bluuebunny/crossref_metadata_2025 huggingface dataset:
593 Water Stress Influences Soil/Root Respiration Rate and Root Morphology of Young Apple Trees
Authors: Psarras Georgios , Merwin Ian A.
Published: February 2019

One-year-old potted `Mutsu' apple (Malus domestica) trees on MM.111 and M.9 rootstocks were grown outdoors from May to Nov. 1997, under three levels of soil-water availability (–20, –80, and –200 kPa), to evaluate the effects of water stress on soil/root respiration and root morphology. At weekly intervals, we measured soil/root respiration using a portable infrared gas analyzer and rootsystem size or functional activity using an electric capacitance meter. These observations were tested as nondestructive methods to estimate relative differences in root size and morphology in situ compared with final dry weight and form of excavated apple rootstocks. Root size-class distributions were estimated by digital imaging and analysis of harvested root systems. Root growth was substantially reduced by water stress; the magnitude of reduction was similar for both rootstocks, but the percentage of shoot growth reduction was higher for MM.111. Root: shoot ratios were higher and average specific respiration rates over the growing season were lower for M.9 root systems. Water stress increased the root: shoot ratio, specific root length, and carbon costs of root maintenance as indicated by specific respiration rates. Soil/root respiration was more closely correlated than root electric capacitance with actual root system size. The observed r2 values between root capacitance and root dry weight were as high as 0.73, but root capacitance was also confounded by other factors, limiting its usefulness for nondestructive estimation of root size or activity. Rootstock genotype significantly affected root capacitance, which provided better estimates of root dry weight for M.9 than for MM.111.
597 Tree Establishment and Soil Surface Covers
Authors: McDonald Garry V. , Arnold Michael A.
Published: February 2019

The purpose of this study is to determine the effects of a variety of commonly used soil surface covers on the establishment of Cercis canadensis L. var. texensis (Wats.) Rose. `Alba'. Containerized 23.3-L trees were planted into 1.1 × 1.5-m plots separated by metal landscape edging in 20-cm-deep raised beds constructed of exterior treated landscape timbers. Eight soil surface treatments were imposed with five replicates each. Controls included bare soil with no cover. The remaining seven treatments consisted of 8-cm depth of pine bark mulch, Trachelospermum asiaticum (Siebold & Zucc.) Nakai on 30-cm centers mulched with 8 cm of pine bark, solid sodded Stenotaphrum secundatum (Walt.) Kuntze, 8 cm of decorative gravel, 3 cm of recycled paper mulch, brick pavers underline with 5 cm of coarse builders sand (brick-on-sand), and seasonal color mulched with 8 cm of pine bark. The color rotation for summer, fall / winter, and spring is Catharanthus roseus (L.) G. Don, Viola × wittrockiana Gams., and Petunia × hybrida Hort. Vilm.-Andr., respectively. Preliminary data indicates that mulching with pine bark resulted in similar or slightly increased trunk diameter growth over that of bare soil. Brick-on-sand and the recycled paper mulch had smaller increases in trunk diameter than the other treatments. Mid-day leaf water potentials of most treatments were similar to bare soil, but the mid-day water potentials of trees mulched with recycled paper were among the most negative. All treatments except brick-on-sand trees recovered as well or better than trees in the bare soil by the next morning. Poor predawn water potential recovery of brick-on-sand trees may be due to the elevated temperatures observed in their root zone. Bare soil, recycled paper mulch, and the annual treatments had the most negative soil moisture tensions on average. The bare soil may be due to increased evaporative loose over mulched soils. The large biomass of vinca as the season progressed may account for the more negative readings in the annual seasonal color plots.
598 Drought Stress Affects Carbohydrate Partitioning in Three Species of Herbaceous Perennials
Authors: Prevete Kelly J. , Fernandez R. Thomas , Miller William B.
Published: February 2019

Drought stress durations of 2, 4, and 6 days were imposed on Boltonia asteroides `Snowbank', Eupatorium rugosum, and Rudbeckia triloba to determine the effects on carbohydrate partitioning in the plant. Drought stress was imposed on 19 Sept. 1997 on 1.9-L containerized plants. Plants were planted in the field the day following release from stress. Crown and leaf samples of the three species were collected 21, 23, 25 Sept. 1997 and 30 Jan. and 4 May 1998 and were analyzed for low molecular weight sugars and fructans. The species differed in the time it took for longer chain fructans to break down to shorter chain fructans and low molecular weight sugars (glucose, fructose). The drought tolerant Boltonia and Rudbeckia had shifts from longer chain to shorter chain fructans by day 4 of stress. Boltonia had a change in carbohydrate partitioning in the leaf tissue, while Rudbeckia had a change in crown tissue carbohydrate partitioning. Eupatorium did not have a shift in longer chain fructans to shorter chain fructans in crown tissue until day six of stress. The slower shift from longer chain fructans to shorter chain fructans by Eupatorium, compared to Boltonia and Rudbeckia, could explain the lack of drought tolerance of Eupatorium. The shift from high molecular weight sugars to low molecular weight sugars suggests that the higher molecular weight sugars broke down to lower molecular weight sugars in response to drought stress.
604 Yield Response of Microirrigated Herbs to Compost Amendment and N and K Fertilizers on Sand
Authors: Csizinszky A. A.
Published: February 2019

