bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil pH Effects on Growth and Foliar Nutrient Concentrations of Spiraea alba Du Roi and Spiraea tomentosa L.
Authors: Mickelbart Michael V. , Gosney Michael J. , Camberato James , Stanton Kelly M.
Published: February 2019

The North American native plants Spiraea alba and S. tomentosa have potential as landscape plants because they are small- to medium-sized shrubs with showy flowers that persist from early to late summer. However, the cultural requirements of these species are not well documented. Both species grow in slightly acidic soils in their native habitats. The objective of this work was to determine if the growth and/or appearance of these shrubs is affected by the neutral to slightly alkaline soils common throughout the Midwest. Spiraea alba grown from three seed sources and S. tomentosa grown from a single seed source were grown for 2 years in soils of different pH. Elemental sulfur (S) was incorporated into a Drummer silty clay loam with a pH of 7.2 to bring the pH to 5.8 and 6.4 2 years after incorporation, thus establishing plots with three pH levels for assessing growth and appearance. The soil pH increased to 6.4 and 6.8 in the amended plots between Years 2 and 3 after S incorporation. Soil concentrations of exchangeable magnesium (Mg) and calcium (Ca) were lowered with added S. Height and width varied among S. alba from different seed sources, and height and width of all plants were reduced when grown at the highest soil pH. Leaf greenness, specific leaf weight, and individual leaf area were unaffected by pH. Leaf concentrations of nitrogen, potassium, zinc, and manganese were higher in lower soil pH, whereas Mg was lowest at the lowest soil pH. These results suggest that S. alba and S. tomentosa can be grown in neutral pH soils without an effect on plant appearance, but plant size will be less than at pH levels closer to the native soils for these species. Although some micronutrients were present at lower concentrations at the neutral pH, leaf greenness was unaffected, again suggesting that these plants may perform suitably outside of their native habitat pH range.
Consumer Preferences for Low-input Turfgrasses: A Conjoint Analysis
Authors: Hugie Kari , Yue Chengyan , Watkins Eric
Published: February 2019

Traditional turfgrasses found in residential lawns provide a functional and aesthetically pleasing landscape if provided adequate resource inputs, yet, as available natural resources become more limited and public concerns grow stronger about the ecological effects of urban turfgrass management, it becomes increasingly important to pursue alternative landscape options. There are non-traditional turfgrasses that require fewer resource inputs that could be made available to homeowners. The objective of this study was to estimate consumer preferences and the relative importance of aesthetic and maintenance attributes of turfgrasses as well as identify potential market segments of the residential turfgrass market. Conjoint analysis was conducted on survey responses of 116 Minnesota homeowners. The results indicated that maintenance attributes of turfgrasses, specifically irrigation requirement, significantly affected consumer purchasing behavior. The analysis also identified four potential market segments, the Price Conscious segment, the Shade Adaptation segment, the Mowing Conscious segment, and the Water Conscious segment.
In Vitro Growth, Morphogenesis, and Acclimatization of Endangered Rindera umbellata (Waldst. & Kit.) Bunge
Authors: Perić Marija , Dmitrović Slavica , Živković Suzana , Filipović Biljana , Skorić Marijana , Simonović Ana , Todorović Slađana
Published: February 2019

Rindera umbellata (Waldst. & Kit.) Bunge is a rare, critically endangered and horticulturally appealing plant with unexplored pharmaceutical potential. Its distribution is restricted to sandy habitats, whereas propagation in nature is limited by fungal infections of the seeds. To initiate its ex situ conservation and provide material for metabolomic studies, we have introduced R. umbellata into in vitro culture using immature embryos as primary explants. A 72% of the embryos germinated on growth regulator-free medium. The optimization of growth conditions was based on varying carbohydrates (sucrose, glucose, and fructose) in the medium. In vitro growth and development of R. umbellata plants were significantly affected by both the type and concentration of the applied sugars. For most recorded parameters, including leaf elongation, biomass production, rooting percentage, and the number and length of roots, 0.1 m sucrose was optimal. The highest percentage of explants with developed buds was achieved on 0.06 m sucrose (38.77%) or 0.3 m glucose (27.43%). The plantlets obtained on 0.1 m sucrose were successfully acclimatized to greenhouse and field conditions with survival rates of 71.43% and 42.86%, respectively. To our best knowledge, this is the first publication dedicated to this species.
Glycinebetaine Seed Priming Improved Osmotic and Salinity Tolerance in Turfgrasses
Authors: Zhang Qi , Rue Kevin
Published: February 2019

Exogenous application of glycinebetaine (GB), an osmoprotectant, increases tolerance to stresses including salinity in various plants. Information on turfgrass, however, is limited. In this study, GB was used to prime turfgrass seeds to enhance salinity tolerance during germination and seedling growth stage when plants are more sensitive to stresses. Unprimed and primed (50, 100, 150, or 200 mm solution of GB or distilled water) seeds of perennial ryegrass (Lolium perenne L.) (PR), tall fescue (Festuca arundinacea Schreb.) (TF), creeping bentgrass (Agrostis palustris Huds.) (CB), and kentucky bluegrass (Poa pratensis L.) (KB) were germinated in solutions of distilled water, mannitol (causing osmotic stress only), or NaCl (causing both osmotic and ionic stresses). Their osmotic potential (ψS) and salinity level were -0.1 MPa and 0.1 dS·m−1 (no stress), –1.0 MPa and 0.1 dS·m−1 (moderate osmotic stress), and –1.0 MPa and 14.6 dS·m−1 (moderate osmotic and ionic stresses), respectively. Seeds primed with GB showed a higher germination rate (11.0% to 13.9% increase) and seedling growth (19.3% to 20.7% increase) in mannitol or NaCl solution than in distilled water. Different turf species showed different responses to osmotic and ionic stresses. No differences in germination and seedling growth of PR, TF, and KB were observed between mannitol and NaCl treatments, indicating that osmotic stress appeared to more critical than ionic stress under saline conditions. For CB, the seed germination rate and seedling growth were lower (19.3% to 44.2% reduction) in NaCl than in mannitol, showing an accumulative effect of both osmotic and ionic stresses under saline conditions.
Assisting Farmers to Produce High-quality Medicinal Herbs
Authors: Davis Jeanine M.
Published: February 2019

