bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Euphorbia pulcherrima under Reduced Finish Temperatures
Authors: Camberato Diane M. , Lopez Roberto G. , Krug Brian A.
Published: February 2019

The holiday poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch.) is the number two potted flowering crop sold in the United States with a reported wholesale value of $146 million in 2010. Profitability is increasingly threatened as the cost to heat greenhouses has increased by over 90% in the last 10 years. As energy costs continue to increase and poinsettia prices remain relatively constant, growers are seeking cultivars that can be finished under reduced temperatures. Our objectives were to quantify how reduced temperature finishing (RTF) 2 weeks after the start of short days influences height, bract area index, and time to anthesis of poinsettia. Eight red poinsettia cultivars were selected based on their early response attributes (initiate and finish within 6 to 8 weeks), moderate to high vigor, and naturally large bracts. Rooted cuttings were grown at day/night temperature set points (12 h/12 h) of 24/19 °C until 15 Oct. and under a 16-h photoperiod consisting of natural daylengths with day-extension lighting until 1 Oct. On 15 Oct., plants were transferred to day/night temperatures (12 h/12 h) of 20/14, 21/17, or 24/19 °C. Time to anthesis from the start of short days was 60 and 55 days at 24/19 °C and 76 and 68 days at a reduced finishing temperature of 20/14 °C for ‘Prestige Early Red’ and ‘Early Orion Red’, respectively. Final height was not significantly influenced by RTF in either cultivar. Our results indicate that RTF is a viable option that greenhouse growers can use to help reduce energy costs of carefully selected poinsettia cultivars.
Tolerance of Strawberry Cultivars to Oxyfluorfen and Flumioxazin Herbicides
Authors: Samtani Jayesh B. , Ben Weber J. , Fennimore Steven A.
Published: February 2019

Herbicides can be an excellent supplemental treatment in cases where soil fumigant treatments alone fail to control weeds during the growing season or in situations where fumigants cannot be used as a result of regulatory restrictions. Previous studies have shown that oxyfluorfen and flumioxazin can provide satisfactory weed control in bedded strawberry (Fragaria ×ananassa Duch.) production. However, we need to know if tolerance to herbicides is uniform across strawberry cultivars under California conditions. The objective of this study was to determine if tolerance to oxyfluorfen and flumioxazin herbicides varied among strawberry cultivars. Trials were conducted in the 2007–2008 and 2009–2010 growing seasons at Salinas, CA. Treatments included an untreated control; pre-plant applications of flumioxazin at 0.07, 0.11, and 0.21 kg·ha−1 a.i.; and oxyfluorfen at 0.14 and 0.28 kg·ha−1 a.i. The entire trial was fumigated with an emulsified formulation of 60% 1,3-dichloropropene + 32% chloropicrin applied at 281 L·ha−1 by drip injection to all plots. Eight strawberry cultivars were included in the trial in the 2007–2008 growing season, and nine cultivars were included in the 2009–2010 growing season. In both growing seasons, slight to no crop phytotoxicity was observed. In the 2007–2008 growing season, several strawberry cultivars including ‘Albion’, ‘Festival’, ‘211G51’, ‘Palomar’, ‘Plant Sciences 5298’, and ‘Ventana’ had smaller crop plant canopy diameter as compared with the control when treated with 0.21 kg·ha−1 a.i. of flumioxazin. Compared with the control, flumioxazin at 0.21 kg·ha−1 a.i. reduced crop diameter for ‘Plant Sciences 4634’, ‘Plant Sciences 5298’, ‘San Andreas’, and ‘Ventana’ in the 2009–2010 growing season. In the 2007–2008 strawberry-growing season, none of the herbicide treatments reduced fruit yield compared with the control. In the 2009–2010 growing season, in seven of the nine cultivars, there were no significant differences in yield among treatments. For ‘Palomar’ strawberry, yields in plots treated with flumioxazin at 0.11 and 0.21 kg·ha−1 a.i. were significantly lower than the untreated control. With the exception of flumioxazin at 0.21 kg·ha−1 a.i., these herbicides are safe to use and can be incorporated in strawberry production practices for the cultivars tested to achieve satisfactory weed control over the growing season.
Photosynthetic Daily Light Integral During Root Development Influences Subsequent Growth and Development of Several Herbaceous Annual Bedding Plants
Authors: Hutchinson Veronica A. , Currey Christopher J. , Lopez Roberto G.
Published: February 2019

Vegetatively propagated bedding plants are produced during the late winter and early spring when outdoor photosynthetic daily light integral (DLI) is low, especially in northern latitudes. Our objective was to quantify how propagation DLI influences subsequent growth and development of annual bedding plants. Cuttings of Angelonia angustifolia Benth. ‘AngelMist White Cloud’, Nemesia fruticans (Thunb.) Benth. ‘Aromatica Royal’, Osteospermum ecklonis (DC.) Norl. ‘Voltage Yellow’, and Verbena ×hybrida Ruiz ‘Aztec Violet’ were harvested and propagated in a glass-glazed greenhouse. After callusing (≈5 mol·m−2·d−1 for 7 days), cuttings of each species were placed under one of three different fixed-woven shadecloths providing ≈38%, 61%, or 86% shade or no shade with 16 h of supplemental light for 14 days. Rooted cuttings were then transplanted into 11-cm containers and grown in a common greenhouse of 21 ± 1 °C and DLI of ≈12 mol·m−2·d−1 to identify any residual effects on subsequent growth and development during the finish stage. As DLI during propagation increased, time to first open flower decreased for Angelonia, Nemesia, Osteospermum, and Verbena. For example, time to flower for Angelonia and Osteospermum was hastened by 23 and 19 days, respectively, as DLI during propagation increased from 1.2 to 12.3 mol·m−2·d−1. Our research can be used to predict growth and flowering under varying propagation DLIs for the cultivars of Angelonia, Nemesia, Osteospermum, and Verbena in the study.
Costs of Establishing Organic Northern Highbush Blueberry: Impacts of Planting Method, Fertilization, and Mulch Type
Authors: Julian James W. , Strik Bernadine C. , Larco Handell O. , Bryla David R. , Sullivan Dan M.
Published: February 2019