Italian parsley (parsley) Petroselinum crispum, summer savory (savory) Satureja hortensis, sweet marjoram (marjoram) Origanum majoranna, and thyme Thymus vulgaris, were evaluated for their yield potential in multiple harvest during the fall–winter–spring (Dec.–May 1997–98). The herbs were grown with the full-bed polyethylene mulch-micro (trickle) irrigation system. Experimental design was a split-plot arranged in three randomized complete blocks. Main plots were two N–P–K treatments: 0 N–P–K or N and K from a liquid 4N–0P–3.32K fertilizer injected at 0.77 N and 0.64 K kg/ha per day. In the subplots, compost was applied in a 4 to 8 inches wide band on the pre-bed at 0x, 1x, 2x, and 4x rates (1x = 4.5 t·ha–1). Parsley and marjoram yields in the first three harvests and thyme yields in the first two harvests were similar with 0x compost and N + K injected fertilizers to yields with 3x and 4x compost rates with no injected N + K fertilizers. For the season, yields were higher with injected N + K fertilizers with or without compost, than in the compost treated plots with no N + K fertilizers.
607 Estimation of N Mineralization Rate of Composts and Manures
Authors: Hartz T.K. , Mitchell J.P.
Published: February 2019

The rate of N mineralization from 35 samples of manure or compost was estimated by both aerobic laboratory incubation and lath house pot studies at Davis, Calif., in 1996–97. Each manure and compost sample was mixed at 2% by dry weight with a 1 loam soil: 1 coarse sand blend. The amended soil blends were moisture equilibrated under 0.025-MPa pressure then incubated aerobically at constant moisture at 25 °C for 3 (1996) or 6 months (1997); subsamples were collected monthly (1996) or bimonthly (1997) for mineral N determination. Four-liter pots were also filled with the amended soil blends and seeded with fescue (Festuca arundinacea). The pots were watered but not fertilized for 16 (1996) or 18 (1997) weeks in a lath house at ambient summer conditions. N mineralization from the pot study was calculated from total fescue biomass N plus mineral N from pot leachate, minus those quantities in pots of the unamended soil blend. N mineralization rate estimates from the two techniques were highly correlated (r2 = 0.79). Green waste composts typically mineralized <5% of total N, manure composts 5% to10%, and manures (poultry, dairy, and feedlot) 7% to 20%. After 4 months of incubation, N mineralization rate (expressed as percent of total N per month) from the composts and manures was similar to that of the unamended soil blend.
608 Germination and Early Seedling Growth of Alnus maritima from Its Three Disjunct Populations
Authors: Schrader James A. , Graves William R.
Published: February 2019

Genotypic variation and horticultural potential of Alnus maritima [Marsh.] Nutt. (seaside alder), a large shrub or small tree found naturally in only three small, disjunct populations, have not been studied. We examined effects of population of origin and environment on seed germination and the growth and morphology of seedlings. Our first germination experiment showed that 6 weeks of cold stratification applied to half-siblings from Oklahoma optimized germination at 73.2%. When this treatment was applied to multiple half-sib seed sources from all populations in a second experiment, seeds from Oklahoma had a higher germination percentage (55%) than seeds from both Georgia (31.4%) and the Delmarva Peninsula (14.7%). A third experiment showed that growth of seedlings increased with increasing irradiance intensity up to 258 μmol·m–2·s–1, and survival and growth of seedlings from Oklahoma varied with root media. In a fourth experiment, multiple groups of half-siblings from all three populations were grown in one environment to compare variation in growth and morphology within and among populations. Leaves of Oklahoma seedlings were longer (12.8 cm) and more narrow (2.15 length: width ratio) than leaves of seedlings from Georgia (12.0 cm long, ratio = 1.76) and the Delmarva Peninsula (11.6 cm long, ratio = 1.86). Seedlings from Oklahoma and Georgia had a higher growth rate (180.7 and 160.0 mg/day, respectively) than did seedlings from Delmarva (130.1 mg/day), while Oklahoma and Delmarva seedlings were more densely foliated (0.72 and 0.64 leaves and lateral shoots per cm of primary stem, respectively) than those from Georgia (0.46 per cm). These differences indicate both divergence among the three disjunct populations and potential to exploit genetic variation to select horticulturally superior A. maritima for use in managed landscapes.
610 Evaluation of Sawmill Residue as a Component of Nursery Potting Mix
Authors: McLaurin Wayne J.
Published: February 2019