Farmers are looking for new crops to grow to diversify their farms and increase profitability. Medicinal herbs are often of interest because they are generally perceived as being easy to grow, in high demand, return good prices, and serve as useful rotational crops. In reality, most farmers who have not previously grown medicinal herbs do not understand the global herb market. They do not know how to find a buyer or which herbs to grow. To help growers produce and market medicinal herbs, we initiated the Medicinal Herbs for Commerce Project. We also conducted studies on production problems for a variety of herbs. An issue that should be addressed is that there are hundreds of medicinal herbs in commerce and it is impossible for a small number of research programs to independently answer all the questions that are being asked by the industry. Developing a consortium of researchers around the world to coordinate efforts on how best to grow and process medicinal herbs and to create a database of information for farmers and agricultural advisors would be a great service for this industry.
Phenotypic Characterization and Simple Sequence Repeat Identification of Red-fleshed Kiwifruit Germplasm Accessions
Authors: Wang Yan-Chang , Zhang Lei , Man Yu-Ping , Li Zuo-Zhou , Qin Rui
Published: February 2019

Big fruit size and nice red pigmentation combined with good flavor should be the major target for red-fleshed kiwifruit (Actinidia spp.) breeding programs. Genetic diversity and plant characteristics were evaluated on a set of kiwifruit accessions with predominantly red flesh to identify the superior individuals for further breeding or study of commercial application. The leading phenotypic characters varied widely among the accessions. Accession R reached average fruit weight ≈100 g, whereas it ranged from 43.15 to 84.71 g for the other accessions. Fruits of L and Q were flatter in shape than the others. The core volume accounted for fruit proportions ranging from 2.33% to 11.42%. ‘Chuhong’, ‘Honghua’, and K exhibited a round fruit apex, whereas most others showed a depressed apex. R, L, and Q had the highest a* values in the inner pericarp and also the most appealing visual coloration. Results revealed significantly higher soluble solid content (SSC), total sugar, and sugar/acid ratio in Q, R, and L. The 12 pairs of simple sequence repeat (SSR) markers were successfully used to characterize the genetic variability and confirm true-to-type identity for four accessions. However, the limited number of markers had no ability to discriminate among the other 11 accessions. Based on additional 28 SSRs, six of the indistinguishable accessions were confirmed to be genetically different, and three seemed to belong to the same clone vine. The results demonstrated that application of SSR data could improve the efficiency of identifying red-fleshed kiwifruit germplasm.
Comparison of High Tunnel and Field Production of Specialty Cut Flowers in the Midwest
Authors: Ortiz Michael A. , Hyrczyk Krystyna , Lopez Roberto G.
Published: February 2019

The U.S. specialty cut flower market has grown over the last several years because stems of many specialty cut flower species cannot be transported long distances and therefore need to be grown regionally. High tunnel production of cut flowers is an alternative to field and greenhouse production that has several benefits. Specialty cut flower species Antirrhinum majus L. ‘Potomac Orange’ and ‘Rocket Red’, Celosia argentea L. var. cristata Kuntze ‘Chief Red’, Dahlia ×hybrida Cav. ‘Karma Thalia Dark Fuchsia’, Dianthus barbatus L. ‘Amazon Neon Cherry’, Eustoma russellianum Salisb. ‘Mariachi Blue’, Helianthus annuus L. ‘Premier Lemon’ and ‘Sunrich Yellow’, Matthiola incana (L.) W.T. Aiton ‘Katz Lavender Blue’, and Zinnia elegans Jacq. ‘Benary Giant Scarlet’ were grown in both field and high tunnel environments in the midwestern United States. High tunnel production resulted in a first week’s harvest of 44.8 (46%), 115, and 21.1 (110%) more stems for Antirrhinum ‘Rocket Red’, Dianthus, and Zinnia, respectively. Compared with field production, high tunnel production yielded a greater number of stems/m2 for Antirrhinum ‘Potomac Orange’, Celosia, Dianthus, and Zinnia and longer stems for Antirrhinum ‘Potomac Orange’ and ‘Rocket’, Eustoma, Matthiola, and Zinnia. For example, high tunnel production yielded 185 (39%) and 192 (59%) more stems/m2 and 12.6 (34%) and 8.9 (32%) cm longer stems for Mathiola and Zinnia, respectively. Other stem characteristics such as inflorescence length and flower width showed more variation among cultivars. Our results indicate that cut flower yield and/or quality of Antirrhinum ‘Rocket Red’, Dianthus, Matthiola, Zinnia, Dahlia, Eustoma, and Helianthus ‘Sunrich Yellow’ and ‘Premier Lemon’ significantly increases when produced in high tunnels located in the Midwest.
Screening for Resistance to Verticillium Wilt in Spinach and Isolation of Verticillium dahliae from Seed of Spinach Accessions
Authors: Villarroel-Zeballos Maria I. , Feng Chunda , Iglesias Angela , du Toit Lindsey J. , Correll James C.
Published: February 2019

