Danielle J. Donnelly

Potatoes and human health.

The potato (Solanum tuberosum L.) tuber follows only rice and wheat in world importance as a food crop for human consumption. Cultivated potatoes have spread from the Andes of South America where they originated to 160 countries around the world. Consumption of fresh potatoes has declined while processed products have increased in popularity. As the potato becomes a staple in the diets of an increasing number of humans, small differences in potato nutritional composition will have major impacts on population health. The potato is a carbohydrate-rich, energy-providing food with little fat. Potato protein content is fairly low but has an excellent biological value of 90–100. Potatoes are particularly high in vitamin C and are a good source of several B vitamins and potassium. The skins provide substantial dietary fiber. Many compounds in potatoes contribute to antioxidant activity and interest in cultivars with pigmented flesh is growing. This review will examine the nutrient and bioactive compounds in potatoes and their impact on human health.

Potato microtuber production and performance: A review

Almost half a century has passed sincein vitro tubers (microtubers) were first described in potato, but their adoption as a seed propagule has been uneven globally. Consensus is lacking regarding optimal production practices for microtubers and their relative productivity in relation to other propagules for minituber production. There is significant uncertainty regarding the utility of microtubers for evaluation of agronomic characters. However, the application of microtubers in germplasm conservation is widely accepted. Microtubers are producedin vitro in a plethora of different growing systems with varying environment, media constituents, and storage intervals. Many of the interactions between growth parametersin vitro and subsequent productivity appear to be genotype-specific. Accordingly, microtubers come in different sizes, have different dormancy requirements, and differ widely in relative growth potential and productivity. Despite these differences, there is evidence for strong analogies in growth responses between fieldgrown tubers and microtubers. The use of microtuber technology in seed tuber production, breeding programs, germplasm conservation, and research appears to have enormous potential. This review discusses microtuber production, yield and performance,in vitro screening, and germplasm storage and exchange.ResumenCasi medio siglo ha transcurrido desde que los tubérculosin vitro (microtubérculos) fueran descritos en papa por primera vez, pero su adopción como propágulos semilias ha sido irregular a nivel mundial. Falta consenso con respecto a las prácticas optimas de producción de microtubérculos y su relativa productividad en relación con otros propágulos para la producción de minitubérculos. Existen dudas significativas en relación con la utilidad de los microtubérculos para la evaluación de caracteres agronómicos. Sin embargo, el uso de microtubérculos para la conservación del germoplasma está ampliamente aceptado. Los microtubérculos son producidosin vitro en una infmidad de sistemas de crecimiento con medio ambiente variado, diferentes constituyentes de los medios de cultivo e intervalos de almacenamiento variados. Muchas de las interacciones entre los parámetros de crecimientoin vitro y la subsiguiente productividad parece ser específica para el genotipo. En consecuencia, los tubérculos vienen en diferentes tamaños, tienen diferentes requerimientos de latencia y se diferencian ampliamente en lo que respecta al potential de crecimiento relativo y a la productividad. A pesar de estas diferencias, existe evidencia de fuertes analogías en hi respuesta de crecimiento entre los tubérculos obtenidos en el campo y los microtubérculos. El empleo de la tecnología de microtubérculos en la producción de semilla, programas de mejoramiento, conservación del germoplasma e investigación parece tener un potential enorme. Esta revisión analiza la producción de microtubérculos, rendimiento y comportamiento, tamizadoin vitro y almacenamiento e intercambio de germoplasma.

Microwave-Assisted Extraction of Phenolic Antioxidants from Potato Peels

A response surface method was used to optimize the microwave-assisted extraction parameters such as extraction time (t) (min), solvent (methanol) concentration (S) (v/v) and microwave power level (MP) for extraction of antioxidants from potato peels. Max. total phenolics content of 3.94 mg g−1 dry weight (dw) was obtained at S of 67.33%, t of 15 min and a MP of 14.67%. For ascorbic acid (1.44 mg g−1 dw), caffeic acid (1.33 mg g−1 dw), ferulic acid (0.50 mg g−1 dw) max contents were obtained at S of 100%, t of 15 min, and MP of 10%, while the max chlorogenic acid content (1.35 mg g−1 dw) was obtained at S of 100%, t of 5 min, and MP of 10%. The radical scavenging activity of the extract was evaluated by using the DPPH assay and optimum antioxidant activity was obtained at S of 100%, t of 5 min, and MP of 10%.

Microtuberization of layered shoots and nodal cuttings of potato: the influence of growth regulators and incubation periods

A protocol is presented for the rapid induction of microtubers on micropropagated, layered potato shoots of ‘Kennebec’, ‘Russet Burbank’ and ‘Superior’ in medium devoid of growth regulators. Layered shoots microtuberized more rapidly and produced significantly larger microtubers compared with nodal cuttings. The addition of coumarin or (2-chloroethyl)-trimethylammonium chloride and benzyladenine to microtuberization medium, either had no effect or significantly reduced microtuber weight per shoots compared with medium containing only 80 g × 1-1 sucrose and minimally affected the number of microtubers per shoot. Increasing the incubation period from 28 to 56 days did not affect the number but significantly increased the weight of microtubers per shoot and substantially increased the proportion, up to 20%, of microtubers heavier than 1 gram.

