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- Author or Editor: Mark P. Bridgen x
Alstroemeria, the Inca Lily or Lily-of-the-Incas, is becoming a popular garden plant in the United States. In past years, the primary interest in Alstroemeria has been for its cut flowers. However, recent cold-hardy introductions (USDA hardiness zone 5) have expanded the interest of this colorful plant as a garden perennial throughout the United States. Previously, garden interests were restricted to warmer zones in the southern United States where Alstroemeria could overwinter. This research describes a breeding procedure that has been used with the objective to develop a cold-hardy, white-flowered Alstroemeria. The interspecific hybrids were bred with the use of in ovulo embryo rescue. Reciprocal crosses were made between several white-flowered cultivars and the cold-hardy Chilean species Alstroemeriaaurea during Summer 2004. Ovaries were collected 10–23 days after hand pollination and their ovules were aseptically excised. Ovules were placed in vitro on 25% Murashige and Skoog (MS) medium under dark conditions until germination. Three weeks after germination, they were then placed on 100% MS medium, and subcultured every 3–4 weeks thereafter until they were large enough for rooting. After rooting and acclimation, plants were transferred to the greenhouse. Successful hybrids that were produced in 2004 were evaluated under greenhouse and field trials during 2005, and the number of plants with white-colored flowers was noted. Although certain morphological characteristics indicate if plants are coldhardy, the hybrids will be overwintered outside in Ithaca, N.Y. (USDA zone 5), during the next several years to determine winter hardiness.
Red- and pink-flowering cultivars of Alstroemeria were grown with and without cooling tubes placed in the growing medium. Cooling tubes were placed immediately below, 5 cm below, and 10 cm below the surface of the medium. Cooling was obtained by circulating well water (10 to 15C) through polyethylene tubing. Air and media temperatures were recorded every 3 to 10 days in the morning and in the late afternoon to determine if positioning of the cooling tubes had an effect on the medium temperature. The air temperature was warmer than the noncooled medium, which, in turn, was significantly warmer than the cooled medium. There were no significant differences in media temperatures among the three cooling treatments. Flowering of cooled Alstroemeria cultivars continued for 2 months longer at the end of the summer and reinitiated 1 month earlier than the noncooled control. Both cultivars produced significantly more total flowers when grown in cooled medium. Flower production was greatest in the summer for plants with tubes 10 cm below the surface and least for plants in noncooled medium. This trend continued when flowering was reinitiated; however, by April of the following year, all treatments were equal in flower production.
Presowing treatments and temperature regimes were tested to improve germination of Alstroemeria hybrids 3 to 12 months following harvest. In addition, seeds from 20 intraspecific F1 hybrids of five selections were also tested 3 to 7 or 8 to 12 weeks following harvest. Seeds were pretreated by chipping the seedcoat above the embryo, general abrasion of the entire seedcoat, or soaking 12 hours in distilled water, GA, (0.029, 0.29, 2.9 mm), or KNO3 (0.5 and 1.0 m). Pretreatments were evaluated under three environmental regimes: 8 weeks at a constant 18-25C (warm), 4 weeks at 18-25C followed by 4 weeks at 7C (warm-cold), or 4 weeks at 7C followed by 4 weeks at 18-25C (cold-warm). There was an interaction between pretreatment and environmental regime for percent germination. Germination percentages for the water soak and GA, at 0.29 or 2.9 mm were significantly higher than for the other pretreatments, but were not significantly different from one another. The warm-cold environment yielded higher germination percentages than the other environments. The time to germination was longest for the cold-warm regime. This response depended on the genotype and the age of the seed. Chemical name used: gibberellic acid (GA3).
Callus cultures of Torenia fournieri `Compacta Blue' were initiated on a modified Murashige and Skoog salt medium (MS) with 2.26 uM 2,4-dichloro-phenoxy acetic acid. Shoots were regenerated from these cultures using the MS medium amended with 2.46 uM 3-indolebutyric acid and 8.88 uM 6-benzylaminopurine. These shoots were subjected to Tetranychus urticae Koch (twospotted spidermite) and Trialeurodes vaporariorum (Westwood) (greenhouse whitefly) in vitro. Pests were allowed to feed until such time that the pest population started to decrease due to lack of food. Remaining shoot tissue was placed on MS medium amended with 2.28 uM zeatin to -induce shoot formation. Shoots were acclimated to greenhouse conditions and evaluated for resistance to the pest to which they were subjected in vitro. Highly significant differences in pest numbers were found in somaclones when compared to control plants. A wide range of variability was observed within the somaclonal population.