Verticillium dahliae is a pathogen of spinach (Spinacia oleracea) during spinach seed crop production but not in vegetative leafy spinach crops, because plants remain asymptomatic until bolting has been initiated (conversion from vegetative to reproductive growth). The objectives of this research were to evaluate a set of USDA spinach germplasm accessions for resistance to Verticillium wilt and to determine the range in incidence of natural seed infection/infestation in a subset of the USDA spinach accessions screened for resistance. A total of 120 Spinacia spp. accessions from the USDA North Central Regional Plant Introduction Station spinach germplasm collection and 10 commercial S. oleracea hybrids were screened for resistance to V. dahliae in Trials 1, 2, and 3 in 2006, 2007, and 2008, respectively, in greenhouse evaluations. Each accession was grown in either V. dahliae-infested or non-infested potting mix and rated weekly on a seven-step scale from 1 week before bolting to 4 weeks after bolting. A wide range of disease severity ratings was observed among the accessions evaluated. Most of the accessions were highly susceptible. There was no evidence of qualitative resistance but some showed greater levels of quantitative resistance than others. Plants in soil infested with V. dahliae senesced faster and had significantly reduced biomass compared with plants in non-infested soil of the same accession. In addition, in Trial 2 (2007), 34% (20 of 59) of the seed samples assayed of the accessions were infested or infected with V. dahliae; and in Trial 3, (2008) 16% (21 of 130) of the seed samples of the USDA accessions evaluated were infested or infected with V. dahliae, V. tricorpus, or Gibellulopsis nigrescens (formerly known as V. nigrescens). These results are valuable for characterizing potential genetic variability within spinach germplasm for resistance to V. dahliae.
Seed Germination and Early Seedling Growth of Cynanchum bungei Decne (Asclepiadaceae) in Response to Photoperiod, Temperature, and Seed Size
Authors: Zhang Haiyan
Published: February 2019

Cynanchum bungei Decne is a rare, endemic, and important medicinal plant species in China. Seed germination and early seedling growth of large seeds (greater than 7 mm) and small seeds (smaller than 7 mm) were investigated at three temperatures (15, 20, and 25 °C) in both continuous light and alternating light/dark photoperiods to determine seed propagation requirements. Photoperiod significantly affected seed germination and early seedling growth. Germination and seedling growth at a 12:12-h photoperiod performed better than in continuous light. Temperature had a significant effect on germination index (GI), vigor index (VI), germination velocity (GV), mean germination time (MGT), shoot biomass (SB), root biomass (RB), and taproot length (TL), but no significant effect on final germination percentage (FGP). A temperature of 20 °C was the optimum temperature for seed germination and early seedling growth. Average growth height (AGH) and relative growth rate (RGR) of shoots at 15 °C were greater than that at 20 °C. Large seeds had better germination and seedling performance than small seeds. However, small-seeded seedlings had greater biomass allocated to roots (BAR) and root-to-seedling ratio (RSR) than seedlings from large seeds. Small seeds of C. bungei could be more competent in unfavorable soil and light conditions than large seeds.
Breaking Tuber Dormancy in Helianthus tuberosus L. and Interspecific Hybrids of Helianthus annuus L. × Helianthus tuberosus
Authors: Kantar Michael , Betts Kevin , Hulke Brent S. , Stupar Robert M. , Wyse Donald
Published: February 2019

Tubers of Helianthus tuberosus L. are dormant after production in the late fall until the next spring. In the wild, tuber dormancy is broken after exposure to winter cold, resulting in sprouting and shoot development in the spring when conditions are favorable. The dormancy period typically limits H. tuberosus populations to one growth cycle per year. An efficient method for breaking tuber dormancy is needed to have an additional growth cycle per year in a breeding program, which could take place in winter in the nursery or the greenhouse allowing for increased breeding efficiency. The objective of this research was to compare chemical and cold temperature treatments for artificially breaking tuber dormancy in 12 genotypes of H. tuberosus and interspecific hybrids of Helianthus annuus L. × H. tuberosus. Five cold exposures (2, 4, 6, 8, 10 weeks at 2 °C), three plant hormones (ethylene, cytokinin, and gibberellic acid), and one untreated control were examined. Gibberellic acid was the best chemical treatment, initiating plant growth within 6.5 to 11.5 days in the majority of genotypes tested. The best cold treatment was exposure to 2 °C for 8 weeks, where plant growth began 63.6 to 67.5 days after treatment initiation. Although longer cold treatments shortened the time to emergence while in the greenhouse, the penalty of the long cold treatment per se was too long to be useful. The gibberellic acid treatment strategy described here may not need further optimization, because it is short enough to allow for two growth cycles of H. tuberosus per year.
Response of Selected Wildflower Species to Saline Water Irrigation
Authors: Niu Genhua , Rodriguez Denise S. , McKenney Cynthia
Published: February 2019

