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Michelle Carratu and Roger J. Sauve

Several studies were conducted to evaluate the effects of cultivar, cutting length, and leaf number on rooting of poinsettia. Cuttings were rooted under mist in a soilless medium with 50 cuttings per treatment. Visual rootball ratings were performed after 3 wk. In the first experiment, rooting of ten poinsettia cultivars was compared. The rooting hormone was 0.1% indole-3-butyric acid (IBA). Rooting of `V-14 Red' and `V-14 Marble' was the highest. `V-17 Pink' and `V-17 Marble' had the highest number of callused cuttings. `V-17 White' produced the highest number of extensively rooted cuttings. `V-14 Pink' (3-lf) cuttings 12 cm long rooted better than 5 cm cuttings. Rooting of (7 cm) 3- and 4-leaf cuttings was higher than rooting of 2-leaf cuttings. `V-14 Pink' cuttings treated with 0.8% IBA or 1% IBA + 0.5% 1-napthaleneacetic acid (NAA) rooted better than with 0.1% or 0.3% IBA.

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Michelle Carratu and Roger J. Sauve

Phytophthora cinnamoni infected Rhododendrons subjected to moderate moisture levels had greater survival rates than at the wet or dry levels. We potted rooted cuttings of Rhododendron L. hybrid, “Lee's Dark Purple” in 3 liter containers using a mixture of 3 pine bark: 2 coarse builder's sand: 1 Canadian peat moss (by vol.) and infected them with P. cinnamoni. Tensiometers maintained the moisture levels of the treatments at 0, -5, -10, -15, and -20 kPa. After 90 days, measurements of the plants revealed virtually curvilinear results, with the highest survival rate, plant and root weights at -5 and -10 kPa. Investigation continues on susceptibility of Rhododendrons to P. cactorum, P. cryptogea, P. cinnamoni, and P. citrophthora under wet and dry conditions.

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Margaret T. Mmbaga, and Roger J. Sauvé,

Twenty-five dogwood accessions (one Cornus kousa, three C. kousa × C. florida hybrids, and 21 C. florida) were characterized using amplified fragment length polymorphism. Among the C. florida accessions, four were named cultivars and 17 were selections from Tennessee State University's dogwood breeding program. Amplified fragment length polymorphism band profiles obtained from 13 EcoRI/MseI (+3/+3) primer pairs showed the presence of high genetic diversity between species and within the C. florida accessions. Each accession was distinctly different from each other, and the resistant clones clustered into distinct groups.

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Suping Zhou, Roger J. Sauve and Abdulah Abdulah

Complementary Deoxyribonucleic Acid (cDNA) differential display and reverse Northern dot blot were used to identify genes in Pachysandra terminalis Sieb. & Zucc., a cold-tolerant plant, that are regulated by low temperatures. Rooted cuttings were obtained from stock plants that had been maintained in a greenhouse at 24 °C. These cuttings were subjected to the following cold treatments: 2 weeks at 12 °C, 48 hours at 4 °C, 48 hours at 0 °C, and 4 hours at –1 °C. Following leaf tissue analysis of treated and control plants, some stress-related genes and many novel genes were identified. Northern blot hybridization demonstrated that all novel genes were regulated by the cold treatments.

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Jing-Tian Ling and Roger J. Sauve

Leaf segments of greenhouse-grown Ulmus americana L. plants cultured on a Murashige and Skoog basal salts medium supplemented with 0.22 mg/L thidiazuron formed friable type of callus and regenerated shoots. This friable callus readily formed a cell suspension when the callus was placed in a liquid MS medium containing 2 mg/L 1-naphthaleneacetic acid and 1 mg/L 6-benzylaminopurine. Shoots were regenerated from 3-month-old suspension cell cultures after the suspension cells had been cultured on solid medium. Shoots developed roots on MS medium containing 0.1 mg/L indole-3-butyric acid. Intact plants were successfully established in soil.

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Suping Zhou, Roger J. Sauvé and Margaret T. Mmbaga

A cold acclimatization mechanism regulated by the accumulation of mRNAs and proteins has been tentatively identified in japanese spurge (Pachysandra terminalis Sieb. & Zucc.). Two polypeptides and several cDNA fragments were observed in leaf tissue after acclimation. When these proteins were probed with type III fish antifreeze antibodies, an immune-cross reaction occurred. Nonacclimatized young leaves and stems of japanese spurge survived 20-minute exposures at -5 °C. Although newly emerged leaves and stems were damaged, plants resumed growth at higher temperatures. After acclimation by gradual cold treatments (4 to -5 °C), new proteins began to accumulate in young leaves and plants were more tolerant to extended treatments at -5 °C. Changes in accumulation of proteins and mRNA in leaf tissue of japanese spurge appear to be an adaptation mechanism to subfreezing conditions. This is the first report of the immune-cross reaction between antibodies of type III fish antifreeze proteins and plant proteins

