bluuebunny/crossref_metadata_2025 huggingface dataset:
Spring Cold Injury to Winegrapes and Protection Strategies and Methods
Authors: Poling E. Barclay
Published: February 2019

Active frost protection methods may be expensive, but a correctly selected and operated system can provide more consistent crops and improved cash flow in years of potentially damaging cold events at postbudbreak stages of grape development. The selection of an active frost protection system depends on a number of factors, including the prevailing climatic conditions that occur during the spring season at the vineyard location, the costs associated with different frost control systems as well as considerations related to the reliability and relative simplicity of operating the equipment associated with each method. In winegrape production areas in North Carolina, hoar (white) frosts are the predominant cold threat in the postbudbreak period. A wind machine can be a very cost-effective investment on sites that are prone to a damaging frost event in 1 of 5 years or with a higher frequency of occurrence. However, wind machines have less overall usefulness in growing areas where there is also potential for black frosts (a more damaging radiational event than a hoar frost) and frosts/freezes (events with subfreezing temperatures and winds in the range of 2.2 to 4.5 m·s−1). For black frost events, a well-designed overvine sprinkling system can provide nearly 6 °C protection; sprinkling is also an appropriate management option for frost/freeze events. Windborne freezes are far less common at the postbudbreak stages but represent the most damaging type of cold event that can occur in eastern and midwestern winegrape regions in the United States. Methods that reliably delay budbreak (e.g., dormant oils, evaporative cooling with targeted sprinklers) may represent the best near-term opportunity for growers to decrease or avoid vine injury from freeze events such as the early April Easter freeze of 2007 that devastated grape vineyards through much of the midwest and southeastern United States.
Dry Matter Content and Stability of Carotenoids in Kale and Spinach During Drying
Authors: Lefsrud Mark , Kopsell Dean , Sams Carl , Wills Jim , Both A.J.
Published: February 2019

Drying of spinach (Spinacia oleracea L.) and kale (Brassica oleracea L. var. acephala D.C.) is required to determine percentage of dry matter (%DM) and pigment concentration of fresh leaves. ‘Melody’ spinach and ‘Winterbor’ kale were greenhouse-grown in hydroponic nutrient solutions containing 13 or 105 mg·L−1 N. Using vacuum freeze dryers and convection ovens, plant tissues were dried for 120 h at five different temperature treatments: 1) freeze drying at −25 °C; 2) freeze drying at 0 °C; 3) vacuum drying at +25 °C; 4) oven drying at +50 °C; and 5) oven drying at +75 °C. Spinach leaf tissue %DM was affected, but kale %DM was unaffected by drying temperature. Spinach and kale leaf tissue %DM were both affected by N level. The high N spinach decreased from 7.3 to 6.4%DM when drying temperature increased from +25 to +75 °C. The low N spinach decreased from 12.7 to 9.6%DM as the drying temperature increased from −25 to +50 °C. Kale averaged from 14.8%DM for the high N treatment and from 21.8%DM for the low N treatment. However, drying temperature did not have a significant impact on measured %DM in kale. Lutein, β-carotene, and chlorophyll levels for both spinach and kale leaf tissue were affected by drying temperature. Measured concentrations of all pigments decreased over 70% as the drying temperature increased from −25 to 75 °C. The largest pigment fresh and dry weight concentrations for spinach and kale were measured at drying temperatures below +25 °C. The spinach and kale samples dried between −25 and +25 °C were not significantly different from each other in %DM or pigment concentration measured on a dry or fresh weight basis. Thus, drying leaf tissue for accurate pigment analysis requires temperatures below +25 °C using vacuum or freeze drying technology.
Growth and Nutrient Partitioning of Containerized Malus trilobata Schneid. and Acer syriacum Boiss. and Gaill. Under Two Fertigation Regimes
Authors: Zahreddine Hala G. , Struve Daniel K. , Talhouk Salma N.
Published: February 2019

The native flora of Lebanon is threatened. As part of an ex situ conservation strategy, this study was conducted to determine if Malus trilobata (Schneid.) and Acer syriacum (Boiss. and Gaill.), two native Lebanese trees, were amenable to container production. Therefore, these species' growth and nitrogen, phosphorus, and potassium uptake efficiency and distribution under two fertilizer rates were studied. Malus trilobata seedlings were obtained from seeds collected from two mother trees, whereas Acer syriacum seeds were collected from a single tree. Two-year-old seedlings raised from these seeds were planted in 11-L containers in a 3:1 pine bark:compost substrate. Half the seedlings within each source and species were assigned to either 25 or 100 mg·L−1 N from 21N–3.1P–5.9K water-soluble fertilizer treatments. Seedlings of both Malus trilobata sources grown under 25 mg·L−1 N were taller than those grown at 100 mg·L−1 N. Nitrogen loading occurred in plants of Malus trilobata under the high fertilizer rate, although total plant N, phosphorus, and potassium content was unaffected by fertilizer rate, because larger seedlings had lower nutrient concentrations. There were significant differences in growth among the two Malus trilobata seed sources, but there were no differences in mineral nutrient uptake or nutrient use efficiency. Growth, mineral nutrient uptake, and nutrient use efficiency of Acer syriacum seedlings were unaffected by fertilizer rate. Malus trilobata and Acer syriacum seedlings are amenable to container production. Using container production for these species with subsequent transplanting into managed landscapes might be a viable ex situ conservation method. Further studies are needed.
Plant Density and Nitrogen Fertilizer Rate on Yield and Nutrient Content of Onion Developed from Greenhouse-grown Transplants
Authors: Russo Vincent M.
Published: February 2019