Adventitious shoot regeneration from leaf explants of tissue cultured and greenhouse-grown raspberry

Adventitious shoot regeneration was observed using leaf-petiole explants from shoot-proliferating cultures of ‘Comet’ red raspberry (Rubus idaeus L.). A maximum regeneration rate of 70% (3.7 shoots/explant) was obtained using 4.5–9.1 μM (1–2 mg l−1) N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron or TDZ) with 2.5–4.9 μM (0.5–1 mg l−1) 1H-indole-3-butanoic acid (IBA) or 2.3 μM (0.5 mg l−1) TDZ with 4.9 μM (1 mg l−1) IBA in modified Murashige-Skoog medium. TDZ was more effective than N-(phenylmethyl)-1H-purin-6-amine (BA) at promoting regeneration in combinations tested with IBA (maximum 50% regeneration rate; 1.8 shoots/explant). Variation in the agar concentration or incubation temperature, orientation or scoring of the leaf-petiole explants and use of separate leaf or petiole explants had no effect on shoot regeneration. Incubation in the dark for 1, 2 or 3 weeks prior to growth in the light did not influence the percent regeneration rate but depressed the number of adventitious shoots. Explant source, from micropropagated shoots or greenhouse-grown plants, had an effect on shoot regeneration that was genotype dependent. Only 8 of 22 (36%) raspberry cultivars were capable of regeneration from leaf explants derived from greenhouse-grown plants.

Potato Microtubers as Research Tools: A Review

Although invitro production of potato tubers or microtuberization was achieved more than 40 years ago, the application of microtubers in reliable model research systems has been slow to develop. Several factors such as the use of growth regulators in microtu-ber induction and growth media, the mixotropic nature of thein vitro system, and cultivar-specific responses have led to interpretive difficulties. A cautionary note is also necessary in view of apparent growth and development differences, metabolic alterations, and soma-clonal variation encountered in microtubers that may not be found in field-grown tubers. Evidence for strong and consistent analogies between microtubers and field-grown tubers for their induction, growth and development, and metabolism often is lacking. However, several components such as the rapid and near-synchronous induction and growth, which can be modified by a range of exogenous compounds or conditions, make the microtuber a valuable model system. Complex problems such as dormancy also appear to be particularly amenable to examination by the microtuber system. In addition, the use of microtubers as experimental research tools has potential in the areas of plant metabolism, germplasm selection and evaluation, genetic transformation, somatic hybridization, and molecular farming.ResumenAunque la producciónin vitro de tubérculos de papa, o microtuberización, data de hace 40 años, la aplicación de microtubérculos en modelos confiables de sistemas de investigación ha tenido un lento desar-rollo. Diversos factores, como el uso de reguladores y medios de crecimiento en la inducción de microtubérculos, la naturaleza mixotrófica del sistemain vitro y las respuestas de cultivares específicos han conducido a dificultades de interpretación. Una anotación pre-ventiva es tambión necesaria en vista de las aparentes diferencias en el crecimiento y desarrollo, alteraciones metabólicas y variaciones somaclonales encontradas en los microtubérculos, que no se encuentran en los tubérculos que crecen en campo. La evidencia de fuertes y consistentes analogías para inducción, crecimiento y desarrollo y metabolismo entre microtubérculos y tubérculos que crecen en campo con frecuencia es defectuosa. Sin embargo, diversos componentes, como la rápida y cercana inducción y el crecimiento sincrónico, que pueden ser modificados por un rango de combinaciones y condiciones exógenas, hace de la microtuberización un modelo valioso para el sistema. Problemas complejos como la dormancia también aparentan estar particularmente sujetos a examen por el sistema de microtubérculos. Adicionalmente, el uso de microtubérculos como herramientas de investigación experimental tiene potencial en las áreas del metabolismo de plantas, evaluación y selección de ger-moplasma, transformación genética, hibridación somática y cultivo molecular.