Wildflowers are good candidates for water-wise landscapes because many of them are drought-tolerant after establishment. Little information is available regarding whether these herbaceous wildflowers are tolerant to salt stress. Container experiments were carried out in a greenhouse and a shadehouse under semiarid climate conditions to investigate the salt tolerance of six native wildflowers: Salvia farinacea (mealy cup sage), Berlandiera lyrata (chocolate daisy), Ratibida columnaris (Mexican hat), Oenothera elata (Hooker’s evening primrose), Zinnia grandiflora (plains zinnia), and Monarda citriodora (lemon horsemint). In the greenhouse experiment, mealy cup sage, Hooker’s evening primrose, and plains zinnia were irrigated with a saline solution with an electrical conductivity (EC) of 1.5 (control, nutrient solution), 2.8, 4.1, 5.1, or 7.3 dS·m−1 for 45 days. All plants survived except for plains zinnia at EC of 7.3 dS·m−1. Shoot dry weights decreased as EC of irrigation water increased for all three species. In the shadehouse experiment (second year), plants of all species (plains zinnia was not included) were irrigated with saline solutions at EC of 0.8 (control, tap water), 2.8, 3.9, 5.5, or 7.3 dS·m−1 for 35 days. Plants were fertilized with slow-release fertilizer in the shadehouse experiment. After 5 weeks of treatment, all plants of lemon horsemint in the elevated salinity treatments, regardless of EC levels, were dead. The visual foliar salt damage rating was lowest for lemon horsemint. Chocolate daisy had low survival percentages and low foliar ratings at EC of 5.5 dS·m−1 and 7.3 dS·m−1. For the other three species, survival percentages were 80% and 90% at EC of 7.3 dS·m−1. Hooker’s evening primrose and mealy cup sage had similar low foliar visual ratings at EC of 7.3 dS·m−1, whereas Mexican hat plants had high foliar visual ratings regardless of salinity treatment. All species had similar high uptake of Na+ in shoots, whereas Hooker’s evening primrose had slightly higher Cl− concentrations compared with other species. Based on these results, lemon horsemint was most sensitive to salinity stress followed by chocolate daisy. Hooker’s evening primrose and mealy cup sage were moderately tolerant and may be irrigated with low salinity water at EC of less than 3.9 dS·m−1. Mexican hat was the most tolerant among the six species.
Season and Explant Origin Affect Phenolic Content, Browning of Explants, and Micropropagation of ×Malosorbus florentina (Zucc.) Browicz
Authors: Martini Aekaterini N. , Papafotiou Maria , Vemmos Stavros N.
Published: February 2019

The aim of this study was to develop an efficient protocol for in vitro propagation of the rare and endangered ×Malosorbus florentina, not only enabling conservation of the species, but also its use as an ornamental. Explants excised from adult plants, shoot tip explants, and explants collected in March and April showed more browning and had higher content of total phenolics than explants excised from juvenile tissue, nodal explants, and those collected during any of the other months of the year. Shoot tip explants from adult plants were more difficult to establish in vitro (14%) compared with explants from micropropagated plantlets or sprouts of burned plants (29% to 36%). Nodal explants excised from seedlings were established at the highest percentage (83%), giving the most shoots per explant (5.2). Generally, in vitro cultures established from adult plants, with the exception of one culture, showed lower multiplication rates compared with cultures from juvenile plants. Nodal explants from the base of sprouts produced a higher percentage (60%) of shoots than explants from upper locations (20% to 31%), but any differences in proliferation rates of established cultures ceased after the third subculture. Microshoots from juvenile cultures were more capable of rooting (51% to 58%) than were those from adult plants (16% to 32%), whereas 83% of the plantlets were acclimatized ex vitro independently of their origin, but plantlets of juvenile origin, although developing the same height as those originating from adult plants, had shorter internodes and thus more compact shape.
Nitrification in Pine Tree Substrate Is Influenced by Storage Time and Amendments
Authors: Taylor Linda L. , Niemiera Alexander X. , Wright Robert D. , Evanylo Gregory K. , Thomason Wade E.
Published: February 2019

Pine tree substrate (PTS), for container plant production, is a relatively new alternative to the commonly used pine bark and peat substrates. Fertility management requires knowledge of nitrogen transformations in this new substrate. The objective of this study was to document the occurrence of nitrification in PTS and to determine if nitrification and density of nitrifying microorganisms are affected by substrate storage time and lime and peat amendments. Pine tree substrate was manufactured by hammermilling chips of ≈15-year-old loblolly pine trees (Pinus taeda L.) through two screen sizes, 4.76 mm (PTS) and 15.9 mm amended with peat (3PTS:1 peat, v:v, PTSP). Pine tree substrate and PTSP were amended with lime at five rates and a peat–perlite mix (4 peat:1 perlite, v:v, PL) served as a control treatment for a total of 11 treatments. Substrates were prepared, placed in plastic storage bags, and stored on shelves in an open shed in Blacksburg, VA. Subsamples were taken at 1, 42, 84, 168, 270, and 365 days after storage. At each subsampling day, each substrate was placed into 12 1-L containers. Six of the 12 were left fallow and six were planted with 14-day-old marigold (Tagetes erecta L. ‘Inca Gold’) seedlings; all containers were placed on a greenhouse bench. Substrates were also collected for most probable number (MPN) assays for nitrifying microorganism quantification. Substrate solution pH, electrical conductivity (EC), ammonium-N (NH4-N), and nitrate-N (NO3-N) were measured on fallow treatments. Marigold substrate solution pH, EC, NH4-N, and NO3-N were measured after 3 weeks of marigold growth. Nitrate-N was detected in fallow containers at low concentrations (0.4 to 5.4 mg·L−1) in PTS in all limed treatments at all subsampling days, but in the non-limed treatment, only at Days 270 and 365. Nitrate-N was detected in the fallow containers at low concentrations (0.7 to 13.7 mg·L−1) in PTSP in the 4- and 6-kg·m−3 lime rates at all subsampling days. Nitrite-oxidizing microorganisms were present in PTS at all subsampling days with the highest numbers measured at Day 1. Ammonium-to-nitrate ratios for the marigold substrate solution extracts for both PTS and PTSP decreased as pH increased. This study shows that nitrifying microorganisms are present and nitrification occurs in PTS and PTSP and is positively correlated to substrate pH.
Reaction of Peach Genotypes to Bacterial Leaf Spot: Correlations with Environmental Conditions, Leaf Phenology, and Morphology
Authors: Sachet Marcos R. , Citadin Idemir , Scariotto Silvia , Santos Idalmir dos , Zydek Pedro H. , Raseira Maria do Carmo B.
Published: February 2019

