Sugar Content Of Tubers Research Articles

Potassium management in potato production in Northwest region of China

Field trials were conducted to study response of potato (Solanum tuberosum L) yield and quality to potassium (K) application, soil indigenous K supply (IKS) and productivity (IKP), K use efficiency and critical level of soil test K to establish scientific methods for K management in potato production. Results indicated that K application increased tuber yield by a range of −2.8 to 7.2Mgha−1 with an average of 3.2Mgha−1, 90% positive responses. Potassium application produced an average of 4.9 percentage more commercial rate, 11.3g more mean tuber weight and 0.4 percentage more tuber starch content and 0.2 percentage less tuber sugar content than those of treatment without K application. The average agronomic efficiency of potassium (AEK) was 30.2kg tuber kg−1K2O, 56% observations was in 10–40kg tuber kg−1K2O. 79.2% of the observations showed negative K balance in potato fields with an average of 101.7kgKha−1 deficit. 87.5% of all the observations showed positive benefit from K application with an average return of US$715ha−1. The average IKS and IKP was 141.8kgKha−1 and 25.9Mgha−1 which can be explained 25% and 30% of variations, respectively, by soil exchangeable K. Significant negative quadratic relationship (R2=0.75, P<0.01) between yield response and relative yield, and significant linear relationship (R2=0.80, P<0.01) between yield response and AEK were obtained. There was a significant relationship (R2=0.74, P<0.01) between total uptake K by potato plant and total tuber yield. The critical level of soil exchangeable K at 90% relative yield was 105mgkg−1 which can be a reference for K recommendation.

Sugar metabolism, chip color, invertase activity, and gene expression during long-term cold storage of potato (Solanum tuberosum) tubers from wild-type and vacuolar invertase silencing lines of Katahdin.

BackgroundStoring potato tubers at low temperatures minimizes sprouting and disease but can cause an accumulation of reducing sugars in a process called cold-induced sweetening. Tubers with increased amounts of reducing sugars produce dark-colored, bitter-tasting fried products with elevated amounts of acrylamide, a possible carcinogen. Vacuolar invertase (VInv), which converts sucrose produced by starch breakdown to glucose and fructose, is the key determinant of reducing sugar accumulation during cold-induced sweetening. In this study, wild-type tubers and tubers in which VInv expression was reduced by RNA interference were used to investigate time- and temperature-dependent changes in sugar contents, chip color, and expression of VInv and other genes involved in starch metabolism in tubers during long-term cold storage.ResultsVInv activities and tuber reducing sugar contents were much lower, and tuber sucrose contents were much higher, in transgenic than in wild-type tubers stored at 3-9°C for up to eight months. Large differences in VInv mRNA accumulation were not observed at later times in storage, especially at temperatures below 9°C, so differences in invertase activity were likely established early in the storage period and maintained by stability of the invertase protein. Sugar contents, chip color, and expression of several of the studied genes, including AGPase and GBSS, were affected by storage temperature in both wild-type and transgenic tubers. Though transcript accumulation for other sugar-metabolism genes was affected by storage temperature and duration, it was essentially unaffected by invertase silencing and altered sugar contents. Differences in stem- and bud-end sugar contents in wild-type and transgenic tubers suggested different compartmentalization of sucrose at the two ends of stored tubers.ConclusionsVInv silencing significantly reduced cold-induced sweetening in stored potato tubers, likely by means of differential VInv expression early in storage. Transgenic tubers retained sensitivity to storage temperature, and accumulated greater amounts of sucrose, glucose and fructose at 3°C than at 7-9°C. At each storage temperature, suppression of VInv expression and large differences in tuber sugar contents had no effect on expression of AGPase and GBSS, genes involved in starch metabolism, suggesting that transcription of these genes is not regulated by tuber sugar content.

