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Grace M. Pietsch, Paul H. Li, and Neil O. Anderson

Cold acclimation has been extensively studied in woody species such as Cornus sericea and Malu × domestica. These studies have shown that cold acclimation is initiated by short days and completed with the addition of a cold treatment. It is unknown whether herbaceous perennials respond in a similar manner to these environmental cues. Our research objective was to examine short day photoperiod effects on cold acclimation in herbaceous gaura populations collected at different latitudes. Gaura drummondii collected in Texas, and Gaura coccinea collected in Minnesota and Texas were clonally propagated, grown under a 16-hour long day photoperiod and 25/20 °C [day/night (D/N)] temperature for 8 weeks. Plants were then subjected to 0, 1, 2, 3, 4, or 5 weeks of 8-hour short days at 20/15 °C (D/N) temperatures. Cold acclimation was determined using electrolyte leakage (freezing stem pieces from –1 to –9 °C) and measuring electrical conductivity after treatment and tissue death. Mean separations showed two distinct statistical groupings of 0-2 weeks and 3–5 weeks of short days for Minnesota gaura, whereas Texas gaura overlapped for 0–5 weeks of short day treatments. It is unknown what environmental cue(s) initiate cold acclimation in Gaura native to southern latitudes such as Texas.

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Neil O. Anderson, Peter D. Ascher, and Emily E. Hoover

Two-species CBC hybrids between Phaseolus vulgaris and P. acutifolius exhibit transgressive segregation for seed color and patterning, root peroxidases, and seed proteins. CBC pedigrees between P. vulgaris and P. coccineus (differing for species-specific traits) were created to test whether variation would be similar or greater than with P. acutifolius. P. vulgaris `Soldier' (Vermont) × 2- and 4-way intraspecific P. coccineus accessions were used as parents. CBC1 through CBC3 were evaluated for segregation of species-specific genes. Hybrid breakdown was evident in all CBC generations, particularly nonflowering dwarf cripples. Transgressive segregants were found as early as CBC2. One individual was found that had crossovers for species traits: a determinate, red-flowered plant with P. coccineus flowers and P. vulgaris introrse stigmas. By CBC3, all of the variation reported for three-species CBC hybrids (P. coccineus × [P. vulgaris × P. acutifolius]) was evident.

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Mark S. Strefeler, Neil O. Anderson, and Peter D. Ascher

Our objective was to determine whether repeated applications of 2-chloroethylphosphonic acid (ethephon) + gibberellic acid (GA3) to stock chrysanthemum plants that are day-neutral for flower bud initiation would increase the number of quality cuttings. Across five cultivars, there were no significant differences between controls and plants receiving 250 ppm ethephon in the total number of cuttings per plant. The percentage of cuttings with crown buds was greater for cuttings from controls than for ethephon-treated plants. Applying 500 ppm ethephon significantly reduced the number of cuttings. We conclude that chrysanthemum clones day-neutral for flower bud initiation and development with low long-day leaf number could be selected to form a 4 to 5 week production group.

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Neil O. Anderson, Peter D. Ascher, and Barbara E. Liedl

Since its evolution as an invasive species in Quebec (1930s), L. salicaria has spread across North American wetlands virtually unchecked. Initially, it was theorized that the rapid invasion was due to the absence of phytophagous insects (present in the native habitat). However, evolutionists theorized that invasive characteristics probably arose from introgressive hybridization with a native species (L. alatum), since their ecotypes overlap. Several horticultural cultivars are also fertile interspecific hybrids. These two species differ for diagnostic traits (number of flowers/axil, plant height, phyllotaxy, style morphology, seed dormancy). Minnesota L. salicaria populations were examined for evidence of introgression. Lythrum salicaria introgressive genotypes were found for all diagnostic traits. Seed dormancy was the most common, i.e., OP seed showed significant seed dormancy (F = 5.2, P = 0.024). Such hybrids would have adaptive advantages as weeds, having evolved for each ecotype by introgression with locally adapted L. alatum populations.