In breeding programs, it is essential to understand how characteristics are expressed by the germplasm in relation to the selection environment. The reactions of 15 peach genotypes to bacterial leaf spot (BLS) during three growing seasons (2008–09, 2009–10, and 2010–11) were investigated. Quantitative assessments were made from three plants per genotype through a modified healthy leaf area duration (HAD) method. None of the genotypes were immune to the disease. The most resistant were ‘Cascata 1055’, ‘Conserva 985’, ‘Cascata 967’, and ‘Cascata 1065’. There was a reduction in HAD with increased precipitation. The leaf dry matter (g/leaf), leaf blade length, leaf length (with petiole), and leaf area (cm2/leaf) were inversely correlated with genotype resistance to BLS. The HADs of susceptible genotypes were influenced by the number of wet days regardless of temperature. The most susceptible genotypes were those with earlier budburst and fruit ripening. A shorter duration of healthy leaf area was related to earlier budburst and flowering in the subsequent year. We found no relationship between HAD and productivity.
Serial Transmission of Plant Viruses by Cutting Implements during Grafting
Authors: Bausher Michael G.
Published: February 2019

Reciprocal grafts of two tomato (Solanum lycopersicum L.) cultivars were made by hand using commercial grafting techniques. The razor blade used to cut the rootstock or scion was first contaminated by making a single cut on tomato plants infected with either Tomato spotted wilt virus (TSWV) or Tomato mosaic virus (ToMV). Although no transmission of TSWV was observed in these experiments, ToMV was spread plant to plant through razor blade exposure to this virus. The presence of this virus was confirmed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) at 21 days post-inoculation. The highest rate of infection was 25% of the inoculated plants. The greatest number of positive virus assays was found in the first 10 plants of each experiment. These areas contained 84% of the DAS-ELISA-positive plants. Gaps of up to 10 plants occurred during serial inoculation before infection resumed. Random dispersion occurred in two experiments. Similar results were observed whether the contaminated implement was used to cut the rootstock or the scion before graft assembly. This work demonstrates that some viruses from a single contamination can be moved in a serial manner during the grafting process, especially with varieties with minimal or no resistance to viral plant pathogens. Also, visual diagnosis cannot always be relied on as a means of eliminating virus-infected plants, especially when higher greenhouse and annealing temperatures are maintained.
Influence of Mechanical String Thinning Treatments on Vegetative and Reproductive Tissues, Fruit Set, Yield, and Fruit Quality of ‘Gala’ Apple
Authors: Kon Thomas M. , Schupp James R. , Winzeler H. Edwin , Marini Richard P.
Published: February 2019

The objectives of this experiment were to test the efficacy of a mechanical string thinner (Darwin PT-250; Fruit-Tec, Deggenhauserertal, Germany) on apple and to identify an optimal range of thinning severity as influenced by spindle rotation speed. Trials were conducted in 2010 and 2011 at the Pennsylvania State University Fruit Research and Extension Center in Biglerville, PA, on five-year-old ‘Buckeye Gala’/M.9 apple trees that were trained to tall spindle. A preliminary trail on five-year-old ‘Cripps Pink’/M.9 was conducted to determine the relationship between string number and thinning severity. As the number of strings increased, the level of thinning severity increased. A range of spindle speeds (0 to 300 rpm) was applied to the same trees for two consecutive years. As spindle speed increased, blossom density (blossom clusters per limb cross-sectional area) was reduced as was the number of blossoms per spur. In 2010, leaf area per spur was reduced 9% to 45%. In 2011, the fastest spindle speed reduced leaf area per spur 20%. Although increased spindle speed reduced cropload, injury to spur leaves may have inhibited increases in fruit size. The largest gain in fruit weight was 28 g (300 rpm) compared with the control. In both years, the most severe thinning treatments reduced yield by more than 50%. There was no relationship between spindle speed and return bloom. Severe thinning treatments (240 to 300 rpm) caused significant reductions in spur leaf area, yield, and fruit calcium and did not improve fruit size or return bloom. Spindle speeds of 180 and 210 rpm provided the best overall thinning response and minimized injury to spur leaves, but cropload reduction was insufficient in years of heavy fruit set. Therefore, mechanical blossom thinning treatments should be supplemented with other thinning methods. Mechanical string thinning may be a viable treatment in organic apple production, where use of chemical thinners is limited.
Effects of Host Plant Resistance and Fungicides on Severity of Cucumber Downy Mildew
Authors: Call Adam D. , Wehner Todd C. , Holmes Gerald J. , Ojiambo Peter S.
Published: February 2019