A systems trial was established to evaluate factorial 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 applied at 29 and 57 kg·ha−1 of nitrogen (N); sawdust mulch, compost topped with sawdust mulch (compost + sawdust), or weed mat; and two cultivars, Duke and Liberty. The planting was established in Oct. 2006 and was certified organic in 2008. Weeds were managed by hand-hoeing or pulling in sawdust and weed mat-mulched plots and a combination of hand-pulling, propane-flaming, and post-emergent, targeted applications of acetic acid or lemon grass oil to any weeds present in the compost + sawdust plots depending on year. Data were recorded on input costs and returns in Year 0 (establishment year) through Year 3. Plants were harvested beginning the second year after planting. Planting costs were $741/ha higher on raised beds than on the flat, but the higher costs were more than offset by an average of 63% greater yields that improved net returns by as much as $2861/ha. Cumulative net returns after 3 years were negative and ranged from –$32,967 to –$50,352/ha when grown on raised beds and from –$34,320 to –$52,848/ha when grown on flat beds, depending on cultivar, mulch, and fertilizer rate and source. The greatest yields were obtained in plants fertilized with the low rate of fish emulsion or the high rate of feather meal, but fertilizing with fish emulsion by hand cost (materials and labor) as much as $5066/ha more than feather meal. Higher costs of establishment and pruning for ‘Liberty’ compared with ‘Duke’ were offset by higher net returns in all treatment combinations, except feather meal fertilizer with either weed mat or compost + sawdust mulch. Mulch type affected establishment costs, weed presence, and weed management costs, which included product and labor costs for application of herbicides (acetic acid and lemon grass oil) as well as labor for hand-weeding as needed, depending on the treatment. The highest yielding treatment combinations (growing on raised beds mulched with compost + sawdust and fertilized with fish emulsion) improved cumulative net returns as much as $19,333/ha over 3 years.
Controlled-atmosphere Storage of ‘Honeycrisp’ Apples
Authors: Watkins Christopher B. , Nock Jacqueline F.
Published: February 2019

‘Honeycrisp’ is an apple [Malus xsylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] that can be stored in air for several months, but the flavor becomes bland with prolonged storage. Controlled-atmosphere (CA) storage recommendations have not been made in some growing regions, however, because of the susceptibility of fruit to physiological disorders. In the first year of this study, we stored fruit from six orchards in O2 partial pressures (pO2) of 1.5, 3.0, and 4.5 kPa with 1.5 and 3.0 kPa pCO2. In the second year, we stored fruit from three orchards in three storage regimes (2.0/2.0, 3.0/1.5, 3.0/0.5 kPa O2/kPa CO2) with and without treatment of fruit with 1-methylcyclopropene (1-MCP) at the beginning and end of the conditioning regime (10 °C for 7 days) that is commercially used for ‘Honeycrisp’. CA storage had little effect on flesh firmness, soluble solids concentration (SSC), and titratable acidity (TA) over the range of pO2 and pCO2 tested. Greasiness was generally lower in fruit stored in lower pO2 and higher pCO2. Susceptibility of fruit to core browning and senescent breakdown varied between years, but a high incidence of internal CO2 injury in fruit from some orchards occurred in both years. 1-MCP treatment decreased internal ethylene concentration (IEC) and sometimes maintained TA but had little effect on firmness and SSC. Senescent breakdown and core browning incidence were reduced by 1-MCP treatment where orchard susceptibility to these disorders was high. However, 1-MCP treatment sometimes increased internal CO2 injury, especially if treatment occurred at the beginning of the conditioning period. CA storage cannot be recommended for storage of New York-grown ‘Honeycrisp’ apples until management of CO2 injury can be assured.
Fecundity of Winged Euonymus Cultivars and Their Ability to Invade Various Natural Environments
Authors: Brand Mark H. , Lubell Jessica D. , Lehrer Jonathan M.
Published: February 2019