The dormancy mechanism in achimenes (Achimenes hybrids) has not been thoroughly characterized. Rhizomes of five recently developed achimenes cultivars were stored for 0, 4, 8, 12, or 16 weeks at 68 °F. Cultivar A09 demonstrated a strong decrease in the time to root after 4 weeks of storage, rooting after 13 weeks postplanting. The rooting response for cultivars A16, A21, and A22 was significantly less than cultivar A09; they developed roots between 2.6 and 7.6 weeks after 4 weeks of storage. Rhizomes stored longer than 8 weeks resulted in decreased rooting responses for all cultivars. Shoot emergence was delayed in all cultivars with cultivars without any storage period; cultivars A09, A16, and A23 exhibited a stronger delay than other cultivars. After 4 weeks of storage, the number of weeks to shoot development decreased for all cultivars and after each additional 4-week storage period, the number of weeks to shoot development decreased or remained the same. After 16 weeks of storage, shoots developed in less than 4 weeks for all cultivars. Pupation occurred in four of five cultivars on rhizomes given no storage or with only 4 weeks of storage. The results obtained suggest that the dormancy period of some newer achimenes cultivars is abbreviated in comparison with older cultivars.
Abstract
The potential for in vitro floral photoinduction of epidermal and subepidermal thin cell layers (TCLs) taken from the short-day plant Nicotiana tabacum L. ‘Maryland Mammoth’, the long-day plant Nicotiana sylvestris L., and the day-neutral plant Nicotiana tabacum L. ‘Samsun’, in both the floral and vegetative states, was examined. Whether cultured under long days (16 hr) or short (8 hr), only TCLs from the flowering day-neutral species flowered in vitro. These were termed responsive TCLs. TCLs from photoperiodic plants yielded only vegetative buds; these were termed nonresponsive. Vegetative bud formation in nonflowering TCLs generally was greater than in flowering TCLs but did not approach the number of flower buds on flowering TCLs. In vitro grafts of responsive TCLs to nonresponsive TCLs resulted in flowering only in the responsive portion, regardless of the position of the graft. Just as the nonresponsive TCLs were not induced to flower by some graft-transmissible substance, responsive TCLS were not inhibited from flowering when grafted to nonresponsive TCLs.
Abstract
Torenia fournieri L., commonly known as the wishbone flower, bluewings, or torenia, is a bedding plant from the Scrophulariaceae. Native to Indochina, torenia plants grow well in full sun or partial shade but prefer cool, moist, shaded areas. Torenia are oppositely branched, round in habit, and attain a height of 30 cm. These low-growing annuals are attractive in garden borders but are also well-adapted to pot culture and hanging baskets. Torenia flowers are located on terminal racemes and consist of a five-winged tubular calyx. The common name, wishbone flower, refers to the shape and position of the stamens, which arch together, fusing at the anthers to resemble a chicken wishbone.
The effects of Ca and N on cut flower production of Alstroemeria were determined in separate greenhouse experiments. Calcium was supplied as Ca(NO3)2 and CaCl2 at 0, 1, 2, 4, 8, and 12 mmol·L-1 added to tap water containing Ca at ≈0.2 mmol·L-1. Nitrogen was supplied as KNO3 and Ca(NO3)2 providing total N at 0, 3.5, 7, 14, 28.5, and 57 mmol·L-1 in tap water containing N <0.2 mmol·L-1. Nutrient solutions were applied at 7- or 10-day intervals to plants growing in a soilless medium in 2.6- or 5.5-L containers. Flowering stems were harvested when the primary florets opened. Total N concentration was measured in leaf tissue from the upper portion of flowering stems. Flower production was not affected by Ca supply, but increased with N supply to a maximum of about four stems per plant on a weekly basis at 28.5 mmol·L-1, then decreased to less than three stems per plant at 57 mmol·L-1. Nitrogen concentration in leaf tissue on a dry mass basis was maintained at 45 ±3 g·kg-1 in plants supplied with N at 28.5 mmol·L-1, 52±5 g·kg-1 at 57 mmol·L-1, but <40 g·kg-1 with N supply of 14 mmol·L-1 or lower. Nitrogen fertilization of Alstroemeria should be managed to maintain leaf tissue N close to 45 g·kg-1.
