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Erin M. Silva, Bill B. Dean and Larry Hiller

Successful pollination of onion (Allium cepa L.) flowers greatly depends on adequate nectar production. In order to understand the nectar production dynamics of onion flowers, nectar was collected at regular intervals during a 24-hour period. Hourly nectar volumes were compared to a variety of environmental conditions, including amount of solar radiation, relative humidity, temperature, wind speed, and evapotranspiration. Production patterns showed mid- to late-morning peaks and late evening peaks in nectar volume. Nectar appeared to be reabsorbed by the flowers during the afternoon and overnight hours. Individual flowers produced the highest amount of nectar several days after initially opening. Nectar production was significantly and inversely related to relative humidity while the effects of temperature, evapotranspiration, wind speed and solar radiation on nectar production were not significant in this study.

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Kevin A. Lombard, Emmanuel Geoffriau and Ellen Peffley

Direct spectrophotometric determination of quercetin content in onions (Allium cepa L.) was investigated as a possible alternative to high-performance liquid chromatography (HPLC) analysis. Quercetin content in five onion varieties was monitored at 362 nm and quantified using simple spectrophotometric and HPLC methods. HPLC revealed that 3,4'-Qdg and 4'-Qmg comprised up to 93% of total flavonol content detected in the studied varieties. These major quercetin conjugates combined (3,4'-Qdg + 4'-Qmg) and total flavonol conjugates quantified by HPLC correlated closely with spectrophotometer values. Correlation coefficients were 0.96 (P < 0.0001) for 3,4'-Qdg + 4'-Qmg and 0.97 (P < 0.0001) for total flavonol conjugates in onion. Simple spectrophotometric procedure proved to be a valid, efficient, and cost-effective method for the quantification of total quercetin in onion. Chemical names used: quercetin-3,4'-O-diglucoside (3,4'-Qdg); quercetin-4'-O-glucoside (4'-Qmg).

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Jorge E. Arboleya, Joseph G. Masabni, Michael G. Particka and Bernard H. Zandstra

This research was supported by the Michigan Agricultural Experiment Station and the Michigan Onion Research Committee.

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John B. Masiunas

Thanks to R. Lindstrom and W. Shoemaker for their technical assistance and to the Dutch Valley Growers, Inc., for donating the onion seed. Mention of a trade name does not constitute a guarantee of the product or an endorsement by the Univ

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Steven J. Damon, Russell L. Groves and Michael J. Havey

Onion thrips is an important insect pest of onion causing direct damage to leaves and stored bulbs ( Alston and Drost, 2008 ), reduced bulb and seed yields ( Elmore, 1949 ; Jones et al., 1934 ), and transmission of serious pathogens such as iris

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Timothy Coolong and Mark A. Williams

Onions are grown throughout the United States using multiple production systems in a range of climates. Onions are typically divided into short-day, intermediate-day, and long-day types; with bulbing occurring in response to daylengths greater than

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Christopher S. Cramer

1 Associate Professor of Horticulture. This research was funded in part by the NMSU Agricultural Experiment Station and the New Mexico Dry Onion Commission. The author gratefully acknowledges technical assistance of Joe N. Corgan and Jose Luis

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Clinton C. Shock, Erik Feibert and Lamont D. Saunders

Funds for this study were provided in part by the Oregon State Univ. Experiment Station, Project 304. Financial support from the Idaho Eastern-Oregon Onion Research Committee, the Malheur County Onion Growers, and onion seed companies is gratefully

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Christopher J. D’Angelo and Irwin L. Goldman

Onion ( Allium cepa ) is a globally important vegetable crop. It is grown in more than 160 countries and on more than 4.9 million ha. Global onion production has been increasing steadily since 1990 ( FAO, 2016 ). The most widely produced marketable

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Eduardo D. Munaiz, Russell L. Groves and Michael J. Havey

Feeding by onion thrips routinely causes severe damage to onion foliage and significantly reduces both bulb and seed yields ( Diaz-Montano et al., 2010 ; Elmore, 1949 ; Fournier et al., 1995 ; Jones et al., 1934 ; Kendall and Capinera, 1987