Herbaceous Ornamentals Research Articles

Herbaceous ornamental plants with conspicuous aesthetic traits contribute to plant invasion risk in subtropical urban parks

Global ornamental horticulture is a major pathway for plant invasions, while urban parks are key areas for introducing non-native ornamental plants. To react appropriately to the challenges (e.g., biological invasion issues) and opportunities (e.g., urban ecosystem services) of herbaceous ornamentals in urban parks, we conducted a comprehensive invasive risk assessment in 363 urban parks in Chongqing, a subtropical city in China. The results found more than 1/3 of the 119 non-native species recorded in urban parks had a high invasion risk, and more than five species had potential invasion risk in 96.29% of the study area, indicating herbaceous ornamentals in urban parks are potentially a pool of invasive species that deserves attention. Moreover, humans have chosen herbaceous ornamentals with more aesthetic characteristics in urban parks, where exotic species were more prominent than native species in floral traits, such as more conspicuous flowers and longer flowering periods. The findings can inform urban plant management, provide an integrated approach to assessing herbaceous ornamentals' invasion risk, and offer insights into understanding the filtering effects of human aesthetic preferences.

Cryopreservation of herbaceous Asteraceae seeds: Effects of seed reserves on seed germination and seedling regrowth

Carbohydrate, lipid and protein, the three main storage reserves of seeds, are the main sources of raw materials and energy for seed germination and early growth stage of seedlings. In this study, the seed of 16 Asteraceae herbaceous ornamentals were used to compare the changes in seed germination, seedling growth indexes and four major storage reserves of seeds before and after cryopreservation. After cryopreservation, seed germination and seedling growth were preserved in most species (11/16), while one species showed significantly improved post-thaw germination and four had decreased germination. In seeds with preserved germination, no clear variation was noted with regards to the four kinds of storage reserves, or only a slight change in one. However, significantly reduced soluble protein, soluble sugar and fat content and increased starch content were detected in seeds showing reduced germination after cryopreservation. The correlation study further showed that the changes in seed germination were positively correlated with soluble protein, soluble sugar and fat, and negatively correlated with starch. In seedling growth indexes, only cotyledon area was correlated to the content of soluble protein, starch, fat, and seed germination after cryopreservation. These results support the use of soluble protein, soluble sugar, starch and fat as indicators of seed germination after cryopreservation, but not for predicting the seedling growth indexes.

Air temperature during cutting propagation of cold-intermediate and -sensitive crops can be reduced if root-zone heating is provided

Asexual propagation of herbaceous ornamentals occurs from late winter to early spring coincides with seasonally low daily light integrals (DLIs) and average daily temperatures (ADT) outdoors. Supplemental lighting and air and root-zone heating (RZH) can be used to promote rapid callus induction and rooting of cuttings. Due to the range of greenhouse crop base temperatures (cold-tolerant, cold-intermediate, and cold-sensitive), one strategy is to reduce the air ADT of certain crops while using RZH as a potential energy saving strategy. Therefore, the objective of this study was to quantify how reduced air ADT and increased RZH temperatures influence root initiation and development of cold-intermediate and-sensitive herbaceous annual and perennial crops propagated by shoot-tip cuttings. Unrooted vegetative cuttings of angelonia ‘Archangel Raspberry’ (Angelonia angustifolia), lantana ‘Landmark Sunrise Rose Improved’ (Lantana camara), New Guinea impatiens ‘Clockwork White Improved’ (Impatiens hawkeri), scaevola ‘Scalora Brilliant’ (Scaevola aemula), thunbergia ‘Sunny Lemon Star’ (Thunbergia alata), verbena ‘Cadet Upright Red’ (Verbena × hybrida), geranium ‘Moxie! Deep Rose’ (Pelargonium interspecific), Kwik Kombos ‘Pink Lemonade Mix’ [petunia ‘Dekko Star Rose’ (Petunia × hybrida), lobelia ‘Techno Heat Light Blue Improved’ (Lobelia erinus), and calibrachoa ‘Callie Yellow Improved’ (Calibrachoa × hybrida)] and portulaca ‘Cupcake Carrot’ and ‘Colorblast Lemon Twist’ (Portulaca grandiflora) were inserted into a soilless medium and placed in a greenhouse with an air ADT of 21°C and RZH set point of 24°C to callus. After 6 d, trays of cuttings were placed between two greenhouses with an air ADT of 16 or 21°C and among 3 benches which provided RZH set points of 21, 24, or 27°C. After 14 or 16 d post-callus, measurements were collected for all genera and geranium and portulaca ‘Colorblast Lemon Twist’ were transplanted into a common environment. The air ADT and RZH individually influenced stem length of angelonia, lantana, kwik kombos, portulaca, thunbergia, and verbena, and interacted to influence angelonia and lantana. Under an air ADT of 21°C, angelonia was 30%-45% taller than an air ADT of 16°C. Stem length of geranium, New Guinea impatiens, and scaevola were not influenced by air ADT or RZH. With an RZH set point of 21°C, the root dry mass of thunbergia was 72% greater under an air ADT of 21 than 16°C. Lantana shoot dry mass was 23% smaller under an air ADT of 16°C and RZH of 21°C compared to an RZH of 24°C. Finished plants of geranium and portulaca were not influenced by air ADT or RZH and were comparable in size and date of marketability between treatments. Due to little to no differences in crop timing or quality, the majority of the crops studied can be propagated with an air ADT and RZH of 16 and 24°C, respectively, without negative effects during or after propagation.

