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Jenny L. Bolivar-Medina, Camilo Villouta, Beth Ann Workmaster and Amaya Atucha

). Flower formation is a multistep process, from floral meristems differentiation to anthesis, and all of the steps are influenced by endogenous factors, such as resource allocation ( Alvarez-Buylla et al., 2010 ; Liu et al., 2009 ; Polito et al., 2002

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Beatrice Nesi, Debora Trinchello, Sara Lazzereschi, Antonio Grassotti and Barbara Ruffoni

verify the sanitary status of in vitro meristem-derived plants. Han et al. (2006) obtained a good percentage of virus-free material in vitro by using anther-derived callus in Lilium × ‘Enchantment’, but this method may induce somaclonal variants. We

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Hisanao Suzue, Munetaka Hosokawa and Susumu Yazawa

In horticulture, there are several procedures that require the exposure of shoot apical meristems (SAMs) by removing all leaf primordia such as for induction of polyploidy by colchicine treatment ( Oiyama and Okudai, 1986 ), for production of

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Michael G. Bausher

. The meristems regrowth was quite vigorous on all the rootstocks surveyed and in each case, regrowth came from the area of the rootstocks cotyledon. In the 2007 study, there was rootstock adventitious bud growth (ABG) observed regardless of the

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Alessandro Chiari and Mark P. Bridgen

Meristems from three different positions were excised from in vitro plants of Alstroemeria genotype A30. Explants were removed from the most-distal vegetative shoot apical meristems, rhizome tip apical meristems, and rhizome tip axillary meristems. Meristems were cultured on four different media to compare the effect of meristem position and medium on the ability to produce Alstroemeria rhizomes from meristems. The meristem culture media were Murashige & Skoog salts plus 8.39 μM pantothenic acid, 1.19 μM thiamine, and 0.55 mm myo-inositol (MSM), MSM plus 8.88 μM of 6-benzylaminopurine (BA), MSM plus 8.88 μM BA, and 0.72 μM gibberellic acid (GA3), and MSM plus 0.72 μM GA3. Meristems that were removed from the vegetative shoot apices did not develop rhizomes on any medium. Rhizome tip apical meristems developed less than 10% rhizomes when subcultured on media containing BA and GA3. However, rhizome tip axillary meristems developed rhizomes on all media with best results achieved when the medium was supplemented with BA.

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Karen L. Thies and Clinton H. Graves Jr.

A meristem micropropagation system was developed to produce Agrobacterium -free muscadine grape. Meristems were cultured on a modified Woody Plant Medium (mWPM) supplemented with 0.45 μm BAP. After 2 weeks, cultures were transferred to mWPM containing 8.92 μm BAP to enhance shoot proliferation. Propagules were subsequently subdivided and transferred to fresh medium at 2- to 4-week intervals. New shoots were excised and inserted in mWPM supplemented with 0.57 μm IAA to promote root formation. This method has been successfully used to produce Agrobacterium -free plants of muscadine cultivars Carlos, Doreen, Jumbo, Magnolia, and Sterling for research purposes and for a foundation planting in Mississippi. Chemical names used: benzylaminopurine (BAP); indole3-acetic acid (IAA).

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Tiffany L. Law and Gregory A. Lang

shoots along the trunk, whether oriented vertically or horizontally. The mechanism of apical dominance is not fully understood, but it is generally accepted that basipetal transport of auxin produced in the terminal meristem suppresses growth of lower

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Barbara M. Reed

Cold hardening is an effective method for conditioning meristems for cryopreservation. ABA plays a role in hardening and produces increased hardiness in suspension cultured cells. This study was designed to determine if growth, in vitro, on ABA (5×10-5 M) for one week, would substitute for one week of cold hardening, and if ABA would provide additional conditioning when added in combination with cold hardening treatments. In vitro plantlets of Rubus spp. were grown for one week with or without cold hardening and with or without ABA. Meristems from these plants were frozen at 0.8C* min-1 to -35 C, then plunged into LN2, thawed, and plated on recovery medium. One month after thawing, cold-hardened plants with and without ABA treatment had recovery rates of up to 83%. Survival of plants grown at room temperature ranged from zero to 8% and zero to 28% for plants grown on ABA at room temperature. At the rates tested, ABA is less effective than cold hardening in conditioning apical meristems of in vitro Rubus plants for cryopreservation and provides no additional protection to cold-hardened meristems.

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James M. Dangler, Robert W. Scheuerman, Robert N. Campbell and Christopher A. Clark

For about 30 years, the Univ. of California has used advanced laboratory techniques in addition to traditional methods to produce pathogen-free and true-to-type sweetpotato seedstock. The effort continues with the varieties important in the marketplace today. This program serves as a model for the use of meristem culture by foundation sweetpotato programs in other states.

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Michael E. Kane and Craig K. Chandler

Many horticultural crops are infected with bacterial, fungal, or viral pathogens that reduce yield and/or quality. Recovery and maintenance of pathogen eradicated crops, such as strawberry (Fragaria × ananassa Duch.), have been possible following the isolation and culture of apical meristems or meristem-tips in vitro. A laboratory exercise has been developed to provide experience in the procedures required for the isolation, surface disinfection, and in vitro establishment of meristem-tip explants excised from strawberry stolons. Stolons are obtained from greenhouse-grown strawberries (`Sweet Charlie') maintained in hanging baskets under a 14-h photoperiod. Stolons are cut into single-node segments and terminal tips. The leaf blades are removed and the nodal sections are rinsed and then surface-disinfected by successive agitation in 70% ethanol and 1.05% sodium hypochlorite, followed by three rinses in sterile deionized water. In the transfer hoods, each student attempts to isolate meristem-tips and shoot tips of various sizes under high magnification provided by a stereomicroscope. Explants are inoculated onto Murashige and Skoog basal medium (Murashige and Skoog, 1962) supplemented with 30 g/liter sucrose, 80 mg/liter adenine sulfate, 1.0 mg/liter benzyladenine, 1.0 mg/liter indole-3-acetic acid, and 0.01 mg/liter gibberellic acid (GA3) and solidified as 45°slants with 1.25 g/liter Phytagel and 3.0 g/liter TC agar. Growth responses are monitored weekly. After 6 weeks, students record the percentage of visibly contaminated cultures and number shoots produced per explant. The relationship between initial explant size and in vitro growth is also determined. Students index their cultures for the presence of cultivable bacteria and fungi using sterility test media.