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Rosilene Barbosa de Franca, Gerson Renan de Luces Fortes, and Adriano Nunes Nesi

The aim of this work was to evaluate the effect of sucrose on the in vitro muliplication of potato, cultivars Baronesa, Macaca, and Cristal. The nutrient medium used was the MS basal salts and vitamins added to 100 mg·L-1 myo-inositol. Four sucrose concentrations (20, 30, 40, and 50 g·L-1) were tested. The pH was adjusted to 5.9 before autoclaving. Each treatment had 15 explants, which were collected from the lower part of the shoot containing two buds. This material was inoculated in a 250-mL flask with 40 mL of nutrient medium. After inoculation the flasks were kept in a growth room under 25 ± 2 °C, 16-h photoperiod, and 19 μMol·m-2·s-1 radiation provided by cool-white fluorescent lamps for 30 days. This trial was designed in a randomized block with three replicates. Every 7 days, the parameters were collected as follows: number of buds, shoot length and number of shoots. It was observed that `Baronesa' presented the highest number of buds and rate of multiplication. `Cristal' had a slightly better performance for these parameters. Plants treated with sucrose at 50 g·L-1 led to a higher number of shoots. However, `Macaca' treated with sucrose at 40 g·L-1 had the highest shoot length.

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Lurline Marsh

Explants (cotyledon, cotyledonary node, second node, hypocotyl, epicotyl, and leaf) of cowpea (Vigna unguiculata) genotypes MN13 and Pinkeye Purple Hull were cultured on Murashige and Skoog basal nutrient medium. The medium was supplemented with 1 mg·L–1 benzyladenine (BA) or 1 mg·L–1 benzyladenine plus naphthalene acetic acid (BA + NAA) or 2 mg·L–1 2,4-dichlorophenoxy acetic acid (2,4-D). Cultures were maintained at 22°C for 1 month, after which they were transferred to 1 mg·L–1 BA + NAA. Cotyledons, hypocotyl, epicotyl, and leaf segments produced only calli after subculturing in BA + NAA. The second node and cotyledonary node explants cultured on the BA or BA + NAA followed by subculture on BA + NAA produced calli, shoots, and roots. The plants were then transplanted to promix but later died.

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P. J. Kaltsikes and P. J. Bebeli

The genetics of the ability of tomato pollen to germinate and grow in vitro under low temperature was investigated in two crosses namely “Resista” × “Hilda” and “Resista” × “Monita”. In each cross the following generations were utilised: F1, F2, BC1 and BC2, and their reciprocals, along with the parents. Pollen was placed on microscope slides having cavities filled with a liquid nutrient medium (water, 10% sucrose and 50 ppm boric acid) and allowed to germinate and grow for six hours at 15° C and then killed with acetocarmine. Germination rates and pollen tube length were determined and analyses on a genetic model allowing only for additive and dominance gene effects.

For pollen germination rate both additive and dominance gene effects were significant while for tube length only the additive effects were. Dominance was towards lower rates of germination. At least three genes control pollen germination rates while seven or more are involved in pollen tube length determination.

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Jihad Abdulnour, Danielle Donnelly, and Nayana N. Barthakur

Calcium45 uptake by in vitro-grown `Bintje' potato plantlets increased linearly as the salt concentration of the nutrient medium was decreased from 2 to 0.5 MS. The increase in Ca45 absorption was significant for shoot tips and stems (P ≤ 0.05), but not for foliage. In shoot tips and stems, Ca45 uptake increased linearly as medium Ca increased, independent of boron (B) medium concentrations. However, in leaves, this increase was linear at low B concentrations (0.05 mM) and parabolic at relatively higher B concentrations (0.1 and 0.2 mM). When medium Ca was 9 mM, Ca45 absorption was reduced significantly (P ≤ 0.01) by increasing B concentration in the medium.

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Bernard A. L. Nicoulaud and Arnold J. Bloom

We examined root ammonium absorption by tomato seedlings (Lycopersicon esculentum Mill. `T-5') after first exposure of the roots to ammonium. Some plants received a nutrient medium containing nitrate as the sole N source. In a second treatment, the leaves were sprayed daily with a urea solution, while the roots were in N-free medium. The last two treatments were initially grown in medium that contained ammonium nitrate, but then either were shifted to a N-free medium for 10 days or had their roots excised and were rerooted in N-free medium for 21 days. Root ammonium absorption remained constant after first exposure to ammonium for the plants exposed to nitrate alone, whereas root ammonium absorption declined with time for the other three treatments. These results indicate that for tomato a) ammonium in the rhizosphere does not induce root ammonium absorption and b) some product of ammonium metabolism represses root ammonium absorption.

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Samir Debnath*

The morphological development of lingonberry (Vaccinium vitis-idaea L.) plants propagated either by conventional softwood cuttings or by in vitro shoot proliferation from nodal explants or by shoot regeneration from excised leaves of micropropagated shoots, was studied in cultivars `Regal', `Splendor', and `Erntedank'. Significant differences were observed between the treatments. In vitro-derived plants produced more shoots branches and rhizomes in contrast to conventional cuttings which rarely produced rhizomes. Plants propagated from cuttings had a lower number but vigorous shoots and thicker rhizomes than in vitro-derived plants. Source propagule had significant effect on multiplication rate. Another experiment evaluated the effect of indole-3-butyric acid (IBA) application to softwood cuttings on subsequent rooting, shoot development, and rhizome production. Treating cuttings with IBA did not significantly improve rhizome formation and elongation. In vitro culture on nutrient medium apparently induces the juvenile branching characteristics that favored rhizome production. The advantage of rhizome production of in vitro-derived plants over stem cuttings varied among genotypes.

