David G. Holm

Pyrosequencing reveals a highly diverse and cultivar-specific bacterial endophyte community in Potato Roots

In this study, we examined the bacterial endophyte community of potato (Solanum tuberosum) cultivar/clones using two different molecular-based techniques (bacterial automated ribosomal intergenic spacer analysis (B-ARISA) and pyrosequencing). B-ARISA profiles revealed a significant difference in the endophytic community between cultivars (perMANOVA, p < 0.001), and canonical correspondence analysis showed a significant correlation between the community structure and plant biomass (p = 0.001). Pyrosequencing detected, on average, 477 ± 71 bacterial operational taxonomic units (OTUs, 97% genetic similarity) residing within the roots of each cultivar, with a Chao estimated total OTU richness of 1,265 ± 313. Across all cultivars, a total of 238 known genera from 15 phyla were identified. Interestingly, five of the ten most common genera (Rheinheimera, Dyadobacter, Devosia, Pedobacter, and Pseudoxanthomonas) have not, to our knowledge, been previously reported as endophytes of potato. Like the B-ARISA analysis, the endophytic communities differed between cultivar/clones (∫-libshuff, p < 0.001) and exhibited low similarities on both a presence/absence (0.145 ± 0.019) and abundance (0.420 ± 0.081) basis. Seventeen OTUs showed a strong positive (r > 0.600) or negative (r < −0.600) correlation with plant biomass, suggesting a possible link between plant production and endophyte abundance. This study represents one of the most comprehensive assessments of the bacterial endophytic communities to date, and similar analyses in other plant species, cultivars, or tissues could be utilized to further elucidate the potential contribution(s) of endophytic communities to plant physiology and production.

Flavonoid profiling and transcriptome analysis reveals new gene–metabolite correlations in tubers of Solanum tuberosum L.

Anthocyanin content of potato tubers is a trait that is attracting increasing attention as the potential nutritional benefits of this class of compound become apparent. However, our understanding of potato tuber anthocyanin accumulation is not complete. The aim of this study was to use a potato microarray to investigate gene expression patterns associated with the accumulation of purple tuber anthocyanins. The advanced potato selections, CO97216-3P/PW and CO97227-2P/PW, developed by conventional breeding procedures, produced tubers with incomplete expression of tuber flesh pigmentation. This feature permits sampling pigmented and non-pigmented tissues from the same tubers, in essence, isolating the factors responsible for pigmentation from confounding genetic, environmental, and developmental effects. An examination of the transcriptome, coupled with metabolite data from purple pigmented sectors and from non-pigmented sectors of the same tuber, was undertaken to identify these genes whose expression correlated with elevated or altered polyphenol composition. Combined with a similar study using eight other conventional cultivars and advanced selections with different pigmentation, it was possible to produce a refined list of only 27 genes that were consistently differentially expressed in purple tuber tissues compared with white. Within this list are several new candidate genes that are likely to impact on tuber anthocyanin accumulation, including a gene encoding a novel single domain MYB transcription factor.

Ranger Russet: A long Russet potato variety for processing and fresh market with improved quality, disease resistance, and yield

Ranger Russet, a new full-season potato variety, was jointly released to growers by the U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Oregon, Washington, and Colorado on May 14, 1991. Ranger Russet was tested in irrigated performance trials in the Western U.S. since 1979. It produces a large yield of high quality, long, russet-skinned tubers that are well suited for baking and processing into french fries. Ranger Russet is more resistant than Russet Burbank to Verticillium wilt, viruses X and Y, leafroll net necrosis, and Fusarium dry rot. It is highly resistant to hollow heart.CompendioRanger Russet, una nueva variedad de papa para la temporada principal, fue entregada conjuntamente a los productores por el Departamento de Agricultura de los Estados Unidos y las Estaciones Experimentales Agrícolas de Idaho, Oregón, Washington y Colorado el 14 de mayo de 1991. Ranger Russet fue probada en ensayos de comportamiento bajo irrigación en el oeste de los Estados Unidos desde 1979. Rinde abundantes tubérculos alargados y rojizos de gran calidad que son apropiados para el horneado y su procesamiento como papas fritas a la francesa. Ranger Russet es más resistente que Russet Burbank a la marchitez porVerticillium, a los virus X y Y, a la necrosis en red del virus del enrollamiento de la hoja y a la pudricion seca porFusarium. Es muy resistente al corazón vacío.

