Effects of Drying Processes on the Antioxidant Properties in Sweet Potatoes

The effects of different drying methods （hot-air drying, microwave drying and vacuum-freeze drying） on the antioxidant activity and antioxidants in sweet potato （lpomoea batatas L. Lain.） tubers were investigated to determine the potential drying process. Sweet potato tubers were cut into 5 mm thick slices, steamed at 100℃ for 10 rain, then dried in either hotair, microwave, or vacuum-freeze. The dried sweet potatoes in microwave possessed the highest antioxidant activity, while the lowest activity was observed in hot-air dried samples. The phenolic contents were positively correlated with scavenging activity and reducing power of DPPH^＋. The microwave drying retains the highest antioxidant activity with the highest content of phenolic compounds in dried sweet potatoes. β-carotene and ascorbic acid showed minor contribution to the antioxidant activity in dried sweet potatoes.     

Postharvest Treatment with β-Aminobutyric Acid Induces Resistance Against Dry Rot Caused by Fusarium sulphureum in Potato Tuber

The effectiveness ofpostharvest β-aminobutyric acid （BABA） treatment was studied for inducing resistance against dry rot caused by Fusarium sulphureum in tubers and slices of two potato cultivars （resistant cultivar Shepody and susceptible cultivar Xindaping）. The results showed that BABA at 100 mmol L-1 significantly reduced lesion diameter in inoculated both tubers and slices. The chemical at 100 mmol L-1 showed an effective reduction in infection ability ofF. sulphureum inoculated 48 and 72 h after treatment in slices of resistant cultivar, and 72 and 96 h in susceptible ones. BABA increased the activitives of peroxidase （POD）, polyphenoloxidase （PPO） and phenylalanine ammonialyase （PAL）, and accumulated the contents of lignin, flavonoids and phenolics in slices. The resistant cultivar had a stronger resistant response than the susceptible one. These findings suggest that the BABA treatment can induce the resistance in potato tubers, however, the inducing degree depends on the original level of resistance present in each cultivar.     

The Differentiation-and Proliferation-Inhibitory Effects of Sporamin from Sweet Potato in 3T3-L1 Preadipocytes

The aim of this study was to investigate the effect of different concentrations of sporamin on the differentiation and proliferation of 3T3-LI preadipocytes, providing the theoretical basis for the development of food to treat obesity and diabetes, The isolation and purification of sporamin from sweet potato species 55-2 were performed by ammonium sulphate precipitation in combination with ion-exchange and gel filtration chromatography. With berberine as a positive control, different concentrations ofsporamin （0.000, 0.125, 0.025, 0.250, 0.500, and 1.000 mg·mL^-1 were used to treat 3T3-L1 preadipocytes. Intracellular fat accumulation and the degree of adipogenesis were quantified using Oil Red O staining and colorimetry, Preadipocytes differentiation was measured by 3（4,5-dimethylthiazolyl-2-yl）-2,5-diphenyltetrazolium bromide （MTT） spectrophotometric assay. Two sporamin proteins, which were separated into sporamin A （31 kD） and sporamin B （22 kD）, could be purified by ion-exchange and gel filtration chromatography. After being treated by different concentrations of sporamin, the differentiation of 3T3-L1 preadipocytes was significantly inhibited, compared with the positive control. When the sporamin solution concentration was 0.500 mg mL-1, the accumulation of lipid droplets within the cells was significantly decreased and the optical density （OD） value of the solution from destained Oil Red O reached to 0.35, which was the lowest value （P〈 0.05）. The proliferation of 3T3-L1 preadipocytes was significantly inhibited by treating at higher sporamin concentrations. In addition, the inhibitory effect was more obvious with the prolonged treatment time （P〈 0.05）. The differentiation and proliferation of 3T3-L1 preadipocytes could be inhibited significantly by the addition of higher concentration sporamin. It was, therefore, suggested that the sporamin was potentially effective for weight loss.     

Physiological Indices and Selection of Methods on Rapid Identification for Sweet Potato Drought Resistance

The relationships between the changes of relative water content （RWC）, malondialdehyde （MDA） contents, superoxide dismutase （SOD） activity and free proline contents in sweet potato leaves, and drought resistant ability under different concentration of polyethylene glycol （PEG） treatment applied at rhizosphere of sweet potato seedlings were studied. A highly positive correlation between RWC and drought resistance （r =0.783, P〈0.01）, a highly negative correlation between MDA contents and drought resistance （r = -0.848, P〈0.01）, a highly positive correlation between SOD activity and drought resistance （r = 0.777, P〈0.01） was observed. Free proline contents in leaves was not related obviously to the sweet potato drought resistance under 25% PEG treatment. The stronger the drought resistance of variety, the less decrease of RWC and increase of MDA contents, the more increase of SOD activity. By determining these physiological indices in sweet potato leaves under 25% PEG treatment, rapid identification of drought resistant ability of different varieties can be obtained in the lab.     