Onions (Allium cepa L.) can be established from seed or transplants. The latter planting material can be dormant or actively growing when transplanted to the field. Onion transplants can be produced in a greenhouse, but additional information is needed regarding the cultural requirements after transplanting. Greenhouse-grown transplants of ‘Candy’, intermediate-day variety, and ‘Texas Grano 1015 Y’, short-day variety, were established at densities of ≈34,000, 68,000, or 102,000 plants/ha and 100 (recommended) and 400 kg·ha−1 of nitrogen in mid-March of 2006 and 2007. Nitrogen fertilizer rate did not affect yield. Yield of ‘Candy’ was greater than for ‘Texas Grano 1015 Y’. Yield of both cultivars increased as density increased, and yield of ‘Texas Grano 1015 Y’ was higher in 2006 than in 2007. ‘Candy’ had higher numbers of large-sized bulbs and ‘Texas Grano 1015 Y’ more small bulbs. Bulb nutrient content was affected by year with nitrate-N, potassium, sodium, and SO4 being higher in 2006 and nitrite-N, calcium, magnesium, PO4, and soluble solids higher in 2007. ‘Candy’ had a higher soluble solids (°Brix) content than did ‘Texas Grano 1015 Y’. In 2007, precipitation was higher than in 2006. This may have contributed to the year response and it appears that ‘Candy’ was better able to respond in a more uniform manner to the changed environmental conditions. For plants developed from greenhouse-grown transplants, the recommended rate of fertilizer and the highest plant density are beneficial to improved marketable yield.
Texture and Other Quality Attributes in Olives and Leaf Characteristics after Preharvest Calcium Chloride Sprays
Authors: Tsantili Eleni , Christopoulos Miltiadis V. , Pontikis Constantinos A. , Kaltsikes Pantousis , Kallianou Chariklia , Komaitis Michalis
Published: February 2019

The effect of three preharvest sprays with water or 58.5 mm calcium chloride (CaCl2) on texture and other quality attributes was investigated in ‘Konservolia’ olives harvested at the black-ripe stage and measured after 1 and 15 days of storage in air at 10 °C with 85% relative humidity. Effects on fruit calcium (Ca) and magnesium (Mg) concentrations during the period of spray applications were also studied. Concentrations of Ca, Mg, and chlorophyll and photosynthesis rate in leaves were measured on the day of final fruit harvest. No foliar or fruit toxicity was observed. In leaves, Ca sprays increased Mg but did not affect Ca and chlorophyll concentration and photosynthesis rate. In fruits, Ca sprays prevented the gradual decrease in Ca concentration that occurred in untreated fruits and maintained Mg at constant levels during ripening on the tree but did not affect fruit size and oil content as measured 1 day after storage. Ca-treated fruits were firmer with lower soluble pectin (SP) concentration and higher calcium pectate (CaP) than controls in both storage days, whereas the protopectin levels were similar in all fruits. Results showed positive linear correlation between Ca concentration and either firmness or CaP, whereas that between Ca and SP was negative as found in fruits stored for 1 day. Fruit production rates of carbon dioxide and ethylene, L* and chroma (C*) of peel, and hue angle (h°) of flesh were unaffected either by Ca treatment or storage time. Ca treatment did not affect fruit weight loss, the decreases in peel h° and flesh L*, but increased flesh C* during storage. The results indicate positive effects of preharvest calcium sprays on olive firmness without any negative effect on fruits or leaves.
‘Covington’ Sweetpotato
Authors: Yencho G. Craig , Pecota Kenneth V. , Schultheis Jonathan R. , VanEsbroeck Zvezdana-Pesic , Holmes Gerald J. , Little Billy E. , Thornton Allan C. , Truong Van-Den
Published: February 2019

‘Covington’ is an orange-fleshed, smooth-skinned, rose-colored, table-stock sweetpotato [Ipomoea batatas (L.) Lam.] developed by North Carolina State University (NCSU). ‘Covington’, named after the late Henry M. Covington, an esteemed sweetpotato scientist at North Carolina State, was evaluated as NC98-608 in multiple state and regional yield trials during 2001 to 2006. ‘Covington’ produces yields equal to ‘Beauregard’, a dominant sweetpotato variety produced in the United States, but it is typically 5 to 10 days later in maturity. ‘Covington’ typically sizes its storage roots more evenly than ‘Beauregard’ resulting in fewer jumbo class roots and a higher percentage of number one roots. Total yields are similar for the two clones with the dry matter content of ‘Covington’ storage roots typically being 1 to 2 points higher than that of ‘Beauregard’. ‘Covington’ is resistant to fusarium wilt [Fusarium oxysporum Schlect. f.sp. batatas (Wollenw.) Snyd. & Hans.], southern root-knot nematode [Meloidogyne incognita (Kofoid & White 1919) Chitwood 1949 race 3], and moderately resistant to streptomyces soil rot [Streptomyces ipomoeae (Person & W.J. Martin) Wakswan & Henrici]. Symptoms of the russet crack strain of Sweet Potato Feathery Mottle Virus have not been observed in ‘Covington’. The flavor of the baked storage roots of ‘Covington’ has been rated as very good by standardized and informal taste panels and typically scores as well or better in this regard when compared with ‘Beauregard’.
LED Lighting in Horticulture
Authors: Morrow Robert C.
Published: February 2019

