Tuberous Roots Of Sweet Potato Research Articles

MYB44 competitively inhibits the formation of the MYB340-bHLH2-NAC56 complex to regulate anthocyanin biosynthesis in purple-fleshed sweet potato

BackgroundAnthocyanins, which have important biological functions and have a beneficial effect on human health, notably account for pigmentation in purple-fleshed sweet potato tuberous roots. Individual regulatory factors of anthocyanin biosynthesis have been identified; however, the regulatory network of anthocyanin biosynthesis in purple-fleshed sweet potato is unclear.ResultsWe functionally determined that IbMYB340 cotransformed with IbbHLH2 in tobacco and strawberry receptacles induced anthocyanin accumulation, and the addition of IbNAC56a or IbNAC56b caused increased pigmentation. Furthermore, we confirmed the interaction of IbMYB340 with IbbHLH2 and IbNAC56a or IbNAC56b via yeast two-hybrid and firefly luciferase complementation assays; these proteins could form a MYB340-bHLH2-NAC56a or MYB340-bHLH2-NAC56b transcriptional complex to regulate anthocyanin biosynthesis by binding to the IbANS promoter rather than the IbUFGT promoter. Furthermore, it was found by a transient expression system in tobacco leaves that IbMYB44 could decrease anthocyanin accumulation. Moreover, the interaction of IbMYB44 with IbMYB340 and IbNAC56a or IbNAC56b was verified. This result suggested that IbMYB44 acts as a repressor of anthocyanin in sweet potato.ConclusionsThe repressor IbMYB44 affected anthocyanin biosynthesis by competitively inhibiting the IbMYB340-IbbHLH2-IbNAC56a or IbMYB340-IbbHLH2-IbNAC56b regulatory complex formation. Overall, the present study proposed a novel regulatory network whereby several vital TFs play key roles in regulating anthocyanin biosynthesis, and it provides strong insight into the potential mechanism underlying anthocyanin biosynthesis in sweet potato tuberous roots with purple color.

Identification of Rhizospheric Actinomycete Streptomyces lavendulae SPS-33 and the Inhibitory Effect of its Volatile Organic Compounds against Ceratocystis Fimbriata in Postharvest Sweet Potato (Ipomoea Batatas (L.) Lam.).

Black spot disease, which is caused by the pathogenic fungal Ceratocystis fimbriata, seriously affects the production of sweet potato and its quality during postharvest storage. In this study, the preliminary identification of the rhizosphere actinomycete strain SPS-33, and its antifungal activity of volatiles in vitro and in vivo was investigated. Based on morphological identification and phylogenetic analysis of the 16S rRNA gene sequence, strain SPS-33 was identified as Streptomyces lavendulae. Volatile organic compounds (VOCs) emitted by SPS-33 inhibited mycelial growth and sporulation of C. fimbriata in vitro and also induced a series of observable hyphae morphological changes. In an in vivo pathogenicity assay, exposure to SPS-33 significantly decreased the lesion diameter and water loss rate in sweet potato tuberous roots (TRs) inoculated with C. fimbriata. It increased the antioxidant enzymes’ activities of peroxidase, catalase, and superoxide dismutase as well as decreased malondialdehyde and increased total soluble sugar. In the VOC profile of SPS-33 detected by a headspace solid-phase micro extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), heptadecane, tetradecane, and 3-methyl-1-butanol were the most abundant compounds. 2-Methyl-1-butanol, 3-methyl-1-butanol, pyridine, and phenylethyl alcohol showed strong antifungal effects against C. fimbriata. These findings suggest that VOCs from S. lavendulae SPS-33 have the potential for pathogen C. fimbriata control in sweet potato postharvest storage by fumigant action.

