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  • Author or Editor: Irwin Goldman x
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Carrot (Daucus carota var. sativus) cultivars with common root shape, appearance, and end-use are grouped and commercialized in market classes. The shape of the carrot storage root is the result of growth and development, which is highly influenced by genotype; however, the extent to which planting density affects root shape traits and its interaction with genotype remains unexplored. To observe the effects of market class and density on carrot root shape characteristics, five cultivars classified in five different market classes, including Imperator, Nantes, Danvers, Chantenay, and Ball, were each grown at five planting densities ranging from 0.5 million to 4.5 million plants/ha. A generalized complete block design with a two-way factorial treatment arrangement of the two factors, density and genotype, was used in three environments. Roots were phenotyped using a digital imaging pipeline and scored for root size (length, maximum width) and compound root shape traits including traits derived from the principal component analysis of root contour profiles like root fill and tip and shoulder curvature. The results suggest that planting density had minimal impact on the shape of carrot roots, and the expected shape for each market class was maintained regardless of planting density; however, the analysis was constrained by the presence of interactions among genotype, density, and environment, which influence the contribution of main effects to shape. For the Nantes, Danvers, Chantenay, and Imperator market classes, planting density influenced the size of the carrot root, with size decreasing by up to 50% in length and width at high planting densities. We found high estimates of broad-sense heritability for traits that determine the shape of the carrot root, such as root fill and length-to-width ratio, which capture size-independent variation of the storage root. Although environmental signals play a role, our results suggested that the shape of the carrot root is primarily determined by genotype, and that planting density generally does not have a significant effect on its shape.

Open Access

Foods that can aid in prevention of disease are of increasing interest. Some vegetables experimentally enriched with selenium (Se) accumulate selenium as Se-methylselenocysteine (MeSeCys), a non-protein amino acid implicated with superior chemopreventive properties. The effects of increasing concentrations of Se on the gain in biomass (GIB) and total Se concentration of broccoli (Brassica oleracea), mung bean (Vigna radiata), and onion (Allium cepa ‘Red creole’) sprouts were evaluated against sulfur (S) as control. Trial 1 included treatments of selenate-Se and sulfate-S at levels of 127 μmol·L−1 and 1270 μmol·L−1. Trial 2 used additional treatments of 635 μmol·L−1 for broccoli and mung beans and 12,700 μmol·L−1 for onion. Sprouts were harvested at 3 and 5 days for broccoli and mung bean and at 5 and 7 days for onion. Broccoli was the most sensitive to Se, showing ≈45% GIB reduction at 635 μM Se. Mung bean GIB was 23% lower at 1,270 μM Se and onion GIB showed a small 16% reduction at 12,700 μM Se, suggesting high Se tolerance. These data clearly demonstrated species variation in tolerance to and uptake of Se during sprout production. The lowest treatment level, 127 μM selenate-Se, resulted in Se concentrations that exceeded the level desirable for fresh sprout consumption, suggesting that Se-biofortified sprout production for fresh consumption could be easily accomplished with little effect on growth rate or yield. Chemical name used: selenate (SeO4 2–) sulfate (SO4 2–).

Free access

Oxalic acid (C2O4 2–) is a compound of interest as a result of its relationship with kidney stone formation and antinutritive properties. Because table beet [Beta vulgaris ssp. vulgaris (garden beet group)] is considered a high oxalate food, breeding to decrease oxalic acid levels is an area of interest. In this study, a field trial was conducted over 2 years for 24 members of the Chenopodiaceae using two different planting dates to determine if variation exists for both total and soluble oxalic acid levels in roots and leaves. Total and soluble oxalic acid was extracted from homogenized root core and leaf tissue samples and a colorimetric enzymatic assay was used to determine total and soluble oxalic acid levels. Mean values ranged from 722 to 1909 mg/100 g leaf tissue and 553 to 1679 mg/100 g leaf tissue for total and soluble oxalate levels, respectively. Beet cultivar Forono and swiss chard [B. vulgaris ssp. vulgaris (leaf beet group)] cultivar Burpee's Fordhook Giant Chard produced the respective highest and lowest soluble and total oxalic acid leaf levels. Swiss chard cultivars produced 38% less total oxalate compared with table beet cultivars based on overall means. Root soluble oxalate values ranged from 103 to 171 mg/100 g root tissue and total values ranged from 95 to 142 mg/100 g root tissue. Significant variation for both total and soluble oxalic acid levels were detected, indicating progress could be made toward breeding for lower oxalic acid levels in table beet. However, gains in oxalic acid nutritional quality may be limited because it would take a substantial decrease in levels for table beet to be reclassified as a low oxalate food.