A high daily light integral can influence photoperiodic flowering responses in long day herbaceous ornamentals

Commercial producers of herbaceous ornamentals have reported that long-day plants sometimes flower under short-day conditions when the photosynthetic daily light integral (DLI) is high, but little research-based information is available to support the phenomenon. We grew seedlings of tickseed (Coreopsis grandiflora), echinacea (Echinacea × hybrida), lavender (Lavandula angustifolia), lobelia (Lobelia × speciosa), and salvia (Salvia longispicata × farinacea) in a controlled-environment greenhouse. They were then transplanted and grown under photoperiods of 10, 11, 12, 13, 14, or 15 h under an average DLI of 5.3 or 13.4 mol·m−2·d−1 and at an air temperature setpoint of 20 °C. Based on flowering percentage, the DLI influenced the photoperiodic responses in four species. Flowering percentages of tickseed, echinacea, lavender, and lobelia were lower under the low DLI compared with the high DLI under photoperiods <11, <12, <12, or <13 h, respectively. Time to flower for all species generally decreased as photoperiod increased. In addition, most species had more inflorescences and were more compact under the higher DLI. Under the high DLI, all echinacea and lobelia plants flowered under all photoperiods tested. Salvia flowered in all treatments, and formed fewer leaves before flowering under photoperiods ≥14 h compared to other photoperiods. However, under the higher DLI, salvia plants took slightly longer to flower under 15 h than 14 h. To clarify its photoperiodic response, we performed an additional experiment with salvia the following year. At germination, seedlings were placed under photoperiods of 14, 15, or 16 h, or a 9 h day with a 4-h night interruption and received an average DLI of 9.2 mol·m−2·d−1. Flowering was delayed under the 16 h and night-interruption treatments compared to under 14 and 15 h. We conclude that photoperiod and DLI interact to influence flowering of at least some long-day plants and that salvia has an intermediate photoperiodic flowering response.

Invasion potential of herbaceous ornamental perennials in northern climate conditions

We studied invasion potential of perennial herbaceous ornamental plants in Finland by using their reproduction success as an indicator. Altogether, 220 clones from 166 species were included in the studies. In common gardens, 50% of the species were found to produce seedlings and 75% rhizomes, respectively. Twelve of the clones produced neither seedlings nor rhizomes. Rankings of the invasion potential based on the two reproduction modes did not correlate. The species known for their invasion potential in temperate or cool climates were among the highest ranking seedling producers in the common gardens. In the field experiment, the highest seedling production (73%) was found in the semi-dry moisture regime, followed by the dry (40%) and the moist (27%) regimes. In the greenhouse experiment, 83% of the studied clones and 84% of the species emerged. Temperature sum required for the production of viable seeds for one third of the studied species is reached at least every second year in latitudes 62–63°N. Several perennial herbaceous ornamentals have potential for northward range expansion.

Peer review of the pesticide risk assessment of the active substance fenamiphos.

The conclusions of EFSA following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State Greece and co‐rapporteur Member State Cyprus for the pesticide active substance fenamiphos are reported. The context of the peer review was that required by Commission Implementing Regulation (EU) No 844/2012. The conclusions were reached on the basis of the evaluation of the representative uses of fenamiphos as a nematicide in fruiting vegetables (i.e. tomato, aubergine, cucumber, pepper and courgette), herbaceous ornamentals and in nursery stock (both perennial and herbaceous species). The reliable end points, appropriate for use in regulatory risk assessment are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.