Solid-state lighting based on the use of light-emitting diodes (LEDs) is potentially one of the biggest advancements in horticultural lighting in decades. LEDs can play a variety of roles in horticultural lighting, including use in controlled environment research, lighting for tissue culture, and supplemental and photoperiod lighting for greenhouses. LED lighting systems have several unique advantages over existing horticultural lighting, including the ability to control spectral composition, the ability to produce very high light levels with low radiant heat output when cooled properly, and the ability to maintain useful light output for years without replacement. LEDs are the first light source to have the capability of true spectral composition control, allowing wavelengths to be matched to plant photoreceptors to provide more optimal production and to influence plant morphology and composition. Because they are solid-state devices, LEDs are easily integrated into digital control systems, facilitating special lighting programs such as “daily light integral” lighting and sunrise and sunset simulations. LEDs are safer to operate than current lamps because they do not have glass envelopes or high touch temperatures, and they do not contain mercury. The first sustained work with LEDs as a source of plant lighting occurred in the mid-1980s to support the development of new lighting systems to be used in plant growth systems designed for research on the space shuttle and space station. These systems progressed from simple red-only LED arrays using the limited components available at the time to high-density, multicolor LED chip-on-board devices. As light output increases while device costs decrease, LEDs continue to move toward becoming economically feasible for even large-scale horticultural lighting applications.
Light as a Growth Regulator: Controlling Plant Biology with Narrow-bandwidth Solid-state Lighting Systems
Authors: Folta Kevin M. , Childers Kayla Shea
Published: February 2019

In the mission of plant husbandry, light is a critical yet passive entity. The potential to actively implement dynamic lighting strategies to control plant growth and development holds great promise in the future of plant cultivation. In other words, rather than simply using a single stable light condition to maintain photosynthesis, might it be possible to continually adjust fluence rate, wavelength combinations, and photoperiods to actively manipulate plant morphology and production? Research over the past 100 years suggests that it is so, and today's solid-state, narrow bandwidth lighting platforms offer a unique opportunity to test this hypothesis. The goal of this report is to describe the potential use of light as a growth regulator. Here light-emitting diode technology is well suited for the application, because light quantity, quality, photoperiod, and combinations thereof can be controlled with great precision. Specific light combinations may be adjusted throughout the life of a plant to potentially optimize traits of interest such as synchronization of flowering, maintenance of vegetative growth programs, control of plant stature, or acceleration of juvenility. This report describes the plant photosensory networks and how they sense and respond to light. The connection between light and internal hormone stasis is explored and then extended to questions of designing specific regimes to control plant growth and development. The concept of static signaling states is presented as a means to tightly control plant habits, in essence, using light to stabilize plant signal transduction pathways and their associated outcomes. Finally, the concepts presented are applied to the diploid strawberry Fragaria vesca to demonstrate the usefulness of the approach. These experiments provide proof-of-concept and lay a foundation for further studies.
How Cold Can You Go? Frost and Winter Protection for Grape
Authors: Davenport Joan R. , Keller Markus , Mills Lynn J.
Published: February 2019

Although the inland Pacific Northwest has a warm climate during the growing season, grapes grown in this region may be exposed to colder than optimal temperatures at several times during the year. In addition to damage from spring and fall frosts, intermittent winters with little to no snow cover and subzero temperatures can cause vine dieback and death. Temperature patterns in the recent past indicate that both fall and midwinter are times when risk of bud damage from cold events is probable, making proper site selection and cultivar choice critical. Water is not used for frost protection in this climate, but wind machines have proven to be useful. In frost-prone sites, annual sucker growth with cane burying is practiced as an insurance strategy. Modifying pruning strategies has not been shown to be advantageous after fall cold events. If rootstocks are used, research has shown greater scion survival with higher graft positions.
Day-neutral Strawberry Production for Season Extension in the Midsouth
Authors: Ballington James R. , Poling Barclay , Olive Kerry
Published: February 2019

Until recent years, there have been few attempts in the midsouth to evaluate alternative types of strawberries (e.g., day-neutrals); alternative cultural systems (e.g., tunnel culture); or specific products (e.g., rowcovers) that could be used for either season extension and/or off-season production. In the early 2000s, research was undertaken to evaluate day-neutral (DN) strawberry production in higher elevations in western North Carolina for harvest in the summer and fall. The effect of DN cultivar, plastic mulch color, planting dates, and plant types was studied in at the Upper Mountain Research Station, Laurel Springs, NC (elevation 914 m) over several seasons. In the 2004 season, the DN ‘Everest’ had yields of nearly 1 kg/plant on white plastic mulch using plugs transplanted in late Sept. 2003. However, ≈95% of ‘Everest's’ production occurred in July and August, when U.S. strawberry prices to growers in wholesale fresh markets have averaged $1.32 and $1.68 kg, respectively (2001 to 2005). Assuming a production level of ≈1 kg/plant, market prices above $2.48 kg (breakeven cost) will be needed to make day-neutral strawberry production in the southern Appalachians a profitable venture. We observed peak periods of heavy production in midsummer and more research is needed to identify cultural strategies with plastic mulches, plant types, and possibly rowcovers to increase fall fruit volumes.
Cytogenetic Characterization and Nuclear DNA Content of Diploid and Tetraploid Forms of Stokes Aster
Authors: Barb Jessica Gaus , Werner Dennis J. , Tallury Shyamalrau P.
Published: February 2019