Cucurbit downy mildew caused by the oomycete Pseudoperonospora cubensis (Berk. And Curt) Rostov is a major disease of cucumber (Cucumis sativus L.) (Palti and Cohen, 1980) globally. Chemical control of downy mildew is necessary to achieve high yields in the absence of adequate host plant resistance. Most of the currently grown cultivars have some resistance to downy mildew. Before the resurgence of the disease in 2004, host plant resistance was sufficient to control the disease without fungicide use, and downy mildew was only a minor problem on cucumber. There are currently no cultivars that show resistance at a level equal to that observed before 2004. However, differences in resistance exist among cultivars, ranging from moderately resistant to highly susceptible. In this study, we evaluated the disease severity and yield of four cucumber cultivars that differed in disease resistance and were treated with fungicide programs representing a range of efficacy levels. The experiment was a split plot design with six replications and four years. Disease was evaluated as chlorosis, necrosis, and reduction in plant size on a 0 to 9 scale. Cultigen had a large effect in all four years. Fungicide has a smaller effect on resistance component traits and a larger effect on yield traits. The effects of cultivar resistance and fungicides appear to be additive until a threshold where maximum yield is reached. Highly resistant cultigens such as PI 197088 required only the least effective fungicides to achieve highest yields, whereas moderately resistant cultigens required a more effective fungicide to reach a similar level of yield. Susceptible cultigens did not achieve high yield even with the most effective fungicide treatments. It is likely that, even as highly resistant cultivars are released, growers will need to continue a minimal fungicide program to achieve maximum yield.
Tailoring Organic Apples by Cultivar Selection, Production System, and Post-harvest Treatment to Improve Quality and Storage Life
Authors: Tahir Ibrahim I. , Nybom Hilde
Published: February 2019

A series of pre- and post-harvest experiments were conducted to enhance apple tree productivity and improve fruit quality and storage life by altering production system and post-harvest treatments in an organic orchard. Increasing the light distribution and carbohydrate uptake (summer pruning and covering the orchard ground with reflective textile) improved tree productivity, fruit color, content of anthocyanin, ascorbic acid, and total phenolic compounds and reduced incidence of fungal storage diseases. Optimal harvesting time could be determined from the starch index in some cultivars, whereas the Streif index [firmness (soluble solids concentration × starch hydrolysis score)−1] was more accurate for other cultivars. In yet others, titratable acidity and flesh firmness also produced important information. By contrast, soluble solids concentration and skin color are not useful as a result of their sensitivity to weather conditions and light intensity. Post-harvest fruit treatment with hot water (46 °C for 120 seconds) decreased fungal decay during storage in two cultivars, whereas spraying the fruit with 10% ethanol decreased fungal decay in all investigated cultivars. Optimization of storage conditions [cultivar-specific controlled atmosphere (CA) and ultra-low oxygen (ULO) storage procedures] maintained fruit quality and reduced the amount of fungal decay.
Mulch and Fertilizer Management Practices for Organic Production of Highbush Blueberry. I: Plant Growth and Allocation of Biomass during Establishment
Authors: Larco Handell , Strik Bernadine C. , Bryla David R. , Sullivan Dan M.
Published: February 2019

A systems trial was established in Oct. 2006 to evaluate management practices for organic production of northern highbush blueberry (Vaccinium corymbosum L.). The practices included: flat and raised planting beds; feather meal and fish emulsion fertilizer each applied at rates of 29 and 57 kg·ha−1 nitrogen (N); sawdust mulch, compost topped with sawdust mulch (compost + sawdust), or weed mat; and two cultivars, Duke and Liberty. Each treatment was irrigated by drip and weeds were controlled as needed. The planting was certified organic in 2008. After one growing season, allocation of biomass to the roots was greater when plants were grown on raised beds than on flat beds, mulched with organic mulch rather than a weed mat, and fertilized with the lower rate of N. Plants also allocated more biomass belowground when fertilized with feather meal than with fish emulsion. Although fish emulsion improved growth relative to feather meal in the establishment year, this was not the case the next year when feather meal was applied earlier. After two seasons, total plant dry weight (DW) was generally greater on raised beds than on flat beds, but the difference varied depending on fertilizer and the type of mulch used. Shoots and leaves accounted for 60% to 77% of total plant biomass, whereas roots accounted for 7% to 19% and fruit accounted for 4% to 18%. Plants produced 33% higher yield when grown on raised beds than on flat beds and had 36% higher yield with weed mat than with sawdust mulch. Yield was also higher when plants were fertilized with the low rate of fish emulsion than with any other fertilizer treatment in ‘Duke’ but was unaffected by fertilizer source or rate in ‘Liberty’. Although raised beds and sawdust or sawdust + compost produced the largest total plant DW, the greatest shoot growth and yield occurred when plants were mulched with weed mat or compost + sawdust on raised beds in both cultivars. The impact of these organic production practices on root development may affect the sustainability of these production systems over time, however, because plants with lower root-to-shoot ratios may be more sensitive to cultural or environmental stresses.
Cyprosulfamide Safens Isoxaflutole in Sweet Corn (Zea mays L.)
Authors: Robinson Darren E. , Soltani Nader , Shropshire Christy , Sikkema Peter H.
Published: February 2019