Storage elevates phenolic content and antioxidant activity but suppresses antiproliferative and pro-apoptotic properties of colored-flesh potatoes against human colon cancer cell lines.

Colored-flesh potatoes are an excellent source of health-benefiting dietary polyphenols, but are stored for up to 3-6 months before consumption. This study investigated the effect of simulated commercial storage conditions on antioxidant activity (DPPH, ABTS), phenolic content (FCR) and composition (UPLC-MS), and anticancer properties (early, HCT-116 and advanced stage, HT-29 human colon cancer cell lines) of potato bioactive compounds. Extracts from seven potato clones of differing flesh colors (white, yellow, and purple) before and after 90 days of storage were used in this study. The antioxidant activity of all clones increased with storage; however, an increase in total phenolic content was observed only in purple-fleshed clones. Advanced purple-fleshed selection CO97227-2P/PW had greater levels of total phenolics, monomeric anthocyanins, antioxidant activity and a diverse anthocyanin composition as compared with Purple Majesty. Purple-fleshed potatoes were more potent in suppressing proliferation and elevating apoptosis of colon cancer cells compared with white- and yellow-fleshed potatoes. The extracts from both fresh and stored potatoes (10-30 μg/mL) suppressed cancer cell proliferation and elevated apoptosis compared with the solvent control, but these anticancer effects were more pronounced with the fresh potatoes. Storage duration had a strong positive correlation with antioxidant activity and percentage of viable cancer cells and a negative correlation with apoptosis induction. These results suggest that although the antioxidant activity and phenolic content of potatoes were increased with storage, the antiproliferative and pro-apoptotic activities were suppressed. Thus, in the assessment of the effects of farm to fork operations on the health-benefiting properties of plant foods, it is critical to use quantitative analytical techniques in conjunction with in vitro and/or in vivo biological assays.

Combined Effects of Storage and Processing on the Bioactive Compounds and Pro-Apoptotic Properties of Color-Fleshed Potatoes in Human Colon Cancer Cells

Potatoes can be stored for up to 1 year before being processed and consumed. The objective of this study was to determine the extent to which fresh and stored color-fleshed potatoes retain their anticancer properties after baking and chipping compared with unprocessed potatoes. We utilized white-, yellow-, and purple-fleshed potato clones and tested their phenolic and anthocyanin content, antioxidant activity, metabolite profile, and antiproliferative and pro-apoptotic properties. When compared with unprocessed samples, baking or chipping led to significant losses in the phenolic and anthocyanin content and antioxidant activity of the potatoes. However, with storage, total phenolic and anthocyanin content and antioxidant activity increased in baked samples while in the chipped samples they remained constant. Ethanolic extracts of baked and chipped samples suppressed proliferation and elevated apoptosis (p < 0.05) in HCT-116 (p53 wild-type; ras mutated) and HT-29 (p53 mutated; ras wild-type) human colon cancer cell lines. Antiproliferative and pro-apoptotic properties of baked potatoes were similar to that of fresh potatoes, while chipping caused a significant suppression. Phenolic content and antioxidant activity of purple-fleshed potatoes, after baking, were comparable with those of anthocyanin-rich berries. Hence, purple-fleshed potatoes can be a healthier choice for consumers as they possess greater levels of bioactive compounds and anticancer properties even after processing as compared with their white- and yellow-fleshed counterparts.