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Neil O. Anderson*, Emily Hoover, Karina Zambreno, and Jeff Gillman

In Fall 1999, the Univ. of Minnesota implemented a writing intensive requirement for undergraduates. As part of the requirement, students must take one writing intensive (WI) course in their major. Formal and informal writing in critical draft review are key components of intensive writing. The Dept. of Horticultural Science offers an Environmental Horticulture Major which currently has only one writing intensive course in its curriculum. Teaching faculty (13/14), responsible for 21 courses in the curriculum, were interviewed and syllabi were reviewed to gather information on what types of writing are currently being assigned and to discuss where WI courses should be placed in the Environmental Horticulture curriculum in the future. The majority of classes utilize formal writing and the majority of faculty review, or are willing to review, a draft of an assignment. Informal writing assignments are less common, indicating a deficient area of the curriculum. With slight modifications, many classes in the curriculum can meet the requirements to become WI. Faculty agreed that WI courses should be placed in upper level, smaller classes that place less emphasize on production techniques or plant identification.

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Jennifer Drew, Chengyan Yue, Neil O. Anderson, and Philip G. Pardey

The value and role of intellectual property (IP) rights pertaining to plant innovations and their economic consequences on plant values is largely unknown. A hedonic pricing model was adapted to the characteristics of the U.S. wholesale ornamental plant market, specifically the bedding, garden plant and nursery plant markets, to analyze two forms of IP rights used on plants (i.e., plant patents and trademarks). By controlling plant-specific attributes and a variety of market variables that might affect plant values, our empirical analysis reveals sizable price premiums for plant patents that may have been masked in other studies. As expected, plant patent premiums vary considerably between species where the costs of producing and marketing new cultivars differ greatly. Surprisingly, we find that the use of trademarks have a negative effect on plant prices.

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David A. Munter, James J. Luby, and Neil O. Anderson

Zanthoxylum americanum is a common understory species in the northern forests of Minnesota and surrounding regions. It has potential economic importance for its citrus fragrance, pharmacological or insecticidal properties, and produces peppercorns similar to those of the related Zanthoxylum species. Zanthoxylum americanum is a dioecious species but has been reported to have aberrant flowers with autonomous apomixis instead of other potential reproductive barriers. The reproductive biology of Zanthoxylum americanum was investigated in two native Minnesota populations. Determinations of male fertility, whether autonomous apomixis was the predominant floral reproductive mechanism, the presence of seedless fruit (parthenocarpy/stenospermocarpy), and the occurrence of hermaphrodism were made over 2 years. Sex ratios (female:male plants) within each population differed. The mean pollen stainability was 95.8% ± 0.3% (fresh) and 78.6% ± 1.1% (stored 18 months). Parthenocarpy did not occur in either population. Autonomous apomixis was not the primary floral reproductive mechanism. Stenospermocarpy (seedlessness) occurred in 13% of the female fruit clusters. Although commonly described as being dioecious, two additional reproductive strategies were identified: 1) plants with functional protandrous flowers with rudimentary pistils and 2) hermaphroditic flowers with fully functional pistils (protogynous) and anthers. As many as 10% to 30% of the male plants bore at least one fruit/plant each year. One clonal stand had both hermaphroditic and functionally staminate flowers on the same plant. Two evolutionary pathways to dioecy in Z. americanum are proposed.

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David C. Zlesak*, Corinne M. Radatz, and Neil O. Anderson

Haploid (2x) roses derived from modern tetraploid breeding lines would allow for crosses to diploid species at the diploid level. In addition, inheritance studies are easier at the diploid level, using diploids derived from tetraploids possessing economically important traits. Haploidization of 4x roses through anther culture has not been successful due to challenges in callus induction and shoot regeneration. This study investigates rose anther responses to recently reported methods that optimize in vitro adventitious shoot regeneration in rose leaves. Anthers of three cultivars (Akito, Grand Gala, and Orlando) were put in a two-step callus induction (CI) and shoot regeneration procedure with varying CI factors. Experiment one (E1) compared continuous light/dark and silver nitrate (0,30,60 mg·L-1) and experiment two (E2) used the optimal E1 treatment comparing two and four weeks on CI media. Twenty-five anthers per treatment per cultivar were used in E1 and n = 100 for E2. Although no adventitious shoots were generated, callus formed on anther tissue and frequency of formation was variable across treatments. Continuous light resulted in 100% lethality. Darkness and silver nitrate (30 or 60 μm) favored callus generation and significant differences for callus generation were found among cultivars. Darkness and 30 μm silver nitrate were used in E2. Two and four weeks on initiation media were not significantly different for generation of anther-derived callus. Identification of factors which optimize callus formation on rose anthers is a positive step toward reliably generating rose haploids.