Growth Response of Herbaceous Ornamentals to Phosphorus Fertilization

A series of experiments investigated the effects of increasing phosphate–phosphorus (P) concentrations on the growth and development of four horticultural species. In experiment 1, petunia [Petunia atkinsiana (Sweet) D. Don ex W.H. Baxter] plants were grown using eight P concentrations, and we found that the upper bound for plant growth was at 8.72–9.08 mg·L−1 P, whereas concentrations ≤2.5 mg·L−1 P caused P deficiency symptoms. Experiment 2 investigated P growth response in two cultivars each of New Guinea impatiens (Impatiens hawkeri W. Bull) and vinca [Catharanthus roseus (L.) G. Don]. Growth for these plants was maximized with 6.43–12.42 mg·L−1 P. In experiment 3, ornamental peppers (Capsicum annuum L. ‘Tango Red’) were given an initial concentration of P for 6 weeks and then switched to 0 mg·L−1 P to observe whether plants could be supplied with sufficient levels of P, and finished without P to keep them compact. Plants switched to restricted P began developing P deficiency symptoms within 3 weeks; however, restricting P successfully limited plant growth. These experiments indicated that current P fertilization regimens exceed the P requirements of these bedding plants, and depending on species, concentrations of 5–15 mg·L−1 P maximize growth.

Influence of pH and Etridiazole on Pythium Species

Pythium root rot (Pythium sp.) is ubiquitous in Michigan greenhouses that produce herbaceous ornamentals, an industry worth $393 million in the state. Disease symptoms include stunting, flowering delay, root rot, and death. Fungicides that are highly effective against pythium root rot are limited, and pathogen resistance has been documented. The objectives of this study were to determine the sensitivity of Pythium irregulare, Pythium ultimum, and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole and to determine the influence of pH and etridiazole on Pythium mycelial growth and asexual reproduction. Isolates were tested in vitro for sensitivity to etridiazole by growing the pathogen on amended V8-agar plates sealed in plastic containers to minimize fungicide loss from the vapor phase. The majority of isolates of all three species were sensitive to the fungicide with EC50 (effective concentration resulting in 50% inhibition of linear growth) values ranging from 0.10 to 5.03 μg·mL−1. Two isolates of P. irregulare had an EC90 (effective concentration resulting in 90% inhibition of linear growth) value &gt;80 μg·mL−1. The acidity of the medium influenced the ability of etridiazole to inhibit Pythium mycelial growth and asexual reproduction. Agar plates amended with 1 μg·mL−1 etridiazole and adjusted to pH 4.5 limited the mycelial growth of two P. aphanidermatum isolates and two P. irregulare isolates by 90% and 56%, respectively, compared with amended agar at pH 6.5. Sporangial formation by P. aphanidermatum was less frequent on mycelial disks incubated in etridiazole-amended sterile distilled water (SDW) at pH 4.5 than pH 6.5 (P &lt; 0.05). P. aphanidermatum zoospore cyst germination was less sensitive to etridiazole than sporangia or mycelial growth; however, the influence of pH and fungicide on cyst germination was significant (P &lt; 0.01). At 250 μg·mL−1 etridiazole and solution pH 4.5, zoospore cyst germination was inhibited 99.9% compared with 94.2% at pH 6.5. In a greenhouse experiment, disease symptoms were observed on ‘Pinto White’ geranium (Pelargonium ×hortorum) in a potting medium infested with P. aphanidermatum and adjusted to pH 4.5 or 6.5; however, plant health and fresh weight were greater in low pH potting medium. Etridiazole, applied as a drench at transplant, did not improve control of root rot for plants grown at low pH (P &gt; 0.05). Fresh weight of plants grown in infested potting medium adjusted to pH 4.5 and amended with a single drench of etridiazole (100 μg·mL−1) was reduced 20%, statistically similar to the untreated control. Adjusting the acidity of irrigation water at the time of etridiazole application in ebb and flow and flood floor production systems could be beneficial in pythium root rot management of certain ornamental crops if plants have tolerance to low pH.

