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Charlene M. Grahn, Barbara Hellier, Chris Benedict and Carol Miles

field HortTechnology. 1 78 81 Penaloza, P. Ramirez-Rosales, G. McDonald, M.B. Bennett, M.A. 2005 Lettuce ( Lactuca sativa , L.) seed quality evaluation using seed physical attributes, saturated salt accelerated aging, and the seed vigor imaging system

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Geoffrey Weaver and Marc W. van Iersel

photochemical performance of a greenhouse-grown crop of a romaine-type lettuce cultivar ( Lactuca sativa L. ‘Green Towers’) under growing conditions comparable to a commercial production environment. Specific hypotheses tested were whether the current ETR is

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Marie Abbey, Neil O. Anderson, Chengyan Yue, Michele Schermann, Nicholas Phelps, Paul Venturelli and Zata Vickers

year-round ( Abbey et al., 2019 ). However, there were several production issues that needed careful management to have yields comparable to hydroponic greenhouse or field-grown types. Lettuce, Lactuca sativa , is the most commonly grown leafy green in

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Ryan J. Hayes, Bo Ming Wu, Barry M. Pryor, Periasamy Chitrampalam and Krishna V. Subbarao

York, NY Eenink, A. Groenwold, H.R. Dieleman, F.L. 1982 Resistance of lettuce ( Lactuca ) to the leaf aphid Nasanovia ribisnigri . 1. Transfer of resistance from L. virosa to L. sativa by interspecific

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Edward J. Ryder and David C. Milligan

Six genes controlling flowering time or bolting time in Lactuca L. have been reported. Several crosses between parents differing in time to opening of first flower were made to ascertain the inheritance of additional flowering time traits in Lactuca species. The parents in the crosses were of five flowering classes: very late (VL), late (L), early (E), very early (VE), and very, very early (VVE). Segregation from a cross between C-2-1-1 (VL) (L. sativa L.) and `Vanguard 75' (L) confirmed that `Vanguard 75' flowering was controlled by the previously identified gene Ef-2ef-2. Mutant line 87-41M-7 (VVE) was crossed by D-3-22M (VE) and segregated 3VVE:1 VE, indicating a dominant allele, Ef-3, that decreased flowering time an additional 7 days. Cos-like line 796 (VE) was crossed to cultivars Salinas (VL) and Vanguard 75. Segregation indicated a gene Ef-4ef-4, with lateness dominant. PI 175735 (E) (L. serriola L.), crossed with C-2-1-1 produced an F2 population with a bimodal distribution, segregating 3 E:1 VL, indicating a single gene Ef-5ef-5. PI 236396 (E) and PI 250020 (E) were crossed to `Salinas' and `Vanguard 75'. Segregation and morphological similarity indicated the same gene in both PI lines, Ef-6ef-6, with earliness dominant.

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Furn-Wei Lin, Kuan-Hung Lin, Chun-Wei Wu, Yu-Sen Chang, Kuan-Hung Lin and Chun-Wei Wu

's ability to cope with water stress in specific/localized environments will lead to better-informed decisions on the suitability of irrigation management practices. Lettuce ( Lactuca sativa L. var. capitata), a member of the Asteraceae family, is cultivated

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Jernej Demšar, Jože Osvald and Dominik Vodnik

With a high nitrate supply, and most frequently under low-light conditions, lettuce accumulates relatively large amounts of NO3-as a result of an excess of uptake over reduction. Different approaches, which are used to reduce leaf nitrate, often result in a yield loss. A computerized aeroponic system, which supplies different nitrate concentrations in accordance with the changeable light conditions (dynamic light-dependent application of nitrate), was used to reduce nitrate accumulation in lettuce (Lactuca sativa L.) var. Capitata cv. Vanity. Under unfavorable light conditions nitrate was supplied at limited rates (slight, medium, and strong reduction) to the plants. In response to given light conditions the nitrate supply was reduced close to one-half or one-fourth of the full nutrient solution (8 mmol·L-1 NO3-). Controlled nutrition resulted in efficient reduction in leaf nitrate. In the early-spring experiment the average nitrate content in outer leaves was decreased by 9%, 63%, and 92% and in the late-spring experiment the decrease was 23%, 58%, and 76% compared to control. At the same time, the controlled, light-dependent nitrate deprivation did not result in a loss of a lettuce yield (except in the treatment with strong nitrate reduction) and had limited effects on photosynthesis (P N-C i measurements) and photosynthetic pigments.

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J.D. Chung, B.J. Lee, H.S. Lee and C.K. Kim

Lettuce (Lactuca sativa L.) were transformed using microparticle bombardment with two different genes, alpha-glucuronidase (GUS) gene and Chinese cabbage Glutathione Reductase (GR) gene. The adventitious shoots of cotyledonary explant from 4-day-old seedlings were formed (46.7%) in MS basal media supplemented with 5.0 μm IAA and 1.0 μm 2ip. When 1100 psi helium pressure, 9 target distance, and coating with tungsten 10 microparticles were used and explants were treated with osmoticum-conditioning medium (0.6M sorbitol/mannitol), 4 h prior to and 16 h after bombardment, it was identified by GUS assay that these conditions were the most efficient for transformation of foreign genes into cotyledon tissue of lettuce with particle bombardment. PCR confirmed that the band observed in the transgenic plants were originated from T-DNA tranfer with strong hybridization. The genomic Southern analysis showed that the 1.5-kbp fragment was hybridized with radiolabeled 1.5-kbp GR probe. To know whether the expression of the GR gene can be stably maintained in the next generation, when T2 selfing seeds that were obtained from the transformed mother plants were sowed on MS medium supplemented with 200 μm kanamycin, 70% of seedlings were revealed resistance to kanamycin.

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Melek Ekinci, Ertan Yildirim, Atilla Dursun and Metin Turan

growth of sorghum at higher NaCl salinity J. Expt. Bot. 43 81 87 Anuradha, S. Rao, S.S.R. 2001 Effect of brassinosteroids on salinity stress induced inhibition of germination and seedling growth of rice ( Oryza sativa L.) Plant Growth Regulat. 33 151 153

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Ryan J. Hayes, Karunakaran Maruthachalam, Gary E. Vallad, Steven J. Klosterman and Krishna V. Subbarao

Lettuce ( Lactuca sativa L.) is a globally important horticultural crop, and many pre-existing and emerging diseases constrain production throughout the world. Host resistance is often the most sustainable and economically viable control method, if