isolates and these regions were identified as hotspots for recombination in the sweet potato potyviruses.

한국산 고구마 품종인 연미, 증미, 신천미, 신율미를 이용하여 제조한 고구마 소주의 향기성분의 특성

Four varieties of the Korean sweet potato, Yeonmi, Jeungmi, Shincheonmi, and Shinyeulmi, were chosen to prepare the distilled koguma-soju (sweet potato-soju). The relationship between the flavor of the koguma-soju and the content of monoterpene alcohols (MTAs) was studied. The MTAs investigated here were linalool, nerol, geraniol, citronellol, and <TEX>${\alpha}$</TEX>-terpineol. The ranges of MTA concentrations in the koguma-soju made from the four sweet potato varieties were <TEX>$14.0-16.6{\mu}g/L$</TEX> for nerol, <TEX>$24.8-34.7{\mu}g/L$</TEX> for linalool, <TEX>$32.8-38.5{\mu}g/L$</TEX> for geraniol, <TEX>$37.8-54.2{\mu}g/L$</TEX> for citronellol, and <TEX>$76.6-94.7{\mu}g/L$</TEX> for <TEX>${\alpha}$</TEX>-terpineol. Geraniol, nerol, and linalool were found in lower concentrations, while <TEX>${\alpha}$</TEX>-terpineol was present in a higher concentration compared to their average content in the imo-shochu, a distilled Japanese sweet potato-soju. The concentrations of citronellol in the koguma-soju and imo-shochu were similar. The flavor evaluation tests revealed that the koguma-soju produced from the Yeonmi variety had a leafy vegetable or a grass-like, sharp flavor, whereas the Jeungmi-soju was characterized by a fruity or a sulfur-like sharp taste. Floral, vanilla-like, and mild flavors were predominant in the Shincheonmi-soju, while the Shinyeulmi-soju had either a fruity, citrus-like flavor or a rubber-like, rough taste. This study demonstrates that koguma-soju made from different sweet potato varieties have unique characteristic flavors.

The current incidence of viral disease in korean sweet potatoes and development of multiplex rt-PCR assays for simultaneous detection of eight sweet potato viruses.

Sweet potato is grown extensively from tropical to temperate regions and is an important food crop worldwide. In this study, we established detection methods for 17 major sweet potato viruses using single and multiplex RT-PCR assays. To investigate the current incidence of viral diseases, we collected 154 samples of various sweet potato cultivars showing virus-like symptoms from 40 fields in 10 Korean regions, and analyzed them by RT-PCR using specific primers for each of the 17 viruses. Of the 17 possible viruses, we detected eight in our samples. Sweet potato feathery mottle virus (SPFMV) and sweet potato virus C (SPVC) were most commonly detected, infecting approximately 87% and 85% of samples, respectively. Furthermore, Sweet potato symptomless virus 1 (SPSMV-1), Sweet potato virus G (SPVG), Sweet potato leaf curl virus (SPLCV), Sweet potato virus 2 ( SPV2), Sweet potato chlorotic fleck virus (SPCFV), and Sweet potato latent virus (SPLV) were detected in 67%, 58%, 47%, 41%, 31%, and 20% of samples, respectively. This study presents the first documented occurrence of four viruses (SPVC, SPV2, SPCFV, and SPSMV-1) in Korea. Based on the results of our survey, we developed multiplex RT-PCR assays for simple and simultaneous detection of the eight sweet potato viruses we recorded.

Effect of processing conditions on the content of cis/trans carotene isomers as provitamin A carotenoids in Korean sweet potato varieties

The present investigation intends to evaluate the changes in the content of cis/trans carotene isomers as provitamin A carotenoids by steaming and roasting processes in the roots of four Korean sweet potato varieties viz. Shinzami, Younwhangmi, Chuwhangmi and Jinhongmi using a liquid chromatography with diode array detection and the negative ion atmospheric pressure chemical ionization mass spectrometric (LC-DAD-APCI/MS) method and UV spectral pattern library created from several reference data. Except Shinzami, the content of all trans β-carotenes was found to slightly decreased or remained constant when steamed or roasted. The content of cis α-/β-carotenes was potentially increased about 2-fold or greater when raw or steamed and the content was slightly decreased while roasted. In Chuwhangmi, the content of 13-cis α-carotene and all trans α-carotenes were rapidly increased when steamed and slightly decreased when roasted. Chuwhangmi exhibited 27.2 mg/100 g DW content of all trans β-carotenes when roasted and thus, it was considered as a relatively superior cultivar.