Effect of Nitrogen Fertilizer Types and Microelements on Growth, Yield and Chemical Constituents of Tuberous Root of Sweet Potato (Ipomoean batatas L, Lam)

Effect of Nitrogen Fertilizer Types and Microelements on Growth, Yield and Chemical Constituents of Tuberous Root of Sweet Potato (Ipomoean batatas L, Lam)

Sprouting and metabolism of sweet potatoes roots cv. BRS Rubissol during storage

Sprouting and mass loss in sweet potato tuberous roots stored at room temperature compromise the quality and commercialization; nevertheless, sprouting control methods are very limited. The objective was to evaluate the control of sprouting and metabolic changes in tuberous roots of sweet potato cv. BRS Rubissol treated with ethylene (10 ?L L-1), amino-oxyacetic acid - AOA (1 mg L-1) and 1-methylcyclopropene - 1-MCP (1 mg L-1) during storage for five weeks at 25 °C and 90% relative humidity. The following variables were evaluated: mass loss, number and length of sprouts, activity of peroxidase and polyphenoloxidase enzymes, total soluble sugars, starch, anthocyanins, flavonols, malonaldehyde content and total proteins. During storage the mass loss, number and length of sprouts were lower in roots treated with AOA and 1-MCP. The activity of peroxidase and polyphenoloxidase enzymes was higher in roots treated with ethylene. Total soluble sugars increased and the starch contents decreased in all treatments. Levels of anthocyanins and total proteins reduced, while flavonoids and malondialdehyde increased during storage. Sprouting was controlled in roots treated with AOA and 1-MCP, extending shelf life and improving marketing potential.

Diversity and distribution of sweet potato weevils (Cylas spp.) in southern Benin

Sweet potato (SP) weevils, Cylas spp. are important pests of SP throughout the world and particularly in Africa. They cause damage to the crop as a result of their diet and reproduction. This study was undertaken to identify species of Cylas attached to SP production in southern Benin and to assess the distribution of the insects in study areas. A survey was conducted from October to December 2015 in fifteen districts of the departments of Mono, Couffo, Ouémé and Plateau in agro-ecological zones 6, 7 and 8 of Southern Benin. Weevil adults were collected alone in bulk but also along with infested vines and tuberous roots. Sweet potato vines and tuberous roots were incubated in laboratory for emergency of insect adults. Two species of Cylas were identified: C. puncticollis Boheman and C. brunneus Schoenherr. Cylas puncticollis were observed in 82.70% of total samples collected and were found in all districts prospected while C. brunneus were observed in 17.42% of the samples and were observed only in the districts of Adjohoun, Bopa, Houéyogbé, Ifangni and Klouékanmè. The highest incidence (100.00 ± 0.00%) and the lowest incidence (0.00 ± 0.00%) were recorded with C. puncticollis and C. brunneus, respectively, in the districts of Aplahoué, Comè, Sakété, Adja-Ouèrè and Toviklin. All SP farmers used only vine cuttings for planting, with 10% of them treating planting material with chemical insecticides. Eighty percent of farmers use planting materials taken in their own fields whereas 20% obtain them from neighboring fields either free of charge or purchase them. This study gave use more detailed information on the identity and distribution of sweet potato weevils in Benin and was useful for the establishment of control measures against them.

Uncovering anthocyanin biosynthesis related microRNAs and their target genes by small RNA and degradome sequencing in tuberous roots of sweetpotato

