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Larry J. Shoemake, Michael A. Arnold, and Fred T. Davies Jr.

A series of six experiments was conducted over eight years to investigate impacts of provenance on transplant establishment in landscapes and the role of adventitious root regeneration in differential genotypic responses during establishment of Platanus occidentalis L. Fall, spring, and summer transplants of container-grown half-sib families (HSF = seedlings derived from a single mother tree with unknown male parentage), including two selections native to Brazos County, Texas (Brazos-C, Brazos-D), one native to Cookeville, Tenn. (Cookeville), two Kentucky/Tennessee HSF from the Westvaco Corp. (WV-10, WV-14), and two Texas HSF from the Texas Forest Service tree improvement program (TFS-09, TFS-24), were established to determine field/landscape growth responses. Subsequent studies were conducted to investigate differential leaf gas exchange responses of TFS-09 and Cookeville during moderate water deficits and to determine root regeneration potential (RRP) responses of TFS-09, Brazos-C, WV-14, and Cookeville HSF following fall, spring, and summer transplant. To investigate consistency of within-family genotypic responses and to determine relationships among adventitious root initiation from shoot cuttings, RRP, and landscape establishment, five seedlings of TFS-09 and five from Cookeville HSF were clonally propagated and ramets tested under field and RRP conditions similar to those with seedling-derived plants. Regionally native HSF consistently grew taller, had larger trunk diameters, and often had greater survival during the first 3 years in the landscape than HSF not native to the region in which the studies were conducted. Rapidity of root regeneration among HFS at the time of transplant was the best root growth related predictor of successful landscape establishment. Some growth advantages were found using genetically improved HSF, but not as consistent an improvement as with the use of seedlings from regional provenances. Within-family variation in landscape performance was greater with nonregional Cookeville clones than with regional TFS-09 clones, however there was overlap among the more vigorous Cookeville clones and the least vigorous TFS-09 clones. Increased rapidity of root regeneration and drought adaptations related to leaf morphology and gas exchange characteristics may be involved in enhanced growth responses of Texas regional genotypes. No consistent relationships were found among adventitious rooting responses from shoot cuttings and subsequent RRP of the same genotypes from root tissues or their growth during the first 3 years in landscapes.

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V.M. Gingas

Partially expanded male catkins at the pre-pollen shedding stage of Quercus rubra L. and Quercus bicolor Willd. were cultured on MS medium supplemented with BA or 2,4D Explants on 2,4D produced a yellow embryogenic callus, seeming to originate from the pedicels. Subsequent transfers to BA and then, MS without growth regulators, resulted in callus proliferation. After ten weeks in culture, white embryoids developed from the callus of Q. bicolor. Separated and individually cultured embryoids underwent direct, repetitive embryogenesis. Upon transfer to ½-strength MS, embryoid germination and plant regeneration occurred, Callus of Q. rubra degenerated after five months in culture, failing to produce embryogenic structures.

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Paula P. Chee

A procedure for the regeneration of muskmelon (Cucumis melo L.) cv. Topmark via shoot organogenesis from cotyledon explants is described. The best induction medium for a morphogenic response was MS salts and vitamins medium with BA at 1.0 mg·liter-1. Further vegetative bud development was completed by transferring organogenic tissue to MS medium containing BA at 0.05 mg·liter-1 . The shoots were rooted in MS medium containing NAA at 0.01 mg·liter-1. Morphologically normal plantlets were obtained. Chemical abbreviations used: 6-benzylaminopurine (BA); indoleacetic acid (IAA); naphthaleneacetic acid (NAA).

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Hristina H. Stamenova-Berberova and Paul E. Read

Native plants are often ignored in horticulture because they may lack major ornamental traits and many of them are difficult to propagate. Creamy indigo (Baptisia bracteata Mnhl.) is a North American legume with considerable potential as a container-grown or ornamental plant for managed landscapes. Nodal explants from aseptically germinated seedlings were evaluated for axilary shoot and leaf development. The explants were cultured on Murashige and Skoog medium (MS) containing adenine sulfate at 80 mg•L-1, 30% sucrose, and different levels of N-6-benzyladenine (BA) (0.5,1.0,2.0 mg•L-1) supplemented with indole-3-acetic acid (IAA) (0.05, 0.1 or 0.5 mg•L-1) or with IAA omitted. Shoot regeneration occurred within 2 to 3 weeks. The best medium for shoot regeneration was MS supplemented with BA at 1.0 mg and IAA at 0.1 mg•L-1. Shoots were transferred onto rooting medium consisting of Ω MS supplemented with 1.0 mg alpha-naphthaleneacetic acid (NAA) and 1.0 mg indole-3-butyric acid (IBA)/L and 20% sucrose. Rooting took place within 3 to 5 weeks. Plantlets were then planted in soil mix, placed under a polyethylene tent for 2 weeks, and transferred into the greenhouse for further growth.