The standard mix used by most nurseries consist of a 9 pine bark: 1 sand. With the ever-increasing cost of bark, nurseries are looking for an alternative. Sawmill residue may hold potential utility as part of a potting mix. Although sawmill residue is highly variable, it can serve as soil bulk as well as an organic medium. The purpose of this study was to determine if old sawmill residue not treated by pathogen-free requirement procedures could be used “as is” as part of a nursery soil mix. For this study, a sample, a typical conglomerate of undetermined wood chips, bark, and soil particles, was obtained from an “old pile” (just how old is not known) of sawmill residue. To determine how this sample would function in a nursery bark/sand mix, tests were run on its physical properties of pore space and water-holding capacity. The sawmill residue had the following characteristics: a mean 44.2% porosity capacity, 23.4% air space, and 20.8% water holding capacity. A standard fertilizer and lime amendment package was added to the sawmill residue in the same rates as a regular nursery mix. The sawmill residue and the standard nursery mix were then blended according to the treatment percentages. The treatments were sawmill residue/standard nursery mix 0/100, 10/90, 30/70, 60/40, and 100/0. The Ilex crenata `Compacta' liners were planted into standard 1-gallon nursery pots filling to just below the rim. The pots were randomly placed on a well-drained rock surface in full sun. No additional fertilizer was used and watering was done as needed. Plants were grown for 1 year. Visual assessments were made throughout the growing period and at harvest. There was no visible difference in any of the treatments as far as overall growth was discerned. The plants were of uniform height and width showing consistent, even growth and good leaf color. Root system growth and development were evaluated visually and over all treatments were uniformly good. No root problems were noted. There was not any plant loss in any treatment over the entire study. Each plant was cut at the soil line and dried for 24 hours at 1150 °C. Dry weights were taken after the plant material had cooled for 4 hours. Results were based on four plants per treatment times four replications for a total of 16 plants per treatment. There was not any measurable growth difference in dry weight among treatments 1, 2, 3, and 4 [sawmill residue/standard nursery mix 0/100 (41.03 g dry weight), 10/90 (39.83 g dry weight), 30/70 (38.98 g dry weight), 60/40 (37.42 g dry weight)]. However, treatment 5 [100/0 (31.03 g dry weight)] was significantly lower when compared to the remaining four treatments. The lower dry weight may be attributed to the 100% sawmill residue being too heavy and not well-drained enough. However, the roots did not show any damage from being too wet. Further work is being done with the sawmill residue.
613 The Methodological Study of Under-soil Heating System (USHS) for Warm-season Grass
Authors: Miwa Takashi , Kihara Hisakazu , Tonogi Hideaki
Published: February 2019

Recently, full-green turf on sports fields in the winter is highly desirable. The negative factor for warm-season grass pitch is its winter dormancy. Winter overseeding (WOS) is one successful method to make turf seem green. However, maintenance cost for WOS turf is relatively expensive and brings some difficulties. Undersoil heating (USH) has been used for cool-season grass pitch or warm-season grass pitch to make turf green in winter. Our objectives were 1) to confirm USH effectiveness for warm-season grass, 2) to make the specified system itself, and 3) to estimate the approximate heat demand. The results indicate that USH can make warm-season grass green and maintain much higher turf quality even in severe winter conditions. Weed invasion, pests, and diseases levels are quite low during the test period. The characteristics needed to create the system include heating pipe spacing and depth, initial media temperature, and required soil temperature. In addition, USH needs a plastic cover for insulation that is light and that air and water can penetrate. Compared with WOS, USH can reduce maintenance fees and procedures, such as preparation for WOS in a fall and transition into spring. Thus, UHS can prolong total playing period. Moreover, it is easy to maintain the higher turf quality and lower maintenance cost than WOS. In the future, we should concentrate on creating more concrete maintenance program for this method.
615 Growth Performance of Transplanted Young Apple Trees in Relation to Reserve Nitrogen and Carbohydrates
Authors: Cheng Lailiang , Fuchigami Leslie H.
Published: February 2019

Reserve N and carbohydrate levels of bench-grafted Fuji/M26 plants were altered by fertigation with seven N concentrations from 30 June to 1 Sept. in combination with or without 3% foliar urea application in mid-October. The plants were harvested after natural leaf fall and stored at 2 °C. One set of plants were destructively sampled in January for reserve N and carbohydrates analysis, and the remaining plants were transplanted into a N-free medium in the spring and supplied with or without 5 mM 15N-ammonium nitrate in a Hoagland solution for 60 days after budbreak. Plants fertigated with higher N concentrations had higher reserve N content and lower carbohydrate concentrations. Foliar urea application increased whole plant N content and decreased reserve carbohydrate concentration at each given N concentration used in fertigation. Regardless of N supply in the spring, total new shoot and leaf growth of plants fertigated with N was closely related to the amount of reserve N but not reserve carbohydrates. Plants treated with foliar urea had more new shoot and leaf growth than the fertigated controls. By pooling all the data concerning reserve N used for growth regardless of the spring N supply, a linear relationship was found between the amount of reserve N used for new shoot and leaf growth and the total amount of N. We conclude that the growth of apple nursery plants in the spring is mainly determined by reserve N, not reserve carbohydrates. The amount of reserve N used for new shoot and leaf growth in the spring is dependent on the total amount of reserve and is not affected by the current N supply.
617 Effects of Nitrogen, Potassium, and Irrigation on Postharvest Pitting of White Grapefruit
Authors: Dou Huating , Petracek Peter , Ismail Mohamed , Alva Ashok , Calvert David
Published: February 2019

