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Roberto Valverde and Tony H. H. Chen

To generate a linkage map for further genetic analysis of the traits involved in cold hardiness of potato, we are constructing a RAPD-based linkage map using a two-generation interspecific pedigree of Solanum commersonii and S. cardiophyllum, a hardy and non-hardy species, respectively. We initially screened 220 primers of 10-base arbitrary sequences and selected 86 to amplify a total of 577 polymorphic bands: 301 S. commersonii-specific and 276 S. cardiophyllum-specific bands. Segregation of a total of 247 markers was scored on a population of 44 F1 individuals. From these 247 markers, we have identified 117 markers, which segregate 1:1 in the F1 progeny following a test cross configuration. A RAPD linkage map for S. commersonii will be presented.

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Zoran Jeknic and Tony H. H. Chen

The development of bud dormancy in poplar plants is initiated by short-day photoperiods (SD). During the development of bud dormancy, there was a gradual increase in the force required to peel off the bark from the stems. We measured the force required for bark peeling and investigated the cellular changes associated with this phenomenon. Stem samples were collected from plants which had been grown under SD for different period of time up to 10 weeks. At each sampling date, the forces required to peel off the bark were measured by a tensiometer. At the same time, samples were fixed to examine ultrastructural changes by transmission electron microscopy. We have observed that there was a significant increase in the force (in Newtons) required to peel off bark from poplar stems when the development of dormancy was initiated by SD treatment. Many ultrastructural changes were observed, including the accumulation of bark storage proteins, the break down of the central vacuole to form many small vacuoles, thickened cell walls, etc. Efforts have been made to relate ultrastructural alterations to changes in the force required for bark peeling.

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Zoran Jeknic and Tony H.H. Chen

In poplar (Populus deltoides Bartr.ex Marsh), the development of bud dormancy is initiated by short-day (SD) photoperiods. The degree of bud dormancy, expressed as days to budbreak, increased from ≈10 days for plants grown under long-days to >200 days after 10 weeks of SD exposure. We investigated quantitative and qualitative changes in protein fractions extracted from terminal buds, lateral buds, bark, and leaves of poplar plants during the induction of bud dormancy by 2-D PAGE. While total protein contents(as milligrams per gram fresh weight) in leaves, terminal, and lateral buds did not change significantly during SD treatment, bark protein content increased about five-fold in 10 weeks. The results of 2-D PAGE analysis indicated that there was a significant change in protein profiles in terminal and lateral buds, leaves, and bark. The results suggested that SD treatment in poplar plants causes substantial changes in protein profiles during the induction of bud dormancy.

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Jorge H. Siller-Cepeda, Leslie Fuchigami and Tony H. H. Chen

Many seeds of woody plants require low temperature or other treatments to overcome dormancy. Changes in catalase activity and glutathione has been proposed to be associated with the breaking of dormancy. We examined the level of glutathione and catalase activity of cherry seeds (Prunus mahaleb cv. Lambert) exposed to several dormancy breaking agents. Seeds imbibed in water for 24 hrs. were either stratified at 4°C or at 25°C for up to 12 weeks, or exposed to other dormancy breaking agents. Germination test, glutathione and catalase activity were determined weekly and/or after treatment. Analysis of levels and state of glutathione were performed by high pressure liquid chromatography (HPLC), and catalase activity was assayed spectrophotometrically. Total glutathione in dry and imbibed seeds were similar, but, ratio between the reduced and oxidized form were different. Low temperature stratification for 12 weeks increased the reduced form of glutathione six-fold, while percent germination increased up to 94%.

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Jorge H. Siller-Cepeda, Leslie Fuchigami and Tony H. H. Chen

Many seeds of woody plants require low temperature or other treatments to overcome dormancy. Changes in catalase activity and glutathione has been proposed to be associated with the breaking of dormancy. We examined the level of glutathione and catalase activity of cherry seeds (Prunus mahaleb cv. Lambert) exposed to several dormancy breaking agents. Seeds imbibed in water for 24 hrs. were either stratified at 4°C or at 25°C for up to 12 weeks, or exposed to other dormancy breaking agents. Germination test, glutathione and catalase activity were determined weekly and/or after treatment. Analysis of levels and state of glutathione were performed by high pressure liquid chromatography (HPLC), and catalase activity was assayed spectrophotometrically. Total glutathione in dry and imbibed seeds were similar, but, ratio between the reduced and oxidized form were different. Low temperature stratification for 12 weeks increased the reduced form of glutathione six-fold, while percent germination increased up to 94%.