Potato clone variation in blackspot and soft rot susceptibility, redox potential, ascorbic acid, dry matter and potassium

Tubers of 11 potato clones were compared for susceptibility to blackspot and soft rot, redox potential, ascorbic acid, dry matter, and potassium content. Evaluations were made before and after 6 mo storage at 3.9C. Clonal behavior was generally consistent over 2 yr. Significant differences occurred among clones for each factor except redox potential.Blackspot and soft rot were positively correlated in 5 of 8 comparisons. Neither blackspot nor soft rot was correlated with ascorbic acid or redox potential. Blackspot was positively correlated with dry matter in the fall but not after storage and was negatively correlated with potassium. Soft rot evaluated in air or air plus 8% CO2 was positively correlated with dry matter in only 2 of 8 comparisons. Soft rot susceptibility did not increase with storage when inoculated discs were incubated in air but did increase when the discs were incubated in air plus 8% CO2.Ascorbic acid was negatively correlated with redox potential only before storage and decreased to varying degrees in all clones during storage.ResumenTubérculos de 11 clones fueron comparados en susceptibilidad a mancha negra y pudrición blanda, potencial redox, ácido ascórbico, materia seca y contenido de potasio. Las evaluaciones fueron hechas antes y después de 6 meses de almacenamiento a 3.9°C. El compartamiento clonal fue generalmente consistente a lo largo de 2 años. Ocurrieron diferencias significativas entre los clones para cada factor, excepto potencial redox.La incidencia de mancha negra y pudrición blanda fue correlacionada directamente en 5 de 8 comparaciones. Ni mancha negra ni pudrición blanda mostraron correlación con ácido ascórbico o potencial redox. La presencia de mancha negra estuvo correlacionada positivamente al contenido de materia seca en el otoño, pero no después del almacenamiento y estuvo negativamente correlacionada con el contenido de potasio. La pudrición blanda, evaluada en aire, o aire más 8% CO2, estuvo correlacionada positivamente con materia seca en sólo 2 de 8 comparaciones. La susceptibilidad a pudrición blanda no aumento con el almacenamiento cuando los discos inoculados fueron incubados en aire, pero si aumentó cuando los discos fueron incubados en aire más 8% CO2.El ácido ascórbico estuvo correlacionada negativamente con el potencial redox sólo antes del almacenamiento y decredió en grado diferente en los distintos clones durante el almacenamiento.

Frontier Russet: A new potato variety for early fresh and processing use with resistance to Fusarium dry rot

Frontier Russet, a new, medium-early potato variety, was jointly released to growers by the U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Oregon, Washington, and Colorado on April 9, 1990. It was tested in irrigated yield trials since 1979. Frontier Russet produces a moderately high yield of high quality, oblong to long, cylindrical, russet-skinned tubers. The tubers are well suited for baking and for processing into french fries at harvest. Frontier Russet is resistant to Fusarium dry rot and more resistant to Verticillium wilt than other early russets.CompendioFrontier Russet, una nueva variedad de papa de precocidad intermedia, fue entregada a los agricultores conjuntamente por el Departamento de Agricultura de los Estados Unidos y las Estaciones Experimentales Agrícolas de Idaho, Oregón, Washington y Colorado, el 9 de abril de 1990. Esta variedad fue probada desde 1979 en ensayos de rendimiento en campos bajo irrigación. Frontier Russet produce un rendimiento moderadamente alto de gran calidad, con tubérculos oblongos a alargados, cilíndricos, y de piel rojiza. Los tubérculos recién cosechados son muy apropiados para horneado y fritura a la francesa. Frontier Russet es resistente a la pudrición seca porFusarium y más resistente a la marchitez porVerticillium que otras variedades precoces de piel rojiza.

Gemchip: A new potato variety with chipping quality and verticillium resistance for the Western U.S.

Gemchip, a new potato chipping variety, was released jointly by the U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Oregon, Washington, and Colorado on August 9, 1989. Gemchip was tested in irrigated yield and chipping trials in the Western U.S. since 1982. It outyielded Norchip by an average of 23% and Atlantic by 14%, and it chipped well both out of the field and out of storage. Gemchip is moderately late in maturity and resistant to Verticillium wilt.CompendioGemchip, una nueva variedad de papa fritura a la inglesa, fue entregada conjuntamente por el Departamento de Agricultura de los EE.UU. y las Estaciones Experimentales Agrícolas de Idaho, Oregón, Washington y Colorado el 09 de agosto de 1989.Gemchip fue probada desde 1982 en ensayos de rendimiento bajo riego y de calidad de fritura a la inglesa en el oeste de los EE.UU. Produjo en promedio 23% más que Norchip y 14% más que Atlantic y se comporté bien al ser frita a la inglesa tanto recién cosechada como después de su almacenamiento. Gemchip es moderadamente tardía y resistente a la marchitez por Verticilium.

