bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative Distribution of Candidatus Liberibacter asiaticus in the Aerial Parts of the Huanglongbing-infected Citrus Trees in Texas
Authors: Kunta Madhurababu , da Graça John V. , Malik Nasir S.A. , Louzada Eliezer S. , Sétamou Mamoudou
Published: February 2019

The Asian citrus psyllid, Diaphorina citri Kuwayama, one of the known vectors for citrus greening disease or Huanglongbing (HLB) pathogens, has been present in Texas for over a decade, but the detection of the disease is recent. HLB has been confirmed in only two adjacent commercial citrus groves of grapefruit and sweet orange. A study was conducted to compare the population of Candidatus Liberibacter asiaticus (CLas) cells in different plant parts including peduncle, columella, leaves, seeds, young shoots, flower buds, flowers, and bark of 6-year-old known infected grapefruit and sweet orange trees. The bacterial population was estimated using a previously described grand universal regression equation Y = 13.82 – 0.2866X, where Y is the log of the target copy number and X is the Ct (threshold cycle) of the assay. Except for bark tissue, there was no significant difference in the concentration of CLas cells in other plant parts between the two cultivars. Within the cultivar, the bacterial concentration also varied with the plant part, with peduncle, columella, midrib having significantly higher titer of CLas compared with other plant parts. The obtained results here are in agreement with previous studies conducted on Florida samples, but the consistently lowest bacterial titer recorded in young shoots, leaf blade, and especially leaf margins relative to the midrib has never been previously reported.
The Effects of Individual Environmental Concerns on Willingness to Pay for Sustainable Plant Attributes
Authors: Khachatryan Hayk , Campbell Ben , Hall Charles , Behe Bridget , Yue Chengyan , Dennis Jennifer
Published: February 2019

This study adds to the consumer choice literature by linking consumers’ environmental concern (EC) orientations (egoistic, altruistic and biospheric) to willingness to pay (WTP) premiums for proenvironmental attributes. Results from a mixed-ordered probit model showed that individuals were willing to pay a premium for energy-saving production practices ($0.131), non-plastic containers such as compostable ($0.227), plantable ($0.122), and recyclable ($0.155), and locally grown plants ($0.222). Individuals scoring high on the EC scale expressed higher WTP across all attributes—$0.148 for energy-saving practices, $0.288 for locally grown plants, and $0.255, $0.143, and $0.175 for compostable, plantable, and recyclable containers, respectively. Using the results, we discuss the practical implications for nursery and garden stores (i.e., communicating product attributes related information to consumers).
The Chloroplast psbK-psbI Intergenic Region, a Potential Genetic Marker for Broad Sectional Relationships in Anthurium
Authors: Suzuki Jon Y. , Matsumoto Tracie K. , Keith Lisa M. , Myers Roxana Y.
Published: February 2019

Nuclear and chloroplast genetic markers have been extensively used for plant identification and molecular taxonomy studies. The efficacy of genetic markers to be used as DNA barcodes is under constant evaluation and improvement with identification of new barcodes that provide greater resolution and efficiency of amplification for specific species groups as well as distantly related plants. In this study, chloroplast DNA genetic markers for Anthurium, the largest genus in the Araceae family, were adapted from chloroplast markers previously designed for Lemna minor, a member of the same plant family. Primers for chloroplast region trnH-psbA, previously used for molecular systematic studies in Anthurium, as well as primers for the rpoB, rpoC1, psbK-psbI, matK, rbcL, and atpF-atpH regions, all located within the large single copy sequence in the chloroplast genome, were evaluated and found to efficiently amplify target sequences when using DNA of varied quality and concentration extracted from silica-dried leaves of selected accessioned species of Anthurium. The trnH-psbA, psbK-psbI, and atpF-atpH intergenic region primers were further evaluated using Anthurium species spanning different subgeneric groups. Of the intergenic region primers tested, psbK-psbI primers were the most robust, yielding well-defined amplicons across Anthurium species that were consistent, with exceptions, within sectional groupings. Application of the psbK-psbI region amplicon as a visual marker for surveying sectional relationships in Anthurium is novel and serves as a model for the development of a diagnostic method for genotyping plants and testing for sample integrity from among species or germplasm collections. This work further demonstrates the use of dried plant tissue banks as a genetic reference and information resource to support basic research as well as ornamental plant characterization and improvement.
Volatile Profile Comparison of USDA Sweet Orange-like Hybrids versus ‘Hamlin’ and ‘Ambersweet’
Authors: Bai Jinhe , Baldwin Elizabeth , Hearn Jack , Driggers Randy , Stover Ed
Published: February 2019