Substrates and fertilizers for organic container production of herbs, vegetables, and herbaceous ornamental plants grown in greenhouses in the United States

The value of organic greenhouse production in the United States is $112 million, and organic floriculture production has increased 40% in greenhouses since 2008. The U.S. National Organic Program (NOP) guidelines allow organic production in containers. One of the primary concerns for current and potential organic container growers is managing container substrate and plant fertility. This manuscript provides a review of current literature on organic substrates and fertilizers for container grown herbs, vegetables and herbaceous ornamentals according to NOP guidelines. Organic-approved substrates can be purchased from commercial suppliers or produced in house. Many organic substrate components are similar to those used in conventional production (peat moss, pine bark, perlite, vermiculite, rice hulls, and whole pine tree) but lack a synthetic wetting agent. Growers who mix their own substrates often add compost at percentages ranging from 20 to 50%. Compost has high water holding and cation exchange capacity. It is often locally or regionally produced and purchased, which impacts variability and quality. For this reason, growers often need to manage substrates with compost more carefully. Single source or blended organic fertilizers may be incorporated in substrates prior to planting. These are derived from a variety of plant and animal based sources. A small number of mined components may be added to substrate-incorporated fertilizers (i.e. limestone). These fertilizers will typically last for four to five weeks, and are often supplemented with liquid fertilizers for longer-term crops or species with high nitrogen requirements. Liquid fertilizers also tend to be more quickly plant available compared to substrate-incorporated fertilizers. With careful management, it is possible to grow container plants in organic production systems that are comparable to those produced in conventional production systems.

First Report of a 16SrI (Aster Yellows) Group Phytoplasma in Phlox in the United States

Phlox are herbaceous perennial ornamentals native to North America grown for their flower color, range in flowering time, scent, and differing forms. Candidatus Phytoplasma asteris, first found to occur in Chinese asters, is spread by aster leafhoppers and in 2001 was reported to be a serious threat to phlox. There have been several reports of Ca. P. asteris in garlic and small grains in Minnesota. This is the first report of Candidatus Phytoplasma asteris in phlox in Minnesota and the United States. Accepted for publication 28 June 2016. Published 6 September 2016.

Rooting Stem Cuttings of Herbaceous and Woody Ornamentals in Substrates Containing Eastern Redcedar (Juniperus virginiana)

Propagation substrates can strongly influence rooting success of stem cuttings. Eastern redcedar (Juniperus virginiana L.) chips (ERC) have been suggested as a propagation substrate component. This study investigated ERC as a perlite substitute in a perlite:sphagnum peat moss (3:1 v/v) rooting substrate. Stem cuttings of coleus [Solenostemon scutellarioides (L.) Codd], English ivy (Hedera helix L.), forsythia (Forsythia ×intermedia Zab.), lantana (Lantana camara L.), and spreading euonymus (Euonymus kiautschovicus Loes.) were rooted in substrates containing increasing concentrations of ERC hammer-milled to pass a 4.8 mm (0.19 in) screen. All species rooted well (≥ 95%) in all substrates except forsythia which rooted poorly in all substrates (8 to 36%). ERC concentration did not affect mean root number or mean root length in any species except spreading euonymus where mean root number peaked at 0 and 100% ERC content and mean root length decreased with increasing ERC content. Bulk density, container capacity, and total porosity increased as ERC replaced perlite. Physical properties of all substrates were suitable for cutting propagation. ERC can effectively replace perlite in rooting substrates for many ornamental species.

POSTHARVEST SCREENING OF SELECTED POTENTIAL HERBACEOUS AND WOODY ORNAMENTALS OF PAKISTAN

Pakistan has a huge diversity of ornamentals being grown in various regions, but the local cut flower industry is dominated by roses, gladioli, marigolds and tuberoses only. Several herbaceous and woody ornamentals were screened for their suitability to be used as specialty cut flowers. Nine ornamental species were selected that had elegant flowers and sturdy stems. Stems were harvested at optimal marketing stage in the mornings, placed in buckets containing tap water and transported to postharvest laboratory within 2-4 h of harvest. At arrival, stems were recut to uniform stem length depending on species, labeled and placed in respective preservative solutions. Preservative treatments included distilled water (DD, control), pulsing with 5% sucrose supplemented with 100 mg L-1 AgNO3 for 24 h followed by shifting into DD water, or 2% sucrose solution supplemented with 100 mg L-1 AgNO3 until termination. Cut stems of Jatropha integerrima had longest vase life when placed continuously in 2% sucrose solution until termination, while Nerium oleander, Tecoma stans, Callistemon lanceolatus, and Sambucus ebulus had a longer vase life when pulsed with 5% sucrose solution for 24 h followed by placement in DD water until termination. Stems of Alpinia zerumbet, Hippeastrum hybrids, Cassia alata, and Justicia brandegeana had longer vase life in DD water and sucrose treatments either had no or negative effect on their postharvest longevity. All the tested species had acceptable vase life of 4 to 10 d with good quality flowers and sturdy stems and can be used by the local industry for diversification and to provide more choices to the customers.