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Suping Zhou, Roger J. Sauvé, Margaret T. Mmbaga and Chaim Frenkel

Leucanthemum maximum `Silver Princess' plants, that were gradually acclimated for 7 days at 10 °C followed by 28 days at 7 °C, were subjected to the following cold treatments: 30 days at 4 °C; 4 or 5 days at 0 °C and for 3 hours at –1 °C to identify cold inducible proteins that may be responsible for cold tolerance in this cold tolerant species. Change in antioxidant enzymes activity in fully expanded leaves was assessed after each treatment. Catalase activity began to increase after 30 days at 4 °C and reached its peak after a 5-day exposure to 0 °C. The activity of cellular glutathione peroxidase and glutathione reductase significantly increased after a 4-day exposure to 0 °C. Changes in activity of four active superoxide dismutase isoforms, one basic guaiacol peroxidase and two o-dianisine peroxidase isoforms were also detected following the full series of cold treatments (30 days at 4 °C; 4 or 5 days at 0 °C and for 3 hours at –1 °C).

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Jing-Tian Ling, Henock Zerit and Roger J. Sauve

Seeds of Chinese elm cultivar King's Choice were collected from field-grown plants and germinated aseptically. Hypocotyl segments were excised from 2-week-old seedlings and cultured on Murashige and Skoog (MS) medium supplemented with TDZ alone or in combination with 0.05 mg/L NAA. At least 50% of explants produced shoots 4 weeks after culture initiation. At thidiazuron (TDZ) from 0.05 to 5.0 mg/L, the number of shoots/explant increased as concentration increased. Addition of 0.05 mg/L NAA stimulated shoot regeneration when TDZ concentration was 0.5 mg/L or less, but suppressed it if TDZ concentration was higher than 0.5 mg/L. Regenerated shoots elongated quickly on MS medium supplemented with 1 mg/L gibberellic acid and initiated rooting on MS medium containing 0.1 mg/L indole-3-butyric acid.

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Roger J. Sauve, Suping Zhou, Yingchun Yu and Wolfram George Schmid

A randomly amplified polymorphic DNA (RAPD) technique was used to identify and determine the phylogenetic relationships of 37 hosta accessions representing the major subgenera, sections and groups in the genus Hosta. Results of this study show that RAPD markers were able to differentiate not only the main groups, whose plants shared many genetic traits, but also cultivars within a species. Some accessions were identified by a single primer while others had high intercross linkage and required many markers for their separation. The phylogenetic clustering showed that H. plantaginea, the only night-blooming species, and H. ventricosa, the only known natural tetraploid, are unique and should be classified separately. The four species in the subgenus Bryocles, section Lamellatae H. venusta, H. minor, H. capitata, and H. nakaiana have very low genetic similarity since they do not share many amplified fragments. The other accessions were classified into four main clusters; cluster 1: H. venusta, H. tardiva, H. pycnophylla, H. tsushimensis `Ogon', H. montana, H. tibae, H. montana f. macrophylla, H. kikutii `Kikutii', H. longissima `Longifolia', H. rectifolia `Rectifolia', H. takahashii and H.`Undulata'; cluster 2: H. laevigata, H. sieboldiana, H. pycnophylla × H. longipes f. latifolia, H. longipes `Urajiro' and H. ibukiensis; cluster 3: H. capitata, H. kikutii `Polyneuron', H. nigrescens, H. kikutii `Yakusimensis', H. pachyscapa, H. kikutii `Caput-Avis', H. longipes f. latifolia, H. hypoleuca, H. okamotoi, H. densa and H. takiensis; and cluster 4: H. aequinoctiiantha, H. rupifraga, H. `Amanuma', H. minor and H. kikutii `Densa'.

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Jing-Tian Ling, Nick Gawel and Roger J. Sauve

The genus of Hosta (plantain lily) is a shade-loving herbaceous plant with attractive foliage. Confusion exists in the genus regarding nomenclature and taxonomy. In this study, the possibility of application of RAPD markers to characterize Hosta species and cultivars was investigated. DNA was extracted from 28 Hosta species and cultivars. Thirty-six of 37 primers generated RAPD markers. Phylogenic analysis and principal components analysis showed groupings among cultivars. Results indicated that H. plantaginea and H. ventricosa were the most distant from the other tested species and cultivars. These results suggest RAPDs may be useful in the identification and analysis of relationships among Hosta.