Six ‘Ambersweet’-derived hybrids, similar to sweet orange fruit size, color, and taste and potential as new sweet orange cultivars, were selected to determine their fruit categorization by comparison of their volatile profiles with the parent and ‘Hamlin’, a typical sweet orange. All hybrids are at least ½ sweet orange and varying amounts of mandarin, grapefruit, Poncirus trifoliata, and sour orange in each pedigree. In total, 135 volatiles were detected in the eight hybrid lines/commercial cultivars over two harvests, and 20 compounds were detected in all samples, including terpenes (limonene, β-myrcene, α-pinene, α-terpinene, α-terpineol, and linalool), esters (ethyl butanote, ethyl pentanoate, and ethyl acetate), aldehydes (acetaldehyde, hexanal, and nonanal), and alcohols (ethanol and hexanol). Total abundance of volatiles in January-harvested fruits averaged 30% higher than for fruits of the same trees harvested in November. ‘Ambersweet’ contained the highest total amount of volatiles (mainly as a result of very high levels of monoterpenes), and of them, nootkatone and six other compounds were not detected in any of the hybrids, and some of them were also not detected in ‘Hamlin’. On the other hand, 12 compounds, including pentanal, ethyl 2-butenoate, and ethyl nonanoate, were not detected in ‘Ambersweet’ but were found in ‘Hamlin’ and some of the hybrids. Cluster analysis separated the cultivar/hybrid and harvest time combinations into three clusters. FF-1-76-50, FF-1-76-52 and January FF-1-75-55, all with the same parents (‘Ambersweet’ × FF-1-30-52), were close to FF-1-65-55, but they were separated from ‘Hamlin’ and further separated from ‘Ambersweet’. The cluster containing ‘Hamlin’ has three subclusters: January ‘Hamlin’ and November FF-1-74-14, a hybrid with one-eighth P. trifoliata, which includes a slight off-flavor frequently found in P. trifoliata hybrids, independent of each other, and both were separated from a group of November ‘Hamlin’, FF-1-64-97, and FF-1-75-55. The cluster containing ‘Ambersweet’ included January FF-1-64-97. A principle component analysis (PCA) separated ‘Ambersweet’ from all hybrids and ‘Hamlin’ along the PC1 axis and separated November harvests from January harvests along PC2. This volatile analysis supports the classification of the hybrids as sweet orange.
Ploidy Levels and Pollen Stainability of Lantana camara Cultivars and Breeding Lines
Authors: Czarnecki David M. , Hershberger Amanda J. , Robacker Carol D. , Clark David G. , Deng Zhanao
Published: February 2019

Lantana camara L., a popular nursery and landscape plant, is categorized as an invasive species in Florida, because it produces viable pollen and cross-pollinates with the native species Lantana depressa Small. The invasive potential of L. camara is a challenging issue for the nursery and landscape industry, so sterile non-invasive cultivars are needed to replace fertile invasive ones. This study aimed to determine the ploidy level and male fertility of both commercial L. camara cultivars and breeding lines to identify male-sterile cultivars and assess the effectiveness of sterile triploid production in L. camara. A polyploid series was identified among 32 L. camara cultivars and breeding lines. Male fertility, based on pollen stainability, varied widely among the cultivars/breeding lines. Ploidy level was the most important factor determining L. camara pollen stainability/male sterility. On average, diploids exhibited the highest pollen stainability (64.6%) followed by tetraploids (45.1%), pentaploids (34.6%), and hexaploids (18.0%). Triploids showed the lowest pollen stainability (9.3%), suggesting that generating triploids would be an effective genetic approach to producing sterile L. camara and reducing its pollen-mediated invasiveness. Pollen stainability of triploid cultivars, Balandpawn (LandmarkTM Pink Dawn PP15,516), Lemon Drop, Miss Huff, New Gold, New Red Lantana, Red Butler, Red Spread Lantana, Samson Lantana, and Sunset Lantana was consistently below 10%. A number of triploid cultivars had pollen stainability approaching 20% to 30%, indicating a necessity for careful examination and screening of newly produced triploids to ensure high sterility in selected triploids. Pollen stainability variation was observed within ploidy levels, implying the existence of other genetic and environmental factors that influence the pollen stainability/male fertility of L. camara. Results from this study suggest that there is excellent potential to develop genetically sterile cultivars in L. camara for the U.S. nursery and landscape industry.
The Influence of Deficit Irrigation on Growth, Ornamental Quality, and Water Use Efficiency of Three Potted Bougainvillea Genotypes Grown in Two Shapes
Authors: Cirillo Chiara , Rouphael Youssef , Caputo Rosanna , Raimondi Giampaolo , De Pascale Stefania
Published: February 2019

Bougainvillea is widely used as flowering shrub in gardening and landscaping in the Mediterranean region characterized by limited water supply. The evaluation of deficit irrigation as a possible technique to improve water productivity and selection of genotypes that can better withstand soil water deficits are essential for sustainable production. A greenhouse experiment was conducted to determine the effects of deficit irrigation on three potted Bougainvillea genotypes [B. glabra var. Sanderiana, B. ×buttiana ‘Rosenka’, B. ‘Lindleyana’ (=B. ‘Aurantiaca’)] grown in two shapes, globe and pyramid, on agronomical and physiological parameters. Irrigation treatments were based on the daily water use (100%, 50%, or 25%). The shoot, total dry biomass, leaf number, leaf area, and macronutrient [nitrogen (N), phosphorus (P), and potassium (K)] concentration decreased in response to an increase in water stress with the lowest values recorded in the severe deficit irrigation (SDI) treatment. At 160 days after transplanting (DAT), the percentage of total dry biomass reduction caused by irrigation level was lower in B. ×buttiana ‘Rosenka’ compared with B. glabra var. Sanderiana and B. ‘Lindleyana’ (=B. ‘Aurantiaca’). At 160 DAT, the flower index increased in response to an increase in water stress with the highest values recorded under both moderate deficit irrigation (MDI) and SDI for B. ×buttiana ‘Rosenka’. The biomass water use efficiency (WUE) increased under water stress conditions with the highest values recorded in B. glabra var. Sanderiana and B. ×buttiana ‘Rosenka’ grown under MDI (average 1.43 and 1.25 g·L−1, respectively) and especially with SDI (average 1.68 and 1.36 g·L−1, respectively). A number of tolerance mechanisms such as increase in stomatal resistance, decrease in leaf water potential, and decrease in leaf osmotic potential have been observed, especially under SDI. The MDI treatment can be used successfully in Bougainvillea to reduce water consumption while improving the overall quality and WUE, whereas the genotypes B. glabra var. Sanderiana and B. ×buttiana ‘Rosenka’ could be considered suitable for pot plant production.
Microclimate Modification and Insect Pest Exclusion Using Agronet Improve Pod Yield and Quality of French Bean
Authors: Gogo Elisha Otieno , Saidi Mwanarusi , Ochieng Jacob Mugwa , Martin Thibaud , Baird Vance , Ngouajio Mathieu
Published: February 2019