Stokesia laevis (J. Hill) Greene is a herbaceous perennial native to the southeastern United States. Most cultivars of Stokesia are diploid (2n = 2x = 14) except for ‘Omega Skyrocket’, a tetraploid (2n = 4x = 28) form selected from a natural population. A comparative study of the karyotypes and meiotic behavior of diploid cultivars, seed-derived accessions of ‘Omega Skyrocket’, synthetically derived autotetraploids, and triploid progeny from these taxa strongly suggest that ‘Omega Skyrocket’ is an autotetraploid form of Stokesia. Total karyotype length, 161 μm and 293 μm, and average chromosome length, 11.5 μm and 10.5 μm, of the diploid cultivars and tetraploid accessions of ‘Omega Skyrocket’, respectively, were determined. The karyotype of the diploid cultivars consisted of eight metacentric (m) and six submetacentric (sm) chromosomes with average arm ratio values ranging from 1.12 to 2.06. The karyotype of ‘Omega Skyrocket’ consisted of 23 m chromosomes and 5 sm chromosomes with average arm ratio values ranging from 1.22 to 2.02. Meiotic pairing in the diploids was normal. No meiotic irregularities such as laggards or bridges were observed and disjunction was balanced (7:7). Accessions of ‘Omega Skyrocket’ demonstrated a high frequency (60%) of quadrivalent formation; however, later stages of meiosis were regular with balanced disjunction (14:14) occurring in 95% of the cells. Meiotic configurations in synthetically derived autotetraploids and triploid hybrids from crosses of diploid cultivars × ‘Omega Skyrocket’ consisted of univalents, bivalents, trivalents, quadrivalents, and pentavalents. Abnormalities, including laggards, unequal and/or premature disjunction, chromosome bridges, and chromosome stickiness were observed. Average nuclear 2C DNA content was 20.3 pg for the diploid cultivars and 39.9 pg for the newly synthesized autotetraploids. Average nuclear 2C DNA content for ‘Omega Skyrocket’ was 37.3 pg, which was 8.2% less than twice the average 2C DNA content of the diploid accessions and 6.4% less than the newly synthesized autotetraploids, suggesting that genomic downsizing in ‘Omega Skyrocket’ has occurred. Similarity of the karyotypes of the diploids and ‘Omega Skyrocket’ and the slight reduction in nuclear DNA content suggest that ‘Omega Skyrocket’ has diverged little from its original diploid progenitor.
Modeling Chilling Requirement and Diurnal Temperature Differences on Flowering and Yield Performance in Strawberry Crown Production
Authors: Tanino Karen K. , Wang Ruojing
Published: February 2019

In North America, over 800 million strawberry crowns are produced by nurseries each year for the strawberry fruit industry. A modeling approach is a quantifiable method to help nurseries predict optimal crown harvest date and potential fruit yield associated with the annual strawberry crown growing environment. Most available models that quantify growth conditions, e.g., chilling effects, use controlled environment chambers and target prediction of time of strawberry flowering, not fruit yield. This study used commercial field fruit yield data over a 6-year period and five geographically distinct locations to construct models to predict the effects of chilling, diurnal temperature difference, and their interaction with daylength on fruit yield and time to flower. Accumulative chilling unit (ACU) was estimated by using nonweighted (simple, M0) and weighted [Mu (Utah Model), M1, M2] accumulation of effective temperature units. The results showed that flowering time correlated with accumulative chilling hours using either a simple (M0) accumulation model or a weighted accumulation model (Mu, M1, M2). The best correlation of flowering time with ACU was a quadratic function (y = 82.27 − 0.049x + 1.74e−5x2, where y = flowering time, x = ACU) and effective temperatures were from –2 to 15 °C. By contrast, fruit yield was only correlated with ACU using specific weighted accumulation models. The correlation was influenced by weighting factors and effective or inhibitive temperatures involved in the model. Therefore, temperatures have differential effects on fruit yield and on flowering time. When pooled across regions and years, fruit yield could be predicted only by the weighted accumulation Model 2 (M2), a quadratic function (y = –72.15 + 0.98x + 0.0022x2) of the ACU accumulated from 45 d before crown harvest. Fruit yield response to ACU had an optimal level with yield reduction at other values. By contrast, fruit yield linearly increased with increasing difference in diurnal temperature across years and locations. However, the days to first flower were affected interactively by the diurnal temperature difference and daylength when geographically distinct locations are compared. The greater the difference in diurnal temperature at 2 to 3 months before crown harvest, the higher the subsequent fruit yield and the shorter the flowering time. An accumulative diurnal temperature unit of 180 degree-days resulted in 30% yield enhancement of Saskatchewan-grown crowns over California-sourced crowns. The greater diurnal temperature difference may be the major contributor to the Northern Vigour® response of strawberry crowns produced in northern latitudes such as Saskatchewan.
Effect of Root-promoting Products in the Propagation of Organic Olive (Olea europaea L. cv. Cornicabra) Nursery Plants
Authors: Centeno Ana , Gómez-del-Campo María
Published: February 2019

Olive cuttings root well using synthetic auxin indole-3-butyric acid (IBA). However, European and North American regulations do not allow the use of synthetic products to obtain organic vegetative propagation materials. In this work, we evaluated different products that could replace IBA in the propagation of olive cv. Cornicabra leafy-stem cuttings. In 2003, six products with a known auxin effect were assessed: IBA, algae extract, brewer's yeast, a bed of sunflower seed, seaweed dry extract (Sm-6 Organico™), and an extract of macerated seeds (Terrabal Organico™). The basal end of cuttings was treated with one of these products and placed on a mist bed with basal temperature control. After 2 months, rooting percentage, number of roots per cutting, number of cuttings with callus formation, and number of cuttings with basal thickening were determined. No significant differences were found in rooting percentage or number of roots per cutting between IBA and Terrabal Organico™ and Sm-6 Organico™. These last products had significantly higher percentage of rooted cuttings without callus formation than IBA. In 2004, a new trial was conducted in which seven treatments were evaluated: IBA applied for 7 s; Terrabal Organico™ applied for 1, 4, and 8 h; and Sm-6 Organico™ applied for 1, 4, and 8 h. No significant differences in rooting percentage or number of roots per cutting were observed between IBA and Terrabal Organico™ applied for 1 h, whereas all the Sm-6 Organico™ treatments had significantly lower rooting percentages than IBA. Both rooting percentage and the percentage of rooted cuttings without callus development decreased significantly as treatment duration with Terrabal Organico™ increased. Therefore, Terrabal Organico™ could produce a toxic effect on cuttings when treatment duration is increased. Thus, Terrabal Organico™ could be a valid alternative to IBA in the propagation of organic olive plants of cv. Cornicabra when applied to the basal end of cuttings for 1 h.
Grafting to Manage Soilborne Diseases in Heirloom Tomato Production
Authors: Rivard Cary L. , Louws Frank J.
Published: February 2019

