No description available.

Thesis (M.S.)--Ohio State University. / Includes bibliographical references (leaves 79-81). Available online via OhioLINK's ETD Center

The Andean area of South America is the center of origin and diversity of the staple crop potato. Native Andean landraces represent a remarkable gene pool to exploit for the improvement of potato varieties. In the present study, the potential of the native germplasm was evaluated as a source of health-promoting compounds, and more particularly of dietary antioxidants. These phytochemicals receive an increasing interest due to their prospective effects on the prevention of various diseases such as cancers and cardiovascular diseases. In this study, a genetically diverse sample of 74 native potato cultivars (Solanum tuberosum L.) was field grown in 2004 in Huancayo (Peru, 3280 m above sea level). Using screening methods, we found a large variability of total phenolic, total carotenoid, and total vitamin C contents among the potato germplasm. The hydrophilic antioxidant capacity was also measured and was highly correlated with the total phenolics. On the basis of their contrasting contents, 23 potato cultivars were further selected for an in-depth analysis of their carotenoid, polyphenol, and tocopherol profiles. A wide range of antioxidant patterns could also be highlighted as well as cultivars of particular interest from a nutritional point of view. The stability of the ranking of cultivars across environment in terms of phenolic and carotenoid content was subsequently confirmed using 13 contrasted cultivars cultivated in 2005 in another highland environment (Huancani, Peru). This finding supports the fact that the potato genotype is the most determining factor of the observed variability. The effects of a drought stress on the dietary antioxidant contents were then investigated using a selection of five high antioxidant-contrasting cultivars. Drought-induced variations were complex with levels of antioxidants showing increase, decrease or remaining stable, depending on the genotype and the type of antioxidant considered. A gene expression analysis was finally used to gain an insight into the regulation of the production of the polyphenols. We demonstrated that the expression of 8 out of 13 polyphenol-related genes were coordinated and correlated with the polyphenol levels (both constitutive and drought-induced), supporting the fact that the production of polyphenols is, at least in part, controlled at the transcriptional level. Taken together, these results provide useful information concerning the health-promoting potential of the staple crop potato, and particularly of the native germplasm. We demonstrated the high diversity in potato tubers in terms of dietary antioxidants, identified genotypes with nutritionally interesting antioxidant composition, and highlighted their behavior under different environmental and drought stress conditions.

Sweet potato SPCP2 is a full-length cDNA isolated from senescent leaves and encodes a putative papain-like cysteine protease. The SPCP2 contained 1101 nucleotides (366 amino acids) in its open reading frame, and exhibited high amino acid sequence identities (ca. 68% to 83%) with plant cysteine proteases, including Actinidia deliciosa, Arabidopsis thaliana, Brassica oleracea, Phaseolus vulgaris, Pisum sativa, Vicia faba, Vicia sativa and Vigna mungo. SPCP2 gene expression was enhanced significantly in natural senescent leaves and in sprouting storage root. Transgenic Arabidopsis plants with ectopic constitutive SPCP2 expression showed earlier floral transition from vegetative to reproductive growth, reduced rosette leaves when flowering, enhanced germination percentage of transgenic progeny seeds in salt-containing MS medium, higher Fv/Fm value, higher relative water content and enhanced tolerance during drought treatment. Based on these results, we conclude that sweet potato papain-like cysteine protease, SPCP2, is a functional gene, and its expression causes altered developmental characteristics and enhances drought and salt stress responses in transgenic Arabidopsis plants.

Acrylamide is considered a carcinogen in animals and a possible carcinogen in humans. It has been found in starch rich foods cooked at high temperatures. Vacuum frying (10 Torr) was studied as a possible alternative to reduce acrylamide formation in potato chips. Seven potato cultivars were analyzed to determine their influence on acrylamide formation during traditional and vacuum frying. The White Rose cultivar produced the highest level of acrylamide during both traditional and vacuum frying. Vacuum frying (10 Torr, 118oC, 8 min) produced chips with lower acrylamide content than those produced under traditional frying (165oC, 4 min) for all cultivars. The cultivar Atlantic was used to determine the kinetics of acrylamide formation during traditional and vacuum frying at different temperatures because it is a good chipping cultivar and it was the most abundant in the lab. Acrylamide accumulation under vacuum frying was modeled using first-order kinetics, and during traditional frying it was modeled using the logistic kinetic model. The behavior of the kinetics of acrylamide content in potato chips fried under the two processes was different mainly due to the different temperatures used. During traditional frying, higher temperatures areused (150oC to 180oC) and acrylamide after some time is produced but also starts degrading, producing a constant level of acrylamide content at longer times. During vacuum frying (10 Torr), acrylamide increased exponentially (but at lower levels) for all frying times. The effect of potato components was studied by infusing leached potato slices with predetermined amounts of glucose and asparagine. Increasing glucose and asparagine content in the slices increased the acrylamide content in the potato chips. Color could not be used as an indication of acrylamide content, since potato chips with similar color had very different acrylamide concentrations.