Effects of N, K, and water relation on the incidence and severity of postharvest pitting in white grapefruit were evaluated in two field experiments. In the first experiment, a factorial combination of 3 N (56, 168, and 336 kg·ha–1) and 3 K (52, 156, and 312 kg·ha–1) rates were used with three broadcast applications per year. In the second experiment, there were two irrigation regimes (at 30% and 60% depletion of available soil moisture, ASM, content) with three subtreatments of variable N and K rates (Kg·ha–1) at 56: 52; 112: 104, and 336: 312 kg·ha–1. The fruit were harvested three times each season, waxed with shellac wax, and stored at 70°F for evaluation of pitting. The pitting incidence was lower at the optimal N and K rates than that at the low or high rates. The irrigation at 30% ASM significantly reduced pitting incidence. The higher incidence of pitting was found in an area in the grove with higher water table. This study suggested that effects of water may play an important role on peel physiology and pitting.
622 Toxicity of Indian Mustard (Brassica juncea) and Allyl Isothio-cyanate to Masked Chaffer Beetle Larvae (Cyclocephala sp.)
Authors: Noble Ryan R.P. , Charron C.S. , Sams C.E.
Published: February 2019

The development of alternative methods for control of soilborne pathogens is imperative since the U.S. Clean Air Act bans the use of methyl bromide after 2005. One possibility is to exploit the pesticidal properties of compounds released by macerated Brassica tissues. In this study, masked chaffer beetle larvae were placed in sealed 473-mL jars with 335 g of soil amended with 1%, 2%, 4%, or 8% (g·g–1) Brassica tissue. The most prevalent volatile toxic compound of Brassica juncea (PI 458934) is allyl isothiocyanate (AITC). AITC production was measured in the jars at 0.25, 4, 8, 24, and 48 h using a solid-phase microextraction device (SPME) and gas chromatography. After 7 days, larvae mortality was determined. Control treatments included untreated soil, soil amended with 8% tomato plant tissue, soil amended with pure AITC, and untreated soil with an atmosphere of ≈20% O2 and 0% CO2 changing over 48 h to 2% O2 and 20% CO2. AITC levels were positively correlated to larvae mortality. The estimated lethal concentration for 50% kill (LC50) was 3.6 μg AITC/L soil atmosphere. AITC levels may be influenced by Brassica mass added, soil bulk density, and environmental factors including temperature and moisture. B. juncea has a high tissue AITC concentration. However, the mass of Brassica tissue required for insecticidal application against Cyclocephala sp. is also high, between 4% and 8% of soil mass. Development and selection of Brassica species that produce higher concentrations of isothiocyanate would increase the effectiveness of Brassica biofumigation as an alternative to methyl bromide for controlling soilborne insects.
623 Does the Aquadome Ameliorate Diural Fluctuations
Authors: Swenson Kimberly , Markhart Albert H.
Published: February 2019

A major limitation to plant growth in spring is low night temperatures. A variety of plant protection systems have been developed to keep the temperatures around the plant warmer than the ambient air. One system that has been developed for use with individual plants is a double walled stiff plastic tent. The space between the walls can be either filled with water or air. The top of the tent can be either open or closed. The objective of this investigation is to quantify the effect of these protection systems under controlled environmental conditions. Two wash-tubs filled with wet soil were placed in a controlled environment growth chamber. One tent was placed on the soil surface of each tub. The chamber was programmed to simulate a cold night. Temperatures started at 20 °C and then decreased to –5 °C at a rate of about 4 °C/h. During this time, ambient air temperature, jacket temperature, soil temperature, and air inside the tent was measured continuously with self-contained data loggers. Water filled tents delayed the time it took for the inside temperature to reach the outside temperature by 2 hours. There was not apparent effect on soil temperature. The effect of water vs. air-filled jackets and the effect of capping the top will also be presented.
624 Consumer Perceptions of Landscape Value using Different Designs, Types of Plant Material, and Plant Sizes
Authors: Muzii Karl J. , Haque M. , Fernandez R.T. , Behe B. , Barton S.
Published: February 2019

The research contained in this thesis quantifies the difference between actual landscape value and perceived value on the part of homeowners. Pertinent information and necessary data were gathered by surveys interviewing consumers over the age of 18, who evaluated a set of 16 home landscape photographs. These surveys were conducted at two sites in South Carolina. The study involved three levels of landscape design with varying complexity and cost factors. Four plant material and hardscape combinations were developed for use in each cost design. Finally, the plant material size was categorized as small, medium, or large. Thirty-six design combinations were created. A subset of 16 computer-generated images was selected to simplify the evaluation. Participating respondents answered a questionnaire providing personal demographic information and their evaluations of the 16-image subset. Participants were supplied a base starting price and a photo of the home without landscaping. Responses were analyzed to determine consumer perceptions of value influenced by landscape design style, plant material, and hardscape selection; plant size; and by the difference between perceived value and actual cost to install. Consumer responses for all landscape designs were positive and indicate that consumers consider landscaping an asset to residential value. Participants valued the home on average between.95% to 11.3%, depending on the complexity of design, plant material, hardscape, and size combinations. The variance between consumer perception and actual cost of material and labor indicates that consumers undervalue the price of a newly installed landscape where all material and labor costs are priced consistent with professional landscaping averages.
626 Effects of Chemical and Mechanical Height Control in Dendranthema grandiflorum
Authors: Holt Kiffnie M. , Jennings Paul H.
Published: February 2019