Low-intensity blue light in night-interruption lighting does not influence flowering of herbaceous ornamentals

The spectral quality of photoperiodic lighting can affect flowering of short-day plants (SDPs) and long-day plants (LDPs) differently. When delivered during the middle of the night (night interruption, NI), red (R; 600–700nm) light alone can inhibit flowering of SDPs, whereas a combination of R and far-red (FR; 700–800nm) light promotes flowering of some LDPs. However, whether or not low-intensity (≈1–2μmolm−2s−1) blue (B; 400–500nm) light, when added to R and/or FR light, influences flowering has not been established. We investigated the effects of mixed B, R, and FR light on flowering of five SDPs [chrysanthemum (Chrysanthemum×morifolium), cosmos (Cosmos sulfureus), two cultivars of dahlia (Dahlia pinnata), and marigold (Tagetes erecta)] and two LDPs [dianthus (Dianthus chinensis) and rudbeckia (Rudbeckia hirta)]. Plants were grown in a greenhouse at a constant set point of 20°C and received a truncated 9-h short day (SD) with or without 4-h NI lighting from incandescent (INC) lamps or white (W), B, B+R, B+FR, B+R+FR, or R+FR light-emitting diodes (LEDs). Each NI lighting treatment delivered a mean photon flux of 1.5μmolm−2s−1 between 400 and 800nm at plant height. Blue light alone was not perceived as a long day by all SDPs and LDPs tested. For all SDPs, W LEDs inhibited flowering most effectively. B+R NI was as effective as W NI at creating a long day for all SDPs except chrysanthemum. B+FR NI inhibited flowering of marigold and dahlia ‘Leanne’, but not chrysanthemum or dahlia ‘Gallery Pablo’. For marigold, B+FR NI was less effective than other NI lighting treatments with R light. B+R+FR and R+FR NI similarly delayed flowering of all SDPs except dahlia ‘Gallery Pablo’. NI lighting treatments containing R light similarly promoted flowering of rudbeckia. We conclude that in at least the crops studied, low-intensity B light during the night does not influence flowering. In addition, W LEDs that emit little FR light are effective at creating long days for SDPs but only some LDPs.

Dissecting the Concept of the Thin Cell Layer: Theoretical Basis and Practical Application of the Plant Growth Correction Factor to Apple, Cymbidium and Chrysanthemum

A thin cell layer (TCL) is a thin layer of plant cells. TCLs have served as a simple, but important biotechnological tool in plant science, with several dozen crop species having had tissue culture regeneration protocols developed using TCLs generated from multiple explant sources. There are two types of TCLs, transverse TCLs, or tTCLs and longitudinal TCLs, or lTCLs. The former is the most common, ranging from 100 μm to 1–2 mm in thickness, usually cutting through several tissue types. In contrast, the latter usually targets a very specific layer of cells or tissues, and may vary in length but is as thick as a tTCL. The developmental question that needs to be addressed will determine the choice between one or the other and its use in plant tissue culture. The often unappreciated beauty of the TCL is not so much in its actual regeneration capacity, but rather in its potential regeneration capacity. Herein, we use data from three model species, a woody temperate fruit tree, Malus sp. (apple; Rosaceae), and two herbaceous ornamentals, Cymbidium (orchid; Orchidaceae) and Dendranthema (chrysanthemum; Asteraceae), to demonstrate the theory and functionality of TCLs. Moreover, using a new concept, the plant growth correction factor, or GCF, the ability to theoretically predicts the organogenic outcome in vitro is presented through mathematical models based on the geometric analysis of explant size and shape. A new factor, the geometric factor, or GF, was also determined for all three plants to compare regeneration from different explant types with different shapes. The GF, which is calculated, is independent of plant species or any in vitro conditions, but depends only on the size and shape of the explant and on tissue that is capable of regeneration. The GF and GCF would, in theory, allow for the direct comparison of plant in vitro studies in different laboratories provided that explant size is known, and to predict the theoretical outcome of a regeneration protocol if different explants were to be used.