French bean [Phaseolus vulgaris (L.)] is among the leading export vegetable in Africa, mostly produced by small-scale farmers. Unfavorable environmental conditions and heavy infestations by insect pests are among the major constraints limiting production of the crop. Most French bean producers grow their crop in open fields outdoors subject to harsh environmental conditions and repeatedly spray insecticides in a bid to realize high yield. This has led to rejection of some of the produce at the export market as a result of stringent limits on maximum residue levels. Two trials were conducted at the Horticulture Research and Teaching Field, Egerton University, Kenya, to evaluate the potential of using agricultural nets (herein referred to as agronets) to improve the microclimate, reduce pest infestation, and increase the yield and quality of French bean. A randomized complete block design with five replications was used. French bean seeds were direct-seeded, sprayed with an alpha-cypermethrin-based insecticide (control), covered with a treated agronet (0.9 mm × 0.7 mm average pore size made of 100 denier yarn knitted into a mesh impregnated with alpha-cypermethrin), or covered with an untreated-agronet (0.9 mm × 0.7 mm average pore size made of 100 denier yarn knitted into a mesh not impregnated with insecticide). Alpha-cypermethrin and agronets were manufactured by Tagros Chemicals (India) and A to Z Textile Mills (Tanzania), respectively. Covering French bean with the agronets modified the microclimate of the growing crop with air temperature increased by ≈10%, relative humidity by 4%, and soil moisture by 20%, whereas photosynthetic active radiation (PAR) and daily light integral (DLI) were decreased by ≈1% and 11.5%, respectively. Populations of silverleaf whitefly [Bemisia tabaci (Gennadius)] and black bean aphids [Aphis fabae (Scopoli)] were reduced under agronet covers as contrasted with control plots. Furthermore, populations of both pests were reduced on French bean grown under impregnated agronets compared with untreated agronets, but only on three of the five sampling dates [30, 44, and 72 days after planting (DAP)] for silver leaf whitefly or at only one of the five sampling dates (30 DAP) for black bean aphid. Covering French bean with agronets advanced seedling emergence by 2 days and increased seedling emergence over 90% compared with control plots. French bean plants covered with both agronet treatments had faster development, better pod yield, and quality compared with the uncovered plants. These findings demonstrate the potential of agronets in improving French bean performance while minimizing the number of insecticide sprays within the crop cycle, which could lead to less rejection of produce in the export market and improved environmental quality.
An Evaluation of U.S. Peach Producers’ Trait Prioritization: Evidence from Audience Surveys
Authors: Yue Chengyan , Gallardo R. Karina , Luby James J. , Rihn Alicia L. , McFerson James R. , McCracken Vicki , Gradziel Tom , Gasic Ksenija , Reighard Gregory L. , Clark John , Iezzoni Amy
Published: February 2019

We conducted audience surveys at three major peach producer meetings across the United States. We found that the relative importance assigned to fruit quality and tree traits by producers varied across producers’ end markets. Fresh peach producers indicated fruit flavor and size were the most important fruit quality traits, whereas processed peach producers viewed fruit size, fruit firmness, and absence of split pits as being the most important traits for a successful peach cultivar. These results have potential to ensure that peach breeding programs are consonant with fresh and processed peach producers’ needs for fruit and tree traits.
Controlled-release Fertilizer Placement Affects the Leaching Pattern of Nutrients from Nursery Containers during Irrigation
Authors: Hoskins Tyler C. , Owen James S. , Niemiera Alex X.
Published: February 2019

Maximizing nutrient use efficiency while minimizing nutrient leaching and non-point source contributions from containerized crop production systems are goals of researchers and growers. These goals have led to irrigation and crop nutrition management practices that reduce fertilizer and irrigation expenditures and reduce the nutrient load into the environment. However, one area that has received little attention, and may lead to the further refinement of crop management practices, is how dissolved nutrients (solutes) move through a substrate while water is being applied during irrigation. A study was conducted to characterize the effect of a controlled-release fertilizer (CRF) placement method on changes in leachate nutrient concentration throughout an irrigation event and to evaluate these changes at different times throughout a production season. A pine bark:sand (9:1, by volume) substrate was placed in 2.7-L nursery containers (fallow) and was treated with topdressed, incorporated, and dibbled CRF or did not receive CRF. The nutrient leaching pattern was evaluated at 3, 9, and 15 weeks after potting (WAP). Leachate nutrient concentration was the highest in the first 50 mL of effluent and steadily diminished as irrigation continued for the topdressed, incorporated, and the no CRF treatments. Effluent nutrient concentration from containers with dibbled CRF generally increased throughout the first 150 mL of effluent, plateaued briefly, and then diminished. The nutrient load that leached with higher volumes of irrigation water was similar between incorporated and dibbled CRF placements. However, the unique nutrient leaching pattern observed with the dibbled CRF placement method allowed for a lower effluent nutrient load when leaching fractions are low. Dibble may be an advantageous CRF placement method that allows for the conservation of expensive fertilizer resources and mitigates non-point source nutrient contributions by reducing undesired nutrient leaching during irrigation.
Screening of Blackberry and Raspberry Cultivars for Susceptibility to Fire Blight Disease in Turkey
Authors: Bastas Kubilay Kurtulus , Sahin Fikrettin
Published: February 2019