Organic heirloom tomato production is limited in the southeastern United States by foliar and soilborne diseases, thermal stress, and weathered soil structure. Heirloom cultivars command a premium market, but tolerance to disease and abiotic stress is often poor. Organic growers need research that supports the advantages of market niches afforded by heirloom tomatoes through the development of integrated systems to manage pests and reduce risks of associated crop losses or low yields. Two major soilborne diseases common in the southeast, bacterial wilt (caused by Ralstonia solanacearum) and fusarium wilt (caused by Fusarium oxysporum f.sp. lycopersici), were effectively managed using susceptible heirloom scions grafted onto resistant rootstock. In naturally infested soil, bacterial wilt incidence for nongrafted ‘German Johnson’ was 79% and 75% in 2005 and 2006, respectively. ‘German Johnson’ showed no symptoms of bacterial wilt in either year when grafted onto the resistant genotypes CRA 66 or Hawaii 7996. Fusarium wilt incidence was 46% and 50%, respectively, in nongrafted and self-grafted ‘German Johnson’ controls. When ‘Maxifort’ rootstock was grafted with ‘German Johnson’, no symptoms of fusarium wilt were seen, and plants with ‘Robusta’ rootstock had an intermediate level of disease (29%). An evaluation of commercially available rootstock was carried out in three separate experiments in diverse organic production systems to determine yield impacts with low disease pressure. ‘Maxifort’ rootstock significantly increased yield in one location (P = 0.05), but ‘Maxifort’ and ‘Robusta’ rootstock did not consistently impact yield at the other two locations. Grafting is an effective management tool for organic growers in the southeast United States to reduce risk of crop loss resulting from soilborne diseases and will be a valuable component in an integrated pest management program.
Postharvest Quality of Dragon Fruit (Hylocereus spp.) after X-ray Irradiation Quarantine Treatment
Authors: Wall Marisa M. , Khan Shakil A.
Published: February 2019

The quality of three dragon fruit clones (Hylocereus spp.) was determined after x-ray irradiation for disinfestation of quarantine pests. Fruit were treated with irradiation doses of 0, 200, 400, 600, or 800 Gy and stored for 12 days at 10 °C. Irradiation did not affect soluble solids content, titratable acidity, or fructose concentrations. Glucose, sucrose, and total sugar concentrations decreased linearly as dose increased. Minimal softening occurred in the outer flesh layers for fruit treated with 400 or 600 Gy irradiation. Surface color, peel injury, and bract appearance differed among the three clones with irradiation stress, but in all cases, visible changes were minor. Fruit decay was absent or minimal, and disease ratings were not affected by irradiation. Irradiation treatment of dragon fruit at doses 800 Gy or less would ensure visual and compositional quality while providing quarantine security.
Plant Regeneration through Protocorm-like Bodies Induced from Nodal Explants of Syngonium podophyllum ‘White Butterfly’
Authors: Cui Jin , Liu Juanxu , Deng Min , Chen Jianjun , Henny Richard J.
Published: February 2019

Syngonium podophyllum ‘White Butterfly’, one of the most popular ornamental foliage plants, is propagated almost exclusively through in vitro shoot culture. Ex vitro rooting, however, has been associated with severe Myrothecium leaf spot (Myrothecium roridum Tode ex Fr.). The objective of this study was to establish a method for regenerating well-rooted plantlets before ex vitro transplanting. Leaf and petiole explants were cultured on a Murashige and Skoog (MS) basal medium supplemented with N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU), N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (TDZ), 6-benzyladenine (BA), or N-isopentenylaminopurine (2iP) with α-naphthalene acetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D), respectively. Calli formed from leaf explants cultured on the basal medium supplemented with CPPU or TDZ with 2,4-D or with NAA as well as from petiole explants cultured on the medium supplemented with BA, CPPU, or TDZ with 2,4-D or NAA. The calli, however, failed to differentiate, and shoot organogenesis did not occur. Culture of nodal explants on the MS basal medium supplemented with 9.84 μm 2iP, 8.88 μm BA, 8.07 μm CPPU, or 9.08 μm TDZ with 2.26 μm 2,4-D resulted in the formation of protocorm-like bodies, adventitious shoots, and subsequently well-rooted plantlets. MS basal medium supplemented with 19.68 μm 2iP and 1.07 μm NAA resulted in the highest percentage (92.9%) of nodal explants producing protocorm-like bodies and an average of 16.9 well-rooted plantlets per nodal explant. Adventitious shoots were able to root in the initial induction medium, but better root development occurred after shoots with protocorm-like bodies were transferred onto MS basal medium supplemented with 9.84 μm 2iP and 2.69 μm NAA. Regenerated plantlets were stable and grew vigorously with 100% survival rates after ex vitro transplanting to a container substrate in a shaded greenhouse.
Nitrogen Uptake and Mobilization by Hydrangea Leaves from Foliar-sprayed Urea in Fall Depend on Plant Nitrogen Status
Authors: Bi Guihong , Scagel Carolyn F.
Published: February 2019