Procedures were developed to determine if live, adult two-spotted spidermites (Tetranychus urticae Koch) could be surface disinfested before being introduced into in vitro cultures of torenia (Torenia fournieri L.). Three time periods (5, 10, and 15 minutes) and five levels of sodium hypochlorite (0.05% to 0.25%) were evaluated. Surface disinfestation was accomplished by agitating 2 × 3 cm pieces of infested bean leaves in sodium hypochlorite solutions and then drying in a mite drier apparatus. All sodium hypochlorite concentrations disinfested the mites completely, however high concentration levels were lethal to the mites. Exposure periods of 10 and 15 minutes also significantly increased mortality. For optimum disinfestation of two-spotted spidermites with minimum mortality, a concentration of 0.05% sodium hypochlorite and 0.05% Tween-20 for 5 minutes should be used.
Hemp (Cannabis sativa L.) is commonly grown for the medicinal secondary metabolites produced by pistillate inflorescences. Micropropagation is a valuable method of propagating hemp plants because of the aseptic process and the production of true-to-type propagules. The hemp cultivar TJ’s CBD was used for a series of experiments to compare media inputs and practices for the clonal micropropagation of hemp. For stage I, shoot tips harvested from stock plants that were grown in a growth chamber produced less endogenous contamination in newly established cultures than shoot tips harvested from the greenhouse. In addition, stage I disinfection treatments with 20%, 40%, and 60% bleach (7.5% sodium hypochlorite) for 10 minutes had no differences in surface contamination rates. All concentrations were able to clean explants equally, and no damage to the explants was observed. For stage II, there were no differences in growth and multiplication rate between shoot tip or nodal explants. In addition, no differences were observed between the gelling agent’s agar, agargellan, and gellan gum at standard rates. When basal nutrient formulations were compared at standard rates and with their respective vitamins, Murashige and Skoog, Linsmaier & Skoog, and Driver & Kuniyuki Walnut media were found to be superior to Lloyd & McCown Woody Plant Medium. Media pH levels of 4.0, 5.0, 5.8, 6.0, and 7.0 were compared, and no differences were observed in final fresh weights, shoot lengths, or quality ratings. The pH levels of 5.8, 6.0, and 7.0 generated a greater number of lateral nodes. Sucrose levels of 0%, 1.5%, 3.0%, 4.5%, and 6.0% (wt/vol) were also compared, with the 1.5% and 3.0% rates showing greater fresh weights, shoot lengths, and quality ratings. Growth room temperatures of 22, 24, 26, and 28 °C were compared, with temperatures of 28 and 26 °C generating greater fresh weights, shoot lengths, numbers of nodes, and quality ratings compared with cooler temperatures. The cytokinins 6-enzylaminopurine (BA), 6-(γ,γ-dimethylallylamino) purine (2iP), and thidiazuron (TDZ) were compared at 1.0, 5.0, and 10.0 μM concentrations. The 5.0-μM TDZ treatment generated greater fresh weights and numbers of lateral nodes; however, it also produced the shortest shoot lengths and lowest quality ratings. The 2iP treatments at 1.0 and 5.0 μM, and the BA treatment at 1.0 μM produced the greatest quality ratings. The 5.0-μM 2iP level was considered the best treatment for stage II multiplication based on high ratings, in addition to the greater final fresh weights, shoot lengths, and numbers of nodes that were produced. For stage III experiments, the auxins indole 3-butyric acid (IBA) and 1-naphthylacetic acid (NAA) were compared at concentrations of 0.25, 0.5, and 2.5 μM. Auxin treatments of 0.25 μM NAA, 0.5 μM NAA, and 2.5 μM IBA generated the greatest final shoot fresh weights, root fresh weights, and numbers of nodes. However, the 2.5-μM IBA treatment resulted in a higher overall rating. For stage IV, ex vitro rooting and acclimation trials compared a dome and an intermittent mist system, as well as treated the unrooted cuttings with an externally applied auxin. Acclimating with a dome produced greater shoot heights, fresh shoot weights, and overall ratings compared with the mist system. The auxin treatment mildly increased fresh root weight, but was not as important to acclimation success as the domed environment. It has been concluded that a micropropagation system that uses lower rates of sucrose, higher growing temperatures, and lower rates of the cytokinins BA and 2iP are optimal for the micropropagation of hemp. In addition, when acclimating hemp plants from tissue culture, an in vitro stage III can be bypassed and plants can be rooted ex vitro during stage IV acclimation with a dome with or without additional auxin treatments.