Winged euonymus [Euonymus alatus (Thunb.)] is an important landscape shrub that has demonstrated its potential to be invasive in numerous states across the central and northern United States. Nine cultivars were evaluated for their potential to produce fruits and seeds in a randomized, replicated field planting. Seeds from all cultivars were evaluated for germination rate and initial survival in a deciduous woodland. Seeds collected from ‘Compactus’ were also sown in five natural environments (full sun meadow, edge of woods, moist woods, dry woods, pine woods) to determine which habitat types support its germination and establishment. Seed production for cultivars varied from 981 to 6090 seeds per plant. The dry deciduous woods and pine woods were the only environments that supported significant germination rates that could be as high as 37.8%. Seedling survival was at least 77% in the deciduous dry woods and at least 55% in the pine woods. In the first replication, establishment rates for cultivars in the dry deciduous woods ranged from a low of 6.5% for ‘Odom’ Little Moses™ to a high of 42.5% for ‘Monstrosus’. In the second replication, all cultivars achieved over 30% establishment and most exceeded 40% establishment. An estimate of the annual seedling contribution per plant per cultivar was calculated by combining seed production data with establishment data for each cultivar. This estimate was predicted to range from 588 to 3763 and therefore none of the nine cultivars evaluated should be considered non-invasive based on our findings. Our findings show that germination and seedling survival rates are high for E. alatus and because the species is long-lived, cultivars will likely have to be completely seed-sterile to be considered non-invasive according to demographic models.
Improving the CROPGRO-Tomato Model for Predicting Growth and Yield Response to Temperature
Authors: Boote Kenneth J. , Rybak Maria R. , Scholberg Johan M.S. , Jones James W.
Published: February 2019

Parameterizing crop models for more accurate response to climate factors such as temperature is important considering potential temperature increases associated with climate change, particularly for tomato (Lycopersicon esculentum Mill.), which is a heat-sensitive crop. The objective of this work was to update the cardinal temperature parameters of the CROPGRO-Tomato model affecting the simulation of crop development, daily dry matter (DM) production, fruit set, and DM partitioning of field-grown tomato from transplanting to harvest. The main adaptation relied on new literature values for cardinal temperature parameters that affect tomato crop phenology, fruit set, and fruit growth. The new cardinal temperature values are considered reliable because they come from recent published experiments conducted in controlled-temperature environments. Use of the new cardinal temperatures in the CROPGRO-Tomato model affected the rate of crop development compared with prior default parameters; thus, we found it necessary to recalibrate genetic coefficients that affect life cycle phases and growth simulated by the model. The model was recalibrated and evaluated with 10 growth analyses data sets collected in field experiments conducted at three locations in Florida (Bradenton, Quincy, and Gainesville) from 1991 to 2007. Use of modified parameters sufficiently improved model performance to provide accurate prediction of crop and fruit DM accumulation throughout the season. Overall, the average root mean square error (RMSE) over all experiments was reduced 44% for leaf area index, 71% for fruit number, and 36% for both aboveground biomass and fruit dry weight simulations with the modified parameters compared with the default. The Willmott d index was higher and was always above 0.92. The CROPGRO-Tomato model with these modified cardinal temperature parameters will predict more accurately tomato growth and yield response to temperature and thus be useful in model applications.
Factors Affecting Airborne Concentrations of Podosphaera xanthii Conidia and Severity of Gerbera Powdery Mildew
Authors: Granke Leah L. , Crawford Layla E. , Hausbeck Mary K.
Published: February 2019

To determine the factors affecting airborne conidial concentrations of Podosphaera xanthii Braun and Shishkoff and powdery mildew severity in greenhouse-grown potted gerbera (Gerbera jamesonii H. Bolus), airborne concentrations of conidia were monitored in a glass and polyethylene greenhouse. Temperature, relative humidity, and leaf wetness were recorded onsite, and the percentage of foliage with visible disease was assessed weekly at the glasshouse and every 2 weeks at the polyethylene greenhouse (1 to 10 visual rating scale). Peak airborne conidial concentrations occurred at 0800/1600 and 0900/1400 hr at the glasshouse and polyethylene greenhouses, respectively. Few conidia were sampled between 2200 and 0500 hr at either greenhouse. Worker activity was associated with conidial release in the glasshouse, but not in the larger polyethylene greenhouse, and worker activity may have influenced the daily periodicity of conidial concentrations. Airborne conidial concentrations were not related to environmental conditions in the same hour as conidial detection. An increase in disease severity was positively related to relative humidity and negatively related to leaf wetness at both greenhouses; in addition, temperature was negatively related to an increase in disease severity in the glasshouse. In light of the results of this study, frequent scouting and fungicide applications for powdery mildew are advised. Wide plant spacing and adequate ventilation are also recommended to reduce relative humidity in the microclimate.
Biochar Affects Macronutrient Leaching from a Soilless Substrate
Authors: Altland James E. , Locke James C.
Published: February 2019

Byproducts of pyrolysis, known collectively as biochar, are becoming more common and readily available as ventures into alternative energy generation are explored. Little is known about how these materials affect greenhouse container substrates. The objective of this research was to determine the effect of one form of biochar on the nutrient retention and release in a typical commercial greenhouse container substrate. Glass columns filled with 85:15 sphagnum peatmoss:perlite (v:v) and amended with 0%, 1%, 5%, or 10% biochar were drenched with nutrient solution and leached to determine the impact of biochar on nutrient retention and leaching. Nitrate release curves were exponential and peaked lower, at later leaching events, and had higher residual nitrate release over time with increasing biochar amendment rate. This suggests that biochar might be effective in moderating extreme fluctuations of nitrate levels in container substrates over time. Peak phosphate concentration decreased with increasing biochar amendment rate, whereas time of peak release, girth of the peak curve, and final residual phosphate release all increased with increasing biochar amendment. Additional phosphate levels in leachates from biochar-amended substrates, in addition to the higher phosphate concentrations present in later leaching events, suggest this form of biochar as a modest source of phosphate for ornamental plant production. Although there was not sufficient potassium (K) from biochar to adequately replace all fertilizer K in plant production, increasing levels of this form of biochar will add a substantial quantity of K to the substrate and should be accounted for in fertility programs.
Influence of Induced Polyploidy on Fertility and Morphology of Rudbeckia Species and Hybrids
Authors: Oates Kelly M. , Ranney Thomas G. , Touchell Darren H.
Published: February 2019