Fire blight is the most destructive bacterial disease of rosaceous plants containing berry fruits. The present study was conducted to determine host resistance among the extensively grown raspberry cultivars (Willamette, Rubin ve Aksu Red, Heritage, and Royalty) and blackberry cultivars (Bursa-1, Bursa-2, Bursa-3, Chester, Loch Ness, and Jumbo) to Erwinia amylovora, which is the causal agent of the fire blight disease. In the greenhouse and field experiments, the plants were inoculated with two virulent strains of E. amylovora to evaluate whether cultivar–strain interactions exist. Disease index (%) and disease severity (%) were determined regarding diseased plant symptoms and classified into four susceptibility groups (HR, MR, S, and HS). Raspberry cultivar Willamette and blackberry cultivar Bursa-1 appeared to be highly susceptible with average 50% disease severity ratings. One of the raspberry cv., Royalty, was moderately resistant with an average 25% disease severity rating. This is the first study determining resistance reactions of native and common blackberry and raspberry varieties against fire blight in Turkey. As the cultivation of berries expands to new regions and larger acreages, a serious outbreak of fire blight may be potentially much more destructive in the future. Therefore, phytosanitary measures are needed to prevent any further spread of the bacterium to new blackberry- and raspberry-growing areas. The study will serve as an initial guide for growers and breeders for their appropriate raspberry and blackberry selections in Turkey.
Effect of Temperature on Anthocyanin Synthesis and Ethylene Production in the Fruit of Early- and Medium-maturing Apple Cultivars during Ripening Stages
Authors: Honda Chikako , Bessho Hideo , Murai Mari , Iwanami Hiroshi , Moriya Shigeki , Abe Kazuyuki , Wada Masato , Moriya-Tanaka Yuki , Hayama Hiroko , Tatsuki Miho
Published: February 2019

The objective of this study was to investigate the effects of temperature treatments on anthocyanin accumulation and ethylene production in the fruit of early- and medium-maturing cultivars that were harvested early during fruit ripening. We first investigated the effects of various temperature treatments on anthocyanin accumulation in detached apples of ‘Tsugaru’, ‘Tsugaru Hime’, ‘Akane’ and ‘Akibae’ using an incubator. Three years of experiments demonstrated that at harvest, the lower-temperature treatments induced anthocyanin accumulation in ‘Tsugaru’, ‘Tsugaru Hime’, and ‘Akibae’ fruits, whereas the increases in anthocyanin accumulation under the 25 °C treatment were similar to those under the 15 and 20 °C treatments in ‘Akane’ fruit. The rate of ethylene production did not increase substantially during the temperature treatments in any of the four cultivars, except after the treatments of ‘Tsugaru’ fruit at harvest. The inhibition of ethylene action by the application of 1-methylcyclopropene (1-MCP) to detached fruits at harvest suppressed anthocyanin development under 15 and 20 °C temperature treatments in ‘Tsugaru’, ‘Tsugaru Hime’, and ‘Akibae’, but not in ‘Akane’. In the second experiment, we investigated changes in the anthocyanin concentration in attached fruit of ‘Misuzu Tsugaru’ under different temperature conditions in a greenhouse. At harvest, the anthocyanin concentration in fruit under the hotter climatic condition (29 °C 12 hours/19 °C 12 hours) was lower than that under the control condition (25 °C 12 hours/15 °C 12 hours). During the last week before harvest, anthocyanin development proceeded rapidly in fruit skin not only under the control condition, but also under the hotter climatic condition. The rapid accumulation of anthocyanin in the fruit skin of ‘Misuzu Tsugaru’ at harvest under a relatively high temperature (25 °C) condition was confirmed by the experiment using an incubator. At harvest, the maximum level of ethylene production in fruits sampled from trees grown under the hotter climatic condition was 9-fold higher than that in fruits from trees grown under the control condition. These results indicate that the comparison of pigmentation potential after the 15 or 25 °C treatments using detached fruit was effective for estimating anthocyanin accumulation in fruit skins under hotter climatic conditions in early- and medium-maturing cultivars that were harvested early and that a hotter climatic condition during ripening increased ethylene production in apple fruit after harvest.
Effects of Acute Moisture Stress on Creeping Bentgrass Cuticle Morphology and Associated Effects on Foliar Nitrogen Uptake
Authors: Bethea Frank G. , Park Dara , Mount Andrew , Menchyk Nick , Liu Haibo
Published: February 2019

Foliar fertilization is a common practice to deliver nitrogen (N) to turfgrasses. The mechanisms of foliar applied nutrient uptake, particularly the effects of the leaf cuticle layer, have not been clearly characterized in turfgrasses. The objectives of this study were to determine the effect of acute moisture stress on the morphological and compositional components of the cuticle and the resulting effect on foliar-applied N absorption. Creeping bentgrass (Agrostis stolonifera L.) was irrigated to return 100% or 50% evapotranspiration rate (ET) for 10 days to examine cuticular modifications resulting from acute moisture stress and foliar N uptake with and without a surfactant. Acute water stress increased the total cuticle wax by 11%, mostly as a result of the compound 1-hexacosanol, and increased crystalloid density creating a rougher leaf surface. The 50% ET treatment significantly reduced recovery of 15N-labeled urea by 14%, which was attributed to the increased total cuticle wax and crystalloid density making the surface less receptive to foliar applications. The surfactant addition to the urea solution increased 15N-labeled urea recovery by 21% and absorption of 15N in 50% ET plants to levels consistent with the 100% ET plants. These results suggest that acute moisture stress modifies the cuticle wax load and morphology, thereby hindering foliar absorption; however, a surfactant addition can help to mitigate this effect and increase absorption of N.
Identification, Nomenclature, Genome Sizes, and Ploidy Levels of Liriope and Ophiopogon Taxa
Authors: Lattier Jason D. , Ranney Thomas G. , Fantz Paul R. , Avent Tony
Published: February 2019

