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Don Waneck, H. Mathews, J. Stamp, and R. Bestwick

Zygotic embryo explants of grape cultivar AXR#1 were isolated from maw-e seeds and cultured on medium supplemented with naphthoxy acetic acid beta-(NOA) and benzylaminopurine (BA). Embryo explants dedifferentiated to form embryogenic callus. Globular stage embryos were visible in 9-10 months. On transfer 10 a growth regulator free medium supplemented with charcoal these globular embryos underwent further stages of embryo development. In a period of 30-40 days embryogenic tissues turned into clumps of somatic embryos displaying different stages of development Cotyledonary stage embryos were separated and transferred to basal medium. These embryos developed into complete plants. Cold and desiccation treatment of somatic embryos significantly enhanced the rate of plant conversion. Hypocotyl segments of elongated somatic embryos were good source explant for induction of shoot organogenesis. The hypocotyl-length and the proximity to-shoot-apex were found to influence the rate of shoot induction from hypotyl segments. Multiple shoot complexes which formed on hypocotyl segments were separated and individual shoots were grown on a root induction medium resulting in complete plant development. The possibility of both embryogenic and organogenic modes of plant regeneration make somatic embryos a highly versatile explant source for experiments on genetic manipulation.

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Seong Min Woo and Hazel Y. Wetzstein

as blueberry, cranberry, and rhododendron. This has led to the development of efficient plant regeneration protocols achieved through organogenesis from cultures derived from leaf tissue, shoot tips, and axillary buds. Plants regenerated from this

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Ying Chen, Xinlu Chen, Fei Hu, Hua Yang, Li Yue, Robert N. Trigiano, and Zong-Ming (Max) Cheng

breeding ( Portillo et al., 2007 ). Therefore, the most effective means for genetic improvement is through biotechnology. Micropropagation systems and regeneration systems through either organogenesis or somatic embryogenesis have already been established

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Wenhao Dai and Cielo Castillo

condition may help keep the optimal ratio of endogenous auxin to cytokinin in in vitro tissues for callus/shoot regeneration. Dark treatment (etiolating plant tissues) may also speed up the process of organogenesis by stimulating dedifferentiation of plant

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Nevena Mitić, Mariana Stanišić, Jelena Milojević, Ljiljana Tubić, Tatjana Ćosić, Radomirka Nikolić, Slavica Ninković, and Rade Miletić

pale green. Prior incubation in the dark proved to be a key factor for regeneration from leaf explants in both ‘Golden Delicious’ and ‘Melrose’. The dark treatment was reported to promote organogenesis in various fruit tree species, including apple

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Samir C. Debnath and Danny L. Barney

micropropagated highbush blueberry HortScience 24 373 375 Cao, X. Hammerschlag, F.A. 2000 Improved shoot organogenesis from leaf explants of highbush blueberry HortScience 35 945 947 Compton, E.C. 1994 Statistical methods suitable for the analysis of plant tissue

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Samuel Salazar-García, Elizabeth M. Lord, and Carol J. Lovatt

Inflorescence and flower development of the `Hass' avocado (Persea americana Mill.) were investigated at the macro- and microscopic level with three objectives: 1) to determine the time of transition from vegetative to reproductive growth; 2) to develop a visual scale correlating external inflorescence and flower development with the time and pattern of organogenesis; and 3) to quantify the effect of high (“on”) and low (“off”) yields on the flowering process. Apical buds (or expanding inflorescences) borne on summer shoots were collected weekly from July to August during an “on” and “off” crop year. Collected samples were externally described and microscopically analyzed. The transition from vegetative to reproductive condition probably occurred from the end of July through August (end of shoot expansion). During this transition the primary axis meristem changed shape from convex to flat to convex. These events were followed by the initiation of additional bracts and their associated secondary axis inflorescence meristems. A period of dormancy was not a prerequisite for inflorescence development. Continued production of secondary axis inflorescence meristems was observed from August to October, followed by anthesis seven months later. In all, eleven visual stages of bud development were distinguished and correlated with organogenesis to create a scale that can be used to predict specific stages of inflorescence and flower development. Inflorescence development was correlated with minimum temperature ≤15 °C, whereas yield had little effect on the timing of developmental events of individual inflorescence buds. However, the high yield of the “on” year reduced inflorescence number and increased the number of vegetative shoots. No determinate inflorescences were produced during the “on” year. For the “off” year, 3% and 42% of shoots produced determinate and indeterminate inflorescences, respectively.