Rooted chrysanthemum cuttings of five cultivars were transplanted into 6 1/2″ pots and greenhouse-grown for 7 weeks under natural daylength conditions. Plants were pinched back twice, on the 3rd week and the 5th week following transplanting. At 7 weeks, plants were arranged in a complete randomized-block design with four plants per cultivar per treatment and three replications. Spacing of the pots was kept constant through the duration of the experiment. The chemical group was sprayed with 2500 ppm B-Nine until run-off on the first day of treatment. The mechanical group was brushed 40 times, twice a day, for 5 weeks. The brushing mechanism was adjusted daily to account for growth so as to stimulate only the top 2 to 3 inches of the plant. Measurements of all plants were taken on the first and last day of the mechanical treatment. Data collected included height, internode length, and leaf area. Plants were then allowed to flower under the naturally shortening daylength, and the flowering date was recorded. The chemical and mechanically treated plants were shorter than the controls with a greater response occurring with the cultivars `Emily' and `Cheery Emily', which had a more open and upright growth habit. Cultivar response differences and effects on internode length, leaf area, and flowering date were noted and will be discussed.
629 Are Trichome Number Related to Parthenolide Content in Feverfew?
Authors: Hatch Gretchen , Markhart Albert H.
Published: February 2019

The concentration of active ingredient in a given dry weight of a medicinal herb is important to the consumer and producer of herbal remedies. Feverfew is a commonly used medicinal herb where the active compound has been identified. There is considerable variability in the amount of the active ingredients in different genotypes of feverfew. Important secondary plant compounds are often produced in the trichomes of leaves. The objective of this investigation is to determine if there is a correlation between the number of leaf trichomes and the level of active ingredient in several feverfew genotypes. Rooted cuttings of feverfew (Chrysanthemum parthenium) genotypes previously characterized for parthenolide content were grown under identical conditions in an environmentally controlled greenhouse. Light and scanning electron microscopy were used to describe and quantify the number and type of trichomes on the youngest fully expanded leaf of each plant from each genotype. The relationship between trichome number and parthenolide content will be presented.
642 A Training Series in Organic Farming Systems
Authors: Creamer N.G. , Baldwin K.R. , Louws F.J.
Published: February 2019

Consumer demand for organically produced food and the desire by many farmers to eliminate chemical fertilizers and pesticides is increasing the need for research and educational programs to support organic farmers. To date, the land-grant universities and the cooperative extension service have been viewed by organic farmers as unresponsive to this need. The primary reason for the unresponsiveness has been inadequate training and resource materials available to extension agents. In 1998, we conducted an intensive training for agriculture agents in North Carolina. Funding was provided by the USDA SARE Professional Development Program. More than 50 agents participated in a series of workshops that were offered together as a graduate course worth four NCSU credits. Much of the training was conducted on the Organic Unit at The Center for Environmental Farming Systems (CEFS), a 100-acre facility dedicated to research and education in organic farming systems. The hands-on training consisted of lectures, demonstrations, field trips, and class exercises. The topic areas included soil biology/ecology; crop rotation; organic nutrient management; composting; cover crop management; organic weed, insect, and disease management; appropriate tillage practices; organic greenhouse management; marketing organic produce; integrating animals into organic crop production systems; delivery systems for disseminating information to organic producers, and; social and community development aspects of sustainable agriculture. Unique features of the workshops were the interdisciplinary approach to teaching them, and the integration of information about interactions between production factors. The training was very well-received and will serve as a model for future extension programming. A training manual, slide sets, extension publications, and a Web site are being created to further support agents as they conduct programming in their own counties.
649 Summary of the Status of Precision Agriculture
Authors: Sanders Douglas C.
Published: February 2019

The diversity of site-specific management opportunities is demonstrated by the list of topics and speakers we have in the colloquium. These techniques will help use to better understand, adapt, and adjust horticultural management to the benefit of producers, researchers, and the consumer. With these technologies we will be able to reduce costs, environmental impacts, and improve production, and quality. Horticulture will use more both remote and manually operated devices that allow more intensive planning and management of our production systems. This colloquium has just scratched the surface of the potential of these techniques in horticulture. We hope that the sampling will whet your appetite for great depth of study of the opportunities that are just around the corner.
650 How are Molecular Maps and DNA Libraries Being Used for Genetics and Germplasm Research of Horticultural Crops?
Authors: Weeden Norman F.
Published: February 2019

Molecular maps and DNA libraries are now possible to construct in nearly every horticultural crop. Comparison of linkage relationships both within and among families of flowering plants is giving us the capability to predict where genes will be even in crops lacking linkage maps. The dissection of quantitative traits into Mendelian components has been successfully performed in many crops, and candidate genes have occasionally been matched with QTLs or morphological mutations on the basis of map position. Breeders are now able to predict what combination of traits will be difficult to achieve as a result of repulsion phase linkage and what traits might be associated with problems due to linkage drag. Maps and libraries also help in identification of homologous genes in different species and gene-rich regions within a chromosome. More generally, DNA libraries are giving us access to every gene in a genome, leading to much more powerful studies concerning the anatomy, ontogeny and physiology of horticultural crops.
653 Use of Beneficial Rhizobacteria to Enhance Growth and Induce Systemic Disease Protection in Transplants
Authors: Kloepper Joseph W. , Reddy M.S. , Ryu Choon-min , Murphy John F.
Published: February 2019