There is little published information on the sensitivity of sweet corn to the PRE and POST application of isoxaflutole + cyprosulfamide. Four field trials were conducted during 2010 and 2011 in Ontario, Canada, to determine the sensitivity of ‘Merit’, ‘GH 4927’, ‘BSS 5362’, and ‘GG 741’ sweet corn hybrids to the PRE and POST application of isoxaflutole alone or in combination with cyprosulfamide. Isoxaflutole applied PRE or POST at 105 and 210 g a.i./ha caused as much as 12% visual injury, 18% reduction in height. and 24% reduction in marketable yield of some sweet corn hybrids evaluated. Isoxaflutole + cyprosulfamide applied PRE or POST at 105 and 210 g·ha−1 caused up to 7% initial injury in some sweet corn hybrids but the injury was transient with no effect on sweet corn height, cob size, and yield. Isoxaflutole applied POST was more injurious to sweet corn than when applied PRE; however, there was no differences in sweet corn injury between the PRE and POST applications of isoxaflutole + cyprosulfamide. Based on these results, there is potential for use of isoxaflutole + cyprosulfamide applied at 105 g a.i./ha in ‘Merit’, ‘GH 4927’, ‘BSS 5362’, and ‘GG 741’ sweet corn hybrids.
In Vitro Propagation of Alexandrian Laurel (Danae racemosa L. Moench), a Valuable Ornamental Plant
Authors: Shen Xiuli , Yang Guochen , Lu Zhongge (Cindy)
Published: February 2019

To overcome the limitations of traditional propagation, this research was initiated to develop an alternative means for efficient production of Alexandrian laurel (Danae racemosa L. Moench). An in vitro propagation protocol has been developed for Danae racemosa L. Moench using seeds as a source of material for culture initiation. Seedlings were produced after seeds were cultured for 3 month on MS (Murashige and Skoog, 1962) medium. Shoot multiplication occurred on MS medium with or without 6-benzylaminopurine (BAP) with 100% multiplication percentage. However, shoot number was significantly increased from an average of 2.8 to more than six with the addition of 5 or 25 μM BAP. Among two indole-3-butyric acid (IBA) treatments tested for rooting of seedlings, incorporation of 5 μM IBA in MS medium significantly increased rooting percentage to 86.4% compared with 71.2% without IBA. The greatest number of roots (three) was produced by 5-minute IBA pulse. However, both IBA treatments significantly reduced root length. The longest root (12.8 mm) was observed on MS medium without any IBA treatment and the shortest (6.1 mm) was produced by IBA pulse. In vitro-propagated plantlets grew well after transfer to a substrate of peat and pine bark (1:1) in the greenhouse. No morphological variation was observed.
Seedling Tolerance of Cool-season Turfgrasses to Metamifop
Authors: Gómez de Barreda Diego , Yu Jialin , McCullough Patrick E.
Published: February 2019

Grassy weeds may reduce cool-season turfgrass establishment after seeding and herbicide use is often warranted. Field experiments were conducted to evaluate the tolerance of creeping bentgrass (Agrostis stolonifera L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.) to fenoxaprop and metamifop applications at 1, 2, 3, or 4 weeks after seeding (WAS). Creeping bentgrass groundcover was reduced from 34% to 71% at 8 WAS from the nontreated by fenoxaprop at 50 g a.i./ha and metamifop at 400 and 800 g a.i./ha at all application timings. Metamifop at 200 g·ha−1 reduced creeping bentgrass cover 10% to 18% from the nontreated at 8 WAS when applied 1, 2, or 3 WAS, but treatments at 4 WAS did not reduce cover. Perennial ryegrass treated with fenoxaprop and metamifop at 800 g·ha−1 at 1 WAS had cover reduced from the nontreated on two and one dates, respectively, whereas tall fescue cover was never reduced greater than 5% from the nontreated. Results suggest applications to creeping bentgrass should be delayed greater than 4 WAS for fenoxaprop at 50 g·ha−1, greater than 4 WAS for metamifop at 400 and 800 g·ha−1, and 3 WAS for metamifop at 200 g·ha−1. Additionally, fenoxaprop applications should be delayed 2 WAS for perennial ryegrass and tall fescue, whereas metamifop could be safely applied at all rates at 1 WAS.
Temporal Variations in Leaf Miner, Butterfly, and Stem Borer Infestations of Cycas micronesica in Relation to Aulacaspis yasumatsui Incidence
Authors: Marler Thomas E.
Published: February 2019

Four phytophagous insects are among the major threats to Cycas micronesica K.D. Hill on Guam, and the temporal comparisons of infestation levels may inform horticultural and conservation decisions. Incidence of Aulacaspis yasumatsui Takagi, Erechthias Meyrick sp., Chilades pandava Horsfield, and Dihammus marianarum Aurivillius infestations on Cycas micronesica plants were recorded every 6 months from 2004 to 2013 to determine if the incidence of A. yasumatsui was related to patterns of the other three insects. Dihammus marianarum infestations reached ephemeral maximum and minimum levels ≈2 years after A. yasumatsui infestations reached maximum and minimum levels. Erechthias sp. infestations disappeared in early 2006 when Cycas micronesica leaves were being killed by acute A. yasumatsui infestations. Erechthias sp. infestations increased thereafter as A. yasumatsui incidence declined in response to biological control. Chilades pandava infestations appeared to increase and decrease inversely with A. yasumatsui infestations throughout the years. Aulacaspis yasumatsui may be indirectly affecting D. marianarum damage by direct control of changes in overall tree health. Aulacaspis yasumatsui may be indirectly influencing Erechthias sp. through direct control over leaf longevity. The C. pandava and A. yasumatsui populations appear to exhibit direct competition with inverse patterns of incidence.
A Five-year Study on the Effect of Cluster Thinning and Harvest Date on Yield, Fruit Composition, and Cold-hardiness of ‘Vidal Blanc’ (Vitis spp.) for Ice Wine Production
Authors: Dami Imed , Ennahli Said , Scurlock David
Published: February 2019