Endogenous Hormone Concentration in Developing Tuberous Roots of Different Sweet Potato Genotypes

A field trial was conducted to investigate the changes of endogenous hormone concentration （EHC） during formation and thickening of tuberous roots in sweet potato （Ipomoea batatas L.） of different genotypes： Xushu 18, Minamiyutaka, and L trifida-K123. The results of this study suggested that the concentrations of zeatin riboside （ZR）, dihydro-zeatin riboside （DHZR）, abscisic acid （ABA）, indole-3-acetic acid （IAA）, and isopentenyl-adenine （IPA） of Xushu 18 and Minamiyutaka were significantly higher than those of I. trifida-K123. Dry tuberous root yields were positively correlated with the concentration of ABA, ZR, and DHZR at 1 or 5% significant level, but were not obviously correlated with the concentrations of IAA, IPA, and GA4. The concentrations of ABA, ZR and DHZR played very important roles in the tuberous root formation and thickening in sweet potato. The concentrations of ZR, DHZR, ABA, and IAA in the upper or inner portion of tuberous roots were significantly higher than those toward the end of the root or its outer portion. Meanwhile, EHC of large-sized tuberous roots were significantly higher than those of medium- or small-sized tubers during the early thickening period. In the rapid thickening period of tuberous roots, EHC of medium-sized tubers were the highest, However, at the late-thickening period, EHC of small-sized tubers ranked the highest.     

Effects of Variation in Activities of Starch-Sugar Metabolic Enzymes on Reducing Sugar Accumulation and Processing Quality of Potato Tubers

The experiment was designed, via storing potato tubers of cv. E-Potatol and E-Potato3 in different temperatures, to explore the variation patterns of reducing sugar (RS) and total sugar (TS) contents and enzyme activities that are involved in the pathway of starch-sugar metabolism aiming at identifying the main factors that influence the chip color. The results showed that low temperature in storage was a main factor that accelerated the accumulation of RS of the stored tubers and a very significant linear relationship existed between RS content and chip color index (CCI) of the tubers. Further analysis elucidated that when tubers stored at 4℃, the activities of ADP glucose pyrophosphorylase (AGPase), UDP glucose pyrophosphorylase (UGPase) and sucrose synthase (SuSy) were negatively exponential to the RS content significantly while that of acid invertase and alkaline invertase was significantly linear to RS content. It suggested that these enzymes could play main roles in the cold sweetening of potato tubers through regulating starch-sugar metabolism.     

Effect of germination on the nutritional quality of Pearl millet

Changes in proximate composition, trypsin inhibitor activity, phytic acid, tannins, in vitro protein digestibility and amino acids content of Pearl millet were investigated after germination for 5 days. Germination significantly increased protein content of pearl millet, with a parallel decrease in lipid and carbohydrates. Trypsin inhibitor activity and the phytic acid content showed significant decrease whereas tannin content increased after 5 days germination. In vitro protein digestibility （IVPD） was significantly decreased with germination, suggesting that tannins may be responsible for enzymes inhibition. Amino acid analysis revealed significant increase in essential amino acids and none essential amino acids.     

The Effect of Washing and Inhibitor on Cathepsin Activity of Silver Carp

The effect of washing and temperature on the activity of cathepsins of Silver carp was studied. The result showed that the activity of cathepsin L was higher than those of cathepsin B and H. The total catalysis activity of these three enzymes was the highest at 55 C after washing. The inhibiting effect of soybean protein and potato starch on cathepsin L also had been studied,the results showed that soybean protein and potato starch could decrease activity of cathepsins L significantly.     

Ethylene Gas for Sprout Control in Processing Potato Storages

Ethylene was tested as a sprout inhibitor on potatoes intended for processing over the 2006-2007 and the 2007-2008 storage seasons. Russet Burbank, Shepody, Innovator, FL-1867, and FL-1833 were loaded into the University of Maine potato research facility in October of 2006. Ethylene gas was metered into the storage until a concentration of 0.1 ppm was reached and then held for one week. At weekly intervals, the ethylene concentration was increased to 0.3 ppm, 0.6 ppm, 12 ppm, 5.0 ppm and 102 ppm. Subsequently, the concentration was maintained at 10.0 ppm for the duration of the storage season. Control potatoes received chlorpropham （CIPC） for sprout control. The trial was repeated in the 2007-2008 storage season. The Agtron readings were performed on the processed potatoes at the end of the storage season. There was no difference in the US color grade between the CIPC-treated and ethylene-treated tubers within any tested variety in either storage season. Sprout inhibition of the ethylene-treated potatoes was acceptable for normal storage length of the potato varieties tested. Ethylene may have promise as an alternate to CIPC for sprout control in potato storages.     