AmaRosa, a Red Skinned, Red Fleshed Fingerling with High Phytonutrient Value

The diversity of traits in varieties of potato outside of its South American birthplace is a small subset of that available in the Andean center of origin. Among the traits that evoke most interest are skin and flesh pigments. Recent studies have pointed to the high antioxidant activity and potential healthful benefits from these pigments or other antioxidant compounds. The market for potatoes with unusual color patterns has been supplied largely by heirloom varieties of uncertain origin and the highly successful Yukon Gold. Interest has intensified and been transformed into a focused effort in the breeding of specialty varieties, remarkable for their unusual colors. The purpose of this paper is to describe a new potato variety in the Fingerling Class with red skin and red flesh.ResumenLa diversidad de caracteres en variedades de papa fuera de su lugar de origen en Sudamérica, es un pequeño subgrupo del que esta disponible en su centro de origen andino. Entre los caracteres que atraen más interés son los pigmentos de la piel y de la pulpa. Estudios recientes han enfatizado a la alta actividad antioxidante y a los potenciales beneficios para la salud de estos pigmentos u otros compuestos antioxidantes. El mercado de papas con patrones de color inusuales se ha surtido grandemente por variedades antiguas de origen incierto y por la altamente exitosa Yukon Gold. Se ha intensificado el interés y se ha transformado a un esfuerzo enfocado en el mejoramiento de variedades de especialidad, que sobresalen por sus colores poco comunes. El propósito de este artículo es describir una nueva variedad de papa en la clase de variedaes tipo dedo con piel y pulpa rojas.

Selenium and Sulfur Content and Activity of Associated Enzymes in Selected Potato Germplasm

Potato plants are being supplemented with selenium (Se) to enrich tubers with Se for health benefits. Se is not an essential nutrient and interferes with the metabolism of sulfur (S) in plants. The objective of the present investigation was to study the activities of Se-independent glutathione peroxidase (Se-Ind-GPx), Se-dependent glutathione peroxidase (Se-Dep-GPx), and thioredoxin reductase (TRxR) enzymes in stored potato tubers grown on a non-Se-enriched field; and assess their relationship with tuber Se and S levels. The results indicate that these enzyme activities and the Se and S levels in the tubers were significantly influenced by genotype. Se-Dep-GPx activities were influenced by Se levels in the tubers. S content of tubers of all genotypes tested were below the critical nutrition concentration. In spite of this deficiency, the levels of S (which were very high in comparison with Se) influenced the activities of Se-Ind-GPx and TRxR in the tubers. Tubers of some of the genotypes tested can supply more than the recommended dietary allowance (RDA) of Se to adult humans.ResumenLas plantas de papa están siendo suplementadas con selenio (Se) para enriquecer los tubérculos con Se para beneficio de la salud. El Se no es un nutrimento esencial e interfiere con el metabolismo del azufre (S) en plantas. El objetivo de la presente investigación fue estudiar las actividades de las enzimas glutatión-peroxidasa independiente de Se (Se-Ind-GPx), glutatión-peroxidasa dependiente de Se (Se-Dep-GPx) y thioredoxin reductasa (TRxR) en tubérculos de papa almacenados provenientes de un campo no enriquecido con Se; y analizar su relación con los niveles de Se y S en el tubérculo. Los resultados indican que las actividades de estas enzimas y los niveles de Se y S en tubérculos fueron influenciados significativamente por el genotipo. Las actividades de Se-Dep-GPx se influenciaron por los niveles de Se en los tubérculos. El contenido de S en tubérculos de todos los genotipos probados estuvo debajo de la concentración crítica de nutrición. A pesar de esta deficiencia, los niveles de S (que fueron muy altos en comparación de Se) influenciaron las actividades de Se-Ind-GPx y TRxR en los tubérculos. Tubérculos de algunos de los genotipos probados pueden surtir mas de lo recomendado para la dieta de Se en humanos adultos.