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Peter T. Hyde, Elizabeth D. Earle, and Martha A. Mutschler

Fecund gynogenic lines from onion ( Allium cepa L.) breeding materials Plant Sci. 167 1055 1066 Alan, A.R. Mutschler, M.A. Brants, A. Cobb, E. Earle, E.D. 2003 Production of gynogenic plants from hybrids of Allium cepa L. and A. roylei Stearn Plant

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Juan Carlos Díaz-Pérez, Jesús Bautista, Gunawati Gunawan, Anthony Bateman, and Cliff Martin Riner

Production of organic fruits and vegetables has doubled in the last 10 years in response to growing demand ( Dorais and Alsanius, 2015 ; Engelbrecht et al., 2012 ). Vidalia onions ( Allium cepa L.) are sweet, short-day, low-pungency, yellow Granex

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Juan Carlos Díaz-Pérez, Jesús Bautista, Anthony Bateman, Guna Gunawati, and Cliff Riner

pathway in onion J. Amer. Soc. Hort. Sci. 128 776 783 Develash, R.K. Sugha, S.K. 1977 Factors affecting development of downy mildew ( Peronospora destructor ) of onion ( Allium cepa ) Indian J. Agr. Sci. 67 71 74 Hamilton, B.K. Yoo, K.S. Pike, L.M. 1998

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M.J. Havey

The primary source (S cytoplasm) of cytoplasmic-genic male sterility (CMS) used to produce hybrid-onion (Allium cepa L.) seed traces back to a single plant identified in 1925 in Davis, California. Many open-pollinated populations also possess this cytoplasm, creating an undesirable state of cytoplasmic uniformity. Transfer of cytoplasms from related species into cultivated populations may produce new sources of CMS. In an attempt to diversify the cytoplasms conditioning male sterility, the cytoplasm of Allium galanthum Kar. et Kir. was backcrossed for seven generations to bulb-onion populations. The flowers of galanthum-cytoplasmic populations possess upwardly curved perianth and filaments with no anthers, making identification of male-sterile plants easier than for either S- or T-cytoplasmic male-sterile onion plants. Mean seed yield per bulb of the galanthum-cytoplasmic populations was measured in cages using blue-bottle flies (Calliphora erythrocephala Meig.) as pollinators and was not significantly different from one of two S-cytoplasmic male-sterile F1 lines, a T-cytoplasmic male-sterile inbred line, or N-cytoplasmic male-fertile lines. Male-sterile lines possessing either the S or galanthum cytoplasm were each crossed with populations known to be homozygous dominant and recessive at the nuclear locus conditioning male-fertility restoration of S cytoplasm and progenies were scored for male-fertility restoration. Nuclear restorers of male fertility for S cytoplasm did not condition male fertility for the galanthum-cytoplasmic populations. It is intended that these galanthum-cytoplasmic onion populations be used as an alternative male-sterile cytoplasm for the diversification of hybrid onion seed production.

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Kevin A. Lombard, Ellen Peffley, Leslie Thompson, Emmanuel Geoffriau, and Jay Morris

The flavonol quercetin has been reported as having many health benefits, including a reduction in the risk of developing cardiovascular disease, stroke, and some types of cancer. The overall content of quercetin in onion was examined in four yellow varieties (`Rio Rita', `RNX 10968', `Predator', and `Tamara') and one red variety purchased at a local grocery store. Each bulb was quartered, with one quarter saved as a control and the other three quarters subjected to three cooking treatments that simulated common domestic processing methods of preparing onion. The treatments included sautéing in sunflower oil for 5 minutes at 93 °C, baking for 15 min. at 176 °C, and boiling for 5 minutes in distilled water. Samples were frozen in liquid nitrogen, ground to a fine powder, blended with 80% EtOH, and filtered for quercetin extraction. The filtrate was then analyzed with a spectrophotometer (uv 374 nm). Quercetin concentrations were obtained in mg quercetin/kg fresh weight of tissue by regressing spectrophotometer readings onto a standard curve. Significant differences between varieties were found when examining fresh samples alone with the red variety containing the highest content of quercetin. Results of cooking showed that sautéing produced an overall 27% gain in quercetin concentration (significantly higher than the fresh control), baking produced an overall 4% gain in concentration (insignificant from the fresh control), while boiling produced an overall 18% loss in quercetin concentration (significantly lower than the fresh control).

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Sayed Gamiely, D.A. Smittle, H.A. Mills, and G.I. Banna

Yields of `Granex 33' and `Behairy' onions (Allium cepa) closely correlated with the weight of the seeds used to establish the stand. Elemental content was consistently higher in heavier seeds, but elemental concentrations in the seeds were generally negatively related to seed weight, onion growth, and yield. A combined size-aspiration grading was an effective means of eliminating seed with low-yield potential.

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Marisa M. Wall and Joe N. Corgan

Individual onion (Allium cepa L.) bulbs were evaluated for pungency by measurement of enzymatically produced pyruvate and by flavor perception. In four separate experiments, pyruvate values were highly and significantly correlated to mean sensory ratings. Correlation coefficients (r) were 0.92, 0.84, 0.95, and 0.79, and regression coefficients (R2) were 0.84, 0.71, 0.91, and 0.62. The high correlations indicate that pyruvate analysis can be used as a reliable selection technique for pungency in onion breeding programs.

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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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Ali Fuat Gokce and Michael J. Havey

Cytoplasmic-genic male sterility (CMS) is used to produce hybrid onion seed. For the most widely used source of CMS in onion, male sterility is conditioned by the interaction of sterile (S) cytoplasm and the homozygous recessive genotype at a single nuclear male-fertility restoration locus (Ms). Maintainer lines used to seed-propagate male-sterile lines possess normal fertile (N) cytoplasm and the homozyous recessive genotype at the Ms locus. Presently, it takes 4 to 8 years to establish if maintainer lines can be extracted from an uncharacterized population or family. We previously developed a PCR marker useful to distinguish N and S cytoplasms of onion. To tag the nuclear male-fertility restoration locus (Ms), we evaluated segregation at Ms over at least three environments. Segregations of AFLPs, RAPDs, and RFLPs revealed molecular markers flanking the Ms locus. We are working to convert these linked molecular markers to nonradioactive PCR-based detection. The organellar and nuclear markers were used to select plants from open-pollinated onion populations and determine if the number of test-crosses required to identify maintaining genotypes.

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Thomas W. Walters, Leroy A. Ellerbrock, Jan J. van der Heide, James W. Lorbeer, and David P. LoParco

Greenhouse and field methods were developed to screen Allium spp. for resistance to Botrytis leaf blight (caused by Botrytis squamosa Walker). In the green-house, plants were sprayed with laboratory-grown inoculum and incubated in a temperature-controlled enclosure containing an atomizing mist system. For field inoculations, a portable misting system with windbreaks was erected, and the plants were sprayed with laboratory-grown inoculum. Greenhouse and field incubation conditions maintained leaf wetness without washing inoculum from the leaves. Botrytis leaf blight symptoms in greenhouse and field evaluations were identical to symptoms in commercial onion fields. A total of 86 selected USDA Allium collection accessions were evaluated using these methods. All A. fistulosum accessions and A. roytei were highly resistant to immune, as were most accessions of A. altaicum, A. galanthum, A. pskemense, and A. oschaninii. Nearly all of the A. vavilovii and A. cepa accessions were susceptible. However, one A. cepa accession (PI 273212 from Poland) developed only superficial lesions, which did not expand to coalesce and blight leaves. This work confirms previous reports of Botrytis leaf blight resistance in Allium spp., and suggests that strong resistance exists with A. cepa.