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K.H. Wang, A.R. Kuehnle, and B. Sipes

Burrowing nematode, Radopholus similis, reduces flower-yield-infected anthurium fields. Genetic resistance is one alternative to chemical control of the disease in anthurium. Seventeen commercial anthurium varieties, established in vitro on anthurium nutrient medium, were inoculated with burrowing nematodes to screen for tolerance. Three months after inoculation, plant responses were compared by number of nematodes recovered and by symptom index and plant weight loss with respect to non-inoculated plants. Results show that `Mauna Kea' and `Flamingo' anthuriums are among the most tolerant, while `Ozaki' is one of the most susceptible. These results are consistent with grower field evaluation. Nematode count is positively correlated with symptom index and weight loss. The mechanism of tolerance or resistance of anthurium toward burrowing nematode is unclear. However, due to the fact that burrowing nematode is a migratory endoparasite, a preinfectional resistance or tolerance mechanism is more likely to take place.

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Gerson Renan de Luces Fortes* and Ana Carolina Pereira e Silva

Brazilian ginseng (Pfaffia sp.) is largely known as having anabolic, analgesic, anticancerous, anti-inflammatory, antileukemic properties, and more. Embrapa Genetic Resources and Biotechnology is the major Conservation Center in Brazil. This species could only be stored under in vitro conditions. There are more than two hundred native acessions collected from different locations in the country. So far very few works are found in the literature and there is no specific protocol for in vitro conservation. The aim of this study was to test five different acessions from in vitro collection under one specific nutrient medium. The acessions were catalogued as 2205-12; 2202-04; 2209-11; 2209-10 and 2205-21. One-bud microcutting was inoculated on a MS nutrient medium without growth regulators and added with vitamins, myoinositol (100 mg·L-1), sucrose (30 mg·L-1) and agar (6 mg·L-1). The pH was adjusted to 5.7 before the agar addition. Each treatment was replicated 7 (seven) times and each plot consisted of six test tubes with 5-mL solution. The trial was replicated twice. The evaluations were performed once weekly where the shoot growth was taken along with the number of buds and roots formed. The highest shoot growth were obtained for the acessions 2205-12 and 2209-10. Acession 2209-11 had an intermediate shoot growth and number of buds, but had the highest number of roots per shoot (4.27) compared to 2.14 and 3.75 for acessions 2205-21 and 2209-10, respectively. The highest rate of multiplication was achieved for acessions 2205-12 (4.49) and 2202-04 (4.46) as compared to 3.60 for acession 2205-21. It was clearly shown that acession 2205-21 is a recalcitrant one as in vitro multiplication is concerned. All the acessions rooted in this medium.

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K.A. Malik, Christena Visser, and praveen K. saxena

In vitro regeneration by shoot organogenesis and-or somatic embryogenesis is accomplished by culturing the explants on a nutrient medium supplemented with phytohormones. Auxins in general, and 2,4-D in particular, have been shown to induce somatic embryogenesis whereas shoot regeneration is stimulated by cytokinins. In studying the morphoregulatory role of thidiazuron (TDZ) - a substituted urea with cytokinin-like activity - we found that it induces a high frequency of both organogenesis and somatic embryogenesis depending upon the plant species. For instance, whole seedlings of peanut developed somatic embryos and those of bean and pea produced shoots in response to culture on TDZ (1-40 μM)-supplemented media. In cultured explants of geranium, the use of TDZ (0.2-1 μM) effectively replaced the requirement of 2,4-D or BAP and IAA for obtaining somatic embryos. The frequency of regeneration was two to ten times higher than that achieved with auxin-cytokinin combinations. While no direct evidence is currently available to establish a relationship between TDZ and endogenous phytohormones, our results suggest that it may act by establishing endogenously the auxin:cytokinin ratio permissive of induction and expression of morphogenically competent cells.

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D. Marshall Porterfield, Mary E. Musgrave, and Thomas W. Dreschel

A ground-based comparison of plant nutrient delivery systems that have been developed for microgravity application was conducted for dwarf wheat (Triticum aestivum L. `Yecora Rojo') and rapid-cycling brassica (Brassica rapa L. CrGC#1-33) plants. These experiments offer insight into nutrient and oxygen delivery concerns for greenhouse crop production systems. The experiments were completed over a 12-day period to simulate a typical space shuttle-based spaceflight experiment. The plant materials, grown either using the porous-tube nutrient delivery system, the phenolic foam support system, or a solidified agar nutrient medium, were compared by plant-growth analysis, root zone morphological measurements, elemental composition analysis, and alcohol dehydrogenase enzyme activity assay. The results of these analyses indicate that the porous tube plant nutrient delivery and the phenolic foam systems maintain plant growth at a higher level than the solidified agar gel medium system. Root zone oxygenation problems associated with the agar system were manifested through biochemical and morphological responses. The porous tube nutrient delivery system outperformed the other two systems on the basis of plant growth analysis parameters and physiological indicators of root zone aeration. This information is applicable to the current crop production techniques used in greenhouse-controlled environments.