Liriope Lour. and Ophiopogon Ker Gawl., collectively known as liriopogons, represent important evergreen groundcovers grown throughout the world for their ornamental features and medicinal qualities. As a result of the diversity of desirable traits and evidence of wide hybridization, there is considerable potential for breeding and improvement of liriopogons. However, confusion over taxonomy and proper identification and lack of information on ploidy levels and cytogenetics of individual clones and cultivars have constrained breeding efforts. Objectives of this study were to validate the identification and nomenclature and determine genome sizes and ploidy levels for an extensive reference collection of species and cultivars of liriopogons. Identification was accomplished using existing keys, nomenclature was corrected, and numerous accessions were reassigned based on morphology. Genome sizes were determined by flow cytometry. Ploidy levels for each species were confirmed by traditional cytology. Results confirmed a basic chromosome number of x = 18 for liriopogons with aneuploidy, polyploidy, and cytochimeras found in some cases. The Liriope examined included diploids (L. graminifolia, L. longipedicellata, L. minor, and some of the L. platyphylla), tetraploids (L. muscari and the remaining L. platyphylla), and hexaploids (L. exiliflora and L. spicata). The Ophiopogon studied included diploids (O. intermedius, O. jaburan, O. planiscapus, and O. umbraticola) and a tetraploid/hypotetraploid species (O. japonicus). Monoploid (1Cx) genome sizes varied by genus and species with 1Cx values ranging from 4.27 pg in L. exiliflora to 8.15 pg in O. jaburan. These results clarify nomenclature and taxonomy and provide specific information on genome sizes and ploidy levels of cultivated liriopogons. This information and associated reference collection will aid future taxonomic revisions and enhance efforts to develop new cultivars of liriopogons.
Photosynthetic Acclimation of Sweet Pepper Plants to Screenhouse Conditions
Authors: Kitta Evagelini , Katsoulas Nikolaos , Kandila Anna , González-Real Maria M. , Baille Alain
Published: February 2019

Leaf gas exchange and photosynthetic light acclimation of sweet pepper leaves were investigated in a Mediterranean area (central Greece) in the open field and in three screenhouse nets differing in color, shading intensity (SI), and porosity from May to Oct. 2011. The screenhouse nets were two insect-proof white nets (W13 and W34, SI = 13% and 34%, respectively) and a green shading net (G36, SI = 36%). Leaf net CO2 assimilation (An), transpiration rate (E), and stomatal conductance (gS) were measured by means of a portable gas exchange device on leaves located in three canopy layers. The differences in light regime within the canopy induced by the three shading nets had only a slight effect on An, thereby resulting in substantially higher light-use efficiency under shading than in the open field. The observed tendency toward higher gS in shaded plants was counterweighted by a lower intercellular-to-ambient CO2 concentration gradient, leading to similar An in leaves of shaded and non-shaded plants. Ontogenic effects (leaf aging) appeared to be the main factor determining the decreasing seasonal trend of leaf photosynthetic attributes. Overall, shaded sweet pepper plants display a physiological light acclimation allowing them to maintain the photosynthetic activity to a level similar to that observed in non-shaded plants across a wide range of growth light regimes, irrespective of the type of net and its shading intensity.
An Evaluation of U.S. Strawberry Producers Trait Prioritization: Evidence from Audience Surveys
Authors: Yue Chengyan , Gallardo R. Karina , Luby James , Rihn Alicia , McFerson James R. , McCracken Vicki , Whitaker Vance M. , Finn Chad E. , Hancock James F. , Weebadde Cholani , Sebolt Audrey , Iezzoni Amy
Published: February 2019

The primary goal of this research was to evaluate the relative importance of strawberry fruit quality and plant traits to strawberry producers. Previous studies focus on strawberry traits that impact postharvest quality and marketable yield; however, studies emphasizing the importance of these traits to strawberry producers are scarce. To investigate U.S. strawberry producer trait preferences, a series of audience surveys were conducted at four strawberry producer meetings across the United States. Results indicate that fruit firmness, fruit flavor, and fruit shelf life at retail were the most important fruit/plant traits to producers for a successful strawberry cultivar to possess. Growing state and producers’ years involved in the decision-making process of strawberry farms impacted the relative importance of the fruit/plant traits. This study directly contributes to a larger investigation of supply chain members’ trait preferences to improve the efficiency of Rosaceae fruit crop breeding programs and to increase the likelihood of new cultivar adoption. The overall project should result in a more efficient approach to new strawberry cultivar development and commercialization.
Statistical Model for Describing Macronutrient Impacts on Container Substrate pH Over Time
Authors: Barnes Jared , Nelson Paul , Whipker Brian E. , Dickey David A. , Hesterberg Dean , Shi Wei
Published: February 2019

