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YanLing Zheng, GaoJuan Zhao, and HuanCheng Ma

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

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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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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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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.

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Joseph K. Peterson, Howard F. Harrison, D. Michael Jackson, and Maurice E. Snook

Periderm and cortex tissues of 14 genetically diverse sweetpotato [Ipomoea batatas (L.) Lam.] clones were grown under low stress conditions and analyzed for their content of scopoletin ((7-hydroxy-6-methoxycoumarin) and scopolin (7-glucosylscopoletin). A wide range of concentrations of both compounds was found in both tissues. The two compounds were tested in vitro for their biological activity (concentration-activity relationships) using several bio assays: germination of proso-millet (Panicum milliaceum L.) seed; mycelial growth of the sweetpotato fungal pathogens Fusarium oxysporum Schlecht. f. sp. batatas (Wollenw.) Snyd. & Hans, F. solani (Sacc.) Mart., Lasiodiplodia theobromae (Pat.) Griffon & Maubl., and Rhizopus stolonifer (Ehr. ex Fr.) Lind; and growth and mortality of diamondback moth[Plutella xylostella (L.)] larvae on artificial diet. The glycoside scopolin showed little activity, except moderate inhibition of F. oxysporum. The aglycone scopoletin inhibited seed germination and larval growth; however, at much higher concentrations than were measured in the tissues. Mycelial growth of the four pathogenic fungi, however, was inhibited at concentrations occurring in some sweetpotato clones.

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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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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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Yueju Wang, Michael Wisniewski, Richard Meilan, Minggang Cui, Robert Webb, and Leslie Fuchigami

Ascorbate peroxidase (APX) plays an important role in the metabolism of hydrogen peroxide in higher plants, affording them protection against oxidative stress. We studied the effect of overexpressing a cytosolic ascorbate peroxidase (cAPX) gene—derived from pea (Pisum sativum L.)—in transgenic tomato plants (Lycopersicon esculentum L.). Transformants were selected in vitro using kanamycin resistance and confirmed by polymerase chain reaction (PCR) and northern analyses. An APX native-gel assay indicated that, in the absence of stress, APX activity in transgenic plants was several times greater than that measured in wild-type (WT) plants. Several independently transformed lines were propagated and evaluated for resistance to chilling and salt stress. After placing seeds at 9 °C for 5 weeks, percent germination was greater for seeds obtained from transgenic lines (26% to 37%) compared to the WT (3%). Plants from transgenic lines also had lower electrolyte leakage (20% to 23%) than WT (44%) after exposure to 4 °C. Visual assessment of transgenic and WT lines exposed to salinity stress (200 or 250 mm) confirmed that overexpression of APX minimized leaf damage. Moreover, APX activity was nearly 25- and 10-fold higher in the leaves of transgenic plants in response to chilling and salt stresses, respectively. Our results substantiate that increased levels of APX activity brought about by overexpression of a cytosolic APX gene may play an important role in ameliorating oxidative injury induced by chilling and salt stress.

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Bruce W. Wood

− )] known to be requisite for a degree of in vitro pollen grain germination and subsequent germ tube growth. Findings from other species are suggestive that other important growth promoting or inhibiting chemicals, such as flavonols, are also present under

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Carlos De la Cuadra, Alexis K. Vidal, Patricia Peñaloza, Leví Mansur, and Carlos Huenchuleo

. compacta lives in the same habitat as Z. elegans and that its germination temperature requirements are known ( De la Cuadra et al., 2017 ), it can be hypothesized that the germination temperature requirements of Z. elegans seeds are similar to those of