Genes driving potato tuber initiation and growth: identification based on transcriptional changes using the POCI array

The increasing amount of available expressed gene sequence data makes whole-transcriptome analysis of certain crop species possible. Potato currently has the second largest number of publicly available expressed sequence tag (EST) sequences among the Solanaceae. Most of these ESTs, plus other proprietary sequences, were combined and used to generate a unigene assembly. The set of 246,182 sequences produced 46,345 unigenes, which were used to design a 44K 60-mer oligo array (Potato Oligo Chip Initiative: POCI). In this study, we attempt to identify genes controlling and driving the process of tuber initiation and growth by implementing large-scale transcriptional changes using the newly developed POCI array. Major gene expression profiles could be identified exhibiting differential expression at key developmental stages. These profiles were associated with functional roles in cell division and growth. A subset of genes involved in the regulation of the cell cycle, based on their Gene Ontology classification, exhibit a clear transient upregulation at tuber onset indicating increased cell division during these stages. The POCI array allows the study of potato gene expression on a much broader level than previously possible and will greatly enhance analysis of transcriptional control mechanisms in a wide range of potato research areas. POCI sequence and annotation data are publicly available through the POCI database (http://pgrc.ipk-gatersleben.de/poci).

Relationships between yield and mineral concentrations in potato tubers

There is concern that modern cultivars and/or agronomic practices have resulted in reduced concentrations of mineral elements essential to human nutrition in edible crops. Increased yields are often associated with reduced concentrations of mineral elements in produce, and a number of recent studies have indicated that, when grown under identical conditions, the concentrations of several mineral elements are lower in genotypes yielding more grain or shoot biomass than in older, lower-yielding genotypes. Potato is a significant crop, grown worldwide, yet few studies have investigated whether increasing yields, through agronomy or breeding, affects the concentrations of mineral elements in tubers. This article examines the hypothesis that increasing yields, either by the application of mineral fertilizers and/or by growing higher-yielding varieties, leads to decreased concentrations of mineral elements in tubers. It reports that the application of fertilizers influences tuber elemental composition in a complex manner, presumably as a consequence of soil chemistry and interactions between mineral elements within the plant, that considerable variation exists between potato genotypes in the concentrations of mineral elements in their tubers, and that, like in other crops, higher-yielding genotypes occasionally have lower concentrations of some mineral elements in their edible tissues than lower-yielding genotypes.

Bio-fortification of potato tubers using foliar zinc-fertiliser

Worldwide, many people are zinc (Zn)-deficient. Dietary Zn intake can be increased by producing crops with higher concentrations of Zn in their edible portions. This can be achieved by applying Zn-fertilisers to varieties with an increased ability to acquire Zn and to accumulate Zn in their edible portions. Potato (Solanum tuberosum L.) is an important food crop and is, therefore, a target for bio-fortification with Zn. Field trials incorporating a core collection of 23 potato genotypes, performed over 4 years (2006 – 2009), indicated significant genotypic effects on tuber Zn concentration and suggested that tuber Zn concentration was influenced by environmental effects, but also found that genotype environment (G E) interactions were not significant. Tuber Zn concentrations averaged 10.8 mg kg–1 dry matter (DM), and the ratio between the lowest and the highest varietal tuber Zn-concentration averaged 1.76. Tuber Zn concentrations could be increased by foliar Zn-fertilisation. Tuber yields of ‘Maris Piper’ were unaffected by foliar applications of < 1.08 g Zn plant–1. The relationship between tuber Zn concentration and foliar Zn application followed a saturation curve, reaching a maximum at approx. 30 mg Zn kg–1 DM at a foliar Zn application rate of 1.08 g plant–1. Despite a 40-fold increase in shoot Zn concentration compared to the unfertilised controls following foliar Zn fertilisation with 2.16 g Zn plant–1, only a doubling in tuber Zn concentration was observed. This suggests that the biofortification of tubers with Zn was restricted by the limited mobility of Zn in the phloem. A significant positive linear relationship between tuber Zn concentration and tuber N concentration supported the hypothesis of co-transport of Zn and N-compounds in the phloem.

