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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

cultivars of lettuce ( Lactuca sativa ) ( Koontz and Prince, 1986 ; Soffe et al., 1977 ), as well as for other vegetable species ( Soffe et al., 1977 ) and strawberry ( Fragaria × ananassa) ( Tsuruyama and Shibuya, 2018 ). Plant growth generally increases

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Gustavo F. Kreutz, Germán V. Sandoya, Gary K. England, and Wendy Mussoline

Lettuce ( Lactuca sativa L.) is one of the most valuable vegetables in the world. The United States ranks as the second largest lettuce producer after China, harvesting ≈105,000 ha worth $3.5 billion in 2019 [ Food and Agriculture Organization of

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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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Edwin James


Analysis of tissues of lettuce, Lactuca sativa L., seedlings failed to reveal the presence of anthocyanin, pheophytin or phenolic compounds as the cause of red cotyledons (physiological necrosis). Electron microscope study showed that the cells in the necrotic tissues were completely disintegrated with only the mitochondria identifiable.

In greenhouse and field plantings, necrotic seedlings that survived produced heads equal in size and total yield to those from normal seedlings. Seedlings with slight spotting were a few days behind normal seedlings in establishment, whereas those which were badly necrotic were about 2 weeks delayed. After 8 weeks in the greenhouse or field there was no differences in plant sizes. Seedlings with only slight necrosis appeared to be satisfactory for field seeding but badly necrotic ones would probably not give a satisfactory stand.

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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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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.