New food from a potato somatic hybrid: nutritional equivalence and safety assessment by a feeding study on rats

Potato tubers from the STBd somatic hybrid line that exhibited improved tolerance to salinity and resistance to fungal and PVY infections were characterised. They were compared for their chemical composition to the Spunta variety produced by conventional agronomic practices. This study aimed to compare nutritional value and safety by feeding rats with STBd or commercial tubers added to the standard diet (20/80 w/w). The analysis of soluble sugar, fat, fibre and ash content of tubers did not reveal any significant differences between the hybrid line and the control Spunta variety. Small differences were observed in dry matter, starch and protein content of hybrid potatoes in comparison to controls. However, all values were within normal ranges reported in the literature. The feeding study on rats showed that overall health, weight gain, food consumption, morphological aspects and weights of organs were comparable between rat groups fed the STBd hybrid and the Spunta variety. Taken together, 28 days of consumption of STBd hybrid potato did not exert any adverse effect on rats compared with commercial Spunta potato. The STBd potato line was therefore considered to be as safe for food utilisation as the commercial variety.

The potato amylase inhibitor gene SbAI regulates cold-induced sweetening in potato tubers by modulating amylase activity.

Potato cold-induced sweetening (CIS) is critical for the postharvest quality of potato tubers. Starch degradation is considered to be one of the key pathways in the CIS process. However, the functions of the genes that encode enzymes related to starch degradation in CIS and the activity regulation of these enzymes have received less attention. A potato amylase inhibitor gene known as SbAI was cloned from the wild potato species Solanum berthaultii. This genetic transformation confirmed that in contrast to the SbAI suppression in CIS-resistant potatoes, overexpressing SbAI in CIS-sensitive potatoes resulted in less amylase activity and a lower rate of starch degradation accompanied by a lower reducing sugar (RS) content in cold-stored tubers. This finding suggested that the SbAI gene may play crucial roles in potato CIS by modulating the amylase activity. Further investigations indicated that pairwise protein-protein interactions occurred between SbAI and α-amylase StAmy23, β-amylases StBAM1 and StBAM9. SbAI could inhibit the activities of both α-amylase and β-amylase in potato tubers primarily by repressing StAmy23 and StBAM1, respectively. These findings provide the first evidence that SbAI is a key regulator of the amylases that confer starch degradation and RS accumulation in cold-stored potato tubers.

Zmiana zawartości cukrów w odmianach bulw ziemniaka w zależności od sposobu odchwaszczania

The research results are derived from a field experiment, which was carried out between the years 2008–2010. The aim of the study was to determine the effect of the weed control methods with herbicides (Command 480 EC 0.2 l/ha, Command 480 EC 0.2 l/ha + Afalon Dyspersyjny 450 SC 1.0 l/ha, Stomp 3.5 l/ha, Stomp 3.5 l/ha + Afalon Dyspersyjny 450 SC 1.0 l/ha) on the total sugar content, reducing sugars and sacharose in the tubers of three cultivars (Cekin, Satina, Tajfun) potato. Statistical analysis showed no significant effect of weed control methods and cultivar on the total sugar content, reducing sugars and sucrose in potato tubers. However, the results showed that sugar content depended significantly on weather conditions during the growing season. Wyniki badań pochodzą z doświadczenia polowego przeprowadzonego w latach 2008–2010. Celem pracy było określenie wpływu sposobów odchwaszczania z zastosowaniem herbicydów (Command 480 EC 0,2 l/ha, Command 480 EC 0,2 l/ha + Afalon Dyspersyjny 450 SC 1,0 l/ha, Stomp 3,5 l/ha, Stomp 3,5 l/ha + Afalon Dyspersyjny 450 SC 1,0 l/ha) na zawartość sumy cukrów, cukrów redukujących i sacharozy w bulwach trzech odmian (Cekin, Satina, Tajfun) ziemniaka jadalnego. Analiza statystyczna nie wykazała istotnego wpływu sposobów odchwaszczania i odmian na zawartość cukrów ogółem, redukujących i sacharozy w bulwach ziemniaka. Zależały one istotnie tylko od warunków pogodowych panujących w okresach wegetacji.

Novel candidate genes influencing natural variation in potato tuber cold sweetening identified by comparative proteomics and association mapping