BackgroundCompared with white-fleshed sweetpotato (WFSP), purple-fleshed sweetpotato (PFSP) is a desirable resource for functional food development because of the abundant anthocyanin accumulation in its tuberous roots. Some studies have shown that the expression regulation mediated by miRNA plays an important role in anthocyanin biosynthesis in plants. However, few miRNAs and their corresponding functions related to anthocyanin biosynthesis in tuberous roots of sweetpotato have been known.ResultsIn this study, small RNA (sRNA) and degradome libraries from the tuberous roots of WFSP (Xushu-18) and PFSP (Xuzishu-3) were constructed, respectively. Totally, 191 known and 33 novel miRNAs were identified by sRNA sequencing, and 180 target genes cleaved by 115 known ib-miRNAs and 5 novel ib-miRNAs were identified by degradome sequencing. Of these, 121 miRNAs were differently expressed between Xushu-18 and Xuzishu-3. Integrated analysis of sRNA, degradome sequencing, GO, KEGG and qRT-PCR revealed that 26 differentially expressed miRNAs and 36 corresponding targets were potentially involved in the anthocyanin biosynthesis. Of which, an inverse correlation between the expression of ib-miR156 and its target ibSPL in WFSP and PFSP was revealed by both qRT-PCR and sRNA sequencing. Subsequently, ib-miR156 was over-expressed in Arabidopsis. Interestingly, the ib-miR156 over-expressing plants showed suppressed abundance of SPL and a purplish phenotype. Concomitantly, upregulated expression of four anthocyanin pathway genes was detected in transgenic Arabidopsis plants. Finally, a putative ib-miRNA-target model involved in anthocyanin biosynthesis in sweetpotato was proposed.ConclusionsThe results represented a comprehensive expression profiling of miRNAs related to anthocyanin accumulation in sweetpotato and provided important clues for understanding the regulatory network of anthocyanin biosynthesis mediated by miRNA in tuberous crops.

Foliar application of uniconazole improves yield through enhancement of photosynthate partitioning and translocation to tuberous roots in sweetpotato

ABSTRACTTo examine the effects of uniconazole (UCZ) on the distribution and transport of photosynthate in sweetpotatoes, three spraying levels of UCZ, 0 (control), 50 and 100 mg L−1, were exposed to an experimental field cultivated with Jishu26 (‘J26ʹ) and Xushu32 (‘X32ʹ) varieties. Compared to control, the distribution of carbon-13 (13C) was significantly higher in the tuberous roots of both varieties treated with UCZ. In addition, UCZ treatments promoted a desirable top-to-base sucrose gradient and significant greater declines in the top-to-bottom amino acid and potassium ion (K+) gradients along the stem. Higher tuberous root yields were found in the UCZ-treated ‘J26ʹ and ‘X32ʹ. In comparison to 50 mg L−1 UCZ, ‘J26ʹ treated with 100 mg L−1 UCZ exhibited significantly higher distribution ratio of 13C in tuberous root, and reductions in the top-to-bottom amino acid and K+ gradients along the stems at 105 and 150 days after planting. Furthermore, 100 mg L−1 of UCZ application exhibited a significantly higher tuberous root yield. For ‘X32ʹ, the two concentrations of UCZ demonstrated no significant differences in these parameters. A reasonable distribution structure of photosynthates that responsible for high yields is associated with the desirable sucrose, ammonia nitrogen (N) or K+ gradient along the stems caused by UCZ application.

First Report of Neoscytalidium dimidiatum Causing Root Rot in Sweet Potato in Brazil