Rudbeckia spp. are adaptable and valuable ornamental wildflowers. Development of new varieties of Rudbeckia spp., with improved commercial characteristics, would be highly desirable. Interspecific hybridization and induced polyploidy may be avenues for improvement within the genus. The objective of this study was to evaluate fertility, morphology, phenology of flowering, and perennialness (overwintering survival) for lines of diploid and induced allotetraploids of R. subtomentosa × hirta and diploid and autotetraploids of R. subtomentosa ‘Henry Eilers’. Polyploid lines were developed and propagated in vitro and then grown ex vitro in a randomized complete block design with 12 replications. Compared with their diploid counterparts, autotetraploid lines of R. subtomentosa ‘Henry Eilers’ had similar internode lengths, plant heights, number of stems, flowering times (date at first anthesis), and fall and spring survival (100%); reduced number of inflorescences and male and female fertility; and increased inflorescence diameters. Compared with their diploid counterparts, allotetraploids of R. subtomentosa × hirta had similar internode lengths, reduced number of inflorescences, delayed flowering times, and increased pollen staining. Allotetraploids had limited male and female fertility compared with no detectable fertility in their diploid counterparts. Plant height and number of stems either decreased or showed no change with induced allotetraploidy. Spring survival of diploid hybrid genotypes ranged from 0% to 82% and was not improved in the allotetraploid hybrids. For a given genotype, some polyploidy lines varied significantly in certain morphological traits (e.g., plant height) indicating somaclonal variation may have developed in vitro or there were variable genomic or epigenetic changes associated with induced polyploidy.
1-Aminocyclopropane Carboxylic Acid Shows Promise as a Chemical Thinner for Apple
Authors: Schupp James R. , Kon Thomas M. , Winzeler H. Edwin
Published: February 2019

The objective of these studies was to evaluate the efficacy of several concentrations of 1-aminocyclopropane carboxylic acid (ACC) for thinning apple at the standard growth stage for chemical thinning timing and a late thinning growth stage. ACC was applied at concentrations of 0, 100, 300, or 500 mg·L−1 to ‘Golden Delicious’/Bud.9 apple trees at 10 mm or 20 mm fruit diameter. Treatments were applied to the point of drip to individual whole trees in a completely randomized design with five (2010) and six (2011) replications. When ACC was applied at 20 mm, there was a linear dose relationship between concentration and fruit thinning in both years. ACC was ineffective at 10 mm. The naturally occurring compound ACC shows potential for use as a reliable late chemical thinner for apple.
Reviving, In Vitro Differentiation, Development, and Micropropagation of the Rare and Endangered Moss Bruchia vogesiaca (Bruchiaceae)
Authors: Sabovljević Marko , Vujičić Milorad , Sekulić Jasmina Šinžar , Segarra-Moragues Jose Gabriel , Papp Beata , Skorić Marijana , Dragačević Luka , Sabovljević Aneta
Published: February 2019

This study provides the results of the developmental biology of the highly rare and endangered moss species Bruchia vogesiaca (recorded in less than 30 localities in the Northern Hemisphere, mainly western, central, and southwestern Europe). The aim of the study was to achieve the fully developed gametophyte and to propagate it for the purpose of conservation, reintroduction, and introduction to potential habitats free from xenic contamination. These gametophytes will be used for the study of genetics and genomics of this species. The micropropagation of B. vogesiaca was successfully applied on BCD medium supplemented with 0.1 μM BA and on BCD supplemented with 0.3 μM IBA and 0.3 μM BA for numerous gametophore production. The highest production of secondary protonema was achieved on MS/2 S/2 medium enriched with 0.1 or 0.3 μM IBA and 0.3 μM BA. Rather successfully applied micropropagation of this threatened moss species enables better knowledge of its biology and is of great value for its conservation biology and developmental research. Chemical names used: indole-3-butyric acid (IBA), N6-benzyladenine (BA), Murashige and Skoog medium (MS).
Exogenous Applications of Benzyladenine and Gibberellic Acid Inhibit Lower-leaf Senescence of Geraniums during Propagation
Authors: Currey Christopher J. , Lopez Roberto G. , Rapaka Vijay K. , Faust James E. , Runkle Erik S.
Published: February 2019