Rooted liners of Hydrangea macrophylla (Thunb.) Ser. ‘Berlin’ were fertigated with different rates of nitrogen (N) from July to Sept. 2007 and leaves were sprayed with 15N-labeled urea in late October to evaluate urea uptake and 15N translocation by hydrangea leaves in relation to plant N status. Four plants from each N fertigation rate were harvested before they were sprayed with urea and 2, 5, 10, and 15 days after urea spray. Increasing rate of N fertigation increased plant N content in October before being sprayed with urea. Leaves rapidly absorbed 15N from urea spray. The highest rate of 15N uptake occurred during the first 2 days after urea spray and then decreased. Export of 15N from leaves occurred rapidly after uptake and the highest rate of 15N export occurred during the first 2 days after urea spray and then decreased. During the first 5 days after urea spray, the rate of 15N uptake by leaves and export from leaves decreased with increasing rate of N fertigation. On a whole plant basis, the total amount of 15N from foliar 15N–urea spray increased with increasing rate of N fertigation; however, the percentage of 15N exported from leaves and the percentage of N that derived from foliar 15N–urea spray decreased with increasing rate of N fertigation. Results suggest that hydrangea plants with lower N status in the fall are more efficient in absorbing and translocating N from foliar urea than plants with higher N status.
Pine Tree Substrate, Nitrogen Rate, Particle Size, and Peat Amendment Affect Poinsettia Growth and Substrate Physical Properties
Authors: Jackson Brian E. , Wright Robert D. , Barnes Michael C.
Published: February 2019

‘Prestige’ poinsettias (Euphorbia pulcherrima Willd. Ex Klotzsch) were grown at different fertilizer rates in three pine tree substrates (PTS) made from loblolly pine trees (Pinus taeda L.) and a peat-based control. Pine tree substrates were produced from pine trees that were chipped and hammer-milled to a desired particle size. Substrates used in this study included peat-lite (PL), PTS produced with a 2.38-mm screen (PTS1), PTS produced with a 4.76-mm screen (PTS2), and PTS produced with a 4.76-mm screen and amended with 25% peatmoss (v/v) (PTS3). Initial and final substrate physical properties and substrate shrinkage were determined to evaluate changes over the production period. Poinsettias were grown in 1.7-L containers in the fall of 2007 and fertilized at each irrigation with 100, 200, 300, or 400 mg·L−1 nitrogen (N). Shoot dry weight and growth index were higher in PL at 100 mg·L−1 N but similar for all substrates at 300 mg·L−1 N. Bract length was generally the same or longer in all PTS-grown plants compared with plants grown in PL at each fertilizer rate. Postproduction time to wilting was the same for poinsettias grown in PL, PTS1, and PTS3. Initial and final air space was higher in all PTSs compared with PL and container capacity (CC) of PTS1 was equal to PL initially and at the end of the experiment. The initial and final CC of PTS2 was lower than PL. The incorporation of 25% peat (PTS3) increased shoot dry weight and bract length at lower fertilizer rates compared with 4.76 mm PTS alone (PTS2). Substrate shrinkage was not different between PL and PTS1 but greater than shrinkage with the coarser PTS2. This study demonstrates that poinsettia can be successfully grown in a PTS with small particles (2.38-mm screen) or a PTS with large particles (4.76-mm screen) when amended with 25% peatmoss, which results in physical properties (CC and air space) similar to those of PL.
Managing Phosphorus for Citrus Yield and Fruit Quality in Developing Orchards
Authors: Obreza Thomas A. , Rouse Robert E. , Morgan Kelly T.
Published: February 2019

No calibrated phosphorus (P) soil test exists to guide Florida citrus fertilization. Applying P fertilizer to citrus when it is not needed is wasteful and may cause undesirable P enrichment of adjacent surface water. The objective of this study was to establish guidelines for P management in developing Florida grapefruit (Citrus paradisi Macf.) and orange (Citrus sinensis L. Osb.) orchards by determining the effect of P fertilizer rate on soil test P and subsequently calibrating a P soil test for citrus yield and fresh fruit quality. Two orchards were planted on sandy soil with 3 mg·kg−1 (very low) Mehlich 1 soil test P. In Years 1 through 3, P fertilization increased soil test P up to 102 mg·kg−1 (very high). In Years 4 through 7, canopy volume, yield, and fruit quality did not respond to available soil P as indexed by soil testing. As tree size and fruit production increased, leaf P was below optimum where soil test P was below 13 mg·kg−1 (grapefruit) or 31 mg·kg−1 (oranges). Total P in the native soil at planting was ≈42 mg·kg−1, which was apparently available enough to support maximum tree growth, fruit yield, and fruit quality for the first 7 years after planting. Trees were highly efficient in taking up P from a soil considered very low in available P. Citrus producers can likely refrain from applying P fertilizer to young trees on Florida sandy soils if soil test P is very high or high and probably medium as well.
Subirrigation of Quercus rubra Seedlings: Nursery Stock Quality, Media Chemistry, and Early Field Performance
Authors: Bumgarner Mindy L. , Salifu K. Francis , Jacobs Douglass F.
Published: February 2019