In January 2018, a large number of tuberous roots of sweet potato were lost in a production field in Jaiba, State of Minas Gerais, Brazil. Immediately after harvest, the roots showed dark spots on the surface, extending to the center, causing an internal, brown to black necrosis. Two symptomatic roots (cultivar Canadense) from different parts of the field were subjected to fungus isolation by removal of fragments between symptomatic and healthy tissue, followed by surface sterilization in 70% ethanol and then in sodium hypochlorite (1%) for 1 and 3 min, respectively, rinsing in sterile water, and incubation in PDA plates for 25°C in the dark. A gray to black, fast-growing fungus with abundant arthroconidia in aerial mycelia was isolated from all samples after 4 days of incubation. Hyphal tips were excised and transferred to new PDA plates, and two pure cultures (isolates) were obtained. Based on these characteristics, the fungus was identified as Neoscytalidium. For morphological analysis, culture sporulation was induced as described by Machado et al. (2014). Microscopic examination of the fungal structures identified arthroconidia with one to two septa, released by hyphal fragmentation, 4.2 to 9.5 × 3.2 to 5.3 μm, and a pycnidial synanamorph with hyaline, ellipsoid to nearly fusiform conidia, 7.4 to 12.7 × 4.2 to 6.3 μm. The morphological characteristics were similar to Neoscytalidium dimidiatum (Phillips et al. 2013). To confirm species identification, genomic DNA was extracted, and sequences of the internal transcribed spacer of the rDNA and translation elongation factor 1-α (TEF1-α) were obtained (Machado et al. 2014) and deposited in GenBank (accession nos. MH636327, MH636328, MH349427, and MH349428, respectively). According to a BLAST search, the TEF1-α sequences showed 99% identity with N. dimidiatum (accession no. KF553902). A combined phylogenetic tree obtained by Bayesian inference using MrBayes version 3.1.1 (Ronquist and Huelsenbeck 2003) grouped the isolates within the N. dimidiatum clade, confirming the species identification. One representative isolate (URM 7888) was deposited in the culture collection “Micoteca URM Profa. Maria Auxiliadora Cavalcanti” at the Universidade Federal de Pernambuco (Recife, Brazil). The pathogenicity test was performed by inoculating asymptomatic roots (cultivar Canadense), previously sterilized on the surface with 0.5% sodium hypochlorite and unwounded or wounded with a sterile scalpel at two equidistant points, with conidia suspension. Arthroconidia suspension (20 μl, 2.4 × 10⁶ conidia/ml) obtained from 7-day-old colonies was pipetted onto the inoculation sites. Sterile distilled water was used for the control instead of inoculum. Five roots were used for each treatment. The inoculated roots were maintained in plastic boxes containing moistened paper towels at approximately 25°C for 15 days. After 7 days, it was possible to observe initial symptoms of internal brown to black rot, which increased in size after 15 days. The fungus was reisolated, and pathogenicity was confirmed. The control and unwounded roots remained asymptomatic. In Brazil, N. dimidiatum has been reported causing collar and root rot in physic nut (Machado et al. 2012), black root rot in cassava (Machado et. al., 2014), and dieback in mango (Marques et al. 2013). To our knowledge, this is the first report of N. dimidiatum causing root rot of sweet potato in Brazil.

Occurrence of internal browning in tuberous roots of sweetpotato and its related starch biosynthesis

Although sweetpotato is an important crop worldwide, there has been almost no research on the occurrence of internal browning (IB) to date. In this study, we clarified the mechanism of occurrence of the disorder by using two types of cultivars with different IB susceptibility. In cells around the secondary vascular tissue, large size of starch grains accumulated in IB-susceptible cultivar compared with resistant one. Histochemical observation performed on cells around the secondary vascular tissues showed the presence of high levels of polyphenol oxidase activity, chlorogenic acid, and hydrogen peroxide in cells from the IB-affected regions in IB-susceptible cultivar. Likewise, high levels of starch content, hydrogen peroxide concentration, and polyphenol content were detected in the affected regions of IB-susceptible cultivar. In IB-susceptible cultivar, both the transcript levels of gens related starch and polyphenol biosynthesis were higher at an early stage of root maturation, while the levels in resistant cultivar were low at this stage and thereafter increased relatively more moderately. These observations suggest that the occurrence of IB disorder in sweetpotato largely depends on the morphology and timing of accumulated starch grain in cells around the secondary vascular tissues.

Response of Sweet Potato Plants to Mineral and Bio-Fertilization

Two field experiments were carried out during the two successive summer seasons of 2016 and 2017 at a private farm near Kafr saad center, Damietta Governorate, Egypt to study the impact of NPK fertilization at (100%, 50% and 0% NPK of the recommended doses) and some bio-stimulants (without, effective microorganisms (EM) 2ml/L, microbial mixture 1L/20L, yeast extract 10g/L and seaweed extract 1g/L) as well as their interaction on yield and its components and quality parameters of sweet potato plants Abees cultiver. Obtained results showed that increasing NPK fertilization levels from 0% to 100% of the recommended doses gave significant increments in total yield/fed, dry matter and quality parameters i.e. crude protein (%), total carbohydrates (%), starch%, total sugar %, beta-carotene and vitamin-C (vit.c) in tuberous roots of sweet potato in the two seasons. All bio-stimulants treatments increased significantly of all the previous mentioned parameters and decreased nitrate and nitrite contents in tuberous roots compared with untreated plants, EM gave the best values of all studied parameters. Doses 100 % and 50 % NPK plus EM gave the best significant increases in the studied parameters in both seasons and the interaction between 0% NPK plus EM decreased significantly nitrate and nitrite contents in the both seasons.