Although many factors that influence substrate pH have been quantified, the effect from fertilizers continues to be elusive. A multifactorial experiment was conducted to test macronutrient effects using a rarely used statistical method known as the central composite design. Five nutrient factors, including nitrogen (N) carrier ratio (NH4+ vs. NO3–) and concentrations of phosphorus (P) (as H2PO4–), potassium (K), combined calcium (Ca) and magnesium (Mg), and sulfur (S), were varied at five levels each encompassing the proportionate range of these nutrients in commercial greenhouse fertilizers. Although a typical factorial experiment would have resulted in 55 = 3125 treatments, the central composite design reduced the number to 30 fertilizer treatments. An experiment was conducted twice in which ‘Evolution White’ mealy-cup sage (Salvia farinacea Benth.) was grown in 14-cm-diameter pots (1.29 L) in a 3 peat:1 perlite (v/v) substrate amended with non-residual powdered calcium carbonate to raise the substrate pH to ≈5.6 to 5.8. Harvests occurred after 3 and 6 weeks of growth. A statistical model described substrate pH over time with significant effects including four main effects of N carrier ratio, P, K, and combined Ca and Mg; three squared terms of N carrier ratio, P, and K; and seven interaction effects. The resulting model was used to calculate substrate pH levels between 25 and 45 days after planting, and it showed that N carrier had the greatest impact on substrate pH.
Interaction of Irrigation and Soil Management on Sweet Cherry Productivity and Fruit Quality at Different Crop Loads that Simulate Those Occurring by Environmental Extremes
Authors: Neilsen Gerry H. , Neilsen Denise , Kappel Frank , Forge T.
Published: February 2019

‘Cristalina’ and ‘Skeena’ sweet cherry cultivars (Prunus avium L.) on Gisela 6 (Prunus cerasus × Prunus canescens) rootstock planted in 2005 were maintained since 2006 in a randomly blocked split-split plot experimental design with six blocks of two irrigation frequency main plot treatments within which two cultivar subplots and three soil management sub-subplots were randomly applied. The focus of this study was the growth, yield, and fruit quality response of sweet cherry to water and soil management over three successive fruiting seasons, 2009–11, in a cold climate production area. The final 2 years of the study period were characterized by cool, wet springs resulting in low yield and yield efficiency across all treatments. Soil moisture content (0- to 20-cm depth) during the growing season was often higher in soils that received high-frequency irrigation (HFI) compared with low-frequency irrigation (LFI). HFI and LFI received the same amount of water, but water was applied four times daily in the HFI treatment but every other day in the LFI treatment. Consequently, larger trunk cross-sectional area (TCSA) and higher yield were found on HFI compared with LFI trees. Soil management strategies involving annual bloom time phosphorus (P) fertigation and wood waste mulching did not affect tree vigor and yield. Increased soluble solids concentration (SSC) occurred with LFI. Decreased SSC occurred with delayed harvest maturity in trees receiving P fertigation at bloom. The largest fruit size was correlated for both cultivars with low crop loads ranging from 100 to 200 g fruit/cm2 TCSA. Overall cool, wet spring weather strongly affected annual yield and fruit quality, often overriding cultivar and soil and water management effects.
Mapping the Incompatibility and Style Color Loci in Two Hazelnut Progenies
Authors: Ives Colton , Sathuvalli Vidyasagar R. , Colburn Brooke C. , Mehlenbacher Shawn A.
Published: February 2019

Pollen–stigma incompatibility in european hazelnut (Corylus avellana L.) is of the sporophytic type and under the control of a single locus with multiple alleles (haplotypes). The S-locus was previously assigned to linkage group 5 (LG5) and linked DNA markers were identified. The loci that control leaf color and style color are linked to the S-locus. We investigated segregation for leaf and style color and S-alleles in two progenies, mapped the loci, and compared the two new maps with the LG5 reference map using simple sequence repeat (SSR) markers. Segregation for color, S-alleles and SSR markers fit expectations. The color loci and the S-locus mapped to LG5 between SSR markers B028 and B774. The three maps aligned and the SSR markers were collinear. The SSR markers closest to the S-locus are KG819, KG847, and BR259. In progeny 05050, which segregated for style and leaf color, no recombination was observed between the two traits. Recombination between the S-locus and the style color locus was 5.4 cM in progeny 05050 and 10.1 cM in progeny 00064. The style color locus was placed very close to SSR marker B028 in both progenies. On the reference map, random amplified polymorphic DNA (RAPD) markers 564-500M, 345-1050dF, and 204-950dF and intersequence simple sequence repeat (ISSR) marker 815-540dF are very close to the S-locus. The identification of closely linked markers will facilitate the map-based cloning of the S-locus and color loci in hazelnut.
Biocontainer Use in a Petunia ×hybrida Greenhouse Production System: a Cradle-to-gate Carbon Footprint Assessment of Secondary Impacts
Authors: Koeser Andrew K. , Lovell Sarah T. , Petri Aaron C. , Brumfield Robin G. , Stewart J. Ryan
Published: February 2019

This study assessed the material and energy inputs required to produce a Petunia ×hybrida plant from initial propagation to delivery at a regional distribution center. Impacts were expressed in terms of their contribution to the carbon footprint or global warming potential (GWP) of a single finished plant in a ≈10-cm diameter container. Beyond this baseline assessment, the study investigated the secondary impacts (e.g., irrigation demand) associated with container type used. Life cycle assessment data were sourced from interviews, published literature, propriety data sources, direct metering at the greenhouse facility, and original findings from a series of university greenhouse experiments. Results show that a traditional plastic container accounts for ≈16% of overall CO2e emissions (0.544 kg) during petunia production. Although the container was a significant contributor to GWP, electrical consumption for supplemental lighting and irrigation during plug production proved to be the leading source of CO2e emissions (over 47%) in our model system. Differences in GWP when considering secondary impacts associated with the various biocontainers were minor, especially when compared with the other elements of production. Our results demonstrate that biocontainers could potentially be as or more sustainable than plastic pots once pot manufacturing and end-of-life data are considered. However, use of more efficient supplemental lighting sources may ultimately have the greatest impact on overall GWP for the production system assessed.
Field Evaluation of Carbon Sources for Anaerobic Soil Disinfestation in Tomato and Bell Pepper Production in Tennessee
Authors: McCarty D. Grant , Eichler Inwood Sarah E. , Ownley Bonnie H. , Sams Carl E. , Wszelaki Annette L. , Butler David M.
Published: February 2019