BackgroundHigher plants evolved various strategies to adapt to chilling conditions. Among other transcriptional and metabolic responses to cold temperatures plants accumulate a range of solutes including sugars. The accumulation of the reducing sugars glucose and fructose in mature potato tubers during exposure to cold temperatures is referred to as cold induced sweetening (CIS). The molecular basis of CIS in potato tubers is of interest not only in basic research on plant adaptation to environmental stress but also in applied research, since high amounts of reducing sugars affect negatively the quality of processed food products such as potato chips. CIS-tolerance varies considerably among potato cultivars. Our objective was to identify by an unbiased approach genes and cellular processes influencing natural variation of tuber sugar content before and during cold storage in potato cultivars used in breeding programs. We compared by two-dimensional polyacrylamide gel electrophoresis the tuber proteomes of cultivars highly diverse for CIS. DNA polymorphisms in genomic sequences encoding differentially expressed proteins were tested for association with tuber starch content, starch yield and processing quality.ResultsPronounced natural variation of CIS was detected in tubers of a population of 40 tetraploid potato cultivars. Significant differences in protein expression were detected between CIS-tolerant and CIS-sensitive cultivars before the onset as well as during cold storage. Identifiable differential proteins corresponded to protease inhibitors, patatins, heat shock proteins, lipoxygenase, phospholipase A1 and leucine aminopeptidase (Lap). Association mapping based on single nucleotide polymorphisms supported a role of Lap in the natural variation of the quantitative traits tuber starch and sugar content.ConclusionsThe combination of comparative proteomics and association genetics led to the discovery of novel candidate genes for influencing the natural variation of quantitative traits in potato tubers. One such gene was a leucine aminopeptidase not considered so far to play a role in starch sugar interconversion. Novel SNP’s diagnostic for increased tuber starch content, starch yield and chip quality were identified, which are useful for selecting improved potato processing cultivars.

Transgene coding of a key enzyme of the glycolytic pathway helps to decrease sugar content in potato tubers

Cold-stored potato tubers gradually accumulate reducing sugars. A proposed reason is a cold-induced blocking of glycolysis. The introduction and expression of the bacterial gene Lbpfk coding for cold-tolerant phosphofructokinase might counteract this effect. We have recently introduced this gene into several Czech potato cultivars. The obtained transgenic lines were then tested for three years in field trials. In 17 transgenic lines derived from two of the cultivars we have investigated the accumulation of reducing sugars during two and four months of cold storage. Although in all transgenic lines the sugar content still increased between the 2&lt;sup&gt;nd&lt;/sup&gt; and the 4&lt;sup&gt;th&lt;/sup&gt; month of cold-storage, the level of reducing sugars was in all transgenic lines after both two and four months of cold storage considerably lower than in the original cultivars. The extent of sugar accumulation was also influenced by the parental genotype. No significant differences in sugar accumulation were observed between the transgenic lines from the same parent.&amp;nbsp;

Seleção de clones de batata para processamento industrial em condições de clima subtropical e temperado

O objetivo deste trabalho foi selecionar clones de batata para processamento industrial, cultivados em condições de clima subtropical e temperado do Sul do Brasil. Foram avaliados 30 clones avançados e três cultivares (testemunhas), na primavera de 2007 e 2008, e no outono de 2008, em Júlio de Castilhos, RS (condição de clima subtropical), e no verão de 2008 e 2009, em São Joaquim, SC (condição de clima temperado). Utilizou-se o delineamento experimental de blocos ao acaso, em arranjo fatorial (33 clones em 5 ambientes), com duas ou três repetições de dez covas. Foram avaliados: a produção por cova, a aparência, a cor de chips e os teores de matéria seca e de açúcares redutores dos tubérculos. Houve interação significativa entre clones e ambientes para todas as características avaliadas, exceto quanto à cor de chips. A produção por cova e o teor de matéria seca dos tubérculos foram maiores no cultivo de verão. As condições ambientais de cultivo afetaram todos os caracteres avaliados. As condições de cultivo do Sul do Brasil possibilitam a seleção de clones de batata, com suficiente teor de matéria seca, para atender às exigências da indústria de processamento de batata.

Effect of Composted Organic and Mineral Fertilizers Mixture on Some Important Characters of Potato Plants Grown in Desert Land

