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Jules Janick and Irwin L. Goldman

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Lynn Maher and Irwin L. Goldman

The earthy flavor of table beet is due to an aromatic terpene derivative called geosmin. It has been hypothesized that geosmin presence in beet is due to geosmin-producing bacteria such as Streptomyces spp. that exist in the soil. However, recent findings suggest that beet may produce geosmin endogenously without microbial influence. The purpose of this study was to determine whether such endogenous production of geosmin occurred in beet by making use of an aseptic tissue culture (TC) environment to remove potential microbial influences on geosmin production. Four table beet accessions (‘Bull’s Blood’, ‘Touchstone Gold’, ‘W364B’, and ‘Pacemaker III’) were grown in three separate TC experiments and in the greenhouse and measured for geosmin concentration via gas chromatography–mass spectrometry (GC-MS). Sequencing of 16S ribosomal RNA was used to identify potential microbial contaminants in TC. Operational taxa units (OTUs) classification resulted in RNA sequences with homology to bacterial RNA of either chloroplast (98%) or mitochondria (2%) origin. Other OTUs identified were considered within the range of sequencing error. In 15 of the 16 TC–grown samples used for the 16S rRNA aseptic validation and in all the greenhouse-grown plant samples, geosmin was detected. Geosmin concentrations from bulked beet tissue of each accession were higher in the TC environment than the greenhouse environment. The lack of microbial detection in the TC environment and the subsequent identification of geosmin from beets grown in the aseptic environment is a strong indication that geosmin is produced endogenously by beets. This finding raises several interesting questions about the functional significance of this molecule for Beta vulgaris.

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Min Wang and Irwin L. Goldman

Genetic relationships among 37 accessions of Beta vulgaris, including 21 table beet, 14 sugar beet, and two Swiss chard (Beta vulgaris ssp. cicla) accessions, were evaluated using randomly amplified polymorphic DNA (RAPD). Genetic distance was estimated based on the presence or absence of polymorphic RAPD bands. Multidimensional scaling plots of genetic distance values revealed that table beet inbred lines from the University of Wisconsin Table beet Breeding Program clustered in an intermediate position between sugar beet breeding lines and standard table beet germplasm, likely because of their origin from an introgression program designed to incorporate sugar beet genes.

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Veronica L. Gaertner and Irwin L. Goldman

Half-sib recurrent selection programs were initiated at the University of Wisconsin-Madison in 1978 and 1995 to increase betalain (betacyanin and betaxanthin) concentration in red and yellow table beets (Beta vulgaris L. ssp. vulgaris), respectively. Cycles of selection from both the red and yellow table beet breeding programs were evaluated for pigment and total dissolved solids (TDS) distribution in five tissue sections (outer, middle and center zones of the root; leaf and petiole) in two environments (early and late planting) during 2002. Betaxanthin concentration increased with the later planting date in the majority of the tissue zones in the yellow and red table beet populations. Absolute pigment concentration of the outer root zone increased the most over cycles of selection: 46.6 mg/100 g fresh weight (FW) betaxanthin and 201 mg/100 g FW betacyanin for yellow and red populations, respectively. However, the greatest rate of gain was in the center and middle tissue zones. Selection based on the outer 2 cm of root tissue has effectively increased pigmentation of the entire beet plant. A correlated response to selection in leaf and petiole tissue was measured for pigment concentration in both populations. The contribution of each tissue zone to total pigment concentration of the beet plant remained constant throughout cycles of selection averaging 39%, 25%, 25%, 6%, and 5% for outer, middle, center, petiole and leaf tissue zones, respectively. Across all table beet populations, pigment concentration of the outer root zone was 55% and 62% higher than middle and center zones, respectively. TDS of the outer root zone was 10% and 12% higher than middle and center zones, respectively.

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Thomas C. Koch and Irwin L. Goldman

Carotenoids and tocopherols are health-functional phytochemicals that occur in a wide range of fruit and vegetable crops. These two classes of compounds are synthesized from a common precursor, geranyl-geranyl pyrophosphate, and are typically analyzed separately via high-performance liquid chromatography (HPLC) techniques. Because carotenoids and tocopherols are present in many edible horticultural crops, it would be advantageous to measure them simultaneously in plant tissues. Herein we report a one-pass reverse-phase HPLC method for extraction and analysis of carotenoids and tocopherols in carrot that can be extended to other high-moisture plant organs. Elution times ranged from 5 minutes for α-tocopherol to 24 minutes for β-carotene. This method improves the efficiency of analyzing these compounds by up to 50%, and should increase the efficiency of assessing carotenoid and tocopherol profiles in horticultural crops.

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Kathryn S. Orvis and Irwin L. Goldman

Organosulfur compounds in onion extracts inhibit the aggregation of human blood platelets. Antiplatelet activity is important to human cardiovascular health. We hypothesized that modification of sulfur fertility may increase organosulfur compound concentration and thereby affect platelet inhibitory activity in onion. Four contrasting onion genotypes were grown at four sulfur levels in a hydroponic system in the greenhouse and in contrasting sulfur environments in seven field locations in Wisconsin, Oregon, and New York. The contrasting field sites were comprised of sandy soils with a mean sulfate level of 5.4 ppm and muck soils with a mean sulfate level of 20.3 ppm. Onions grown in field environments with increased soil sulfur concentrations had significantly higher antiplatelet activity (33% higher than sand-grown onions; P < 0.001). The greenhouse experiment was conducted in hydroponics with nutrient solutions containing four sulfur levels ranging from 0.8 mM to 15 mM sulfate. The 10-mM sulfur treatment resulted in onion bulbs with 10% higher antiplatelet activity over those grown in the 0.8-mM sulfur treatment (P < 0.06). These data suggest that sulfur concentration in nutrient solution and in soil may be directly responsible for the increased antiplatelet activity in onion extracts observed in this study.

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Thomas C. Koch* and Irwin L. Goldman

Carotenoids (provitamin A) and tocopherols (vitamin E) are powerful antioxidants in plants and in the human diet. Carrot (Daucus carota) has been selected for increased levels of carotenoids, contributing to its orange color and reported health benefits. Selection for increased tocopherol has shown success in seed oils, but little progress has been made in the edible portions of most vegetable crops. HPLC measurement following a simultaneous heptane extraction of both compounds has shown a significant (P ≤ 0.001) positive correlation of α-tocopherol with α-carotene (r = 0.65) and β-carotene (r = 0.52). To increase both the tocopherols and carotenoids in plants, 3 populations have been established from select open-pollinated varieties grown in 2002. These populations consist of half-sib families with these differing selection schemes: based strictly on increased α-tocopherol levels; an index to increase α-carotene, β-carotene and α-tocopherol; and a random population in which no selection is occurring. After one cycle of selection, populations were grown on muck soil during the summer of 2003. Compared with the random population, an increase of 24.68% in α-tocopherol concentration was recorded for the population selected strictly on α-tocopherol while increases of 8.47% in α-tocopherol, 9.31% in α-carotene and 7.31% in β-carotene were recorded for the population with index selection. The continuation of these carrot populations shows promise to produce carrot germplasm with improved human nutritive value.