Anaerobic soil disinfestation (ASD) is a biologically based, non-fumigant, pre-plant soil treatment developed to control soilborne plant pathogens and plant-parasitic nematodes in specialty crop production systems. Soil treatment by ASD includes the incorporation of a labile carbon (C) source, tarping with plastic, and irrigation of the topsoil to saturation (5 cm irrigation) to create conditions conducive to anaerobic decomposition of the added C source. A field study was implemented beginning in Fall 2010 and repeated in the same plot locations in Fall 2011 in Knoxville, TN, to evaluate ASD. Soil properties, weed and Rhizoctonia solani population dynamics, and crop performance were evaluated after ASD treatment with several potential C sources for ASD before production of fresh-market tomato (Solanum lycopersicum L. ‘Red Defender’) and red bell pepper (Capsicum annum L. ‘Red Knight X3R’). Treatments included: 1) untreated control; 2) mustard seed meal (biofumigant control); 3) ASD with dried molasses; 4) ASD with soil-incorporated Indian mustard (Brassica juncea L.), white mustard (Sinapis alba L.), and arugula (Eruca sativa Mill.) cover crop with molasses added at cover crop incorporation; 5) ASD with soil-incorporated Indian mustard, white mustard, and arugula cover crop; 6) ASD with soil-incorporated cereal rye (Secale cereale L.) cover crop with molasses added at cover crop incorporation; and 7) ASD with soil-incorporated cereal rye cover crop. Accumulated soil anaerobic conditions were significantly greater than the untreated control in all ASD treatments except the ASD mustard/arugula treatment. Although not related to accumulated anaerobic conditions, populations of R. solani were lowest and equivalent to the biofumigant control for ASD cereal rye and ASD mustard/arugula treatments. Differences in weed populations and soil inorganic nitrogen among treatments were limited. Yield of bell pepper and tomato did not differ among treatments, which may have been partly the result of the low pest pressure observed at the site over the 2 years of the study.
Long-term Yield and Harvest Time Fruit Quality Attributes in Various Fuji Apple Strains
Authors: Fallahi Esmaeil , Fallahi Bahar , Shafii Bahman , Zamani Zabihollah
Published: February 2019

‘Fuji’ apple (Malus ×domestica Borkh) has gained popularity in the past decades, but poor color of this apple mandates introduction of new strains. To pursue this objective, long-term effects of five ‘Fuji’ apple strains, consisting of ‘Autumn Rose’, ‘Desert Rose’, ‘Myra’, ‘September Wonder’, and ‘Top Export’ on RN 29 rootstock on fruit yield (in 7 years) and harvest time quality attributes (in 6 years) under climate conditions of southwest Idaho were studied during 2004–10. Fruit of ‘September Wonder Fuji’ trees were larger than those of other strains in 5 of 6 years. The type or pattern of peel color among the “low-coloring” and “high-coloring” strains varied widely. Fruits of ‘Autumn Rose Fuji’, ‘Myra Fuji’, and ‘Top Export Fuji’ always had less but ‘September Wonder Fuji’ and ‘Desert Rose Fuji’ had more red color. Fruit of ‘September Wonder Fuji’ had lower firmness but higher starch degradation pattern (SDP) than those of other strains every year as a result of the earlier maturity of this strain. Fruit of ‘Top Export Fuji’ had the lowest SDP among all strains. Fruit of ‘Autumn Rose Fuji’ tended to have lower soluble solids concentration in 3 of 6 years of this study. Considering all yield and quality attributes at harvest, ‘September Wonder’ was a great choice for an early-maturing and ‘Desert Rose’ was suitable for a late-maturing ‘Fuji’ strain. ‘Myra Fuji’ was particularly desirable for its attractive pink color that resembles bagged ‘Fuji’ without the expensive cost of labor associated with bagging.
Sweet Corn Weed Control and Yields in Response to Sowing Date and Cropping Systems
Authors: Rajablarijani Hamid Reza , Mirshekari Bahram , AghaAlikhani Majid , Rashidi Varahram , Farahvash Farhad
Published: February 2019

The high vulnerability of sweet corn (Zea mays L. var. saccharata) to weed competition and the urgent reduction of the dependence on chemical herbicides are major challenges facing the agricultural community. To investigate the effects of plastic mulches on weed control and yields in sweet corn under different sowing dates, a 2-year experiment was conducted at Varamin, Iran, in 2010 and 2011. The mulch treatments included black plastic mulch, semitransparent biodegradable mulch, an unmulched weeded control, and an unmulched unweeded control. The sowing dates were 5 June, 20 June, and 6 July. Results revealed that delayed sowing (6 July) reduced weed dry weight by 51% and 41% compared with the 5 June sowing date in 2010 and 2011, respectively, without reducing crop yield. The black plastic mulch treatment had the lowest weed biomass. The sowing date × mulch interactions on kernel number per ear, length of ear, percentage of unfilled ear tip, and yield of sweet corn were statistically significant (P < 0.01) in both years. The maximum kernel number per ear (535) and the highest fresh ear yield (24,684 kg·ha−1) in 2010 were obtained on the 6 July sowing date under biodegradable mulch. The plants sown on 6 July produced the highest fresh kernel yield with the black plastic mulch (12,893 kg·ha−1) and unmulched weeded control (11,777 kg·ha−1) in 2010 and 2011, respectively. The highest percentage of unfilled ear tips in both years was observed in the unmulched unweeded plots sown on 5 June. According to our findings, to suppress the weeds and avoid the sweet corn yield loss in such a hot summer that we had, using the black plastic mulch and delayed sowing are recommended.
Comparative Evaluation of Seedling Hypocotyl Elongation and Mature Plant Assays for Determining Ethylene Sensitivity in Bedding Plants
Authors: Edelman Nichole F. , Kaufman Bethany A. , Jones Michelle L.
Published: February 2019