Two field experiments were conducted at the Research Farm of the Environmental Studies and ResearchInstitute, Menoufiya University, Sadat City, Egypt; during the two winter seasons of 2006/2007 and 2007/2008. The objective of this investigation was to study the effects of two methods of composite of organic and mineral fertilizers mixture through , two systems of fertilizing, i.e., external compost with mineral fertilizers, external compost with bio-fertilizer; internal compost with mineral fertilizers; and internal compost with bio-fertilizer as well as the control; on some characters of potato tubers ofDiamont local cultivar. The obtained results indicated generally that the most important findings were as follows:- Plant height had the significantly highest value for the external compost with mineral fertilizer.-The four treatments under study did not vary significantly regarding plant fresh weight being significantly higher than the control.-Treatments of the external compost with mineral and biofertilizer and internal compost with bio-fertilizer gave highly significantly increment in tuber weight as compared to the control.-The significantly highest total yield (ton/fed) was achieved by treatment of external compost with mineral and bio-fertilizer.-Treatments of the external compost with bio-fertilizer and internal compost with bio-fertilizer gave significantly the highest tuber dry matter (%).- Starch and sugar content of tubers exhibited significantly different values due to the treatment applied and the season of growth.In conclusion, despite the superiority of the four treatments to the control, the treatment of externalcompost with mineral fertilizers was the best in terms of improvement the vegetative and yield properties. This treatment was followed by the treatment of external compost with bio-fertilizer.

Analysis of sugars by liquid chromatography-mass spectrometry in Jerusalem artichoke tubers for bioethanol production optimization

Sustainability of biofuels is increasingly taken into account; therefore, sustainable production technologies are needed. There has been a long history of converting Jerusalem artichoke into ethanol. Jerusalem artichoke (Helianthus tuberosus L.) is a low-requirement crop, it has a high carbohydrates yield and, nowadays, it does not interfere with food chain. It is, then, a promising energy crop for sustainable bioethanol production. However, the main storage carbohydrate of Jerusalem artichoke, inulin, can not be directly fermented by classic fermentation yeasts, so, either a hydrolysis followed by fermentation with classical yeast or the use of yeasts with inulinase activity are required to obtain bioethanol. Therefore, it is needed to know not only total sugar content, but also their composition, for the bioethanol production optimization from Jerusalem artichoke tubers. Several methods have been used in literature for carbohydrates analysis present in Jerusalem artichoke tubers. However, for further development of carbohydrate analysis, faster and more reliable identification and peak confirmation, mass spectrometry (MS) detection is required. In this paper, liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS) was used as an alternative technique to analyse sugars content and composition in tubers from Jerusalem artichoke. Two simple, rapid, sensitive and specific LC-ESI-MS methods were developed under the positive ionization mode. Glucose, fructose, sucrose, kestose and inulin were determined. Furthermore, inulin profile can be characterized. Analytical reversed phase LC columns were used using only water as eluent. These methods can be useful to optimize the whole bioethanol production chain from Jerusalem artichoke.

Resistance levels and fitness of glufosinate-resistant transgenic sweet potato in field experiments

Transgenic herbicide-resistant sweet potato plants [ Ipomoea batatas (L.) Lam.] produced through a biolistic transformation were used in this study. The objectives of this research were to (a) quantify resistance levels of transgenic sweet potato expressing the bar gene to glutamine synthetase (GS)-inhibitors, glufosinate and methionine sulfoximine, protoporphyrinogen oxidase (PPO)-inhibiting herbicide, oxyfluorfen and photosynthesis-inhibiting herbicide, paraquat; (b) compare the relative chlorophyll content, quantum yield, growth, and tuberous root yield between transgenic and wild-type sweet potato; (c) compare the response of transgenic and wild-type sweet potato plants to chilling and high temperature, and (d) compare amino acids, minerals and sugar contents of transgenic and wild-type sweet potato tubers. The transgenic sweet potato lines were 20–82-fold more resistant to glufosinate than the wild-type. The representative transgenic line 7171 also showed resistance to methionine sulfoximine, but was not resistant to oxyfluorfen and paraquat, which have different target sites. The stem length, number of leaves, petiole length, shoot fresh weight, and storage roots of transgenic lines were lower than those of the wild-type in field experiments. Reduced growth and root yield were not due to reduced quantum yield and relative chlorophyll contents. Glufosinate increased the ammonium accumulation in leaves of wild-type plants, but had minimal or no effect on leaves of transgenic line 7171. There were differences in mineral contents, free sugars, total amino acids, and free amino acids in the petiole and storage roots between wild-type and line 7171. There was no difference in drought tolerance between wild-type and line 7171, but the transgenic line was more tolerant to chilling temperature than wild-type plants. Follow-up research is required to elucidate the mechanisms underlying the growth and yield differences, different nutritional values, and differential response to low temperature between wild-type and transgenic sweet potato.