Antioxidant capacity of japchae, Korean stir-fried sweet potato noodles with vegetables

Antioxidant capacities of japchae, a Korean traditional food were investigated. Japchae showed concentration dependent radical scavenging abilities with half maximal inhibitory concentration values (IC50) of 0.68 and 1.36 mg/mL from DPPH and ABTS assays, respectively. Positive correlations were observed between radical scavenging effects and the contents of total polyphenol (TPC), retinol, β-carotene, and ascorbic acid. Lipid peroxidation was inhibited by japchae with IC50 values of 1.49 and 1.40 mg/mL based on ferric thiocyanate (FTC) and thiobarbituric acid reactive substances (TBARS) assays, respectively.

Physicochemical properties of starch isolated from eight different varieties of Korean sweet potatoes

The physicochemical properties of sweet potato starch (SPS) isolated from different Korean varieties, purple-fleshed Shinjami and Borami, orange-fleshed Juwhangmi and Shinwhangmi, and white/cream-fleshed Shinyulmi, Shinchunmi, Yeowhangmi, and Jeungmi, were investigated. The crude protein contents of Shinwhangmi and Jeungmi SPS were higher, and the crude lipid contents of Shinwhangmi and Shinyulmi SPS were lower than those of others. The amylose (AM) contents ranged from 14.66% (Juwhangmi) to 30.51% (Shinchunmi). The water binding capacity (WBC), swelling powers, and solubilities at 80°C were 95.78–79.32%, 15.69–23.39 g/g, and 3.77–11.01%, respectively. The XRD patterns were A and Cb-types. The granular shapes exhibited polygonal and semi-oval, but the sizes differed among different varieties. The initial pasting temperature ranged from 69.4 (Juwhangmi) to 76.4°C (Shinchunmi). Differences between onset and conclusion temperatures of orange-fleshed SPS were greater than those of others. The molecular weight of AM and amylopectin (AP) were (1.26–1.92) × 106 and (5.37–5.99) × 107, respectively. The gelatinization temperatures, amylose contents, and WBCs of SPS were correlated with unit chains of DP6-12 (negative) and DP13-24 (positive) in their APs.

The total phenolic contents and DPPH radical scavenging activities of Korean sweet potatoes according to plants parts, varieties, and by distribution and cooking methods

The total phenolic contents and DPPH radical scavenging activities of Korean sweet potatoes according to plants parts, varieties, and by distribution and cooking methods

Omics-based biomarkers for the identification of six Korean cultivars of sweet potato (Ipomoea batatas L. Lam)

SummaryThis study was conducted to develop biomarkers to identify 26 cultivars of Korean sweet potato (Ipomoea batatas L. Lam) using omics-based methods. Random amplification of polymorphic DNA (RAPD) markers revealed that 75 random 10-mer primers generated 50 polymorphic RAPD markers from the 28 Korean sweet potato cultivars. Six sweet potato cultivars were selected for further analysis by proteomic and metabolomic approaches based on their flesh colour (two each having cream, orange, or purple flesh) and by a dendrogram generated using the polymorphic RAPD bands. Changes in the proteomes of these six sweet potato cultivars were investigated by two-dimensional gel electrophoresis (2-DGE) coupled with matrix-assisted, laser desorption/ionisation tandem time-of-flight mass spectrometry (MALDI-TOF/TOF MS) analysis. Overall, ten protein spots were expressed differentially between the six cultivars and identified by MALDI-TOF/TOF MS. Among these, an ATP-dependent zinc metalloprotease and the chaperone protein, ClpC1, accumulated specifically in the cultivars ‘Singeonmi’ and ‘Jami’, respectively. Furthermore, metabolomic analysis, using reversed-phase high performance liquid chromatography (HPLC) coupled with liquid chromatography-electrospray ionisation mass spectrometry (LC-ESI-MS), revealed that four polyphenolic compounds accumulated differentially in the six sweet potato cultivars. Members of the caffeoylquinic acid family were detected at the highest levels in ‘Juhwangmi’. These results suggest that the proteins and metabolites that accumulate differentially may be used as biomarkers to identify Korean sweet potato cultivars.