Draft Genome Sequence of Burkholderia vietnamiensis Strain RS1, a Nitrogen-Fixing Endophyte Isolated from Sweet Potato.

Burkholderia vietnamiensis strain RS1 is an endophytic bacterium with nitrogen-fixing ability that was isolated from tuberous roots of sweet potato. Here, we present its draft genome of 6,542,727 bases that contains a cluster of genes associated with nitrogen fixation. This genome sequence will provide important insights into the plant growth-promoting potential of endophytic bacteria.

Histochemical observations and gene expression changes related to internal browning in tuberous roots of sweet potato (Ipomea batatas)

The mechanism underlying internal browning (IB), or brown discoloration, of the central region of tuberous roots of sweet potato (Ipomoea batatas) was examined. IB disorder begins in roots from approx. 90 days after transplanting, and the severity increases significantly with time. IB damage initially occurs in cells around the secondary vascular tissue, and the area per cell occupied by starch grains in this region was larger than in the unaffected region. High levels of reducing sugars, polyphenol oxidase (PPO) activities, chlorogenic acid, and hydrogen peroxide (H2O2) were detected in cells from the IB damaged regions. The content of sugar and polyphenols was higher in disks (transverse sections) with larger amounts of damaged tissues than in disks of sound root. The transcript levels of acid invertase (IbAIV) tended to be higher with greater IB severity, whereas fluctuation patterns of ADP-glucose pyrophosphorylase (IbAGPase), granule bound starch synthase (IbGBSS), and starch branching enzyme 1 (IbSBE1) were lower with higher IB severity. These observations suggest that the incidence of IB disorder in sweet potato is largely dependent on the excessive generation of reactive oxygen species (ROS) in cells around the secondary vascular tissues due to the abundant accumulation of sugar and/or starch grains during the root maturation period.

Low-temperature conditioning combined with cold storage inducing rapid sweetening of sweetpotato tuberous roots (Ipomoea batatas (L.) Lam) while inhibiting chilling injury

Sweetpotato tuberous roots (Ipomoea batatas (L.) Lam) are prone to chilling injury (CI) when stored at low temperature. Here, tuberous roots were subjected to low-temperature conditioning (LTC) at 10 °C for 5 d before exposure to chilling stress under cold storage at 4 °C for 28 d. After investigation of antioxidant and sugar metabolic responses to chilling stress, the results indicated that LTC treatment can enhance sweetness while effectively reducing CI observed in roots stored at 4 °C for 28 d. Moreover, LTC triggered increased sucrose levels, transcription of enzyme genes, and increased superoxide dismutase, catalase, and ascorbate peroxidase activities, while preventing increases in malondialdehyde content, relative leakage, and production of reactive oxygen species during cold storage. Furthermore, LTC may trigger beta-amylase gene transcription via C-repeat binding factor (CBF) pathway induction. Therefore, LTC combined with cold storage can induce fast sweetening in tuberous roots while preventing chilling injury.

Integrating Agronomic Practices for the Mitigation of Crack Formation on Sweet Potato Roots at Umudike, South Eastern Nigeria