Natural diversity of potato (Solanum tuberosum) invertases

BackgroundInvertases are ubiquitous enzymes that irreversibly cleave sucrose into fructose and glucose. Plant invertases play important roles in carbohydrate metabolism, plant development, and biotic and abiotic stress responses. In potato (Solanum tuberosum), invertases are involved in 'cold-induced sweetening' of tubers, an adaptive response to cold stress, which negatively affects the quality of potato chips and French fries. Linkage and association studies have identified quantitative trait loci (QTL) for tuber sugar content and chip quality that colocalize with three independent potato invertase loci, which together encode five invertase genes. The role of natural allelic variation of these genes in controlling the variation of tuber sugar content in different genotypes is unknown.ResultsFor functional studies on natural variants of five potato invertase genes we cloned and sequenced 193 full-length cDNAs from six heterozygous individuals (three tetraploid and three diploid). Eleven, thirteen, ten, twelve and nine different cDNA alleles were obtained for the genes Pain-1, InvGE, InvGF, InvCD141 and InvCD111, respectively. Allelic cDNA sequences differed from each other by 4 to 9%, and most were genotype specific. Additional variation was identified by single nucleotide polymorphism (SNP) analysis in an association-mapping population of 219 tetraploid individuals. Haplotype modeling revealed two to three major haplotypes besides a larger number of minor frequency haplotypes. cDNA alleles associated with chip quality, tuber starch content and starch yield were identified.ConclusionsVery high natural allelic variation was uncovered in a set of five potato invertase genes. This variability is a consequence of the cultivated potato's reproductive biology. Some of the structural variation found might underlie functional variation that influences important agronomic traits such as tuber sugar content. The associations found between specific invertase alleles and chip quality, tuber starch content and starch yield will facilitate the selection of superior potato genotypes in breeding programs.

Bud development in corydalis (Corydalis bracteata) requires low temperature: a study of developmental and carbohydrate changes

Spring geophytes require a period of low temperature for proper flower development but the mechanism that underlies the relationship between cold treatment and flowering remains unknown. The present study aims to compare the developmental anatomy and carbohydrate content of the tuberous geophyte Corydalis bracteata growing under natural winter conditions from 10 to -10 degrees C (field-grown) and under a mild temperature regime of 18 degrees C (indoor-grown plants). Samples were studied under light and electron microscopy. A histochemical test (periodic acid--Schiff's) was employed to identify starch in sectioned material. Sugars were analysed by capillary gas chromatography. Apoplastic wash fluid was prepared. Under natural conditions, shoots were elongated, and buds gained in dry mass and developed normally. For indoor-grown plants, these parameters were lower in value and, from December, a progressive necrosis of flower buds was observed. The tuber consisted of the new developing one, which was connected to the bud, and the old tuber with its starch reserve. Due to the absence of plasmodesmata between new and old tuber cells, sugar transport cannot be through the symplast. Thus, a potential apoplastic route is proposed from old tuber phloem parenchyma cells to the adjacent new tuber cells. Sugar content in buds during the autumn months (September-November) was lower for indoor-grown plants than control plants, whereas the sugar content in tubers during the same period was similar for plants from both temperature treatments. However, the amount of apoplastic sugars in tubers of field-grown plants was almost 15-fold higher than in indoor-grown tubers. The results suggest that low temperature activates the apoplastic route of sugar transport in C. bracteata tubers and a consequent carbohydrate delivery to the bud. In the absence of cold treatment, the carbohydrate reserve is locked in old tuber cells so the nutrient supply to the buds is suppressed, possibly leading to bud abortion.

IMPACTS OF DIFFERENT MATURITY STAGES AND STORAGE ON NUTRITIONAL CHANGES IN RAW AND COOKED TUBERS OF ORANGE-FLESHED SWEET POTATO (IPOMOEA BATATAS) CULTIVARS

ISHS III International Conference Postharvest Unlimited 2008 IMPACTS OF DIFFERENT MATURITY STAGES AND STORAGE ON NUTRITIONAL CHANGES IN RAW AND COOKED TUBERS OF ORANGE-FLESHED SWEET POTATO (IPOMOEA BATATAS) CULTIVARS

Nondestructive Determination of Sugar Content in Potato Tubers Using Visible and Near Infrared Spectroscopy

Near infrared (NIR) spectroscopy was investigated as a method for the nondestructive measurement of sugar content in intact potato tubers. The NIR spectra (400-1100 nm) of potato samples were acquired by fiber optics in the interactance mode. Calibration models for the prediction of the fructose and glucose contents were developed by a partial least squares statistical analysis method. The calibration model gave standard errors of prediction of 0.26 mg/g for fructose and 0.46 mg/g for glucose. The preliminary results showed that NIR spectroscopy gives a reasonable estimate that can be used for nondestructive sorting of potatoes according to their sugar content.