After postharvest shipping, the lower leaves of zonal geranium (Pelargonium ×hortorum) cuttings often turn chlorotic and necrotic during rooting in a propagation environment. Our objective was to quantify the efficacy of spray applications of the plant growth regulators (PGRs) benzyladenine (BA) and/or gibberellic acid (GA) at various stages in propagation to reduce lower-leaf senescence and evaluate effects on subsequent rooting. In Expt. 1, cuttings of ‘Patriot White’ geraniums were harvested and treated with BA (2.5 or 5.0 mg·L−1), BA + GA4+7 (2.5 or 5.0 mg·L−1 each), or GA3 (0.5 or 2.0 mg·L−1) either before or after a 2-day storage period simulating commercial shipping. Post-shipment application of all PGRs eliminated leaf yellowing compared with cuttings treated pre-shipment, but rooting was inhibited. In Expt. 2, the promotion of rooting from a rooting hormone preceding treatment with BA (1.25 to 5.0 mg·L−1), BA+GA4+7 (1.25 to 5.0 mg·L−1 each), or GA3 (0.25 to 2.0 mg·L−1) was evaluated on ‘Patriot White’ geranium cuttings after a 2-day simulated shipping. Applying rooting hormones increased the percentage of fully rooted cuttings treated with BA and/or GA from 16.4% to 51.8%. In Expt. 3, cuttings of different geranium cultivars from a commercial producer varied in susceptibility and suppression of leaf yellowing after BA + GA4+7 applications. We conclude that foliar applications of BA + GA4+7 can suppress lower-leaf senescence and rooting during propagation of some geranium cultivars, and the inhibition of rooting can be at least partially overcome with an application of rooting hormone.
Genetic Resources of Apricots (Prunus armeniaca L.) in Central Asia
Authors: Zaurov David E. , Molnar Thomas J. , Eisenman Sasha W. , Ford Timothy M. , Mavlyanova Ravza F. , Capik John M. , Funk C. Reed , Goffreda Joseph C.
Published: February 2019

Central Asia is a center of diversity for many important fruit and nut tree species, including wild and cultivated apricots (Prunus armeniaca L.). A wealth of apricot germplasm that expresses novel and valuable characteristics such as fruits with high soluble solids, edible kernels, glabrous skin, and diverse colors and flavors, as well as later-blooming flowers, late-maturing fruit, and drought, cold, and salt tolerance, can be found growing across this region. Since the dissolution of the Soviet Union, Central Asia has become more accessible for reciprocal germplasm exchange and scientific collaborations. Thus, opportunities now exist to obtain, study, and use a much wider diversity of Central Asian apricot germplasm in breeding efforts, which can lead to improved crop traits and ultimately an expansion of the regions where this high-value crop can be grown. To bring attention to the valuable P. armeniaca genetic resources found in Central Asia and to promote its better use, management, and preservation, a description and history of the species from a Central Asian perspective, along with recent and ongoing activities, are discussed in this article.
Carbon Isotope Discrimination, Gas Exchange, and Growth of Container-grown Conifers Under Cyclic Irrigation
Authors: Taylor Amanda J. , Fernandez R. Thomas , Nzokou Pascal , Cregg Bert
Published: February 2019

The objective of this study was to quantify the effects of cyclic irrigation on growth and physiology of container-grown conifer species in pot-in-pot (PIP) production in the upper Midwest. Trees of four conifer species (Picea glauca var. densata, Picea pungens, Abies fraseri, and Pinus strobus) were grown in 25-L containers and assigned to one of four combinations of irrigation rate (low or high) and daily irrigation cycle frequency (one or four). Irrigation rates were based on common nursery practice in the region (2 cm rainfall equivalent/day) and one-half the standard rate (1 cm rainfall equivalent/day). Cyclic irrigation increased relative height growth and relative caliper growth of Pinus strobus by over 80% and 35%, respectively, compared with once-daily irrigation. The high-rate irrigation increased relative caliper growth of Picea pungens by 40% compared with the low rate. The effects of irrigation regime on needle- or shoot-level gas exchange varied by species and date of measurement. Carbon isotope discrimination (Δ13C) of needle and wood tissue was positively correlated (r ≥ 0.64, P < 0.001) with needle conductance to water vapor (gwv) and negatively correlated (r ≤ −0.60, P< 0.001) with intrinsic water use efficiency (WUEi). Carbon isotope discrimination of wood and needle tissue decreased with the low irrigation rate, indicating increased WUEi associated with reduced gwv. Cyclic irrigation had relatively little effect on Δ13C except for Pinus strobus. Our findings suggest that carbon isotope composition of wood and needle tissue provides a sensitive and accurate representation of plant response to varying moisture availability. From a water management perspective, identifying optimal irrigation rates appears to be more important than number of daily cycles for these crops grown in the midwestern United States.
Propagation of Four Underused Native Species from Softwood Cuttings
Authors: Cartabiano Julia A. , Lubell Jessica D.
Published: February 2019

Interest in native plants for landscaping is increasing and nursery growers must expand their product offerings by adding new native species. Softwood stem cutting propagation of four underused northeastern U.S. native species [Ceanothus americanus (L.), Corylus cornuta (Marsh.), Lonicera canadensis (Bartr.), Viburnum acerifolium (L.)] was studied. V. acerifolium cuttings containing two nodes taken mid-June to mid-August rooted at nearly 100% with at least 15 roots per cutting. Exogenous auxin application did not enhance rooting of two-node V. acerifolium cuttings. Single-node V. acerifolium cutting success and quality of rooting increased with increasing concentration of auxin applied and reached a maximum of 80% rooting, whereas untreated cuttings only rooted at 53%. C. cornuta cuttings taken mid-June to mid-August rooted at greater than 85%. Hormone concentration did not affect rooting percentage for C. cornuta; however, cuttings treated with 3000 and 8000 ppm indole-3-butyric acid (IBA) had more and longer roots than untreated cuttings. June was the optimal time to collect cuttings of C. americanus (57% rooting) and L. canadensis (49% rooting), and rooting hormone did not significantly impact propagation success. C. cornuta and V. acerifolium could be propagated at a level necessary for consideration as a new commercial crop by general wholesale nurseries looking to add select native shrubs to their product lines. All four species evaluated could be viable commercial crops for nurseries that specialize in native plants.
Asian Germplasm in American Horticulture: New Thoughts on an Old Theme
Authors: Olsen Richard T.
Published: February 2019

