Search

Tropical hibiscus (Hibiscus rosa-sinensis) is a bushy evergreen shrub or small tree native to the temperate regions of Asia and an economically significant crop in Florida. According to the 2017 Census of Agriculture, the market value of the ornamental industry in Miami-Dade County was $697 million, and approximately 25% of the production was in hibiscus. Demand for the cultivation of plants with minimal pesticides is rising due to concerns about potential adverse environmental and health effects. Integrated pest management, or IPM, is an alternative to conventional pesticide application. A broad-based approach, it integrates both chemical and non-chemical practices for sustainable control of pests. To help growers and other stakeholders determine the best approach to changing demands for pesticide management, this publication estimates the costs and returns of producing tropical hibiscus on an established nursery in south Florida using both traditional and IPM methods.

Although crops often respond immediately to enriched CO2 concentrations (e.g., increased photosynthesis), this initial response is often not sustained throughout production, thus reducing the benefit of this input. For horticulture species, the timing and extent of these acclimation responses are still widely uncertain. Therefore, the objective of this research was to determine species-specific acclimation responses to elevated CO2 concentrations for pansy (Viola ×wittrockiana ‘Matrix Blue Blotch Improved’) and petunia (Petunia ×hybrida ‘Dreams Midnight’). Seedlings were transplanted to 11.5-cm pots and placed in growth chambers with air temperature, relative humidity, and radiation intensity setpoints of 21 °C, 55%, and 250 μmol⋅m−2⋅s−1, respectively. Carbon dioxide treatments were established using the two growth chambers with setpoints of either 400 (ambient) or 1000 μmol⋅mol−1 (elevated) maintained during a 16-hour photoperiod. In addition to data collected through destructive harvest, the rate of photosynthesis (A) in response to increasing internal leaf CO2 concentration (A-Ci) and at the operating CO2 concentration (A-Ca) were measured weekly with a portable leaf photosynthesis system at saturating [A-Ci (1000 μmol⋅m−2⋅s−1)] or production [A-Ca (250 μmol⋅m−2⋅s−1)] radiation intensities. For both pansy and petunia, elevated CO2 produced greater total shoot dry mass than ambient CO2 after 4 weeks. However, the decreased maximum rate of photosynthetic electron transport, maximum rate of Rubisco carboxylase, and triose phosphate utilization rate of both species were also observed under elevated CO2. Similarly, A measured at 400 and 1000 μmol⋅mol−1 was reduced for both pansy and petunia grown under the elevated compared with ambient CO2 concentration based on A-Ca responses after 7 days, indicating quick physiological acclimation to this input. These results provide information regarding the timing and extent of physiological acclimation in response to elevated CO2 concentrations. However, because of physiological acclimation potentially occurring within 7 days of treatment initiation, additional research is necessary to develop species-specific recommendations for controlled environment production.

Polyploidy plays an important role in crop improvement. Polyploid plants, particularly those produced through unreduced gametes (2n gametes), show increased organ size, improved buffering capacity for deleterious mutations, and enhanced heterozygosity and heterosis. Induced polyploidy has been widely used for improving floriculture crops, however, there are few reported sexual polyploid plants in the floriculture industry. This study evaluated nine cultivars of Cymbidium Swartz and discovered that 2n male gametes occurred in this important orchid. Depending on cultivars, 2n male gamete formation frequencies varied from 0.15 to 4.03%. Interspecific hybrids generally produced more 2n male gametes than traditional cultivars. To generate sexual polyploid plants, seven pairs of crosses were made, which produced five triploid and two tetraploid hybrids. Two triploid hybrids were evaluated for in vitro regeneration and growth characteristics. Compared to the diploid parents, the triploids were more easily regenerated through rhizomes or protocorms, and regenerated plants had improved survival rates after transplanting to the greenhouse. Furthermore, the sexual polyploid plants had more compact growth style, produced fragrant flowers, and demonstrated heterosis in plant growth. Through this study, a reliable protocol for selection of appropriate parents for 2n gamete production, ploidy level evaluation, in vitro culture of polyploid progenies, and development of new polyploid cultivars was established. Our study with Cymbidium suggests that the use of 2n gametes is a viable approach for improving floriculture crops.