ISSR-Based Molecular Characterization of an Elite Germplasm Collection of Sweet Potato （Ipomoea batatas L.） in China

To determine the genetic diversity and population structure of sweet potato accessions cultivated in China, and to establish the genetic relationships among their germplasm types, a representative collection of 240 accessions was analyzed using inter-simple sequence repeat （ISSR） markers. The mean genetic similarity coefifcient, Nei’s gene diversity, and shared allele distance of tested sweet potato accessions were 0.7302, 0.3167 and 0.2698, respectively. The 240 accessions could be divided into six subgroups and ifve subpopulations based on neighbor-joining （NJ） clustering and STRUCTURE results, and obvious genetic relationships among the tested sweet potato accessions were identiifed. The marker-based NJ clustering and population structure showed no distinct assignment pattern corresponding to lfesh color or geographical ecotype of the tested sweet potato germplasm. Analysis of molecular variance （AMOVA） revealed small but signiifcant difference between white and orange-lfeshed sweet potato accessions. Small but signiifcant difference were also observed among sweet potato accessions from the Southern summer-autumn sweet potato region, the Yellow River Basin spring and summer sweet potato region and the Yangtze River Basin summer sweet potato region. This study demonstrates that genetic diversity in the tested sweet potato germplasm collection in China is lower than that in some reported sweet potato germplasm collections from other regions. Pedigree investigations suggest that more diverse Chinese sweet potato varieties should be formed by broadening the selection scope of breeding parents and incorporating the introduced varieties into future breeding programs.     

Effects of Soil Aeration on Sweet Potato Yield and Its Physiological Mechanism

The effects of soil aeration on physiological characters and root tuber yield of Ipomoea batatas (L.) Lam. CV Lushu7 and Xushu18 were studied. The results showed that soil aeration improvement could increase ATP content and ATPase activity in functional leaves and root tubers and ABA content in root tubers.It also accelerated the transportation of 14C-photosynthate from leaves to root tubers and enhanced dry matter distribution in root tubers and thus root tuber yield was significantly raised. The role of ATP, ATPase and ABA in accelerating the transportation of 14C-photosynthate was discussed based on the changes of soluble carbonhydrate content in sweet potato plant.     

超声-微波协同萃取法提取紫薯色素

分析6种紫薯的主要组成成分,确定紫薯王作为提取紫薯色素的最佳原料,并研究超声-微波协同萃取法的最佳提取工艺条件和紫薯色素的稳定性。结果表明,紫薯色素最佳的提取工艺条件为超声功率50 W,微波功率135 W,微波时间7.5 min,料液比1∶20（g/ml）;紫薯色素在pH值〈3和温度〈60℃的条件下较稳定。     

烟草液泡转化酶抑制子基因调控马铃薯块茎低温还原糖累积的研究

【目的】克隆烟草液泡转化酶抑制子基因，并在马铃薯中表达，从而抑制低温贮藏块茎还原糖积累，提高马铃薯加工品质。【方法】通过RT-PCR法分离Nt-VIF全长cDNA，转化马铃薯植株，PCR、Northern杂交和Southern杂交检测转基因植株，转基因植株块茎在低温和常温条件下贮藏30 d，分析转化酶活性与还原糖含量。【结果】克隆到Nt-VIF全长cDNA，35S调控下正向的Nt-VIF基因cDNA已经成功转入鄂马铃薯3号（E3）植株。转基因植株块茎在4℃和20℃贮藏30 d表明，VI活性受温度调节，高温贮藏块茎的VI活性显著低于低温贮藏的块茎，且高温条件下转基因块茎与对照无显著差异，而低温条件下转基因块茎的VI活性与对照相比下降幅度为22.7%（株系A-3）～78.1%（株系A-31）。转基因块茎还原糖（RS）含量在高温贮藏条件下与对照差异亦不明显，而低温贮藏条件下RS含量下降幅度为20%（株系A-17）～80.5%（株系A-30）。进一步分析还表明，转基因块茎低温贮藏其液泡转化酶活性与还原糖含量呈显著正直线相关（RS = 0.289VI + 0.0736）。【结论】Nt-VIF基因的表达显著抑制了马铃薯液泡转化酶活性，导致还原糖积累降低。     