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Yuexin Wang, Zoran Jeknić, Richard C. Ernst, and Tony H.H. Chen

A protocol was developed for efficient plant regeneration of Iris germanica L. `Skating Party' from suspension cultures. Suspension cultures were maintained in Murashige and Skoog (MS) basal medium (pH 5.9) supplemented with 290 mg·L–1 proline, 50 g·L–1 sucrose, 5.0 μm 2,4-D, and 0.5 μm Kin. Suspension-cultured cells were transferred to a shoot induction medium (MS basal medium supplemented with 10 mg·L–1 pantothenic acid, 4.5 mg·L–1 nicotinic acid, 1.9 mg·L–1 thiamine, 250 mg·L–1 casein hydrolysate, 250 mg·L–1 proline, 50 g·L–1 sucrose, 2.0 g·L–1 Phytagel, 0.5 μm NAA, and 12.5 μm Kin). Cell clusters that proliferated on this medium differentiated and developed shoots and plantlets in about 5 weeks. Regeneration apparently occurred via both somatic embryogenesis and shoot organogenesis. A series of experiments was conducted to optimize conditions during suspension culture to maximize subsequent plant regeneration. Parameters included 2,4-D and Kin concentrations, the subculture interval, and the size of cell clusters. The highest regeneration rate was achieved with cell clusters ≤280 μm in diameter, derived from suspension cultures grown for 6 weeks without subculturing in liquid medium containing 5 μm 2,4-D and 0.5 μm Kin. Up to 4000 plantlets with normal vegetative growth and morphology could be generated from 1 g of suspension-cultured cells in about 3–4 months. Chemical names used: 2,4-dichlorophenoxyacetic acid (2,4-D); kinetin (Kin); 1-naphthaleneacetic acid (NAA).

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Adriana C. de M. Dantas, Adriano N. Nezi, and Gerson R. de L. Fortes

Three different leaf segments (apical, basal, and middle) were treated in combination with aluminum at 0, 5, 10, 15 and 20 mg·L-1. Three kinds of leaf segments were inoculated in flasks in 12 replicates, with the adaxial surface touching the medium composed by basic macro- and micronutrient and MS vitamins added to 2,4-D (1.0 mg·L-1); BAP (5.0 mg·L-1); sucrose (30.0 g·L-1); myo-inositol (100.0 mg·L-1) and agar (6.0 g·L-1). The pH was adjusted to 4.0 before autoclaving. After inoculation, the explants were incubated in a dark growth room for 21 days and then, placed during 80 days, at 25 ± 2 °C, 16-h photoperiod provided by white fluorescent lamps under 19 μE·m-2·s-1 radiation. At the end of this period, the explants were evaluated. It was observed that basal leaf explants provided greener callus and that the heavier ones came from the middle leaf explants. Absence of Al or high Al concentrations favored the number of adventitious buds, whereas intermediate concentrations inhibited them. The absence of Al favored basal explants to form adventitious shoots, while lower concentrations favored apical and basal segments. High Al concentration appear to stimulate adventitious shoots in the basal and middle explants. Although it was evident that callus intensities were lower in higher Al concentration, Al is not so harmful to callogenesis and organogenesis.

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Inmaculada Vila, Ester Sales, Javier Ollero, Jesús Muñoz-Bertomeu, Juan Segura, and Isabel Arrillaga

cuttings ( Hartmann et al., 2002 ), but also tissue culture techniques have been described: Jacquemont et al. (1992) reported on axillary proliferation of ‘Petite Salmon’, a dwarf cultivar; Pal et al. (1990) induced root organogenesis from leaf