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Kimberly A. Pickens, (Max) Z.-M. Cheng, and Stephen A. Kania

The mitotic inhibitors, colchicine and oryzalin, were evaluated for their effects on callus, adventitious shoot formation, and tetraploid induction of Euphorbia pulchurrima `Winter Rose'. In vitro grown leaf sections were placed on various media supplemented with either colchicine or oryzalin at various concentrations for 1 to 4 days. Colchicine was less damaging to leaf tissues than oryzalin. On various colchicine-containing media, prolific calluses were produced and adventitious shoot formation was observed. Regenerated shoots were found to be diploid as determined by flow cytometry. On media supplemented with oryzalin (28.9 μm to 144 μm), leaf tissues produced callus but failed to form adventitious shoots. Samples of calluses produced on oryzalin-containing media were subject to analysis using flow cytometry and were found to be diploid. These results suggest that the colchicine is less toxic on poinsettia tissues and shoot induction than oryzalin. Additional experiments are needed to establish a protocol for in vitro induction of poinsettia tetraploid with colchicine and oryzalin.

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Richard L. Bell, Ralph Scorza, Chinnathambi Srinivasan, and Kevin Webb

`Beurre Bosc' pear (Pyrus communis L.) was transformed with Agrobacterium tumefaciens (E.F. Smith & Townsend) Conn strain EHA101 containing the binary vector pGA-GUSGF into which the rolC gene had been inserted. Leaf explants from in vitro shoot tip cultures were wounded, Agrobacterium-inoculated, and cultured on kanamycin selection medium. Regenerating shoots were transferred to proliferation medium without antibiotics. Three clones tested positive for GUS and nptII enzyme activity. Transformation with the rolC gene was confirmed by DNA, RNA, and protein blot analyses. The number of copies of the rolC transgene varied from one to three. Plantlets of the three transgenic clones were acclimated and transferred to the greenhouse. Preliminary observations of phenotype indicate that the rolC gene reduced height, number of nodes, and leaf area of transgenic `Beurre Bosc'.

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Lunique Estime, Marie O'Shea, Michael Borst, Jennifer Gerrity, and Shih-Long Liao

Typha latifolia L. (broadleaf cattail) callus was initiated from leaf sections, as well as from pistillate and staminate spikes. Two basal media in combination with three growth regulator regimes were tested for their capacity to induce callus from the explants. Pistillate spikes maintained in the dark on B5 medium supplemented with 5 mg·L-1 dicamba and 1 mg·L-1 BA produced the fastest growing cell line compared to other explants and media combinations. A growth curve in suspension culture was generated for this cell line on B5 medium. The mass of the callus increased by 150% by the end of the growth curve. Upon transfer of the callus to MS medium without growth regulators but with 3% sucrose and 3% phytagel, plants could be regenerated from 22% of the cultures. Chemical names used: 3,6-dichloro-2-methoxybenzoic acid (dicamba); N 6-benzyladenine (BA).

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Yaseen Mohamed-Yaseen, Raymond J. Schnell, Robert J. Knight, and T.L. Davenport

A procedure was developed to regenerate plants via tissue culture from embryonic axes of mature avocado seeds. Explants were cultured in Murashige and Skoog (MS) medium supplemented with benzyladenine (BA) and naphthalene-acetic acid (NAA) or thidiazuron (TDZ) and NAA. Culture were kept in the dark for 7-10 days to reduce browning resulting from phenolic oxidation. Multiple shoots (5-8) were formed after transfer to light. Further multiplication were achieved using different combination of BA and NAA or TDZ and NAA. Shoots were cultured in MS supplemented with 2mg/l indolebutyric acid (IBA) for 2 weeks then transferred to MS supplemented with lg/l activated charcoal for root induction. Complete plants were obtained in vitro.

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V.M. Gingas

Partially expanded male catkins of swamp white oak (Quercus bicolor Willd.) and red oak (Quercus rubra L.) were cultured on Murashige and Skoog (MS) medium supplemented with BA or 2,4-D. Explants on 2,4-D produced a yellow embryogenic callus originating from the junction of the pedicel and peduncle. Subsequent transfers to MS with BA and then MS without growth regulators resulted in callus proliferation. After 10 to 14 weeks in culture, white embryoids developed from the callus of Q. bicolor. Separated and individually cultured embryoids underwent direct, repetitive embryogenesis. Upon transfer to l/2-strength MS, embryoid germination and plant regeneration occurred. Callus of Q. rubra degenerated after 5 months in culture, failing to yield embryogenic structures. Chemical names used: dichlorophenoxyacetic acid (2,4-D); benzyladenine (BA).

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Carol Robacker

Immature leaf laminae and petioles of `Regale' and `Fry' muscadine grapes (Vitis rotundifolia Michx.) were cultured on Nitsch and Nitsch (NN) medium supplemented with 9.0 μm 2,4-D and 4.4 μm BA, and gelled with agar. Callus and original explant tissues were transferred to NN medium containing 10.7 μm NAA and 0.9 μm BA to proliferate embryogenic callus, which, when transferred to NN medium without growth regulators, yielded globular embryos. The embryos matured and germinated after being subcultured to fresh medium without growth regulators. Somatic embryogenesis incidence was greater from petioles than laminae: 90% of `Regale' and 50% of `Fry' petioles formed embryos, compared with 14% and 2% of laminae, respectively. Culturing germinated somatic embryos on NN medium with 1 μm BA enhanced shoot growth. Regenerated plants flowered and appeared morphologically normal. Chemical names used: N-(phenylmethyl)- 1H -purin-6-amine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); α- naphthaleneacetic acid (NAA).