The aim of this 5-year study was to investigate the influence of cluster thinning (CT) and harvest date on yield components, fruit composition, and bud cold-hardiness in ‘Vidal blanc’ (Vitis spp.) grapevines grown in northern Ohio. It is unknown whether delaying harvest of ‘Vidal blanc’ for ice wine production would impact negatively winter-hardiness. ‘Vidal blanc’ grapevines were cluster-thinned at post-fruit set [Eichhorn-Lorenz (EL) Stage 31] to two crop levels by retaining 40 (CT40) and 60 (CT60) clusters per vine. Each crop level was harvested at three dates: normal harvest (HD1), fall harvest (HD2) after the first killing frost, and winter harvest (HD3) corresponding to the typical commercial harvest for ice wine. Generally, and as expected, the high crop level CT60 increased crop weight and cropload and decreased total soluble solids and pH. Delayed harvest decreased crop weight, cluster weight, berry weight, and titratable acidity but increased total soluble solids and pH. Bud cold-hardiness, determined by thermal analysis and after two freezing events, was not different among all treatments. It was concluded that CT40 produced optimum vine size and cropload thus balanced vines. Furthermore, delaying fruit harvest in ‘Vidal blanc’ for ice wine production in the northeastern United States and Canada improves fruit composition but has no adverse influence on bud cold-hardiness.
Consumer Willingness to Purchase Impatiens walleriana Alternatives
Authors: Getter Kristin L. , Behe Bridget K.
Published: February 2019

The objectives of this study were to survey Midwest consumers to assess their willingness to buy alternatives to Impatiens walleriana given the confirmed presence of Impatiens downy mildew (IDM; Plasmopara obducens) in Michigan landscapes in 2012. An Internet survey queried consumers from four states (Illinois, Indiana, Michigan, and Ohio) and questions consisted of likelihood to buy, purchasing characteristics considered, impatiens purchases in 2012, and demographic questions. Roughly 500 participants per state responded and almost three-fourths (73.8%) of respondents said they planted impatiens in their landscape in 2012. Of the 16.4% who said their plants did not look healthy at the end of the growing season, 69.3% self-identified the plant as having IDM symptoms. Purchasing characteristics that had the highest mean scores were bloom period, flower color, and longevity, whereas the lowest mean scores were for compact shape with no spindly growth, fragrance, and locally grown. Three impatiens alternative species were acceptable alternatives (scored a positive utility in the conjoint analysis) for shade-tolerant species. Begonia semperflorens was the most preferred followed by Browallia speciosa and then Impatiens hawkeri. Solenostemon scutellarioides was the least preferred. Three impatiens alternative species also scored a positive utility in the conjoint analysis and would serve well for partial shade-tolerant species. Heliotropium arborescens was the most preferred followed by Salvia splendens and then Lobelia erinus. Hypoestes phyllostachya and Iresine herbstii were preferred least as impatiens alternatives. The attribute with the highest relative importance was species for both conjoint analyses, whereas the price attribute was the least important.
An Investigation of U.S. Apple Producers’ Trait Prioritization—Evidence from Audience Surveys
Authors: Yue Chengyan , Gallardo R. Karina , Luby James , Rihn Alicia , McFerson James R. , McCracken Vicki , Bedford David , Brown Susan , Evans Kate , Weebadde Cholani , Sebolt Audrey , Iezzoni Amy F.
Published: February 2019

Systematic studies of the relative importance of apple traits for U.S. apple producers to inform U.S. apple breeding programs have been lacking. To fill this gap, a series of audience surveys with instant feedback at five apple producer meetings across the United States was conducted. The traits included in this study were fruit crispness, juiciness, firmness, flavor, soluble solids concentration, sugar–acid balance, shelf life at retail, freedom from storage disorders, host plant disease resistance, and other fruit and tree traits provided by the producer. Producers rated fruit flavor and crispness as the most important traits for a successful apple cultivar. The relative importance assigned to traits was associated with growing location and producers’ years of experience in the decision-making process of managing apple orchards. This study contributes directly to a larger effort that provides breeding programs with systematic knowledge of trait preferences of supply chain members, including producers, and should result in a more targeted approach to developing and commercializing new apple cultivars.
Hydrogen Sulfide Delays Postharvest Senescence and Plays an Antioxidative Role in Fresh-cut Kiwifruit
Authors: Gao Shuai-Ping , Hu Kang-Di , Hu Lan-Ying , Li Yan-Hong , Han Yi , Wang Hui-Li , Lv Kai , Liu Yong-Sheng , Zhang Hua
Published: February 2019

Hydrogen sulfide (H2S) was recently recognized as an endogenous gaseous molecule involved in seed germination, root organogenesis, abiotic stress tolerance, guard cell movement, and delay of senescence in plants. In the present study, we show that H2S participates in the regulation of postharvest ripening and senescence in fresh-cut kiwifruit, Actinidia deliciosa. Fumigation of fresh-cut kiwifruit with the H2S donor sodium hydrosulfide (NaHS) solution prolonged kiwifruit storage time and alleviated senescence and tissue softening in a dose-dependent manner at an optimal concentration of 1.0 mmol·L−1 NaHS. H2S treatment maintained higher levels of reducing sugars, soluble proteins, free amino acids, ascorbate, and chlorophyll and lowered carotenoid levels. H2S treatment also significantly decreased the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion (•O2−) during fruit storage compared with water controls. Furthermore, the activities of guaiacol peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were increased by H2S treatment, whereas the activity of lipoxygenase (LOX) was decreased compared with untreated controls. Taken together, these results suggest that H2S is involved in prolonging postharvest shelf life and plays an antioxidative role in fresh-cut kiwifruit.