Field experiment was conducted in 2013 cropping season to evaluate the effect of integrating different agronomic practices for mitigating crack formation on sweet potato (Ipomoea batatas) roots. Cracks are malformations on the edible roots of sweet potato which make them look unattractive, form portals for disease and pest invasion, lead to decay and high peeling loss, and reduce marketability and acceptability. The agronomic practices evaluated included; two nutrient sources NPK 20:10:10 and 15:15:15, four different harvest periods 3, 4, 5, and 6 months after planting (MAP) on the three varieties of sweet potato namely TIS87/0087, UMUSPO/1 and CIP440293. It was carried out at the Eastern farm of National Root Crops Research Institute Umudike Abia State which lies between latitude 40 151 and 70 N and longitude 150 291 N and 70 331 E at an elevation of 122m above sea level. The experimental design was a split plot arrangement fitted into a randomized complete block design, main plot was nutrient source, subplot was time of harvest, and sub subplot was variety. There were thirty six treatments replicated three times. The soil was classified as sandy loam. Data were collected on number of roots with cracks, total root number, total root fresh weight, and rot incidence. Results showed that the effect of the nutrient sources was not statistically significant at (P≤0.05) on crack formation more cracks were recorded on varieties UMUSPO/1 and CIP440293 (orange-fleshed) than TIS87/0087 (white-fleshed). Time of harvest was very highly significant (P<0.001) on number of roots with cracks. From this work it can be concluded that time of harvest and variety played important roles in the formation of the cracks in the tuberous roots of sweet potato which reduce the quality of the crop. The type of fertilizer used has no effect on the crack formations, root size and number while early harvest is recommended.

Sporamin induces apoptosis and inhibits NF-κB activation in human pancreatic cancer cells.

Sporamin, a Kunitz-type trypsin inhibitor (TI) from sweet potato tuberous roots, has demonstrated anti-tumor activity through poorly defined mechanisms. Furthermore, the effects of sporamin on pancreatic cancer have not been explored. Herein, we studied the effects of sporamin on two human pancreatic cancer cell lines, PANC-1 and BxPC-3. Sporamin significantly inhibited the cell viability and proliferation activity and induced apoptosis in PANC-1 and BxPC-3 cells. Consistently, in sporamin-treated PANC-1 and BxPC-3 cells, the anti-apoptotic proteins Bcl-2 and Bcl-XL were downregulated and the pro-apoptotic protein Bax was upregulated. Moreover, nuclear factor kappa B activation and IκBα phosphorylation were inhibited, and total IκBα expression was increased in sporamin-treated PANC-1 and BxPC-3 cells. Thus, our results suggest that the anti-tumor effects of sporamin in pancreatic cancer cells might result partly from induction of apoptosis by downregulating nuclear factor kappa B pathway.

Effect of high pressure on the saccharification of starch in the tuberous root of sweet potato (Ipomoea batatas)

We analyzed the effect of high hydrostatic pressure (HHP) treatment on reducing sugar production in the tuberous root of sweet potato (Ipomoea batatas), based on pressure-gelatinization of starch and subsequent saccharification by internal amylases. HHP treatment at up to 600MPa at ambient temperature for 10min did not apparently affect the reducing sugar concentration in tuberous root. However, HHP treatment at 100 to 500MPa and 60°C or 70°C for 10min increased reducing sugar concentration as both the pressure and temperature increased. The reducing sugar concentration after HHP treatment at 500MPa and 70°C for 10min was roughly comparable to that of the thermal treatment control (80°C for 10min under atmospheric pressure). HHP treatment enabled the gelatinization and enzymatic saccharification of starch in the tuberous root of sweet potato, at a lower temperature than required by thermal treatment at atmospheric pressure.

Effect of Foliar spraying with Yeast Extract and Hydrogen Peroxide on Yield and Quality of Sweet Potato

The present investigation was carried out during the two summer seasons of 2015 and 2016 at sharnoob vilage,Damanhur city, Behera governorate, Egypt, to study the effect of foliar application of yeast extract , hydrogen peroxide(H2O2) and combination of them on growth, yield and quality of sweet potato tuberous roots, using two sweet potatocultivars, Abees and Mabrouka. Generally, the results indicated that Abees cv. recorded maximum values of number ofshoots/ plant in the second season, plant length in the first season , foliage fresh weigh/ plant, total sugar %, reducingsugar %, carotene %, dry matter % and starch% contents of roots. Results showed also that spraying of yeast extract gavethe highest means values for all studied traits of vegetative characters of two cultivars; in both seasons. Moreover,spraying of yeast extract gave the highest significant means values for total yield of roots/plant, weight of marketableroots/plant, number of marketable roots/plant, total sugar %, reducing sugar %, carotene %,dry matter of roots % andstarch% contents in roots compared with other treatments in both seasons. The treatment combination of growing Abeescultivar and yeast extract recorded the highest mean values of the most studied characters compared with other treatments.