Use of beneficial rhizobacteria to enhance growth and induce systemic disease protection in transplants. Plant associated bacteria have been studied for the capacity to provide plant growth enhancement and biological disease control. “Rhizobacteria” are bacteria from the rhizosphere that have the capacity to colonize plant roots following introduction onto seeds or into soil. Effects of rhizobacteria on plants may be deleterious, neutral, or beneficial. Beneficial rhizobacteria are termed “PGPR—plant growth-promoting rhizobacteria.” In developmental studies aimed at reducing to practice the concept of induced systemic disease protection mediated by PGPR, we discovered that mixtures of PGPR and an organic amendment into the soilless media used to prepare tomato transplants resulted in highly significant and reproducible plant growth promotion. Time for development of transplants was typically reduced from 6 weeks for controls receiving industry standard fertility and growth regimes to 4 weeks for seedlings grown in soilless mix into which the PGPR had been incorporated. This marked growth promotion was also associated with systemic protection against pathogens. When transplants were inoculated with the tomato spot pathogen, significantly fewer lesions developed on plants grown in the biological system than on control plants. Similar effects on plant growth and systemic disease protection were seen with cucumber, bell pepper, and tobacco, suggesting that the benefits are not highly crop or cultivar specific. Results of recent field studies will be presented. We conclude that incorporation of PGPR into soilless mixes is a technologically useful and feasible way to deliver benefits to transplants.
655 Commercial Biological Products for Reducing Plant Disease and Enhancing Plant Establishment in Flowers and Ornamental Crops
Authors: Wick Robert
Published: February 2019

Several biological control agents for the control of fungal diseases have recently been commercialized. Do the claims of pest control meet the expectations of the growers? Do the biocontrol agents perform consistently? How do they compare to chemicals? These questions have yet to be answered but recent trials indicate mixed results. In Massachusetts, Mycostop worked well against fusarium stem rot but not against fusarium wilt. Deny (Burkholderia cepacia) did not perform well against Rhizoctonia or Pythium root rot of poinsettia. The following information was taken from the 1997 and 1998 Biological and Cultural Tests for Control of Plant Diseases. In Maryland, zinnia damping-off was controlled by both SoilGard (Gliocladium virens) and Bio-Trek (Trichoderma harzianum). The biocontrols performed as well as the conventional fungicide. In North Carolina, GlioGard (Gliocladium virens) and SoilGard gave only partial control against Pythium and Rhizoctonia damping-off of bedding plants. In Pennsylvania, Greygold (mixture of four microorganisms) did not provide adequate control of Botrytis on geranium. In Georgia, Pythium and Rhizoctonia diseases of a variety of plants were evaluated with SoilGard and RootShield (Trichoderma harzianum). Disease pressure was low and the results varied from inconclusive to both positive and negative. In addition, SoilGard apparently reduced fresh weight of several plant species. RootShield was reported to both increase root weight in one case and decrease root weight in another. In Connecticut, Rhizoctonia root rot of poinsettia was not significantly suppressed with SoilGard, RootShield, or Earthgro, a suppressive growing medium. However, the authors stated that the results indicated that the biocontrols had promise. Results of additional trials will be presented.
660 Reducing Floral Initiation and Return Bloom in Stone Fruit Trees: Applications and Implications in Fruit Production
Authors: Southwick Stephen M.
Published: February 2019

Commercially grown apricots (Prunus armeniaca), peaches (Prunus persica), nectarines (Prunus persica), plums (Prunus salicina and Prunus domestica), and pluots (Prunus salicina × Prunus armeniaca) have a tendency to produce high numbers of flowers. These flowers often set and produce more fruit than trees can adequately size to meet market standards. When excessive fruit set occurs, removal of fruit by hand-thinning is common to ensure that fruit size meets market standards. Over the years there have been numerous attempts to find chemical or physical techniques that would help to reduce costs associated with and improve efficiencies of hand-thinning; however, using alternate strategies to hand-thinning have not been widely adopted in stone fruit production. In the past 10 years, through the continuing efforts of scientists throughout the world in public and private institutions and business, it appears that there are chemical sprays capable of reducing the need for hand-thinning in stone fruit. Management of flowering by reducing the number of flowers on apricot, peach, nectarine, plum, and prune has shown promise under climatic conditions such as those found in the San Joaquin Valley of California. By applying gibberellins during May through July, flowers in many stone fruit cultivars can be reduced in the following season. The reduction in flower number does not generally lead to an increase in fruit set. As a result, fruit numbers are reduced, the need for hand thinning can be reduced, and in some cases eliminated. There are risks associated with reducing flower number before climatic conditions during bloom or final fruit set are known. However, given the changes in labor costs and market demands, especially in the developed world, the benefits may outweigh the risks. The application and implications of these summer gibberellin applications toward reducing flower numbers will be discussed as it relates to commercial stone fruit growing.
668 Precocious, Dwarfing, and Productive—Will New Rootstocks Ruin the Sweet Cherry Industry?
Authors: Lang Gregory A.
Published: February 2019