Ethylene gas can cause extensive damage to bedding plants during production, shipping, and retailing. Seedlings exposed to ethylene exhibit the triple response, which includes an exaggerated apical hook, thickened hypocotyl, and reduced hypocotyl elongation. Our objective was to determine if the hypocotyl elongation component of the seedling triple response could be used to predict the sensitivity of mature plants at the marketable stage. Eighteen common bedding plants were evaluated. For the seedling hypocotyl elongation screen, seeds were germinated and grown in the dark on filter paper saturated with various concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC; the immediate precursor to ethylene). The relative hypocotyl length at each ACC concentration was compared with untreated control (0 μM) seedlings. Mature plants, with at least four open flowers, were treated with ethylene (0, 0.01, 0.1, 1, or 10 μL·L−1) in the dark for 24 hours. Phenotypic responses to ethylene, including flower abscission, flower senescence, leaf abscission, leaf chlorosis, and epinasty, were rated on a scale of 0 to 5. Five species exhibited very little reduction in hypocotyl elongation when grown on ACC (low sensitivity). The remaining species were classified as medium or high ethylene sensitivity at the seedling stage. The most common symptoms of ethylene damage observed in mature plants were leaf epinasty, flower abscission, and flower senescence. The severity of these responses was used to identify plants with high, medium, or low sensitivity to ethylene. For six of the bedding plant species that were equally responsive at both developmental stages, the seedling hypocotyl elongation screen would provide a reliable means of predicting the ethylene sensitivity of mature plants.
The Effect of Fertilizer Level and Foliar-applied Calcium on Seed Production and Germination of Gerbera hybrida
Authors: Andreasen Christian , Kemezys Andrius Hansen , Müller Renate
Published: February 2019

Gerbera hybrida is an ornamental plant of great commercial interest, which is primarily propagated by seeds. We investigated whether increasing fertilizer concentrations during seed set enhanced plant biomass, number of flower heads, seed set, and seed weight. Furthermore, we studied whether an additional foliar calcium application influenced the same parameters. Subsequently, the effect of the various treatments on the germination of the obtained seeds was explored. Two identical experiments (A and B) were carried out with five concentrations of nutrient solutions corresponding to an electrical conductivity (EC) of 1.25 mS·cm−1, 2.50 mS·cm−1, 3.75 mS·cm−1, 5.00 mS·cm−1, and 6.25 mS·cm−1. Additionally, plants were sprayed with a 0.5% foliar-applied calcium solution or deionized water (control) three times during the experimental period. In Expt. A, the concentration of fertilizer significantly affected seed production. Number of flower heads and seed weight were not influenced by the dose of fertilizer, but plant biomass and number of seeds were significantly reduced at the highest concentration (6.25 mS·cm−1). In Expt. B, the fertilizer concentration did not affect number of flower heads and seed number, but seed weight and plant biomass were significantly reduced at the highest fertilizer concentration. In both experiments, the seeds germinated slower and less seeds germinated when plants had received the largest amount of fertilizer (6.25 mS·cm−1). In none of the experiments did applied calcium affect the number of flowers, seed production, seed weight, or the total biomass. Our data indicate that seed producers of G. hybrida should not apply standard fertilizer in a concentration higher than corresponding to an EC of ≈1.25 mS·cm−1. It would have been valuable if we also had included a treatment with a lower EC value like 0.75 mS·cm−1 to improve the estimate of the optimal EC level from a curved function for the seed production and quality parameters.
Foliar Fertilization with Zinc in Pecan Trees
Authors: Ojeda-Barrios Dámaris L. , Perea-Portillo Eloísa , Hernández-Rodríguez O. Adriana , Ávila-Quezada Graciela , Abadía Javier , Lombardini Leonardo
Published: February 2019

The objective of this study was to assess the changes in leaflet zinc (Zn), leaf nutritional state, vegetative and physiological parameters, and yield quality in pecan trees sprayed with different Zn compounds. Eight-year-old ‘Western Schley’ pecan trees grafted to native seedlings were treated with ZnNO3 (100 mg·L−1 Zn), Zn-EDTA (50, 100, and 150 mg·L−1 Zn), and Zn-DTPA (100 mg·L−1 Zn) and compared with the Zn-untreated control. After 3 years of evaluation, the trees with the best appearance were those treated with ZnNO3 (100 mg·L−1 Zn) and Zn-DTPA (100 mg·L−1 Zn), which showed leaf Zn concentration increases of 73% and 69%, respectively, when compared with the controls. The chlorophyll values of the Zn-treated trees reached 46 SPAD units, equivalent to 43 mg·kg−1 dry weight (DW) of chlorophyll compared with values of 22 mg·kg−1 DW in Zn-deficient leaves. On a leaf area basis, chlorophyll value was 37% lower under Zn deficiency conditions than that of Zn-treated trees. Nut quality was unaffected by the Zn treatments. Data suggest that Zn-DTPA and Zn-NO3 are good options to carry out foliar Zn fertilization in pecan trees.