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- Author or Editor: Neil O. Anderson x
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.
The change from asexual to sexual propagation for annual and perennial bedding plants has been successfully accomplished for floral crops, e.g., Pelargonium. Seed-propagated cultivars do not necessarily possess the clonal uniformity of vegetatively propagated cultivars. In the development of F1 hybrid garden chrysanthemums, this lack of uniformity was assessed with the use of consumer sensory evaluations. Seedlings (n = 10–20 plants/cross) were transplanted for field trials in St. Paul and five Minnesota branch stations each year during 1988–94 to test for G × E. Early flowering F1 hybrids, developed from inbred parents with general combining ability, were evaluated for flowering earliness, plant uniformity, and a general rating. Consumer rankings of top performers were not significantly different (5% level) from mum breeders. The top performers for all three ratings were selected each year for repeat evaluation the next year. The two highest performing F1 hybrids were submitted for All American Selection Trials in 1995.
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.
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.
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.
Various durations of rooting at 15C and storage at 5.X and exogenous GA, (1000 ppm) application were used on dormant unrooted peony (Paeonia lactiflora Pall.) tubers of `Sarah Bernhardt', `Festiva Supreme' `Krinkled White', and `Scarlet O'Hara'. Four weeks of cooling were sufficient to break dormancy. Days to emergence, first bud color, and anthesis were reduced as the length of cold storage increased from 4 to 20 weeks. Height and number of shoots emerging per pot increased with increased cooling. All flower buds aborted when tubers were cooled for 20 weeks. When noncooled tubers were given a 1000-ppm GA, soil drench, shoots emerged within 7.5 days; untreated tubers failed to emerge after 5 months. When tubers were treated with GA,, all flower buds aborted.
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.
Polyploidy represents a useful tool for increasing marketability of floriculture crops. The efficacy of 250 μM colchicine [0.01% (w/v)] as a means of inducing polyploidy in six South African Watsonia species (W. borbonica subsp. ardernei, W. humilis, W. laccata, W. lepida, W. pulchra, and W. vanderspuyiae), as determined through high-resolution flow cytometry, is reported. Exposure to colchicine during imbibition and as 24-, 48-, or 72-h pulse treatments for in vitro-germinated seeds resulted in seedlings with increased ploidy, reaching a maximum of 60% induction after the 72-h pulse treatment. The greatest proportions of induced individuals from both the pre- and post-germination exposure treatments were of mixed ploidy. These mixoploids were induced in five species. Non-chimeric tetra- and octaploids were produced in low frequencies only for W. vanderspuyiae during radicle-pulse exposure of 24 and 48 h. Increasing colchicine exposure at radicle emergence manifested as aberrant phenotypic expression and was typified by a reduction in leaf length and rooting capacity in vitro coupled with overall slowed growth. In vitro regeneration and multiplication is easily achievable for the genus and should allow for the capture and refinement of desirable polyploid tissues.
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.
The genus Linum L. contains ≈200 primarily blue-flowered species, including several ornamentals, yet no reports exist regarding the cut flower potential of this genus. The objective of this study was to evaluate the cut flower potential of perennial flax cultivars (L. perenne L. ‘Blue Flax’ and ‘Sapphire’; Expt. 1, 2018) and accessions (L. austriacum L., L. lewisii Pursh., and L. perenne; Expt. 2, 2019), and record traits that will enable breeding and selection for improved cut flower performance. The mean vase life across both cultivars in Expt. 1 was 9.2 days. In Expt. 2, L. perenne had the longest average vase life (9.3 days), followed by L. austriacum (9.1 days) and L. lewisii (8.3 days). The floral preservative (Floralife 300) significantly increased vase life by an average of 1.7 days in Expt. 1, and 1.6 days in Expt. 2, and resulted in a significantly greater number of flowers (≈2x) in both experiments. Significant variation was observed among genotypes for most traits, including vase life (6.2 to 11.3 days) and number of flowers (1.3 to 10.5), highlighting the opportunities for improving the potential of cut flower perennial flax through breeding.