Sweet cherries (Prunus avium) can be one of the most profitable tree fruit cultivated in temperate climates. While cherry trees grow naturally to relatively tall heights, new size-controlling cherry rootstocks similar to those used in high-density apple orchards are now a reality. The Gisela series from Germany, the Gran Manier series from Belgium, the Weiroot series, the P-HL series, Tabel Edabriz, and others of international origin are at various stages of scientific and field testing in North America, with some now moving into commercial fruit production. These stocks confer several highly advantageous traits besides vigor control, including precocious fruiting and high productivity. While these obvious traits are exciting, serious problems have also been documented, on occassion, with such phenomena as small fruit size and tree decline. As many of these rootstocks are interspecific Prunus hybrids, might there be significant limitations for fruit quality and orchard longevity? What is known about their susceptibilities to pathogens and pests? What is known about their tolerance to various soil types and/or climatological stresses? Further, with the U.S. and worldwide orchard area planted to fresh-market sweet cherries already expanding to record levels throughout the 1990s and a time-honored agricultural trend toward overproduction until grower profits are minimized (see recent international apple markets), what might be the future impact of such precocious, productive rootstocks on sweet cherry profitability and sustainable production? This overview will address these topics, providing some answers and some areas for future scientific investigation and discussion.
669 The Impact of Gulf Coast Hurricanes on Pecans, Ornamental Trees, and Invasive Exotic Species
Authors: McWilliams Edward L.
Published: February 2019

Hurricanes strike the Gulf Coast of the United States every few years. We briefly describe generalized hurricane tracks for the Gulf Coast and vegetation damage using NDVI satellite imagery as well as slides of damaged urban trees in Florida. The impact of recent hurricanes on both pecan defoliation and production and on initial damage and subsequent recovery of various ornamental trees is described. Pecan harvests were greatly reduced by hurricanes that struck late in the season in both Alabama and Texas. Varieties of pecans varied in their susceptibility to various stresses. Pine forests were sometimes devastated by certain hurricanes while live oaks, various shrubs, and important insects often survived the same storms with little damage. Many exotic ornamental plants including Chinese tallow are either adventive or invasive along the Gulf Coast. Species escape from cultivation over a long period of time and exhibit different invasion lag phases. In Texas and Louisiana, hurricane damage to native trees allowed Chinese tallow seedlings and saplings to subsequently dominate some areas as a result of the disturbance. One delayed ecological response to hurricanes and typhoons is an acceleration of ongoing exotic plant invasions.
678 Turfgrass Response to Phosphorus Applications
Authors: Christians N.E.
Published: February 2019

Phosphorus (P) applications to turfgrasses vary with the development stage of the plant. At establishment, it is common to use “starter fertilizers,” such as 12N–25P–10K, that are high in P and relatively low in nitrogen (N). Mature grass plants, however, are very efficient users of P. As the root system develops, the amount of P added as fertilizer decreases, unless the soil is very deficient in P. A common analysis for mature turf would be a 20N–2P–15K. The reason for this change is the relative immobility of P in the soil. At the time of establishment, the limited root system is unable to obtain sufficient P to meet the plant's needs for this element. The P does not readily move in the soil solution to the vicinity of the plant and it must be placed on the surface in close proximity to the developing root. At maturity, the fibrous, multibranched root systems of grasses make them some of the most efficient species at removing P from the soil. A major concern over the use of P fertilizers on turf in recent years has been the possibility of movement of this element into surface waters. Excess P in surface water may result in algal blooms and other environmental problems. While there is some reason for concern where fertilizers are applied on sidewalks and streets in urban areas, P movement from most turf areas is very limited and properly applied fertilizer results in little damage to the environment.
Chilling Enhances Cane Elongation and Flowering in Primocane-fruiting Blackberries
Authors: Lopez-Medina Jose , Moore James N.
Published: February 2019

Root cuttings of A-1836, APF-13, and NC194 primocane-fruiting (PF) blackberry (Rubus subgenus Rubus) genotypes were dug from the field on 31 July 1997 and stored in plastic bags at 2 °C for 32 days. On 1 Sept. freshly dug root cuttings, along with the cold-treated ones, were planted in pots, which were kept in a lath house for 4 weeks and then moved to a heated greenhouse under natural daylength. Cold-treatment hastened emergence of all genotypes. Transition from vegetative to floral phase was first observed in cold-treated A-1836 and APF-13 at the fifth node, with floral appendages clearly evident in both genotypes at the seventh node 45 days after planting (DAP). Bloom started on 26 Nov. and 5 Dec. 1997 and the first fruits were picked on 10 and 25 Jan. 1998 in cold-treated APF-13 and A-1836, respectively. Plants of cold-treated NC194 and of all non-cold-treated genotypes remained stunted with rosetted leaves, showing no signs of floral initiation until 150 DAP. These findings show that exposure to chilling prior to shoot emergence greatly promotes flowering in PF blackberries, and may have application in greenhouse culture of blackberry.
Tomato Yield and Fruit Size Did Not Respond to P Fertilization of a Sandy Soil Testing Very High in Mehlich-1 P
Authors: Hochmuth George , Carrijo Osmar , Shuler Ken
Published: February 2019