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Earthy aroma and sweet flavor, conferred by the volatile terpenoid geosmin (trans-1,10-dimethyl-trans-9-decalol) and sucrose, respectively, are two essential flavor components of table beet (Beta vulgaris ssp. vulgaris). To elucidate the influence of genotype, growing environment, and fertilizer treatment on geosmin concentration and sucrose [as total dissolved solids (TDS)] in table beet, a field-based genotype × environment study was conducted using a split-split plot design. Four site × year combinations served as whole plots; MgSO4·H2O and CaSO4 comprised split plot fertilizer treatments; open-pollinated cultivars Bull’s Blood and Touchstone Gold, F1 hybrid Merlin, and inbred line W357B constituted split-split plot genotype treatments. Geosmin concentration was measured via gas chromatography–mass spectrometry using headspace solid-phase microextraction, and TDS was measured via refractometry. Variation in geosmin concentration was attributable to a strong genotype effect and significant genotype × year and year × site interactions. Genotypes were observed to have characteristic geosmin concentration and variance, despite being grown in soils with widely divergent physical and chemical properties. While a significant genotype main effect was also present for TDS, it occurred in the context of significant four-way and three-way genotype × environment interactions, plus significant effects of year and year × site interaction. Neither geosmin concentration nor TDS was significantly influenced by fertilizer treatment or fertilizer × environment interactions, averaged across genotypes. Genetics determined a larger proportion of variance for geosmin concentration than TDS in the four table beet genotypes assessed, as reflected in repeatability measurements of 0.90 and 0.43, respectively. This experiment provides support for the primacy of genotype in determining table beet geosmin concentration and a comparatively moderate role of genotype in determining table beet TDS. Thus, genetic manipulation of table beet geosmin could yield cultivars with signature flavor characteristics to serve both niche and mainstream consumer groups, expanding market opportunities for breeders and growers.

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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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Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is the most destructive foliar disease of table beet (Beta vulgaris ssp. vulgaris) in Wisconsin, USA, and globally. Under conducive conditions, symptomatic lesions on the leaf expand and coalesce forming large necrotic areas that can ultimately lead to complete defoliation. This damage reduces productivity and threatens the ability to mechanically harvest. CLS damage also detracts from the visual appeal of fresh market bunched beets to such an extent that growers risk buyer rejection if CLS severity is observed to be greater than 5%. Fungicide use for CLS control is threatened by the emergence of resistant C. beticola strains, and the application of host resistance is constrained by limited knowledge of cultivar reaction to CLS in table beet. This study aimed to address the knowledge gaps of fungicide efficacy and cultivar reaction by conducting replicated field trials in multiple table beet growing environments across Wisconsin. Broad variation for resistance to CLS was observed among the 10 included cultivars. The mean area under disease progress curve (AUDPC) across environments for the most susceptible cultivar was 267% greater than the most resistant cultivar. Spearman correlations between environments for mean cultivar AUDPC value ranged from 0.71 to 0.99, revealing consistent cultivar CLS reactions across environments. Although susceptible cultivars surpassed 5% severity in all environments, the resistant cultivars remained below this threshold in six of the 10 environments. By comparison with resistant sugar beet (Beta vulgaris ssp. vulgaris) cultivars, however, all tested table beets appeared susceptible to CLS, highlighting the potential for a CLS breeding effort in table beet. Neither of the evaluated Organic Materials Review Institute–listed treatments were effective at limiting CLS disease progress, whereas both tested conventional fungicides significantly reduced disease severity over the nontreated plots. These findings may provide helpful guidance to table beet growers affected by CLS in Wisconsin and beyond.

Open Access

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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Consumers perceive flavor as a critically important attribute of vegetable crops. Gas chromatography-mass spectrometry (GC-MS), spectrophotometry, and refractometry of tissue samples collected during multiple years from table beet (Beta vulgaris) at various stages of maturity were performed to characterize the endogenous production of geosmin, oxalic acid, and total dissolved solids within the root. The geosmin concentration was primarily influenced by the cultivar and peaked early during the growing season, with root concentrations at 6 weeks after planting that were 312% higher, on average, than those found in harvest stage roots at 15 weeks after planting. The highest average concentration of geosmin in harvest stage roots was detected in tissue from the cultivar Bull’s Blood (16.08 μg⋅kg−1). The oxalic acid concentration showed a strong cultivar influence and statistically significant variability across the growing season. Hybrid beet cultivar Boro had the lowest soluble oxalic acid concentration (95.73 mg⋅100 g−1 fresh tissue) at all locations and during all years. The oxalic acid concentration peaked 12 weeks after planting, and it was lower at the postharvest sampling date 18 weeks after planting. Total dissolved solids (TDS) concentrations were strongly influenced by year and growing environment and displayed crossover interactions for environment × week. TDS measurements had a moderate negative correlation with root mass. ‘Chioggia Guardsmark’ consistently had the highest TDS during all years and at all locations at 12.01 °Brix. The TDS varied significantly according to time, and diurnal sampling revealed fluctuations as large as 4 °Brix over the course of a 12-hour period. The TDS concentrations increased throughout the growing season, although the rate at which they increased changed according to plant age. The results from this study suggest that interactions between cultivar, time, and environment are important determinants of oxalic acid and TDS concentrations, but they have less influence on geosmin. This information may influence the methods that plant breeders use to collect phenotypic data of important flavor compounds in beets.

Open Access