Thesis (Ph. D., Bioinformatics and Computational Biology)--University of Idaho, April 2009. / Major professor: Alexander V. Karasev. Includes bibliographical references. Also available online (PDF file) by subscription or by purchasing the individual file.

No description available.

Nitrate leaching from research and commercial potato rotations was evaluated using stainless steel zero tension lysimeters, tile drainage and soil samples. The effect of nutrient management versus conventional fertility on marketable potato yield was also investigated. Neither the lysimeters nor the tile lines were able to detect a significant treatment effect on the concentration of NO3--N in collected water samples. However, trends in the NO3--N concentration conformed to nutrient application. Soil samples detected similar trends in soil NO3--N at the research site. Nutrient management fertility had no significant effect on marketable potato yield or soil NO3--N at the commercial sites. A significant crop effect on soil NO3--N was detected. Fall soil samples indicated excess NO3--N in the soil following potato harvest suggesting an overuse of nitrogen fertilizer.

Verticillium dahliae Kleb. causes Verticillium wilt in potato (Solanum tuberosum L.). Hormone signaling pathways are known to play a role in plant defense reactions. A gene expression analysis was performed on a susceptible and a moderately resistant (MR) cultivar of potato after inoculation with either a highly aggressive (HA) or a weakly aggressive (WA) isolate of V. dahliae. Genes related to the salicylic acid (SA), jasmonic acid/ethylene (JA/ET), and abscisic acid (ABA) pathways showed higher expression in the MR cultivar than the susceptible cultivar indicating that they may contribute to resistance. Additionally, a number of genes showed a delayed reaction in the susceptible cultivar and only in plants inoculated with the HA isolate of the pathogen. This trend was observed in genes related to the SA and JA/ET pathways. Overall, this research indicates that more than one hormone signaling pathway may contribute to the defense against V. dahliae by potato.

Potato crops are generally sensitive to drought. Even a short period of water shortage can affect tuber production and quality. However, field potato crops undergoing mild water deficit conditions may acclimate to subsequent severe water deficits. While responses may be both acclimation and genotype-dependent, few studies have examined whole plant physiological factors leading to enhanced drought stress resistance. Identification of these key factors may increase selection efficiency in breeding programs. This study examined the effects of drought acclimation on drought stress resistance in three potato genotypes [‘Fv12246-6’ (Fv), ‘Vigor’ (V) and ‘Russet Burbank’ (RB)] in a low relative humidity greenhouse. Non-Acclimated and Non-Stressed (NA), Drought Acclimated and Drought Stressed (DAS) and Non-Acclimated and Drought Stressed (NAS) treatments were applied. Tuber yield and number were genetically determined and acclimation had no effect on increasing these components under drought stress. However, water conservation mechanisms based on leaf and stem characteristics were both genotype and treatment-dependent. When leaves were drought stressed while attached to the stem, genotype V and RB maintained a higher percentage of leaf water content (%LWC) than Fv, likely from the greater water stored in their stems that may have been delivered through continued leaf transpiration. Acclimation induced a thicker leaf cuticular layer and partially open stomata under drought stress in both RB and Fv. Nevertheless, Fv was the most drought sensitive potato genotype, displaying the highest degree of leaf wilting and lowest %LWC under drought stress. The observed drought stress-induced smaller stomatal size in Fv did not confer greater resistance. In addition, Fv displayed the lowest percentage shoot water content (%SWC) and slowest recovery time after drought stress. RB underwent the fastest recovery from drought stress, possibly due to its equivalent xylem to pith ratio which might have enhanced greater water uptake in RB than in V and Fv. Finally, compared to application of drought stress directly (NAS), a pre-treatment of drought acclimation cycles followed by drought stress (DAS) reduced leaf wilting, induced thicker cuticular layer and more open stomata under stress. Without a DAS approach, potentially key drought stress resistance mechanisms will be missed. The role of the stem as a potential water reservoir to adapt against drought stress should be examined to further identify key elements for drought stress survival and recovery at the level of the potato whole plant.