Phytophthora niederhauserii sp. nov., a polyphagous species associated with ornamentals, fruit trees and native plants in 13 countries

A non-papillate, heterothallic Phytophthora species first isolated in 2001 and subsequently from symptomatic roots, crowns and stems of 33 plant species in 25 unrelated botanical families from 13 countries is formally described here as a new species. Symptoms on various hosts included crown and stem rot, chlorosis, wilting, leaf blight, cankers and gumming. This species was isolated from Australia, Hungary, Israel, Italy, Japan, the Netherlands, Norway, South Africa, Spain, Taiwan, Turkey, the United Kingdom and United States in association with shrubs and herbaceous ornamentals grown mainly in greenhouses. The most prevalent hosts are English ivy (Hedera helix) and Cistus (Cistus salvifolius). The association of the species with acorn banksia (Banksia prionotes) plants in natural ecosystems in Australia, in affected vineyards (Vitis vinifera) in South Africa and almond (Prunus dulcis) trees in Spain and Turkey in addition to infection of shrubs and herbaceous ornamentals in a broad range of unrelated families are a sign of a wide ecological adaptation of the species and its potential threat to agricultural and natural ecosystems. The morphology of the persistent non-papillate ellipsoid sporangia, unique toruloid lobate hyphal swellings and amphigynous antheridia does not match any of the described species. Phylogenetic analysis based on sequences of the ITS rDNA, EF-1α, and β-tub supported that this organism is a hitherto unknown species. It is closely related to species in ITS clade 7b with the most closely related species being P. sojae. The name Phytophthora niederhauserii has been used in previous studies without the formal description of the holotype. This name is validated in this manuscript with the formal description of Phytophthora niederhauserii Z.G. Abad et J.A. Abad, sp. nov. The name is coined to honor Dr John S. Niederhauser, a notable plant pathologist and the 1990 World Food Prize laureate.

Economic Stratification Differentiates Home Gardens in the Maya Village of Pomuch, Mexico

Economic Stratification Differentiates Home Gardens in the Maya Village of Pomuch, Mexico. In this paper, we analyze if economic stratification of peasant families in a Maya village in the Yucatan Peninsula of Mexico influences species composition and structure of home gardens. Our general hypothesis was that composition and structure reflect a higher dependence on home garden produce of relatively poorer families as compared to more prosperous families. We registered the cultivated trees and herbs in samples of twelve home gardens of poorer and wealthier families that had similar assets in the 1980s, and classified them by principal use and geographic origin. Total species richness of cultivated herbs was highest in home gardens of the more prosperous families, whereas total species richness of trees was highest in home gardens of the poorer families. Average species richness of trees and herbs and species composition was similar in both economic strata. Poorer families cultivated relatively more trees for uses other than fruit than richer families. The average and total number of native tree species and density of trees with diameter at breast height of less than 10 cm was significantly higher in poorer families’ home gardens than in those of wealthier families. We conclude that economic stratification leads to different production strategies in home gardens. Richer families are comparatively more interested in obtaining fruit occasionally and emphasize diversity of herbaceous ornamentals. Poorer families emphasize different uses, favor the native flora, and increase tree density. Thereby they contribute more to biodiversity conservation than wealthier families.

Normes OEPP EPPO Standards Schemes for the production of healthy plants for planting Schémas pour la production de végétaux sains destinés à la plantation

Normes OEPP EPPO Standards Schemes for the production of healthy plants for planting Schémas pour la production de végétaux sains destinés à la plantation