Evidence for the complex relationship between free amino acid and sugar concentrations and acrylamide-forming potential in potato

Free amino acids and reducing sugars participate in the Maillard reaction during high-temperature cooking and processing. This results not only in the formation of colour, aroma and flavour compounds, but also undesirable contaminants, including acrylamide, which forms when the amino acid that participates in the reaction is asparagine. In this study, tubers of 13 varieties of potato (Solanum tuberosum), which had been produced in a field trial in 2010 and sampled immediately after harvest or after storage for 6 months, were analysed to show the relationship between the concentrations of free asparagine, other free amino acids, sugars and acrylamide-forming potential. The varieties comprised five that are normally used for crisping, seven that are used for French fry production and one that is used for boiling. Acrylamide formation was measured in heated flour, and correlated with glucose and fructose concentration. In French fry varieties, which contain higher concentrations of sugars, acrylamide formation also correlated with free asparagine concentration, demonstrating the complex relationship between precursor concentration and acrylamide-forming potential in potato. Storage of the potatoes for 6 months at 9°C had a significant, variety-dependent impact on sugar and amino acid concentrations and acrylamide-forming potential.

Acrylamide concentrations in potato crisps in Europe from 2002 to 2011

A dataset of manufacturers' measurements of acrylamide levels in 40,455 samples of fresh sliced potato crisps from 20 European countries for years 2002 to 2011 was compiled. This dataset is by far the largest ever compiled relating to acrylamide levels in potato crisps. Analysis of variance was applied to the data and showed a clear, significant downward trend for mean levels of acrylamide, from 763 +/- 91.1 ng g(-1) (parts per billion) in 2002 to 358 +/- 2.5 ng g(-1) in 2011; this was a decrease of 53% +/- 13.5%. The yearly 95th quantile values were also subject to a clear downward trend. The effect of seasonality arising from the influence of potato storage on acrylamide levels was evident, with acrylamide in the first 6 months of the year being significantly higher than in the second 6 months. The proportion of samples containing acrylamide at a level above the indicative value of 1000ngg(-1) for potato crisps introduced by the European Commission in 2011 fell from 23.8% in 2002 to 3.2% in 2011. Nevertheless, even in 2011, a small proportion of samples still contained high levels of acrylamide, with 0.2% exceeding 2000ngg(-1).

Acrylamide in potato crisps prepared from 20 UK-grown varieties: effects of variety and tuber storage time

Twenty varieties of field-grown potato were stored for 2 months and 6 months at 8 °C. Mean acrylamide contents in crisps prepared from all varieties at both storage times ranged from 131 μg per kg in Verdi to 5360 μg per kg in Pentland Dell. In contrast to previous studies, the longer storage period did not affect acrylamide formation significantly for most varieties, the exceptions being Innovator, where acrylamide formation increased, and Saturna, where it decreased. Four of the five varieties designated as suitable for crisping produced crisps with acrylamide levels below the European Commission indicative value of 1000 μg per kg (Saturna, Lady Rosetta, Lady Claire, and Verdi); the exception was Hermes. Two varieties more often used for French fries, Markies and Fontane, also produced crisps with less than 1000 μg per kg acrylamide. Correlations between acrylamide, its precursors and crisp colour are described, and the implications of the results for production of potato crisps are discussed.

Foraging strategies of natural enemies of the peach-potato aphid Myzus persicae

The foraging strategies of two natural enemies of the peach-potato aphid Myzus persicae: the seven-spot ladybird Coccinella septempunctata and the parasitoid wasp Diaeretiella rapae, were investigated. Specifically the roles of plant semiochemicals in the location of plants infested with M. persicae by these natural enemies were examined. I investigated the olfactory responses of female C. septempunctata to volatiles collected from M. persicae and four Brassica cultivars; Brassica rapa, B. juncea, B. napus cultivar ‘Apex’ and B. napus cultivar ‘Courage’ and wild-type Arabidopsis thaliana that were: undamaged, previously infested by M. persicae and infested with M. persicae. C. septempunctata showed no attraction to volatiles from M. persicae alone. C. septempunctata significantly changed its searching behaviour in response to plant volatiles from B. rapa, B. napus cv. ‘Apex’ and Arabidopsis infested with M. persicae. C. septempunctata was also found to display a significant turning bias when foraging on a branching horizontal wire stem. A model was developed to investigate how turning biases affect the foraging efficiency of C. septempunctata in dichotomous branched environments. Simulations using this model indicated that turning biases could potentially increase searching efficiency. D. rapae showed a significant preference for volatiles from M. persicae infested wild-type Arabidopsis but no preference to volatiles from M. persicae alone or M. persicae honeydew. Volatile emissions by Arabidopsis were shown to be localised to the area of aphid-infestation rather than systemic. Using gas chromatography plants infested with M. persicae were shown to emit a quantitatively different volatile blend than undamaged plants. In experiments with jasmonate mutants of Arabidopsis the jasmonate (octadecanoid) wound response pathway was implicated as being important for the production of M. persicae induced volatiles, attractive to D. rapae. Other wound response pathways were also found to be involved in the production of the full blend of M. persicae induced volatiles.