Tomato (Lycopersicon esculentum Mill.) was grown in southeastern Florida on sandy soils that tested very high in Mehlich-1 P to evaluate the yield response to P fertilization. One location was used in 1995–96, another in 1996–97. Prefertilization soil samples contained 290 (location 1) and 63 (location 2) mg·kg–1 Mehlich-1 P. Both soil test results were interpreted as very high in P, and P fertilizer was not recommended for the crop. Fertilizer treatments at both sites were 0, 25, 50, 100, 150, and 200 kg·ha–1 P. Neither total marketable yield nor yield in any fruit size category was affected by P fertilization in either season. Amounts of cull (undersized or misshapened) fruits increased quadratically with P fertilization in the second season. Whole-leaf P concentrations increased linearly or quadratically with P application, depending on sample periods, and were always above sufficiency values. Although many tomato growers apply P fertilizer irrespective of soil test recommendations, our results showed that added P was not needed on soils testing very high in P. Furthermore, withholding P applications to soils with high P concentrations will minimize potential P pollution of surface water and groundwater.
Variation among Red and Freeman Maples in Response to Drought and Flooding
Authors: Zwack James A. , Graves William R. , Townsend Alden M.
Published: February 2019

Freeman maples (Ace×freemanii E. Murray) are marketed as stress-resistant alternatives to red maples (Acer rubrum L.). Our objective was to compare two cultivars of Freeman maple [`Jeffersred' (Autumn Blaze®) and `Indian Summer'] and five red maples [`Franksred' (Red Sunset®), `Autumn Flame', `PNI 0268' (October Glory®), `Fairview Flame', and unnamed selection 59904] for effects of flooding and water deficit on plant growth, biomass partitioning, stomatal conductance, and leaf osmotic potential. Plants grown from rooted cuttings in containers were subjected to three consecutive cycles during which root-zone water content decreased to 0.12, 0.08, and 0.02 m3·m–3, respectively. Additional plants were flooded for 75 days, while plants in a control treatment were irrigated frequently. Stomatal conductance immediately before imposing drought and after three drought cycles did not differ among genotypes and averaged 220 and 26 mmol·s–1·m–2, respectively. Differences in stomatal conductance after recovery from the first drought cycle and at the end of the second drought cycle did not vary with species. Drought reduced estimated leaf osmotic potential similarly for all genotypes; means for drought-stressed and control plants were –1.92 and –1.16 MPa, respectively. Freeman maples had a higher mean root: shoot weight ratio and a lower leaf surface area: root dryweight ratio than did red maples. Across genotypes, stomatal conductance of flooded plants initially increased by ≈20% and then fell to and remained below 50 mmol·s–1·m–2. Stomatal conductance of `Indian Summer' decreased to ≈20 mmol·s–1·m–2 after 8 days of flooding, indicating that this cultivar may be particularly sensitive to root-zone saturation.
Paclobutrazol Affects Growth and Flower Bud Production in Gardenia under Different Light Regimes
Authors: Kamoutsis A.P. , Chronopoulou-Sereli A.G. , Paspatis E.A.
Published: February 2019

The effects of several shading materials on the response of Gardenia jasminoides Ellis to paclobutrazol were investigated under greenhouse conditions. The three main plot treatments were shading (0%, 67%, 98%), and paclobutrazol (0.0, 0.5, 1.0, and 2 mg/pot) was applied as a soil drench in each main plot after pinching the plants. Both plant size and the number of flower buds per plant decreased as the rate of paclobutrazol increased at all levels of shading. The efficacy of paclobutrazol, however, was generally less under heavy shade, as both translocation of the growth retardant and photosynthesis were reduced. Moderate shading (67%) did not affect the size of plants receiving 0.0 or 0.5 mg of paclobutrazol per pot, but plants grown under heavy shade (98%) were 74% as large as similarly treated nonshaded plants. Medium shade reduced the size of plants receiving 1 and 2 mg paclobutrazol 4% and 6%, respectively, relative to that of similarly treated nonshaded plants, whereas heavy shade reduced plant size 11%. The number of flower buds per plant was reduced 30% by moderate shading, 90% by heavy shading. Significant quadratic relationships were observed between the rate of paclobutrazol applied and (1) plant size, and (2) the number of flower buds per plant. Chemical name used: ±-(R*,R*)-β–[(4-chlorophenyl)methyl]-α-(1,1-dimethyl)-1H-(1,2,4-triazol)-1-ethanol (paclobutrazol).
Gibberellic Acid-induced Flowering of Syngonium podophyllum Schott `White Butterfly'
Authors: Henny R.J. , Norman D.J. , Kane M.E.
Published: February 2019

Syngonium `White Butterfly', growing in 1.6-L pots and treated in August with a single GA3 spray at 250 to 2000 mg·L–1, flowered within 86 days. Mean flower number increased with GA3 concentration. Flowers were normal in appearance and were fertile. Chemical name used: gibberellic acid (GA3).