Polyploidy plays an important role in crop improvement. Polyploid plants, particularly those produced through unreduced gametes (2 n gametes), show increased organ size, improved buffering capacity for deleterious mutations, and enhanced heterozygosity and heterosis. Induced polyploidy has been widely used for improving floriculture crops, however, there are few reported sexual polyploid plants in the floriculture industry. This study evaluated nine cultivars of Cymbidium Swartz and discovered that 2 n male gametes occurred in this important orchid. Depending on cultivars, 2 n male gamete formation frequencies varied from 0.15 to 4.03%. Interspecific hybrids generally produced more 2 n male gametes than traditional cultivars. To generate sexual polyploid plants, seven pairs of crosses were made, which produced five triploid and two tetraploid hybrids. Two triploid hybrids were evaluated for in vitro regeneration and growth characteristics. Compared to the diploid parents, the triploids were more easily regenerated through rhizomes or protocorms, and regenerated plants had improved survival rates after transplanting to the greenhouse. Furthermore, the sexual polyploid plants had more compact growth style, produced fragrant flowers, and demonstrated heterosis in plant growth. Through this study, a reliable protocol for selection of appropriate parents for 2 n gamete production, ploidy level evaluation, in vitro culture of polyploid progenies, and development of new polyploid cultivars was established. Our study with Cymbidium suggests that the use of 2 n gametes is a viable approach for improving floriculture crops. [ABSTRACT FROM AUTHOR]

Life cycle assessment (LCA) was used to analyze the production system components of a 20-cm Chrysanthemum grown for the fall market in the north Atlanta region of the United States. The model system consisted of 2 weeks of mist in a greenhouse followed by 9 weeks on an outdoor gravel bed equipped with drip irrigation. The carbon footprint, or global warming potential (GWP), was calculated as 0.555 kg CO2e and the variable costs incurred during the modeled production system (from rooting purchased cuttings to loading the truck for shipment) totaled $0.846. Use of plastics was important in terms of GWP and variable costs with the container contributing 26.7% of theGWPof the product and 12.2% of the variable costs. The substrate accounted for 44.8% of the GWP in this model but only 12.1% of the variable costs. Consumptive water use during misting was determined to be 3.9 L per plant whereas water use during outdoor production was 34.8 L. Because propagation is handled in various ways by Chrysanthemum growers, the potential impact of alternative propagation scenarios on GWP and variable costs, including the purchase of plugs, was also examined. [ABSTRACT FROM AUTHOR]

Life cycle assessment (LCA) was used to analyze the global warming potential (GWP) and variable costs of production system components for an 11.4-cm container of wax begonia (Begonia ×semperflorens-cultorum Hort) modeled in a gutter-connected, Dutch-style greenhouse with natural ventilation in the northeastern United States. A life cycle inventory of the model system was developed based on grower interviews and published best management practices. In this model, the GWP of input products, equipment use, and environmental controls for an individual plant would be 0.140 kilograms of carbon dioxide equivalents (kg CO2e) and the variable costs would total $0.666. Fifty-seven percent of theGWPand 43% of the variable costs would be due to the container and the portion of a 12-plant shuttle tray assigned to a plant. Electricity for irrigation and general overhead would be only 13% of GWP and 2% of variable costs. Natural gas use for heating would be 0.01% ofGWPand less of the variable costs, even at a northeastern U.S. location. This was because of the rapid crop turnover and only heated for 3 months of a 50-week production year. Life cycle GWP contributions through carbon sequestration of flowering annuals after being transplanted in the landscape would be minor compared with woody plants; however, others have documented numerous benefits that enhance the human environment [ABSTRACT FROM AUTHOR]