North American horticulture cultivates an astonishing diversity of ornamental species, from nearly every floristic region, but its landscapes are dominated by temperate species drawn from eastern Asia. The East Asiatic floristic region is one of the most diverse in the world with a high level of endemism across taxonomic ranks and ancient relicts of a once widespread flora. From this, a large number of ornamental genera and species have been introduced, from either a long history of cultivation in Asia or directly from the wild, where they have since become fixtures in European and American gardens. The success of Asian germplasm in American horticulture is attributable, in part, to a shared evolutionary history, climate matching, and pre-adaptability. Continuing access to these genetic resources is now governed by national legislation and influenced by an evolving international regime of access and benefit-sharing influenced by the Convention on Biological Diversity. Furthermore, updated plant quarantine regulations have added additional requirements for the importation of foreign plant genetic resources. The newly created category within the USDA Animal and Plant Health Inspection Service (APHIS) Q37 regulations known as “not authorized pending pest risk analysis” (NAPPRA) restricts the import of plants for planting that may harbor pests or become pests that are not already established within the United States. To this end, scientists involved in the collection or use of Asian plant genetic resources are affected by recent changes in international and national laws, regulations, and access and benefit-sharing regimes.
Evaluation of the Impacts of Salinity on Biomass and Nutrient Levels of Agave Species with Agricultural Potential in Semiarid Regions
Authors: Bergsten Steven J. , Koeser Andrew K. , Stewart J. Ryan
Published: February 2019

Long used as a source of food, beverages, and fiber, Agave exhibits potential to be cultivated as a crop to produce alternative sweeteners, bioenergy, and a variety of other end uses. However, little is known regarding the productivity levels of Agave when grown in saline soils in semiarid regions. Hydroponic experiments were carried out to evaluate the effects of salinity on biomass accumulation and nutrient levels of young plants of Agave parryi, Agave utahensis ssp. kaibabensis, Agave utahensis ssp. utahensis, and Agave weberi. Salinity treatments (0.6, 3.0, 6.0, and 9.0 dS·m−1) were imposed in each experiment. Both subspecies of A. utahensis were sensitive to salt treatments. In the higher salinity treatments, A. utahensis ssp. utahensis exhibited high mortality; both subspecies had lower plant dry weights. Agave parryi was more tolerant, but experienced a decrease in plant dry weight in the 9.0 dS·m−1 treatment. The biomass of A. weberi was unaffected by any level of salinity. Calcium, Mg, S, and Mn levels decreased in both A. parryi and A. weberi at higher salinity levels. Potassium and P levels in A. parryi decreased in the higher salt treatments. Decreases in nutrients were not severe enough to cause any apparent nutrient deficiencies in A. parryi and A. weberi. Agave parryi and A. weberi tolerated salinity at higher levels than expected, and may show promise for cultivation in saline soils.
Resistance to Papaya ringspot virus-Watermelon Strain (PRSV-W) in the Desert Watermelon Citrullus colocynthis
Authors: Levi Amnon , Coffey John , Massey Laura , Guner Nihat , Oren Elad , Tadmor Yaakov , Ling Kai-shu
Published: February 2019

The bitter desert watermelon, Citrullus colocynthis (L.) Schrad is a wild species valuable for biotic and abiotic stress resistance that could be exploited for improving watermelon cultivars [Citrullus lanatus (Thunberg) Matsum & Nakai var. lanatus]. The objective of this study was to survey and identify C. colocynthis accessions displaying resistance to the Papaya ringspot virus-watermelon strain (PRSV-W). Thirty-one accessions of C. colocynthis, collected in Africa, the Middle East, southwest Asia, and India were evaluated for PRSV-W resistance. Of these 31 accessions, 4 U.S. Plant Introduction (PI) accessions, including 525080 (collected in Qena, Egypt) and PI 537277, PI 652554, and Griffin 14201 (collected at the northern Indian desert of Rajasthan and the neighboring region of Punjab, Pakistan) showed high resistance to PRSV-W. Plants of these four resistant PIs were self-pollinated to produce S1 and S2 seeds that continued to maintain the high levels of PRSV resistance. Since there is a wide genetic distance between watermelon cultivars and C. colocynthis, we performed crosses and backcrosses with watermelon cultivars, including ‘Charleston Gray’ and ‘Sugar Baby’ to produce viable seed that would be useful in the development of genetic populations and in introducing the resistance into watermelon cultivars.
Weed Management, Training, and Irrigation Practices for Organic Production of Trailing Blackberry: III. Accumulation and Removal of Aboveground Biomass, Carbon, and Nutrients
Authors: Dixon Emily K. , Strik Bernadine C. , Bryla David R.
Published: February 2019