Transcriptome profiling of sweetpotato tuberous roots during low temperature storage

Sweetpotato [Ipomoea batatas (L.) Lam] is a globally important root crop with high industrial value. However, because sweetpotato tuberous roots undergo chilling injuries that negatively affect their quality at temperatures below 10 °C, postharvest damage during the winter season is a major constraint for industrialization. To understand chilling injury response during postharvest low temperature storage, we used next-generation sequencing technology to comprehensive analyze the transcriptome of tuberous roots stored at optimal (13 °C) or low temperature (4 °C) for 6 weeks. From nine cDNA libraries, we produced 298,765,564 clean reads, which were de novo assembled into 58,392 unigenes with an average length of 1100 bp. A total of 3216 differentially expressed genes (DEGs) were detected and categorized into six clusters, of which clusters 2, 4, and 5 (1464 DEGs) were up-regulated under low temperature. The genes in these three clusters are involved in biosynthesis of unsaturated fatty acids, pathogen defense, and phenylalanine metabolism. By contrast, genes in clusters 1, 3, and 6 (1752 DEGs), which were generally down-regulated at low temperature, encode antioxidant enzymes or are involved in glycerophospholipid, carbohydrate, or energy metabolism. We confirmed the results of the transcriptome analysis by quantitative RT-PCR. Our transcriptome analysis will advance our understanding of the comprehensive mechanisms of chilling injury during low temperature storage and facilitate improvements in postharvest storage of sweetpotato tuberous roots.

Effects of Planting Density and Harvesting Time on Production of Small-size Tuberous Roots in Sweet Potato

Small-sized tuber of sweet potato (Ipomoea batatas Lam.) is more preferred by Korean consumers, because it is convenient to eat with hands, and can easily be steamed or roasted in small pan as a healthy snack for a small family. The present study was aimed to investigate the effect of high-density plantings and harvesting times on production of smallsized tuber (50~200 g). Four varieties ('Annobeny', 'Daeyumi', 'Shinzami', and 'Yeonhwangmi') were planted in 2-row zigzag high-density planting (, A; , B) and 1-row planting (, control) covered with black vinyl film on May 23th, 2014. Marketable yields and small-sized tuber yields were compared between 120- and 150-day harvesting. Vine length and fresh weight per plant were significantly decreased in 2-row planting A and B plots compared to the control at 120 days after planting. Weight of tuber per plant, mean weight of tuber and number of tuber per plant were significantly decreased in 120-day harvesting of A and B plots than in the control. Marketable yields per 10a were increased by 17% () and 8% () in 120-day harvesting of A and B plots compared to the control (), and those were largely increased by 29% () and 26% () in 150-day harvesting than in the control (). Proportions of small size tuber (50~200 g) were increased by about 65% in 150-day harvesting of A and B plots compared to the control (55.3%). Small-size tuber yield and marketable yield were highly increased in 150-day harvesting of 2-row zigzag high-density planting A ().

Non-invasive acoustic sensing of tuberous roots of sweet potato (Ipomoea batatas) growing belowground

The study applies acoustic means for the detection of belowground tuberous roots of sweet potato by developing a novel non-invasive sensing technology based on propagation of frequency-modulated sound through the soil and its detection with acoustic band-pass filtering devices. The presence of tuberous roots hidden in the bed of sandy soil was successfully detected with the proposed acoustic approach, which is still primitive. However, this investigation may induce further studies and developments for belowground sensing and imaging techniques as novel ecological research tools and to support the introduction of vegetables into so-called plant factories.