The components for two production systems for young foliage plants in 72-count propagation trays were analyzed using life cycle assessment (LCA) procedures. The systems differed by greenhouse type, bench size and arrangement, rainwater capture, and irrigation/fertilization methods. System A was modeled as a gutter-connected, rounded-arch greenhouse without a ridge vent and covered with double-layer polyethylene, and the plants were fertigated through sprinklers on stationary benches. System B was modeled as a more modern gutter-connected, Dutch-style greenhouse using natural ventilation, and moveable, ebb-flood production tables. Inventories of input products, equipment use, and labor were generated from the protocols for those scenarios and a LCA was conducted to determine impacts on the respective greenhouse gas emissions (GHG) and the subsequent carbon footprint (CF) of foliage plants at the farm gate. CF is expressed in global warming potential for a 100-year period (GWP) in units of kilograms of carbon dioxide equivalents (kg CO2e). The GWP of the 72-count trays were calculated as 4.225 and 2.276 kg CO2e with variable costs of $25.251 and $24.857 for trays of foliage plants grown using Systems A and B, respectively. The GWP of most inputs and processes were similar between the two systems. Generally, the more modern greenhouse in System B was more efficient in terms of space use for production, heating and cooling, fertilization, and water use. While overhead costs were not measured, these differences in efficiency would also help to offset any increases in overhead costs per square foot associated with higher-cost, more modern greenhouse facilities. Thus, growers should consider the gains in efficiency and their influences on CF, variable costs (and overhead costs) when making future decisions regarding investment in greenhouse structures. [ABSTRACT FROM AUTHOR]

Agricultural growing practices have been evolving towards organic, sustainable or environmental friendly systems. The aim of modern agriculture is to reduce inputs without reducing the yield and quality. These goals can be achieved by breeding programmes but would be species specific and time consuming. The identification of organic molecules able to activate plant metabolism may allow an improvement in plant performance in a short period of time and in a cheaper way. Biostimulants are plant extracts and contain a wide range of bioactive compounds that are mostly still unknown. These products are usually able to improve the nutrient use efficiency of the plant and enhance tolerance to biotic and abiotic stresses. In this review, the state of the art and future prospects for biostimulants are reported and discussed. Moreover, particular attention has been paid to intensive agricultural systems such as horticultural and floricultural crops. In vegetables, the application of biostimulants allowed a reduction in fertilizers without affecting yield and quality. In leafy vegetables susceptible to nitrate accumulation, such as rocket, biostimulants have been able to improve the quality and keep the nitrates under the limits imposed by EU regulations. Moreover in leafy vegetables, biostimulants increased leaf pigments (chlorophyll and carotenoids) and plant growth by stimulating root growth and enhancing the antioxidant potential of plants. In floriculture, biostimulants used in bedding plant production stimulated the growth of plants, which reached the blooming and commercial stages earlier, thus optimizing space in the greenhouse. [ABSTRACT FROM AUTHOR]

In protected environments, temperature is often regulated to produce ornamental crops for specific market dates. Temperature primarily controls plant developmental rate and thus production time, but it can also interact with light quantity to affect crop quality attributes such as flower number, branching, and biomass accumulation. We quantified how mean daily temperature (MDT) between 14 and 26 °C influenced quality characteristics of 15 common bedding plant crops. American marigold (Tagetes erecta)., cup flower (Nierembergia caerulea), diascia (Diascia barberae), flowering tobacco (Nicotiana alata), geranium (Pelargonium xhortorum), globe amaranth (Gomphrena globosa)., heliotrope {Heliotropium arborescens), nemesia (Nemesia foetans). New Guinea impatiens (Impatiens hawkeri), osteospermum (Osteospermum ecklonis), pot marigold (Calendula officinalis), snapdragon (Antirrhinum majus), stock (Matthiola incana), and torenia (Torenia fournieri) were grown under two mean daily light integrals (9.0 and 18.0 mol⋅m-2⋅d-1) in five environmentally controlled greenhouse compartments with a 16-h photoperiod. As MDT increased from 14 to 26 °C, flower or inflorescence number decreased for nearly all crops. In six crops, flower or inflorescence size decreased as MDT increased, whereas in five crops, there was an initial increase in flower size with an increase in MDT and then a subsequent decrease at MDT greater than 20 °C. In 10 of the crops, shoot weight at flowering decreased linearly or quadratically with an increase in MDT. Branch number was inversely related with MDT in eight crops and was positively correlated with an increase in flower number. We conclude that in a majority of the crops studied, plant quality decreased as the MDT increased, which can at least partially be attributed to earlier flowering at the higher MDTs. Therefore, there is often a tradeoff between faster crop timing and higher plant quality, especially for plants with a low estimated base temperature (Tmin) for development. [ABSTRACT FROM AUTHOR]