Container seedling production systems for forest tree nurseries are challenged by the need for judicious water consumption. Subirrigation systems may provide an alternative to overhead systems by mitigating water use, yet remain relatively untested for propagation of forest tree seedlings. We evaluated effects of overhead versus subirrigation under varying media (40:60, 60:40, and 80:20 peat:perlite) and fertilization (0 or 1.2 g nitrogen/plant) regimes on nursery development and first-year field performance of northern red oak (Quercus rubra L.) seedlings. Fertilization increased aboveground biomass production and nutrient content, but decreased root dry weight. Relative to overhead-irrigated seedlings, subirrigation increased red oak seedling aboveground biomass production as well as above- and belowground nitrogen content under fertilized conditions. Media had no effect on plant response. Subirrigation increased electrical conductivity (5 dS·m−1 greater) and decreased pH in the upper media zone (0 to 5 cm from top), whereas the opposite effect was found in the lower zone. Nursery fertilization was associated with reduced field survival and growth, which may have been the result of transplant stress resulting from higher shoot:root. Subirrigated seedlings had greater field diameter growth. Our results suggest that subirrigation could serve as a viable alternative to overhead systems in container propagation of hardwood seedlings.
‘Mimi’ Sweet Pea for Forcing Culture
Authors: Nakamura Kaoru , Hino Hirotoshi , Gunji Sadao , Hattanda Norio , Murata Toshio , Tominaga Hiroshi , Fukumoto Koichi , Akashi Ryo
Published: February 2019

‘Mimi’ sweet pea (Lathyrus odoratus L.) is a new cultivar in Japan, released by the Miyazaki Agricultural Research Institute. Sweet pea is grown by forcing culture in Japan for cut flower production. As a cut flower, sweet pea is very popular and is marketed from November to April. ‘Mimi’ produces 145% more marketable flowers than the main pink cultivar, Super Rose. ‘Mimi’ also has several desirable qualities as a cut flower. The flower color is strong pink. It is as brilliant under fluorescent lights indoors as it is in the field.
‘Mardía’ Almond
Authors: Socias i Company Rafel , Kodad Ossama , Alonso José M. , Felipe Antonio J.
Published: February 2019

‘Mardía’ is a new almond cultivar released because of its good agronomical traits and very late blooming time, 2 weeks later than ‘Felisia’, the latest blooming cultivar released so far. It is characterized by its slightly upright growth habit, early ripening, high and regular bloom density, autogamy (S6Sf
genotype), high fruit set, tolerance to diseases, hard shell, large kernel, very high content of oleic acid, and low content of linoleic acid.
Hypersensitivity of Ranunculus asiaticus to Salinity and Alkaline pH in Irrigation Water in Sand Cultures
Authors: Valdez-Aguilar Luis A. , Grieve Catherine M. , Poss James , Mellano Michael A.
Published: February 2019

Ranunculus, grown as a field crop in southern and central coastal California, is highly valued in the cut flower and tuberous root markets. However, concerns regarding the sustainability of ranunculus cultivation have arisen when the plantations are irrigated with waters of marginal quality because the viability of the tuberous roots may be compromised. A study was initiated to evaluate the effect of saline irrigation waters, with and without pH control, on the growth of plants and tuberous roots of ranunculus. Treatments consisted of four irrigation water solutions with increasing concentration of Ca2+, Mg2+, Na+, SO42−, and Cl− to meet an electrical conductivity (EC) of 2, 3, 4, and 6 dS·m−1 and pH 6.4. The 3, 4, and 6 dS·m−1 solutions were replicated with uncontrolled pH, which averaged 7.8 over the trial. Ranunculus ‘Yellow ASD’ and ‘Pink CTD’ seedlings were transplanted into greenhouse sand tanks and irrigated twice daily with treatment solutions. Shoot dry weight of plants irrigated with 2 dS·m−1 solutions was 7.20 g and 6.66 g in ‘Yellow ASD’ and ‘Pink CTD’, respectively; however, increasing EC from 2 to 3 dS·m−1 induced an 83% and 78% decrease, respectively. Tuberous root fresh weight of control plants, 7.45 g and 8.42 g for ‘Yellow ASD’ and ‘Pink CDT’, respectively, was decreased by 82% and 89% when EC was 6 dS·m−1. High pH of irrigation water caused an additional decrease in shoot dry weight and tuberous root weight. In control plants, 83% and 76% of tuberous roots of ‘Yellow ASD’ and ‘Pink CTD’, respectively, that were transplanted in the following season produced new shoots; however, tuberous roots sprouting percentage from plants irrigated with EC 4 dS·m−1 water decreased to 42.9% and 58.3% and to 11.1% and 45.0% with EC 6 dS·m−1. The hypersensitivity of ranunculus to salinity was associated with a significant decrease in Ca2+ and K+ tissue concentration. In ‘Yellow ASD’, Ca2+ decreased from 202 mmol·kg−1 in control plants to 130 mmol·kg−1 in plants irrigated with 3 dS·m−1 solutions and pH 6.4. In ‘Pink CTD’, the decrease was from 198 mmol·kg−1 to 166 mmol·kg−1. Potassium was similarly affected. Compared with control plants (405 mmol·kg−1), shoot Na+ concentration was increased by 101% in ‘Yellow ASD’ and by 125% in ‘Pink CTD’ when irrigated with 6 dS·m−1 water. Salt sensitivity of ranunculus, as determined by growth of the flowering stems and viability of the tuberous roots, was increased by irrigation with alkaline waters, which was associated with additional increases in Na+ and Cl– tissue concentration and decreased iron accumulation. Hypersensitivity to salinity makes ranunculus crop a poor candidate for water reuse systems; however, further research is warranted to elucidate the possibility of enhancing its tolerance to salinity by supplemental Ca2+ and K+ and acidification of irrigation water.
Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence?
Authors: Davis Donald R.
Published: February 2019