Seleção assistida por marcadores para teor de matéria seca e açúcares redutores em tubérculos de batata

A seleção precoce de clones que possuam níveis elevados de matéria seca e baixos teores de açúcares redutores é uma necessidade nos programas de melhoramento para a qualidade de processamento da batata (Solanum tuberosum L.) na forma de palitos fritos ou chips. A seleção precoce tornou-se possível com a utilização de marcadores genéticos, visto que permitem a identificação precisa de indivíduos superiores. Assim, procura-se cada vez mais encontrar marcadores capazes de caracterizar tais indivíduos e utilizá-los via seleção assistida. O objetivo deste trabalho foi avaliar a eficiência da seleção assistida, utilizando os marcadores identificados por ANDREU (2004) que estariam associados ao teor de matéria seca e açúcares redutores em tubérculos de batata. Clones provenientes de 20 famílias foram avaliados nas gerações de plântula (P), primeira geração clonal (C1) e segunda geração clonal (C2). As estimativas das correlações simples para os caracteres entre gerações foram significativas, porém, baixas, confirmando a inviabilidade de se efetuar a seleção precoce nas primeiras gerações com base apenas em informações fenotípicas. Os marcadores utilizados forneceram um total de 16 marcas. Pela regressão múltipla stepwise, apenas sete dessas marcas tiveram associação com os caracteres estudados. Além disso, nenhuma marca associada ao teor de matéria seca de tubérculos na geração C1 teve associação significativa na geração C2. Isso também foi observado com o teor de açúcares redutores, o que é um indicativo da interação QTLs x ambientes. A seleção assistida não se mostrou eficiente em relação à fenotípica em nenhum dos casos avaliados, portanto, não sendo útil em uma possível seleção precoce. Esses resultados indicam que tais marcadores não estão próximos aos genes controladores dos caracteres desejados, sendo necessária a identificação de novos marcadores mais associados que possibilitem maior eficiência da seleção assistida.

Yield formation and quality characteristics of early potatoes during a short growing period

The effects of nitrogen fertilization on the yield and quality of early potato (Solanum tuberosum L.) were studied at MTT Agrifood Research Finland during 1996–1997. Cultivars were harvested at three times. The experimental layout was a split-split-plot with harvest times as main plots and nitrogen fertilization and potato cultivars as the subplots. The fertilizer treatments were 60 and 120 kg N ha-1 and the cultivars tested were Timo, Gloria and Van Gogh. The harvest times were 57–62, 70–75 and 85–90 days after planting. Application of 120 kg N ha-1 intensifi ed canopy development and increased leaf area of the stands. At early harvest the tuber yield of all cultivars receiving the higher nitrogen application increased by 0.5–2.5 t ha-1. The highest yielding cultivar was Timo. At last harvest, the higher nitrogen treatment increased yield by 3.0–6.2 t ha-1. The highest yielding cultivars were Timo and Van Gogh. The dry matter content of tubers was very low, 13.8–17.2%, at the fi rst harvest and the higher nitrogen application reduced dry matter content by 0.3–1.0%. The highest fertilizer application rate resulted in the largest tuber size. Nitrogen application, however, affected the quality of potatoes by decreasing the dry matter content. The nitrate content in tubers increased signifi cantly with the increasing level of nitrogen. The range of nitrate content in tubers fl uctuated between 13 and 189 mg kg-1 fresh weight showing good controlling of nitrate values. Harvest time affected sucrose content and the reducing sugar content in tubers, but nitrogen fertilizer did not change the sugar content of tubers. As tuber yield and quality during a short growing season are affected mainly by intercepted radiation, methods to increase tuber yield should focus on reducing the time to emergence, improving haulm growth after emergence and increasing the harvest index.;