Relatively little is known about aboveground nutrient content of organic blackberry, and there is no published work on total carbon (C) content. Treatment effects on biomass, C, and nutrient content, accumulation, and removal were assessed over 2 years in a mature organic trailing blackberry (Rubus L. subgenus Rubus, Watson) production system that was machine harvested for the processed market. Treatments included two irrigation options (no irrigation after harvest and continuous summer irrigation), three weed management strategies (weed mat, hand-weeded, and nonweeded), and two primocane training times (August and February) in two cultivars (Black Diamond and Marion). Floricanes comprised an average of 45% of the total aboveground plant dry biomass, while primocanes and fruit comprised 30% and 25%, respectively. Depending on the treatment, the total aboveground dry biomass accumulation over the course of the season was 5.0–6.5 t·ha−1 per year, while C stock of the planting was an estimated 0.4–1.1 t·ha−1 in late winter. Carbon accounted for ≈50% of the dry biomass of each aboveground plant part, including primocanes, floricanes, and fruit. Weed management had the largest impact on plant biomass and nutrient content. No weed control reduced aboveground dry biomass, the content of nutrients in the primocanes, floricanes, and fruit, and the annual accumulation of dry biomass and nutrients, whereas use of weed mat resulted in the most dry biomass and nutrient content. Nutrient accumulation was similar between the cultivars, although February-trained ‘Marion’ plants had a greater removal of most nutrients in 2014 than the year prior. The amount of nitrogen (N) removed in the fruit was 22, 18, and 12 kg·ha−1 for weed mat, hand-weeded, and nonweeded plots, respectively, in 2013. In 2014, ‘Marion’ and ‘Black Diamond’ differed in N removed in harvested fruit when grown with weed mat at 18 and 24 kg·ha−1, respectively, whereas there was no cultivar effect when plants were grown in hand-weeded or nonweeded plots. Plots with weed mat tended to have the most nutrients removed through harvested fruit in both years. In 2014, N removal from August-trained ‘Marion’ was 5 kg·ha−1 N less than the other training time and cultivar combinations. Plants that were irrigated throughout the summer accumulated more dry biomass, N, potassium (K), magnesium (Mg), sulfur (S), boron (B), and copper in one or both years than those that received no irrigation after fruit harvest. The irrigation treatment had inconsistent effects on nutrient content of each individual plant part between the two years. Removal of nutrients was often higher than what was applied through fertilization, especially for N, K, and B, which would eventually lead to depletion of those nutrients in the planting.
Weed Control and Radish (Raphanus sativus) Response to S-metolachlor on Organic Soils
Authors: Odero Dennis C. , Fernandez Jose V. , Havranek Nikol
Published: February 2019

Field experiments were conducted to determine weed control and radish (Raphanus sativus) response to S-metolachlor on organic soil in the Everglades Agricultural Area (EAA) using a dose–response bioassay. S-metolachlor was applied preemergence at 0.35, 0.7, 1.4, 2.8, 5.6, and 11.2 kg·ha−1. The rate of S-metolachlor required to provide 90% weed control (ED90) and result in 5% and 10% radish injury were determined by fitting a three-parameter log-logistic model. The ED90 values for common lambsquarters, spiny amaranth, and fall panicum control were 2.7, 1.6, and 1.2 kg·ha−1 of S-metolachlor, respectively, at 14 days after treatment (DAT). At 28 DAT, the ED90 values were 3.8, 1.9, and 1.5 kg·ha−1 of S-metolachlor, respectively. Injury on radish increased as S-metolachlor rates increased with maximum injury of 24% and 19% at 14 and 28 DAT, respectively. S-metolachlor at 2.1 and 3.1 kg·ha−1 at 14 DAT and 2.6 and 3.7 kg·ha−1 at 28 DAT would result in 5% and 10% radish injury, respectively. Radish yield decreased with increasing rates of S-metolachlor. At the proposed S-metolachlor use rate of 1.4 kg·ha−1 for root crops, radish yield was 80% of the weed-free yield probably resulting from competition from common lambsquarters, which was controlled 74%. These results show that preemergence S-metolachlor would provide effective control of spiny amaranth and fall panicum in radish on organic soils of the EAA at the proposed use rate for root crops while about three times the proposed use rate would be required to provide effective common lambsquarters control. This implies that infestation of common lambsquarters on radish fields on organic soils will not be effectively controlled by S-metolachlor at the proposed use rate resulting in yield reduction.
Micropropagation of Turbinicarpus valdezianus (Möeller) Glass & Foster (Cactaceae) an Endemic Cactus in Northern Mexico
Authors: Palacios Alejandro Martínez , Navarro Raúl Cárdenas , Hernández Ortega Diana Beatriz , Avila Víctor Chávez
Published: February 2019

An in vitro clonal propagation protocol based on axillary bud development was generated for Turbinicarpus valdezianus. An efficient multiplication rate was obtained using either longitudinal or apical explants from in vitro germinated seedlings. The proliferation capacity of these explants was evaluated by testing the single and interaction effects of five concentrations of 6-furfurylaminopurine (KIN) (0.00, 2.32, 4.64, 9.28, and 18.56 µm) and three concentrations of α-naphthalenacetic acid (NAA) (0.00, 0.54, and 2.70 µm), using Murashige and Skoog (MS) as basal medium. Statistical analysis showed that the highest average shoot proliferation of T. valdezianus was recorded with 9.28 µm of KIN, producing 11.75 and 4.50 plantlets per initial explant, for apical and lateral explants, respectively. Addition of NAA to the medium had an inhibitory effect on shoot proliferation for both explant types. The developed shoots in 9.28 µm of KIN and plant growth regulator (PGR)-free treatments were used for a rooting subculture phase. These shoots were then transferred to PGR-free MS medium, resulting in statistically significant different rooting frequencies of 78% and 97%, respectively. When transplanted in soil, the rooted shoots showed an average survival rate of 90%, without any significant statistical differences between treatments. This propagation protocol has the capacity to produce near to 21 plantlets per seedling in 27 weeks, i.e., 11.78 and 9.00 plantlets per apical and lateral explants, respectively, without callus or adventitious shoot formation. These features made it highly attractive as an in vitro clonal propagation method for T. valdezianus plants and the later implementation of a rescue program for threatened wild populations of this cacti species.
Consequences of Deficit Irrigation and Crop Load Reduction on Plant Water Relations, Yield, and Quality of ‘Ambrosia’ Apple
Authors: Neilsen Denise , Neilsen Gerry , Guak Sunghee , Forge Tom
Published: February 2019