Three kinds of evidence point toward declines of some nutrients in fruits and vegetables available in the United States and the United Kingdom: 1) early studies of fertilization found inverse relationships between crop yield and mineral concentrations—the widely cited “dilution effect”; 2) three recent studies of historical food composition data found apparent median declines of 5% to 40% or more in some minerals in groups of vegetables and perhaps fruits; one study also evaluated vitamins and protein with similar results; and 3) recent side-by-side plantings of low- and high-yield cultivars of broccoli and grains found consistently negative correlations between yield and concentrations of minerals and protein, a newly recognized genetic dilution effect. Studies of historical food composition data are inherently limited, but the other methods can focus on single crops of any kind, can include any nutrient of interest, and can be carefully controlled. They can also test proposed methods to minimize or overcome the diluting effects of yield whether by environmental means or by plant breeding.
Cultivar Sensitivity to Ethylene During Storage and 1-Methylcyclopropene Protection of Aglaonema
Authors: Fan Shu-Ting , Yeh Der-Ming , Wang Tsu-Tsuen
Published: February 2019

This study determined the sensitivity of two Aglaonema cultivars to ethylene and evaluated the effectiveness of 1-methylcyclopropene (1-MCP) to protect sensitive cultivars. Plants of ‘White Tip’ and ‘Chalit's Fantasy’ were exposed to various ethylene concentrations for 7 days during dark storage at 15 °C. Poststorage performance, measured as number of chlorotic leaves and quality rating, was recorded after the plants were placed in the indoor environments for 14 days. Exposure to 4.5 μL·L−1 ethylene resulted in increased chlorotic leaves and reduced quality rating in ‘White Tip’ but did not affect poststorage performance in ‘Chalit's Fantasy’. Exposure to 4.5 μL·L−1 ethylene reduced both the soil plant analytical development-502 (SPAD-502) and variable fluorescence/maximal fluorescence (Fv/Fm) values of the lowest leaves in ‘White Tip’ but not in ‘Chalit's Fantasy’. Chlorotic leaf number increased; the SPAD-502 value, Fv/Fm, and Fm of the lowest leaves decreased in ‘White Tip’ as ethylene concentration increased from 0 to 4.1 μL·L−1. Plants of ‘White Tip’ pretreated with 300 or 900 nL·L−1 1-MCP for 6 h had fewer chlorotic leaves, higher Fv/Fm, and SPAD-502 values and better postproduction quality than those without 1-MCP pretreatment in response to treatment with 1.1 μL·L−1 ethylene during storage.
Primocane-fruiting Blackberries: Potential for Extending Harvest Season and Production Regions
Authors: Strik Bernadine C. , Thompson Ellen
Published: February 2019

Primocane-fruiting blackberries produce fruit on current-season canes (primocanes) and second-season canes (floricanes), if desired. Primocane-fruiting blackberries are likely adapted to a diverse range of climates, particularly because cold hardiness is not an issue when plants are grown for a primocane crop only. The floricane crop of ‘Prime-Jan’® and ‘Prime-Jim’® is from 3 June to 6 July in Arkansas and 30 June to 22 Aug. in Oregon, thus overlapping with other fresh market blackberries. However, although the primocane crop overlaps with the semierect cultivar Chester Thornless, the fruiting season of the primocane-fruiting types is longer. Harvest on primocanes began 17 July and mid-August in Arkansas and Oregon, respectively. The primocanes of ‘Prime-Jan’ and ‘Prime-Jim’ tend to branch naturally, producing a couple of branches near the base. However, soft-tipping primocanes at 1 m early in the season increased branch and flower number, resulting in a threefold yield increase compared with untipped canes. Yield and berry size in Oregon has been from 1.8 to 5.2 t·ha−1, depending on primocane management treatment, and 5.2 to 7.4 g, respectively. However, yield would have been much higher if all fruit could have been harvested as would be possible under protected culture. Our research to date indicates that primocane-fruiting blackberry can be easily manipulated to adjust harvest time. Remowing primocanes to create a delayed flush of growth will delay harvest. Rowcovers or tunnels that increase temperature will advance primocane growth and harvest. Soft-tipping height and frequency can affect cane architecture and season. Management techniques along with new genotypes of primocane-fruiting blackberry will have a great impact on blackberry production worldwide.
Improved Cold-resistant Performance in Transgenic Grape (Vitis vinifera L.) Overexpressing Cold-inducible Transcription Factors AtDREB1b
Authors: Jin Wanmei , Dong Jing , Hu Yuanlei , Lin Zhongping , Xu Xuefeng , Han Zhenhai
Published: February 2019

Dehydration response element binding (DREB)1b is a cold-inducible transcription factor in Arabidopsis thaliana. DREB1b driven by cauliflower mosaic virus 35S promoter was genetically introduced into grape Vitis vinifera L. cv. Centennial Seedless through Agrobacterium-mediated transformation for improving its cold resistance and exploring new genetic breeding approaches to obtain cold-resistant cultivars. In this study, Southern blot analysis showed the DREB1b gene was integrated into the transgenic grapevines with one to two copies. Northern blot analysis showed the presence of DREB1b transcripts in the independent transgenic lines 3, 5, 6, and 7. Further characterization of transgenic grapevines confirmed that both electrolyte leakage conductivity and the freezing point of the transgenic plants were lower than those of wild-type plants. After the cold treatment at –4 °C for 12 h, 26% of transgenic plants wilted among which 95% plants recovered once being placed under the condition of temperature 22 to 25 °C. However, subjected to the same treatment, 98% of nontransgenic plants wilted and only 2% recovered. Our results lead to the conclusion that activity of DREB1b in the transgenic grape could significantly improve its resistance to cold stress.