Effects of water availability on free amino acids, sugars, and acrylamide-forming potential in potato

Irrigation is used frequently in potato cultivation to maximize yield, but water availability may also affect the composition of the crop, with implications for processing properties and food safety. Five varieties of potatoes, including drought-tolerant and -sensitive types, which had been grown with and without irrigation, were analyzed to show the effect of water supply on concentrations of free asparagine, other free amino acids, and sugars and on the acrylamide-forming potential of the tubers. Two varieties were also analyzed under more severe drought stress in a glasshouse. Water availability had profound effects on tuber free amino acid and sugar concentrations, and it was concluded that potato farmers should irrigate only if necessary to maintain the health and yield of the crop, because irrigation may increase the acrylamide-forming potential of potatoes. Even mild drought stress caused significant changes in composition, but these differed from those caused by more extreme drought stress. Free proline concentration, for example, increased in the field-grown potatoes of one variety from 7.02 mmol/kg with irrigation to 104.58 mmol/kg without irrigation, whereas free asparagine concentration was not affected significantly in the field but almost doubled from 132.03 to 242.26 mmol/kg in response to more severe drought stress in the glasshouse. Furthermore, the different genotypes were affected in dissimilar fashion by the same treatment, indicating that there is no single, unifying potato tuber drought stress response.

Field phenotyping of potato to assess root and shoot characteristics associated with drought tolerance

Aims Potatoes are a globally important source of food whose production requires large inputs of fertiliser and water. Recent research has highlighted the importance of the root system in acquiring resources. Here measurements, previously generated by field phenotyping, tested the effect of root size on maintenance of yield under drought (drought tolerance). Methods Twelve potato genotypes, including genotypes with extremes of root size, were grown to maturity in the field under a rain shelter and either irrigated or subjected to drought. Soil moisture, canopy growth, carbon isotope discrimination and final yields were measured. Destructively harvested field phenotype data were used as explanatory variables in a general linear model (GLM) to investigate yield under conditions of drought or irrigation. Results Drought severely affected the small rooted genotype Pentland Dell but not the large rooted genotype Cara. More plantlets, longer and more numerous stolons and stolon roots were associated with drought tolerance. Previously measured carbon isotope discrimination did not correlate with the effect of drought. Conclusions These data suggest that in-field phenotyping can be used to identify useful characteristics when known genotypes are subjected to an environmental stress. Stolon root traits were associated with drought tolerance in potato and could be used to select genotypes with resilience to drought.

”Potato seeking rice”: language, culture, and identity in gay personal ads in Hong Kong

This paper examines the relationship between language, culture, and identity in a corpus of gay personal ads collected from two publications in Hong Kong in the three years before the 1997 transition of sovereignty. Gay personal ads are seen äs an "island of discourse," whose marginal nature is reflected in the use of language and in turn reflects issues of marginalization in the larger social context. Using Fairclough's (1992, 1993) three- dimensional model for critical discourse analysis, an attempt is made to uncover the relationship between text structure and issues ofpower/ideology in the society that produces the texts. On the level of text, it was found that structural components, particularly the degree of grammatical elaboration, differ according to the stated race or cultural background of the authors and their targets. On the level of discourse practice, authors were found to appropriate a variety of "voices"from the larger culture arena, the use of which amplifies or limits the participation of particular classes of individuals. Finally, on the level of social practice, the ads were found to reflect and re-create both the racial stereotypes and heterosexist ideology found in the dominant culture.

Interferência de uma comunidade de plantas daninhas com predominância de Ipomoea hederifolia na cana-soca

Levantamentos recentes da flora de plantas daninhas associada à cultura da cana-de-açúcar apontaram Ipomoea hederifolia como uma das espécies mais importantes. em virtude disso, objetivou-se determinar o potencial de redução da produtividade da cana-de-açúcar e da qualidade do caldo em resposta à interferência de uma comunidade de plantas daninhas com predomínio de I. hederifolia, bem como o período anterior à interferência (PAI). Foi instalado um experimento em Pitangueiras, SP, em que constituíram tratamentos nove períodos crescentes de convivência das plantas daninhas com a cultura (0, 16, 30, 44, 69, 97, 135, 160, 188 e 229 dias após o cultivo e adubação e início da brotação - DAB). O delineamento experimental foi em blocos casualizados, com cada tratamento em quatro repetições. Concluiu-se que o potencial de redução do número final de colmos e de produtividade foi de 34% e 46%, respectivamente. O PAI foi do início da brotação e se estendeu por 33 dias. Com o aumento do período de convivência com a comunidade infestante, houve antecipação do processo de maturação dos colmos, cujo caldo tendeu a apresentar maior valor de açúcar total recuperável (ATR). Com a redução de produtividade devido à interferência, o valor de ATR ha-1 tendeu a ser negativamente afetado.