Impact of hot water treatment on sprouting, membrane permeability, sugar content and chip colour of reconditioned potato tubers following long‐term cold storage

AbstractBACKGROUND: The efficacy of hot water treatment in facilitating successful reconditioning of processing potato (Solanum tuberosum L.) cultivar Hermes following 6 months cold storage at 4.5 °C was examined. Tubers were subjected to hot water treatments (HWTs) at 52.5, 55.0, 57.5 and 60.0 °C for 0–60, 0–50, 0–40 and 0–20 min, respectively, and then reconditioned for 20 days at 16 °C before evaluated for sprouting, fresh weight loss, membrane permeability, sugar content and processing quality.RESULTS: The study demonstrates that in order to achieve complete inhibition of sprouting during potato reconditioning HWTs must exceed the thermal tolerance threshold of the tubers. Short‐duration HWT was effective in retarding sprout growth and tuber dehydration without significantly affecting storage parenchyma membrane permeability, tuber sugar content or processing quality. On the contrary, prolonged HWT caused extensive heat damage, loss of membrane integrity and induced an increase in tuber sucrose and reducing sugar content resulting in deterioration of chip colour in proportion to treatment duration.CONCLUSION: Although HWT at 52.5–60 °C following long‐term cold storage did not improve the processing quality of potato tubers after 20 days of reconditioning, future work is needed to evaluate the effect of short‐duration HWT on the permissible extent of reconditioning and subsequent processing quality. Copyright © 2008 Society of Chemical Industry

Natural DNA variation at candidate loci is associated with potato chip color, tuber starch content, yield and starch yield

Complex characters of plants such as starch and sugar content of seeds, fruits, tubers and roots are controlled by multiple genetic and environmental factors. Understanding their molecular basis will facilitate diagnosis and combination of superior alleles in crop improvement programs (“precision breeding”). Association genetics based on candidate genes is one approach toward this goal. Tetraploid potato varieties and breeding clones related by descent were evaluated for 2 years for chip quality before and after cold storage, tuber starch content, yield and starch yield. Chip quality is inversely correlated with tuber sugar content. A total of 36 loci on 11 potato chromosomes were evaluated for natural DNA variation in 243 individuals. These loci included microsatellites and genes coding for enzymes that function in carbohydrate metabolism or transport (candidate loci). The markers were used to analyze population structure and were tested for association with the tuber quality traits. Highly significant and robust associations of markers with 1–4 traits were identified. Most frequent were associations with chip quality and tuber starch content. Alleles increasing tuber starch content improved chip quality and vice versa. With two exceptions, the most significant and robust associations (q < 0.01) were observed with DNA variants in genes encoding enzymes that function in starch and sugar metabolism or transport. Comparing linkage and linkage disequilibrium between loci provided evidence for the existence of large haplotype blocks in the breeding materials analyzed.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-008-0746-y) contains supplementary material, which is available to authorized users.

Candidate Gene Approach to Identify Genes Underlying Quantitative Traits and Develop Diagnostic Markers in Potato

ABSTRACTPotatoes (Solanum tuberosum L.) and humans (Homo sapiens L.) are both outcrossing species. The phenotypic variation of both is controlled by environmental factors and by natural DNA polymorphisms between individuals. Therefore we adopt similar approaches as used in human population genetics, such as association mapping, to identify loci and their alleles that are causal for complex agronomic characters such as quantitative resistance to pathogens or tuber sugar content. Functional analysis of genes operating in resistance to pests and pathogens or in carbohydrate metabolism, either in potato itself or in other plants including the model species Arabidopsis thaliana (L.) Heynh., provides many functional candidates for these complex agronomic traits. In our approach, functional candidate genes are tested for linkage to quantitative trait loci (QTL) for pathogen resistance or tuber quality traits, thereby selecting positional candidates (genes colocalizing with a QTL). DNA polymorphisms in or physically linked to positional candidate genes are then evaluated in populations of tetraploid potato genotypes and tested for association with phenotypes evaluated in the same populations. We have used the candidate gene approach to identify DNA‐based markers that are diagnostic for quantitative resistance to late blight caused by Phytophthora infestans (Mont.) de Bary, to the root cyst nematode Globodera pallida (Stone), and for chip color in tetraploid potato cultivars and in advanced breeding clones.