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Neil O. Anderson, Mi-kyoung Won, and Dong-chan Kim

Global warming has created increased nighttime temperatures both in field and greenhouse production of chrysanthemums during flower bud initiation (FBI) and development, causing heat delay or complete cessation of flowering. Integration of breeding and selection for heat delay insensitivity (HDI) has become imperative for greenhouse (cut, potted types) and must be accomplished on a genotypic basis, similar to winterhardiness. This is a breeding objective in the joint garden chrysanthemum breeding project between the Chungnam Provincial Agricultural Research and Extension Services and the University of Minnesota. The objectives of this research were to test 10 genotypes (cultivars, seedlings) from both breeding programs when grown in low-temperature (LT) and high-temperature (HT) short-day (SD) and long-day (LD) conditions (four environments: LTSD, LTLD, HTSD, and HTLD); determine the extent of heat delay and HDI for visible bud date (VBD), flowering, and other phenotypic traits; evaluate relative injury (RI) and cell membrane thermostability (CMT), and to select future parents with lowered RI values, higher CMT, shorter heat-induced flowering delay, and/or HDI. ‘Magic Ball’ and ‘Minnwhite’ had the shortest plant height in HTLD and HTSD, whereas ‘Geumbangul’ had stability for height in all treatments. Lowest long day leaf numbers (LDLN) occurred under LTSD in seven genotypes. However, both ‘Geumbangul’ and ‘Magic Ball’ had complete stability for LDLN across all environments. Sigmoid curves for RI% and temperature were found for all genotypes and environments with R 2 = 0.79–0.89. Only ‘Mellow Moon’ had stability or equal VBDs in HTSD, LTSD, and LTLD conditions. This is the first-ever report of stability for VBD across inductive and noninductive HT/LT treatments. Only ‘Centerpiece’ flowered in all environments and also had 0 day of heat for VBD in LT and 1 day of heat delay in HT, as well as three others (Mn. Sel’n. 01-210-43, ‘Autumn Fire’, and ‘Geumbangul’). Few had linear regressions with positive slopes for heat-induced VBD or flowering delay regressed with RI%; most had no slope (R 2 ≈ 0.0) for all treatments (‘Centerpiece’, Mn. Sel’n. 01-210-43), whereas others were negative (‘Mammoth™ Dark Bronze Daisy’, Flw LTLD–LTSD). Surprisingly, one linear regression had a slope of R 2 = 1.0 (‘Geumbangul’, Flw LTLD–LTSD). These responses are all novel in chrysanthemums. Selecting the best parents in both breeding programs to maximize stability of all traits across these four environments with minimal crossing and selection across generations could be accomplished by stacking parental traits. A crossing scheme involving just three parents is proposed to incorporate stability for all traits in just a few generations.

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Neil O. Anderson, Peter D. Ascher, Richard E. Widmer, and James J. Luby

The generation time (0.75 to 1.5 years) in perennial, hexaploid chrysanthemums [Dendranthema grandiflora Tzvelv. (Chrysanthemum morifolium Ramat.)] impedes the rate of progress for sexual breeding programs in creating new clonal cultivars, inbred lines for hybrid seed production, and genetic studies. Modifications to the crossing environment and embryo rescue were evaluated to minimize the chrysanthemum generation cycle. One greenhouse chrysanthemum clone was outcross-pollinated using a bulk pollen source. Following emasculation, inflorescences were either left in situ or the peduncle bases were placed in styrofoam boards floating on a solution of 1% sucrose and 200 ppm 8-HQC under laboratory conditions. Embryogenesis occurred at a faster rate under laboratory conditions as tested with histological techniques; the heart stage appeared as early as the second day after pollination, compared with 11 days using in situ methods. Total embryogenic development time ranged from 25 (laboratory seed development) to 52+ days (in situ ripening). In a second test, embryo rescue (ER) significantly improved percent seed set, percent germination, and percent of progeny reaching anthesis relative to normal development. ER progeny from both garden parents were significantly earlier in total generation time than corresponding non-ER siblings. Laboratory seed development and ER were then used sequentially to obtain an average progeny generation time of =100 days, thus allowing for three generations per year. The potential impact of these two techniques on breeding chrysanthemums and other perennial crops with long generation times is discussed.