MICROTUBER DORMANCY IN THREE POTATO CULTIVARS

Microtuber size, media growth regulators, incubation period, as well as bud maturity and endogenous abscisic acid content of microtubers were evaluated for their effects on length of dormant period of Kennebec, Russet Burbank and Superior microtubers. The dormant period of microtubers was found to be cultivar-specific and a significant correlation was observed betweenin vitro andin vivo dormant periods. Smaller microtubers (≤250 mg) had longer dormant periods than did those greater than 250 mg. Dormant periods were unaffected by addition of coumarin or 2-(chloroethyl)-trimethylammoniumchloride and 6-benzylaminopurine to the culture media or incubation period (28 and 56 days). Developmental age had no effect on individual buds ability to break dormancy and elongate. A positive correlation was observed between tissue levels of abscisic acid and microtuber dormant periods.CompendioSe evaluaron el tamaño, el medio de reguladores de crecimiento, el periodo de incubación, al igual que la madurez de los brotes y el contenido de ácido abscisico endógeno de los tuberculillos, para medir sus efectos sobre la longitud del periodo de reposo de estos en los cultivares Kennebec, Russet Burbank y Superior. Se encontró que el periodo de reposo de los tuberculillos es específico del cultivar y se observó una correlación significativa entre los periodos de reposoin vitro ein vivo. Los tuberculillos más pequenos (μ250 mg) tuvieron periodos de reposo más prolongados que aquellos con más de 250 mg. Los periodos de reposo no fueron afectados por la adición de cumarina o 2-(cloroetil)-cloruro-trimetilamonio y 6-benzilaminopurina al medio de cultivo, tampoco el periodo de incubación (28 y 56 días). La edad de desarrollo no tuvo efecto sobre la capacidad de los brotes individuales para romper el reposo y crecer. Se observó una correlación positiva entre los niveles del ácido abscisico de los tejidos y los periodos de reposo de los tuberculillos.

Relative Salinity Tolerance of Potato Cultivars Assessed By In Vitro Screening

One hundred and thirty European and North American potato cultivars were assayedin vitro for salinity (NaCl) tolerance. A modified single-node cutting bioassay was used in which cultivars were exposed to a range of NaCl levels (0, 40, 80, and 120 mM), in a Murashige and Skoog-based medium, for 1 month. Evaluations were performed twice for each cultivar at each salt level, using five single-node cuttings. Six vegetative growth parameters (shoot and root lengths, fresh and dry weights) were measured at the time of harvest and corrected for differences in cultivar vigor. These relative values were subjected to multivariate cluster analysis. The sum of the relative rankings at 40, 80, and 120 mM NaCl partitioned the cultivars into 8 units. The cultivars Amisk, BelRus, Bintje, Onaway, Sierra, and Tobique were in the most salinity tolerant unit and in the top cluster group for vigor with the exception of Tobique. These cultivars can be recommended for further study.ResumenSe hicieron experimentos in vitro con ciento treinta cultivares de papa europeos y norteamericanos para analizar su tolerancia a la salinidad (NaCl). Se utilizó un bioensayo modificado de esquejes de un solo nudo en el cual los cultivares fueron expuestos a un rango de niveles de NaCl (0, 40, 80 y 120 mM), en un medio Murashige y Skoog durante un mes. Las evaluaciones se realizaron dos veces por cada cultivar en cada nivel de sal, empleando cinco esquejes con un solo nudo. Se midieron seis parámetros vegetales de crecimiento (longitud de las raíces y de los brotes, peso fresco y seco) en la cosecha y se corrigieron debido a sus diferencias en el vigor de la planta. Estos valores relativos fueron sujetos a un análisis de multivariación de grupos. La suma de los rangos relativos a 40, 80 y 120 mM NaCl separaron los cultivares en 8 unidades. Los cultivares Amisk, Belrus, Bintje, Onaway, Sierra y Tobique estuvieron en la unidad con mayor tolerancia a la salinidad y en el grupo con mayor vigor, con excepción de Tobique. Se recomienda el empleo de estos cultivares para un estudio futuro.

In vitro bioassays for salinity tolerance screening of potato

SummaryThree in vitro bioassays (single-node cutting, root tip segment and microtuberization) gave similar results in ranking the salinity (NaCl) tolerance of several potato genotypes (Solanum spp.) and were verified by tuber yield criteria in a field lysimeter trial with salinized irrigation water. Salinity stress consistently depressed growth in the single-node cutting and root tip segment bioassays, reduced microtuber yield in the microtuberization bioassay and decreased tuber yield in field lysimeters. The single-node cutting bioassay was simpler to perform than the root tip segment and microtuberization bioassays and did not exclude certain genotypes as did the microtuberization bioassay. The single-node cutting bioassay can be recommended as a substitute for more labour-intensive and costly field assessments of salinity effects of yield.

The effect of boron on calcium uptake and growth in micropropagated potato plantlets.

SummaryBoron (B) requirements differ widely among plant species and the concentration range between toxicity and deficiency is less for B than for any other nutrient. Excess B can adversely affect calcium (Ca) uptake and plant growth. Potato cvs Bintje and Norland plantlets were micropropagated on Murashige & Skoog (MS) nutrient medium, supplemented with 3 (MS control level) or 9 mM Ca, and a range of H3BO3 levels (0.025 to 0.300 mM B). Medium B levels of 0.100 and 0.300 mM decreased Ca content in leaves and shoots of cv. Norland, but not Bintje. Medium B level of 0.025 mM, which is 25% of the control MS level, enhanced Ca uptake in cv. Norland and did not compromise normal plantlet growth in either cultivar. This lower H3BO3 level (0.025 mM B), and a B-free gelling agent such as Gelrite, could be used for micropropagation of potato and possibly other species susceptible to Ca defifiency disorders.