Uncertain water supplies resulting from changing climatic conditions in western North America led to this investigation of the role of crop load reduction in maintaining performance of high-density ‘Ambrosia’ apple (Malus ×domestica) on M.9 rootstock. A split-plot experimental design was imposed for three growing seasons (2007–09) with six replicates of four main plot irrigation treatments and three crop load subplots comprised of three trees. Four season-long irrigation (Irr) treatments were applied through 2 × 4 L·h−1 drip emitters per tree and included Irr1) control [100% evapotranspiration (ET) replacement], Irr2) 50% ET replacement, Irr3) 50% ET replacement to half the emitters, and Irr4) an increasingly severe treatment commencing at 50% ET replacement (once every 2 days) in 2007 and progressing to 25% and 18% ET replacement, 2008–09. Three target crop loads were established annually, 4–5 weeks after bloom as low (2.5, 3, and 3.75), medium (4.5, 6, and 7.5), and high (9, 12, and 15) fruit/cm2 trunk cross-sectional area (TCSA) 2007–09, respectively, by hand thinning around 4 weeks after bloom. Volumetric soil moisture contents generally reflected the amount of water applied and ranged from 20% for control (Irr1) to <10% for Irr4. Both irrigation and crop load treatments affected midday stem water potential more than leaf photosynthesis and stomatal conductance (gS). By the 2nd and 3rd year stem potential values for irrigation treatments ranged from a maximum of −1.0 to −1.3 MPa for Irr1 to minimums ≤-2.0 MPa for Irr4. gS decreased as midday stem potential decreased, but at any given stem potential value was greater at high crop loads, presumably in response to an increased demand for photosynthates. Fruit size decreased as crop load increased, but as irrigation deficits became more severe, fruit size was more closely correlated with stem water potential than gS. Consequently, fruit size was controlled by two mechanisms, competition for photosynthates and the effects of plant water status on gS. Negative linear relationships between crop load and average fruit size were used to determine the crop load required to produce an average fruit size of 200 g at different irrigation deficits. It was not possible to achieve adequate fruit size when applications were very low, as at 18% to 25% ET in Irr4. Crop load reduction around mid-June had no negative consequences for fruit quality, enhancing fruit color, and soluble solids concentration (SSC) and did not affect the incidence of sunburn, internal breakdown or bitter pit at harvest.
Arbuscular Mycorrhizal Pecan Seedlings Alleviate Effect of Restricted Water Supply
Authors: Babuin Maria Florencia , Echeverria Mariela , Menendez Ana Bernardina , Maiale Santiago Javier
Published: February 2019

Pecan [Carya illinoinensis (Wangenheim) K. Koch] seedlings were inoculated with the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis to evaluate if these organisms establish a symbiotic association and if such an association exerts an influence on restricted water supply response by the plant. After fungal inoculation, plants were grown in a growth chamber. All plants were effectively mycorrhized, with an average infection of 32% for each root. Mycorrhizal colonization led to increased stem height in pecan plants. On restricted water supply, mycorrhizal pecan seedlings presented a higher number of lateral roots and more stem height and diameter than nonmycorrhizal ones. Besides, nonmycorrhizal plants showed an increase in proline content with regard to mycorrhizal ones. Depending on the results, pecan seedlings can be efficiently colonized with the mycorrhizal fungus R. irregularis, under controlled conditions proposed in this work, whereas the symbiotic association with the fungus mitigates restricted water supply.
Response of ‘Italian Riesling’ Leaf Nitrogen Status and Fruit Composition (Vitis vinifera L.) to Foliar Nitrogen Fertilization
Authors: Janjanin Danijela , Karoglan Marko , Ćustić Mirjana Herak , Bubola Marijan , Osrečak Mirela , Palčić Igor
Published: February 2019

Two-year study was conducted on Italian Riesling cultivar with the aim to compare the effect of foliar sprays with different nitrogen forms on grapevine leaf N status, yield, and nitrogen compounds in grape juice. Treatments included no fertilization (control), soil NPK treatment, and three foliar treatments [amino acids, urea, ammonia (NH4+)/nitrate] applied four times during season, also treated with soil NPK. The application of 1% w/v urea significantly increased leaf total leaf N content in the second year of study. However, there were no effects on N compounds in grape juice, since changes in free amino nitrogen (FAN), NH4+, and consequently yeast assimilable nitrogen (YAN) were not consistent among the treatments and experimental years. Although increase of vine leaf N status was achieved by 1% w/v urea, additional modifying of application time (by moving it closer to veraison) is needed, with the aim to increase N compounds in grape juice as well.