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David A. Baumbauer, Colleen B. Schmidt and Macdonald H. Burgess

DW of spinach as the DLI increased from 3 to 27 mol·m −2 ·d −1 , and Gaudreau et al. (1994) reported lettuce yield increases between 140% and 270% with a supplemental DLI of 12 to 13 mol·m −2 ·d −1 compared with plants grown without supplemental

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Rahmatallah Gheshm and Rebecca Nelson Brown

Lettuce is one of the most important fresh market vegetable crops in the United States. In 2017, lettuce was grown on more than 276,000 acres, with a crop value exceeding $3.6 billion [ U.S. Department of Agriculture (USDA), 2018 ]. Most of the U

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Ming Li, Toyoki Kozai, Katsumi Ohyama, Shigeharu Shimamura, Kaori Gonda and Tetsuo Sekiyama

The CSAL is an airtight warehouse-like facility covered with thermally insulated walls and using artificial light as the sole light source for growing the plants. CSAL has been used to grow lettuce plants ( Wheeler et al., 1994a ), soybean and

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James D. McCreight

Lettuce aphid (Nasonovia ribisnigri Mosley) is a recent insect pest to lettuce (Lactuca sativa L.) production in the United States. The single dominant gene, Nr, conditions resistance to the lettuce aphid in Lactuca virosa accession IVT280 from The Netherlands and is available in a limited number of commercial lettuce cultivars. New and genetically unique sources of resistance are sought to broaden the genetic base for resistance to the lettuce aphid. About 1200 lettuce PI lines were evaluated for resistance to lettuce aphid in greenhouse tests using a strain of lettuce aphid obtained from commercial lettuce in Salinas Valley, Calif. In 2002, plants were individually infested with five 24-hour nymphs per plant (controlled protocol), and the numbers of aphids per plant were counted 10–14 days post-infestation (dpi). Beginning in 2003, plants were mass-infested (mass protocol) with nymphs and alates of various ages and numbers. Using the mass protocol, the number of aphids per plant 10–14 dpi were estimated and categorized using a 1–5 scale where 1 = 0 aphids per plant, 2 = 1–10 aphids per plant, 3 = 11–20 aphids per plant, 4 = 21–30 aphids per plant, and 5 = >30 aphids per plant. `Salinas' and `Barcelona' were included as susceptible and resistant controls, respectively. Most of the accessions were susceptible. A few accessions had a few plants with very low numbers of aphids after repeated infestation, but their progeny were susceptible. Two accessions were highly resistant: PI 491093, a Lactuca serriola accession from Turkey, and PI 274378, a L. virosa accession from France. Inheritance of resistance in these two accessions and their allelism to Nr remains to be determined.

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Samuel Contreras, Mark A. Bennett, James D. Metzger, David Tay and Haim Nerson

Lettuce ( Lactuca sativa L.) is one of the most commonly cultivated fresh vegetable crops in the world and its establishment requires high-quality seeds. Lettuce seed thermoinhibition (inability to germinate at high temperatures) and

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Ji Gang Kim, Yaguang Luo, Robert A. Saftner and Kenneth C. Gross

of fresh-cut lettuce. Use of a company name or product by the USDA does not imply approval or recommendation of the product to the exclusion of others that also may be suitable.

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Russell W. Wallace, Annette L. Wszelaki, Carol A. Miles, Jeremy S. Cowan, Jeffrey Martin, Jonathan Roozen, Babette Gundersen and Debra A. Inglis

High tunnels are large, framed structures covered with a single or double layer of greenhouse-grade plastic with no electrical or ventilation systems and are typically used to produce high-value specialty crops including lettuce and other leafy

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Beiquan Mou* and Yong-Biao Liu

Leafminer (Liriomyza spp.) is a major insect pest of many important agricultural crops including lettuce (Lactuca sativa L.). The goals of this study were to evaluate lettuce genotypes for resistance to leafminers and to estimate the heritabilities of leafminer-resistant traits in the field, to examine the association among different resistant traits, and to study the mechanism of leafminer resistance in lettuce. Seventy-eight lettuce accessions and 232 F2 plants of crosses were evaluated for leafminer stings and the production of pupae and flies in the field in 2001 and 2002, and resistant genotypes were subjected to no-choice test. Wild species (Lactuca serriola L., L. saligna L., and L. virosa L.) had significantly fewer stings than cultivated lettuces. Among cultivated lettuces, sting densities were lowest on leaf lettuce and highest on romaine types. The sting results from the field were highly correlated with the results from insect cages (r = 0.770 and 0.756 for 2001 and 2002 tests, respectively), suggesting that a cage test can be used to screen for resistance in the field. Broad-sense heritability estimates for stings per unit leaf area in the field were 81.6% and 67.4% for 2001 and 2002 tests, respectively. The number of pupae produced per plant or per leaf was moderately correlated with sting density but was not correlated with leaf weight. Results suggest that both antixenosis and antibiosis exist in lettuce germplasm and resistant genotypes from choice tests remain resistant under no-choice conditions. These findings suggest that genetic improvement of cultivated lettuce for leafminer resistance is feasible.

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Ki-Ho Son, Jin-Hui Lee, Youngjae Oh, Daeil Kim, Myung-Min Oh and Byung-Chun In

quality and intensity, rather than changing light quality using LEDs. Recently, Bian et al. (2014) reported that the accumulation of phytochemicals in vegetable crops, such as lettuce, cucumber, tomato, radish, and spinach, depended on light quality and

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Hsing-Ying Chung, Ming-Yih Chang, Chia-Chyi Wu and Wei Fang

can provide a cultivation environment that is free from disturbances by the external environment and have steady annual production; therefore, they have great potential for safe crop production ( Kozai, 2013 ). In Taiwan, red leaf lettuce contains