CURRENT STATUS OF GENETICALLY MODIFIED ORNAMENTALS

Biotechnology offers new means of improving ornamental crops by the addition of desirable traits to existing horticulturally-adapted cultivars. Traditional plant breeding involves the exchange of many hundreds or thousands of genes between related species to create novel combinations, and improved genotypes must be selected from thousands of segregating progeny over multiple cycles of selection. Introgression of a single desirable new character, such as disease resistance, from an unadapted relative of a crop species may require multiple backcross generations to regain the horticultural or ornamental qualities of the original cultivar, often resulting in reduced intensity of expression of the back-crossed character. In the case of many ornamental species, related germplasm with the desired disease resistance has not been identified. This is particularly true in the case of viruses, where few sources of resistance are known among ornamentals and related species. However, it has been demonstrated that effective resistance against many plant viruses can be obtained, in model systems and in some field crops, by introduction of virus-derived sequences or various anti-viral genes. Viral infection is a significant problem in many ornamentals, and especially floral crops, because so many ornamentals are vegetatively propagated. Virus infection frequently reduces floral quality and value as well as yield. Transformation of crop species with one or more gene constructs can lead to addition of desirable traits, typically with minimal effects on other desirable characteristics. Transformation systems have currently been developed for over 30 species of herbaceous ornamentals and several woody species, and efforts continue in many laboratories around the world. Several groups are working to introduce virus resistance into various ornamentals, including lilies, gladiolus, chrysanthemums, and various orchids. Other traits of interest include plant architecture, floral longevity, flower color, and resistance to other environmental stresses including drought, pests, and fungal and bacterial diseases. A few genetically modified ornamental crops have been commercialized, notably carnations with altered flower color, and there is future expectation of the introduction of effective virus resistance into commercial floral crops.

(81) Effect of Ethephon on Establishment of Herbaceous Ornamentals in a Landscape—Response of Plants During Production Phase

Use of growth regulators in ornamental plant production is a common nursery practice. Research conducted in determining landscape establishment of herbaceous plants treated with various concentrations of growth regulators is limited. The first phase of this study was conducted to evaluate response of three herbaceous ornamental species to application of ethephon. Containerized plants of irish moss, scotch moss, and salvia were treated once with FLOREL® (ethephon) at 0, 250, 500, or 750 ppm 2 weeks after transplanting into #1 size containers. During the course of the 6-week production period, standard nursery practices of fertigation, pest control, and weed management were followed. Data were collected on growth indices and marketable quality ratings (scale of 1–5) every 2 weeks. Mean initial and final shoot and root dry weights were calculated at the start and end of this phase of the experiment. The experimental design was completely randomized and data analyses were made using the analysis of variance with SAS general linear model procedure. Growth indices (cm) were significantly affected by increasing concentrations of FLOREL®. At 750 ppm concentration the mean growth indices were low (2516 cm) whereas, control (0 ppm) produced the highest mean growth indices (4317 cm). Significant differences in marketable quality ratings were also observed among the treatments where control (0 ppm) plants had the best mean rating (4.3) as compared with 500 ppm (3.6) or 750 ppm (3.5) concentrations. Salvia produced mean growth indices and mean width of 9106 and 513 cm, respectively. However, irish moss had asignificantly higher mean quality rating (4.4) when compared with either salvia (3.7) or scotch moss (3.3).

(210) X-ray-assisted Flower Seed Lot Improvement

Storage of quality herbaceous ornamental seeds is a primary concern of the Ornamental Plant Germplasm Center, a USDA National Plant Germplasm System genebank. In Autumn 2005, 30 accessions, including 10 genera of herbaceous ornamentals, were evaluated for initial seed weight and viability using four replications of 50 seeds except for Begonia, which consisted of two replications of 500 seeds due to extremely small seed size. Seed lots were then recleaned using an Oregon Seed Blower; Begonia were cleaned using the rolling paper method where good, round seeds roll off vibrating paper held at an angle and shrunken seed do not. Heavy and light fractions of all seeds were saved, 50-seed weight calculated, and viability tested. Seed cleaning was assisted by Faxitron X-ray technology to identify the quantity of seeds with embryos in each treatment. Seed cleaning statistically increased the weight for 19 accessions including Actea, Antirrhinum, Oenothera, Penstemon, Ranunculus, Rudbeckia, and Talinum, where the heaviest seed were in the heavy fraction of recleaned seed. Seed weight for some Begonia and Tagetes accessions was statistically increased, while weight of no Petunia accessions was increased. Viability was calculated as the percentage of normal and dormant seeds. Seed cleaning statistically increased the viability of 10 accessions including Actea, Oenothera, Petunia, Ranunculus, and Talinum; seed lot viability was statistically increased for some accessions of Antirrhinum, Penstemon, Rudbeckia; no accessions of Begonia or Tagetes had improved viability. Results suggest that recleaning seed lots to improve seed weight and viability may be effective, but differences between genera as well as species within genera exist.