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Giovanni Iapichino, Tony H.H. Chen and Leslie H. Fuchigami

An efficient adventitious shoot production protocol has been developed for Rhododendron laetum × aurigeranum. Shoot tips taken from greenhouse-grown plants were cultured on Anderson's medium supplemented with 74 μM 2iP. Axillary shoots were excised and cultured on medium containing 23 μM IAA and 74 μM 2iP. After 6 months, brown callus developed at the cut surfaces of the shoot-tip explants. This callus produced many adventitious shoots (up to 70 per explant). Clusters of adventitious shoots were divided, subculture, and continued to proliferate shoots. An estimated 1600-fold increase in the number of shoots could be readily achieved in 6 months. In vitro rooting of adventitious shoots was accomplished in 4 weeks. Seventy-three percent of shoots rooted on 1/4 strength Anderson's medium supplemented with 28 μm IAA. Plantlet survival was 100%3 weeks after transfer to soil. Chemical names used: 1-H-indole-3-acetic acid (MA); N-(3 -methy1-2-butenyl) -1H-purine-6 amine (2iP).

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Abbasb M. Shirazi, Leslie H. Fuchigami and Tony H.H. Chen

In previous work, we have shown that near-lethal heat stress can overcome dormancy in Red-osier dogwood, Cornus sericea L. The objective of this study was to determine the effects of premature breaking of dormancy on the development of cold hardiness. Plants at three stages of dormancy (early, deep, and late) were exposed to 47C for one hour and then placed into 3 post-treatment environments (0C, 23C, and natural conditions). At periodic time intervals, the plants were evaluated for bud break, cold hardiness, and stem injury. These studies suggest that premature breaking of dormancy at the early stage had no effect on hardiness development, whereas at the deep and late stages of dormancy, premature breaking of dormancy caused a faster rate of deacclimation at the warmer post-treatment environments. In addition, we observed that the heat-treated plants died during storage at 0C, and survived at 23C storage and natural conditions.

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Abbas M. Shirazi, Leslie H. Fuchigami and Tony H.H. Chen

Red-osier dogwood sterns, Cornus sericea L., at ten different growth stages were subjected to a series of temperatures ranging from 25C to 60C by immersing them in a water bath for one hour. After heat treatments, the viability of internode tissues were determined by electrical conductivity and ethylene production. Heat tolerance was expressed as LT50, the temperature at which 50% of the tissues were injured. The results suggest that the LT50 of dormant plants remained relatively constant, approximately 53C. During dormancy, heat stress did not stimulate ethylene production from internode tissues. In contrast, tissues from non-dormant plants exposed to heat stress produced increasing levels of ethylene reaching a peak at 40C followed by a steady decrease at higher temperatures. Application of 1-aminocyclopropane-1-carboxylic acid (ACC) to stem segments from dormant plants, following heat treatment, enhanced production of ethylene.

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John M. Englert, Leslie H. Fuchigami and Tony H.H. Chen

Desiccation stress during the postharvest handling of bare-root nursery plants is often responsible for poor performance after transplanting. Alternate methods of handling desiccation sensitive deciduous trees, such as Washington hawthorn (Crataegus phaenopyrum Med.), and herbaceous perennials species, including Iris, Hosta, and Hemerocallis, are needed for improving survival after transplanting.

A new antidesiccant compound called Moisturin has been useful in reducing water loss from Washington hawthorn trees during storage and shipping, and in improving survival and plant performance during establishment. Hawthorn seedlings or multi-stemmed trees treated with Moisturin before a period of water stress had up to 75% less dieback than control or other antidesiccant treatments.

The use of Moisturin treatment and / or protection with plastic bags of topped bare-rooted herbaceous perennials before five weeks of cold storage (2C) was effective in improving the survival of Iris ensata, Iris sibirica, and Hosta plants. Hemerocallis plants survived equally well with all treatments. The greatest effect on reduction of water loss and improvement of survival was when plants were sealed in plastic bags.

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M. Pilar Bañados, Gary D. Coleman and Tony H. H. Chen

In poplar (Populus deltoides) a 32kDa bark storage protein (BSP) accumulates during the fall, and is a major form of stored nitrogen during overwintering. This protein is induced by short-day (SD) photoperiod and may play an important role in nitrogen cycling in the plant. To determine the effect of plant nitrogen status upon BSP gene expression, poplar plants were grown in controlled environmental chambers under either SD or long-day (LD) photoperiods and watered with either 5, 10, 50, and 100 mM NH4NO3 for four weeks. [15N]-NH4NO3 was applied during the first and third weeks. SDS-PAGE and western blot analysis were used to detect the relative amounts of BSP. RNA gel blot analysis was used to determine the changes in BSP gene expression. BSP accumulation was enhanced by increasing levels of nitrogen under both photoperiods, however, SD photoperiod appears to moderate the response. These results indicate that BSP gene expression is dependant upon the nutritional status of the plant. [15N] analysis will also be presented.