Preference of phytoseiid mite, Amblyseius swirskii (Athias-Henriot) was assessed on four cultivars of ornamental pepper banker plant candidates; Red Missile (RM), Masquerade (MA), Explosive Ember (EE) and Black Pearl (BP) for potential control of pestiferous insects in floriculture. Significant differences in cultivar preference by A. swirskii was observed in choice experiments whether the test was pre- (with pollen) or during bloom. Overall, female mites laid more eggs when pollen was provided as a food source. The number of tuft domatia per cultivar leaf appeared to positively influence host preference in the choice plant tests pre-bloom. In addition, cultivar RM had the highest mean number ± SEM of tuft domatia per leaf (5.1 ± 0.3) and motiles per plant (4.0 ± 1.2), followed by MA, EE and BP. In choice tests on blooming plants, A. swirskii showed preference for both cultivars RM and MA compared to EE. These experiments indicated that the number of tuft domatia and availability of pollen can influence the host preference of A. swirskii for an ornamental pepper banker plant cultivar. Results from this study will help growers, researchers, educators and extension personnel in understanding the plant phenology promoting adoption of suitable banker plants for managing greenhouse and landscape insect pests. [ABSTRACT FROM AUTHOR]

Highlights: [•] A variety of garden plants were grown at 14–26°C from transplant to flowering [•] Mathematical models were generated to predict thermal flowering rates [•] The estimated base temperature ranged from −3.9 to 13.8°C [•] Flowering rate models can be used to improve greenhouse crop scheduling [•] There was no relationship between the reported cold hardiness and base temperature [ABSTRACT FROM AUTHOR]

Foliar sprays of 10, 15, or 20 ppm paclobutrazol followed by a second application of 50 ppm were applied to 'Bravo Lavender' and 'Celebrity Blue' petunias and 'Salvador Red' and 'Vista Red' salvia during production to determine their effects on plant growth, flowering and market quality during production, simulated shipping, and while in a simulated retail environment. Paclobutrazol effectively suppressed shoot growth and enhanced market quality of all cultivars during production, while minimally or not affecting time to first flower. Growth suppression and enhanced market quality continued through simulated shipping and the period plants were in the retail environment. While in the simulated retail environment, plants were exposed to six or seven wilt/hydration cycles. The % wilted plants of all four cultivars previously treated with paclobutrazol during production was much less than that of the controls: 'Bravo Lavender' petunia, 21 vs. 67%; 'Celebrity Blue' petunia, 10 vs. 88%; 'Salvador Red' salvia, 15 vs. 69%; and 'Vista Red' salvia; 13 vs. 74%. [ABSTRACT FROM AUTHOR]