Métodos de superação de dormência em sementes de Ipomoea e Merremia

Este trabalho objetivou avaliar os efeitos de métodos de superação de dormência sobre a germinação das sementes de Ipomoea grandifolia, I. hederifolia, I. nil, I. quamoclit, Merremia aegyptia e M. cissoides. Os tratamentos consistiram em ácido sulfúrico concentrado, nitrato de potássio, água quente e calor seco (50 ºC), lixa e fogo. Constatou-se que o ácido sulfúrico promoveu aumento na germinação das sementes de I. grandifolia (58, 37, 22 e 34%), I. hederifolia (76, 49, 82 e 55%), I. quamoclit (43, 33, 66 e 35%), I. nil (69, 79, 72 e 62%), M. cissoides (8, 19, 35 e 57%) e M. aegyptia (24, 64, 56 e 63%) após períodos de imersão de 5, 10, 15 e 20 minutos, respectivamente. A água (20 e 40 minutos), o calor seco (20 e 40 minutos) e o fogo melhoraram a germinação de I. grandifolia (68, 59, 62, 67 e 59%), M. cissoides (50, 52, 18, 25 e 46%) e M. aegyptia (54, 47, 21, 21 e 45%), respectivamente. O calor seco de 20 e 40 minutos melhorou a germinação de I. nil (49 e 36%), e o de 40 minutos, a de I. hederifolia (70%). O uso de nitrato de potássio e lixa não proporcionou melhoria na germinação das sementes.

Estimativa da área foliar de Ipomoea hederifolia e Ipomoea nil Roth: usando dimensões lineares do limbo foliar

Com o objetivo de obter uma equação que, por meio de parâmetros lineares dimensionais das folhas, permitisse a estimativa da área foliar de Ipomoea hederifolia e Ipomoea nil, estudaram-se correlações entre a área foliar real (Sf) e os parâmetros dimensionais do limbo foliar, como o comprimento ao longo da nervura principal (C) e a largura máxima (L), perpendicular à nervura principal. Todas as - equações exponenciais, geométricas ou lineares simples - permitiram boas estimativas da área foliar. do ponto de vista prático, sugere-se optar pela equação linear simples envolvendo o produto C x L, considerando-se o coeficiente linear igual a zero. Desse modo, a estimativa da área foliar de I. hederifolia pode ser feita pela fórmula Sf = 0,7583 x (C x L), ou seja, 75,83% do produto entre o comprimento ao longo da nervura principal e a largura máxima, ao passo que, para I. nil, a estimativa da área foliar pode ser feita pela fórmula Sf = 0,6122 x (C x L), ou seja, 61,22% do produto entre o comprimento ao longo da nervura principal e a largura máxima da folha.

Crescimento e nutrição mineral de Ipomoea nil

Um experimento em casa de vegetação foi conduzido entre novembro de 2005 e abril de 2006, na UNESP, campus de Jaboticabal, SP, objetivando estudar a produção de massa seca, a distribuição e o acúmulo de macronutrientes por Ipomoea nil, uma importante infestante de culturas anuais e perenes no Brasil. As plantas foram cultivadas em vasos de 7 litros com substrato de areia e irrigadas diariamente com solução nutritiva de Hoagland & Arnon. O delineamento experimental foi inteiramente casualizado, com quatro repetições. Os tratamentos corresponderam às épocas de avaliação, em intervalos de 14 dias, iniciandose 21 dias após a emergência (DAE). em cada avaliação, as plantas de quatro vasos foram analisadas quanto ao acúmulo de massa seca e à nutrição mineral. I. nil apresentou pequeno acúmulo de massa seca e de macronutrientes no início da fase experimental. Esses acúmulos se intensificaram após 77 DAE, atingindo o máximo valor teórico aos 123, 122, 124, 121, 119, 121 e 125 DAE, para massa seca, N, P, K, Ca, Mg e S, respectivamente. Folhas e caules foram os principais órgãos responsáveis pelo acúmulo de massa seca por plantas de I. nil. K e N foram os macronutrientes extraídos em maior quantidade por essa espécie.