甘薯sporamin蛋白对3T3-L1前脂肪细胞分化和增殖的影响

 【目的】探讨甘薯sporamin蛋白对3T3-L1前脂肪细胞分化与增殖的影响,为开发预防和治疗肥胖、糖尿病的保健食品提供理论依据。【方法】采用硫酸铵沉淀、离子交换、凝胶过滤层析的方法对‘55-2’甘薯中的sporamin蛋白进行分离纯化。然后,以黄连素为阳性对照,用不同浓度sporamin（0、0.025、0.125、0.250、0.500、1.000 mg?ml-1）处理3T3-L1前脂肪细胞。采用油红O染色和比色定量检测细胞内脂肪生成及细胞分化程度,以MTT法检测细胞的增殖。【结果】经离子交换、凝胶层析可纯化出高纯度的sporamin蛋白A和B（相对分子量分别为31 kD和22 kD）。与空白相比,用不同浓度的sporamin蛋白处理后,3T3-L1前脂肪细胞的分化受到明显抑制。当sporamin蛋白浓度增至0.500 mg?ml-1时,脂滴生成量明显减少,洗脱液吸光度值降至最低为0.35（P＜0.05）。此外,高浓度的sporamin蛋白能有效地抑制3T3-L1前脂肪细胞的增殖,且随着处理时间延长抑制效果更加明显(P＜0.05).【结论】甘薯sporamin蛋白能抑制3T3-L1前脂肪细胞的分化和增殖,具有潜在的减肥作用。     

利用巴西牵牛试管苗检测甘薯组培苗病毒技术研究

为改进甘薯组培苗的病毒检测工艺,以甘薯病毒指示植物巴西牵牛(Ipomoea setosa)种子在MS+GA3 2.0 mg/L培养基上萌发苗的茎尖为外殖体,在MS+IBA 0.2 mg/L的培养基上茎尖能够发育成完整的试管植株且能够以单叶节扦插通过腋芽再植株生长方式快速繁殖;在试管中将巴西牵牛试管苗和甘薯试管苗茎段进行试管微嫁接后在MS0培养基上培养,15天后,与带病毒的甘薯试管苗嫁接的巴西牵牛茎段所带的叶片均表现出黄化、花叶等阳性反应。与不带病毒的甘薯试管苗茎段嫁接的巴西牵牛试管苗茎段所带的叶片都正常生长;用甘薯试管苗的无菌研提汁液感染巴西牵牛试管苗茎段切口后在MS0培养基上培养,15天后,被带病毒甘薯试管苗研提汁液感染的巴西牵牛试管苗茎段所带的叶片都表现出黄化、花叶等阳性反应,继续培养叶片枯死。被不带病毒甘薯试管苗研提汁液侵染的巴西牵牛试管苗茎段所带的叶片都能正常生长;以上2种方法可以替代传统的“巴西牵牛种子苗网室嫁接检测法”检测甘薯组培苗是否带有病毒。具有灵敏度高、检测结果不受外界环境影响、检测成本低、培养条件可控、不受季节性限制等优点。     

甘薯抗赖氨酸及其类似物的个体筛选

以赖氨酸及其类似物处理甘薯萌动种子。筛选对赖氨酸及其类似物反应不敏感、能过量积累赖氨酸的个体.探讨了赖氨酸及其类似物对鲜薯蛋白质含量、总氨基酸含量和赖氨酸的改良效果,并初步研究了R_1,R_2和R_3的遗传表现.研究认为,赖氨酸及其类似物处理甘薯萌动种子可明显地提高后代鲜薯的总氨基酸和赖氨酸含量,且可通过无性繁殖加以固定.     

甘薯早代品系部分数量性状的遗传相关分析

选用12个甘薯杂交组合的136个品系的无性1代和2代的7个农艺性状与鲜重进行相关分析和通径分析,并估算其遗传率。结果表明,大中薯重在两代的选择中都是重点考虑的因素。鲜薯重、大中薯重、地上部重等经济性状的遗传率不高,在早代品系选择时要综合其他性状。     

甘薯中咖啡酰奎尼酸类化合物的HPLC法比较分析

[目的]运用HPLC法比较分析11种甘薯不同部位绿原酸含量,为甘薯尤其是地上部分茎叶的开发利用提供参考。[方法]样品通过质量为200倍的甲醇超声提取20 min,乙腈-0.2%磷酸为流动相,梯度洗脱,对绿原酸、4,5-O-咖啡酰基奎尼酸、3,5-O-咖啡酰基奎尼酸、3,4-O-咖啡酰基奎尼酸形成良好分离,加标回收率分别为：94.74%、102.63%、100.01%和101.05%。[结果]不同甘薯品种间及同一品种不同部位间咖啡酰奎尼酸类化合物含量显著差异;地上部分以双咖啡酰奎尼酸含量为主,块薯中以绿原酸含量最高;各组织部位咖啡酰奎尼酸类化合物总量分别为：茎尖9.77～40.86 mg/g,成熟叶2.68～13.97 mg/g,茎干0.56～7.90 mg/g,块薯0.69～4.33 mg/g。[结论]甘薯茎尖和叶片可以作为绿原酸提取材料加于开发利用,其中紫甘薯系列优于非紫甘薯系列,试验中两个11ZY紫薯材料表现尤为突出。