In plant breeding programs, qualitative and quantitative traits confer market value and, thus, constitute the basis for developing breeding criteria during crop domestication. Some traits such as high male/female fertility are advantageous in the wild and could enable the evolution of cultivated crops into invasive weeds. Other traits, e.g. sterility, are not expected to confer invasiveness. To date there has been very limited involvement in invasion risk assessment by plant breeders. Thus, in this paper we propose that trait-based selection of potential crop species be coupled with species design in the creation of a “non-invasive crop ideotype” as an avenue to reduce invasiveness during domestication. The non-invasive crop ideotype embodies the ideal characteristics for a crop to excel in cultivated environment(s) but minimizes the likelihood it will establish and spread in non-cultivated environments, constituting the underlying foundation for all breeding objectives, choice(s) of breeding methodologies, and propagation techniques for non-invasive crop release. Using ornamental (floriculture) horticultural crops as an example, we identify 10 traits to be used individually or in combination to reduce invasiveness while retaining commercial value: reduced genetic variation in propagules, slowed growth rates, non-flowering, elimination of asexual propagules, lack of pollinator rewards, non-shattering seed, non-fleshy fruits, lack of seed germination, sterility, and programmed death (apotopsis). A non-invasive crop ideotype would constitute the underlying foundation for all breeding objectives, the choice(s) of breeding methodologies, and propagation technique(s). The ideotype should be flexible and should adjust to species- and crop-specific traits to account for the intended use. For example, development of sterile cultivars may have negligible effects in reducing invasiveness if the crops spread vegetatively. A non-invasive crop ideotype may increase the direct participation of plant breeders, who are the professionals directly involved in the collection, development and release of new crops, in reducing the invasive potential of ornamental crops. Future research is required to determine the feasibility of incorporating each trait into various crops, use of classical or molecular techniques for creation of non-invasive crops, trait stability (lack of genotype × environment interaction over years and locations), consumer acceptance, and long-term viability. [ABSTRACT FROM AUTHOR]

The crop domestication process is examined from plant collection to product release for various junctures at which deliberate breeding, selection, and crop transformation may occur to prevent invasive potential. Four primary juncture opportunities for research on techniques and development of selection procedures for non-invasiveness include: The Plant Exploration Phase, Initial Trial Phase, Fast-Tracking Phase, Selection and Improvement Phase. Avoiding the collection of germplasm that appears weedy during plant exploration is an obvious, yet cost-effective way to reduce invasiveness in a selection program. During initial trials, comparing genotypic differences in traits related to invasiveness should allow plant breeders to identify cultivars that pose the least risk before undertaking comprehensive field trials. Genotypes with high commercial value, considered candidates for “fast-tracking”, should only advance quickly to product release if they exhibit a minimum level of invasive risk, i.e., species with low dispersal capacity and that have little potential to impact ecosystems. Fast-growing taxa, those with high seed production, ones likely to be rapidly dispersed by wind, animals, water or people, and others that can significantly alter nutrient or light levels are examples of species that should not be “fast-tracked”. Field trials that have typically been used to evaluate performance of genotypes across a broad range of cultivated environmental conditions need to be expanded to adequately evaluate invasive potential during the selection and improvement phase. Testing in environments that mimic conditions where introductions could naturalize is crucial, as are evaluations of competition with indigenous species. The time and resource investment needed to conduct adequate trials at this stage is potentially very high; more research is needed to ensure the trials conducted are targeting important information gaps for decision-making. Additional research is also needed to develop modeling approaches that effectively forecast long-term dynamics of introductions and to assist in developing field testing priorities. Minimizing invasive potential could significantly reduce introductions that cause inadvertent damage to landscapes and ecosystems. The strategy proposed here will require further development, especially in the context of understanding and assessing risks of pre- and post-release strategies for minimizing damage from invasive species. [ABSTRACT FROM AUTHOR]

Cultivars of Dahlia, Pentas, Salvia and two Impatiens were subjected to severe soil drying, and their foliar water relations were measured when fewer than eight live leaves remained (defined as the lethal point). Salvia was the most dehydration tolerant of the four genera, as characterized by lethal leaf water potential, and showed the highest osmotic adjustment. Dahlia and the two Impatiens cultivars had similar water relations at the lethal point. Length of the drying period, which was varied by growing plants in three pot sizes, did not affect any leaf water relations parameter. The paper also provides a ranking of the foliar dehydration tolerance of 25 other ornamental plants, measured in additional experiments. Foliage of woody species tended to be more tolerant of dehydration than foliage of herbaceous species. [Copyright &y& Elsevier]