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Jules Janick, Christiane Cabral Velho, and Anna Whipkey

Journal Paper no. 12,525 of the Purdue Univ. Agricultural Experiment Station. We thank William Carlson, Southern Forestry Res. Dept., Weyerhaeuser Corp., for providing seed. The cost of publishing this paper was defrayed in part by the payment of

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X. Wang, J.T.A. Proctor, S. Krishna Raj, and P.K. Saxena

Ginseng is a very valuable agricultural species grown for its root, which contains pharmacologically active constituents. One limiting factor for expansion of ginseng production is an efficient method for mass propagation. Currently, seeding is the principal method of propagating ginseng, but the embryo of ginseng seeds at harvest is immature. A stratification schedule consisting of a cool-warm-cool temperature treatment over 18-22 months is required for embryo development and seed germination. An alternative for the efficient production of ginseng is mass propagation through the use of in vitro culture techniques. The objective of this work was to develop a highly efficient system for regeneration of ginseng. The efficacy of three auxins, viz. 2,4-D, NAA and dicamba, were compared for the induction of somatic embryogenesis in American ginseng. Somatic embryos formed on ginseng cotyledonary, zygotic embryo, and shoot explants after 8 weeks of induction by the auxins. Significantly more somatic embryos were induced by culture of any of the ginseng explants on media supplemented with 5 μmol·L-1 2,4-D than any other auxin treatment. Histological and SEM studies confirmed that the regenerants were somatic embryos. Somatic embryos germinated and developed into normal plants in 3-6 months. The development of a regeneration system for ginseng using somatic embryogenesis is a necessary first step for mass propagation and the improvement of American ginseng.

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YanLing Zheng, GaoJuan Zhao, and HuanCheng Ma

moisture contents for pea seeds stored at different temperatures Ann. Bot. (Lond.) 74 531 540 10.1006/anbo.1994.1151 Yamazaki, J. Miyoshi, K. 2006 In vitro asymbiotic germination of immature seed and formation of protocorm by Cephalanthera falcata

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Jameel M. Al-Khayri, Teddy E. Morelock, and Edwin J. Anderson

Cowpea, or southernpea, is an important food legume that provides a source of high-quality protein, especially in the mature seeds. In the United States, industries exist to supply dry and processed seeds. Our aim is to develop a regeneration system for cowpea as a prerequisite for genetic engineering. Our objective was to examine the in vitro responses of shoot tips to growth regulators. Shoot tips isolated from in vitro-germinated seedlings (`Coronet') were cultured on MS medium containing 2,4-D at 0, 0.01, 0.1, or 1 mg·liter–1 and kinetin at 2.5, 5, 10, or 20 mg·liter–1. Cultures were maintained at 12-hour photoperiods and 24C. Callus, shoots, and roots or combinations thereof developed depending on the treatment. Callus formed on 1 mg 2,4-D/liter, regardless of the kinetin level, but at 0.1 mg 2,4-D/liter and 5 or 10 mg kinetin/liter, shoots also grew. Callus, shoots, and roots developed on 2,4-D lower than 0.1 mg·liter–1. Callus induced on 5 mg kinetin/liter and 0.01 mg 2,4-D/liter regenerated shoots on transfer to 5 mg kinetin/liter and 0.1 mg NAA/liter. This work may assist in the development of a micropropagation system for cowpea.

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Kimberly A. Pickens, Jan Wolf, James M. Affolter, and Hazel Y. Wetzstein

Many bromeliad species indigenous to the rain forests of Central and South America are threatened because of over-collection and habitat destruction. Studies were conducted to develop propagation protocols for Tillandsia eizii, a rare ornamental bromeliad of ceremonial significance to the Highland Maya communities in Chiapas, Mexico. We anticipate using in vitro propagation for the conservation of this species with the potential of utilizing bromeliads as an alternative and sustainable forest resource. Protocols were developed for the sterilization and germination of axenic seed. Seedling growth in vitro was assessed and outplanting studies were conducted. Media were evaluated to promote adventitious bud production in experiments using the plant growth regulators naphthaleneacetic acid and benzylaminopurine. Pulse time and duration, as well as the stage of seed development, had a marked effect on bud production. The effects of various potting media on plant growth and survival were assessed. A pure pine bark medium elicited over 95 percent survival. Plants exhibited a “tank-like” morphology characteristic of plants in the wild.

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S.A. Merkle and B.A. Watson-Pauley

We thank Frank Corley and Dale Greene for assistance in obtaining plant materials and Chuck Moore for his photography. This work was supported by McIntire-Stennis funds allocated to the D.B. Warnell School of Forest Resources, Univ. of

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Matteo Serena, Bernd Leinauer, Rossana Sallenave, Marco Schiavon, and Bernd Maier

step in the process of screening for salinity tolerance in any plant species is to conduct a germination test. According to protocols outlined by the Association of Official Seed Analysts ( AOSA, 2009 ), media considered acceptable for use in standard

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Gayle Volk, Virgil Esensee, and Harrison Hughes

Crosses and self's were made among Fragaria × ananassa Duchn. cv. `Douglas' and `Fern' and Fragaria chiloensis (L.) Duchn. Seeds were surface sterilized, germinated and then grown on MS media (no vitamins, sucrose or hormones) with NaCl concentrations of 0 to 0.5% or 0.5% KCl. Polyethylene glycol (PEG), of corresponding water potentials, was used to induce drought stresses. Whole plant dry weights were evaluated after 50 days. Differences in salt tolerance were associated with genotype; progeny involving crosses with F. chiloensis showed greater salt tolerance. Increases in concentration of PEG caused decreased growth. The use of salt containing media may be used to evaluate strawberry seedlings for salt tolerance and, similarly, PEG may be used to evaluate for drought stress in vitro.

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Sean M. Campbell, Brian J. Pearson, and S. Christopher Marble

) found that either physical (abrasion with sandpaper) or chemical (soaking in sulfuric acid) scarification methods can increase germination by 70.5% compared to that of a control ( Makasana et al., 2016 ). Fig. 1. Dried butterfly pea seed pods remaining

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Kim D. Bowman

Phytophthora parasitica Dast. causes several root and trunk diseases of citrus, including damping-off, root rot, foot rot, and gummosis. Phytophthora resistance is needed in Citrus rootstocks and is available in Poncirus trifoliata (L.) Raf. and some hybrids between Citrus and P. trifoliata. Field or greenhouse tests of rootstocks require large amounts of space and time. To provide a preliminary indication of rootstock resistance to P. parasitica, nucellar seedlings of P. trifoliata selections, and Citrus × P. trifoliata hybrids were tested for response to P. parasitica by in vitro inoculation. Seeds of individual selections were germinated in sterile culture and 3-week-old shoots were excised and inoculated with a cultured isolate of Phytophthora. After 1 week of incubation, response to the disease organism was measured by length of stem discoloration. Progression of Phytophthora in the stem also was measured by plating sequential 5-mm segments of the shoot and determining presence or absence of Phytophthora in individual segments. Stem discoloration length corresponded with location of Phytophthora in the stem. Relative resistance, as measured by this technique, approximated field resistance for several common rootstock cultivars. Resistant, intermediate, and susceptible selections were found in populations of Citrus × P. trifoliata rootstock hybrids using in vitro inoculation.