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  • Author or Editor: Rida Shibli x
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Ohelo (V. pahalae Skottsb.) and bilberry (V. myrtillus L.) shoots were regenerated via direct organogenesis from whole leaves and leaf sections and also from hypocotyl explants of bilberry. Explants preincubated for 1 to 2 weeks in darkness yielded ≈75% regeneration frequencies and the highest number of regenerating shoots/explant on TDZ-supplemented media (0.9 to 2.7 μm). When 2iP or zeatin were substituted as the cytokinin source, frequencies of regeneration and shoot productivity were significantly lower. Explants held under constant illumination (no dark pretreatment) had significantly lower regeneration frequencies in all tested cytokinin-supplemented media. 2,4-D stimulated callus formation, but did not support regeneration from vegetative explants. Cells from callus and suspension cultures did not exhibit regeneration in any of the media that supported organogenesis from leaves. Regenerants were successfully micropropagated, although callus formation caused by zeatin and high 2iP levels interfered with shoot proliferation. Zeatin induced hyperhydricity in shoots from both species, but more severely in ohelo. Ex vitro rooting after treatment with 4.9 μm IBA or 5.4 μm NAA was 95% and 60% successful for bilberry and ohelo, respectively, and plants were readily acclimatized after an interval in a fog chamber. Bilberry microshoots also rooted in vitro in the absence of growth regulator treatment. Chemical names used: 1H-indole-3-butanoic acid (IBA); N-(3-methyl-2-butenyl)-1-H-purine-6-amine (2iP); 6-furfurylaminopurine (kinetin); 1-naphthaleneacetic acid (NAA); thidiazuron=1-phenyl-3-(1,2,3-thiadiazio-5-yl)urea (TDZ); 2,4-dichlorophenoxyacetic acid (2,4-D); 6-(4-hydroxy-3-methylbut-2-enylamino) purine (zeatin).

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Some factors that affect the in vitro conservation of wild pear (Pyrus syrica) microshoot cultures were studied. Sorbitol and mannitol at 0.2 to 4.0 M reduced growth significantly and extended the subculture intervals to 5 months when cultures where kept at 15°C. Increasing sucrose to 12% in the medium was not highly effective and the subculture intervals did not exceed 3.0 months. After 2 years of maintaining cultures on slow-growth medium, cultures grew slowly when transferred to fresh control medium. Shoots started to proliferate after three subcultures (6.0 weeks apart) on medium containing 1.0 mg/L BA and 0.1 mg/L NAA. New microshoots were rooted on medium containing 2.0 mg/L IBA and rooted microshoots gave 90% survival when acclimatized ex vitro under intermittent mist.

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Osmotic adjustment in response to decreasing media water availability was observed for in vitro Chrysanthemum morifolium Ramat. cultivars Bright Golden Anne, Deep Luv, and Lucido. Water stress was induced by increasing sorbitol (0, 0.1, 0.2, 0.3, 0.4 M), mannitol (0, 0.1, 0.2, 0.3, 0.4 M), and sucrose (30, 45, 60, 75, 90 g·l-1) concentrations in modified MS media (2 mg·l-1 BA and 0.1 mg·l-1 NAA). Osmotic adjustment was evidenced by a significant reduction in measured cell sap osmotic potential (R2 = 0.78, 0.96, 0.91 for sucrose, sorbitol, and mannitol respectively) in all cultivars. Shoot length, weighted density (apparent mass), and proliferation were significantly reduced by sorbitol and mannitol treatments. Sucrose reduced shoot proliferation, increased length, and had an inconsistent effect on weighted density. Cultures grown on media without hormones showed tremendous increase in root number up to 60 g·l-1 sucrose. Sorbitol had a negligible effect on rooting at 0.1 M but no roots developed at higher sorbitol concentrations or in any mannitol treatments. Plants transferred to a non-water-stress media after they had experienced in vitro water stress exhibited no change in osmotic properties from the stress treatments.

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