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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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Cultivated lettuce ( Lactuca sativa L.) is one of the most consumed vegetables in the United States ( US Department of Agriculture, National Agricultural Statistics Service 2018 ). The United States is the second largest lettuce producer

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‘Black Seeded Simpson’, ‘Buttercrunch’, and ‘New York 12’ lettuce.(Lactuca sativa L.), Plant Introductions (PI) 261653 of Lactuca saligna L., and Acc. No. 500–4 of L. serriola L. regenerated plants from cell suspensions originated from leaf callus. Liquid cultures of these Lactuca spp. in either B5 or Murashige and Skoog (MS) basic medium amended with alpha-naphthaleneacetic acid (NAA) and 6-benzylamino purine (BA) developed roots, shoots, and complete plants when transferred to agar plates of B5 with several concentrations of BA under 16 hr of fluorescent illumination. Shoots were induced to produce a root system when cultured in B5 agar medium amended with NAA. Variation in response between cultivars and between species was observed, with L. serriola and ‘Black Seeded Simpson’ responding best to treatments.

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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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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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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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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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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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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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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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