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Open access

Laura Jalpa, Rao S. Mylavarapu, George J. Hochmuth, Alan L. Wright and Edzard van Santen

Use efficiency of applied nitrogen (N) is estimated typically to be <50% in most crops. In sandy soils and warmer climates particularly, leaching and volatilization may be primary pathways for environmental loss of applied N. To determine the effect of N fertilization rate on the N use efficiency (NUE) and apparent recovery of N fertilizer (APR), a replicated field study with ‘BHN 602’ tomato (Solanum lycopersicum) grown in sandy soils under a fertigated plastic-mulched bed system was conducted using ammonium nitrate as the N source at four different rates (0, 150, 200, and 250 lb/acre). Spring tomato was followed by fall tomato in the same field, a typical cropping sequence in north Florida. Fertigation of N fertilizer was applied weekly in 13 equal doses for both seasons. The highest NUE was 12.05% (spring) and 32.38% (fall), and the highest APR was 6.11% (spring) for the lowest rate of N applied (150 lb/acre). In the fall, APR was unaffected by fertilizer N rates and ranged from 12.88% to 19.39%. Nitrogen accumulation in tomato plants were similar among the three N fertilizer rates applied (150, 200, and 250 lb/acre), though compared with no N fertilizer application, significant increases occurred. Whole plant N accumulation, NUE, and APR declined or remained similar when N rates increased above 150 lb/acre. Additionally, a regression analysis and derivative of the quadratic fresh yield data showed that yields were maximized at 162 and 233 lb/acre N in the spring and fall seasons, respectively.

Open access

Xiaoying Dou, Jinrong Bai, Huan Wang, Ying Kong, Lixin Lang, Fang Bao and Hongzhong Shang

Anthocyanins are major pigments responsible for the color of lily (Lilium sp.) flowers. Anthocyanin synthesis is part of the flavonoid metabolic pathway. Numerous transcription factors, including R2R3-MYBs, basic helix-loop-helix (bHLH), and tryptophan–aspartic acid repeat (also known as WD40 or WD repeat) proteins, known to regulate flavonoid biosynthesis have been identified in various plant species. However, there is limited information available on WD repeat proteins in lilies. In this study, we identified a WD repeat gene in the Oriental hybrid lily ‘Sorbonne’ (Lilium hybrid WD repeat, LhWDR). LhWDR contains no introns, and has a 1100–base pair open reading frame, encoding a putative protein of 370 amino acids. LhWDR was found to be localized in the cytoplasm of transgenic Arabidopsis thaliana root cells. Expression patterns of LhWDR in different organs and at different periods of lily tepal growth revealed that the expression levels of this gene are closely associated with anthocyanin accumulation. A yeast two-hybrid assay demonstrated that full-length LhWDR interacts with the 420 N-terminal amino acids of Lilium hybrid bHLH2. Interestingly, overexpression of LhWDR in A. thaliana led to an upregulation of the dihydroflavonol 4-reductase gene, which is an important structural gene downstream of the anthocyanin pathway. These results indicate that the WD repeat protein LhWDR might interact with a bHLH transcription factor to regulate anthocyanin biosynthesis.

Open access

Leora Radetsky, Jaimin S. Patel and Mark S. Rea

Lighting from red and blue light-emitting diodes (LEDs) is common for crop production in controlled environments. Continuous application of red or blue light at night has been shown to suppress sporulation by Peronospora belbahrii, the causal organism of basil downy mildew (DM), but the suppressing effects of intermittent applications of red and blue LEDs have not been thoroughly researched. This study examined the effects of red (λmax = 670 nm) and blue (λmax = 458 nm) LED top lighting, at two photosynthetic photon flux densities (PPFD = ≈12 and ≈60 µmol·m−2·s−1), using continuous (10-hour) nighttime and two intermittent nighttime exposures, to suppress basil DM sporulation. The two intermittent treatments consisted of one 4-hour exposure and three 1.3-hour exposures spaced 3 hours apart. Continuous nighttime treatments with blue or red LED top lighting at ≈60 µmol·m−2·s−1 were able to suppress basil DM sporulation by more than 99%. At a given nighttime dose of light that did not completely suppress sporulation, continuous lighting was more effective than intermittent lighting, and for these partially suppressing doses, red LEDs were not significantly different from blue LEDs for suppressing sporulation. The present study showed that horticultural lighting systems using red and blue LEDs to grow crops during the day can also be used at night to suppress basil DM sporulation by up to 100%.

Open access

Carol A. Miles, Travis R. Alexander, Gregory Peck, Suzette P. Galinato, Christopher Gottschalk and Steve van Nocker

Hard cider, made by fermenting apple (Malus ×domestica) juice, was at one time the most widely consumed alcoholic beverage in America. Largely abandoned after Prohibition, within the past 2 decades the rise in popularity of craft beverages has led to the reemergence of hard cider as an alternative to beer, wine, and spirits. Today, hard cider represents one of the fastest growing sectors within the craft beverage industry. The recent interest in cider presents additional marketing opportunities for apple growers and businesses currently involved in, or considering entering, the apple cider or craft beverages industries. However, the lack of a strong history or experience in selecting, producing, and using cider apples poses a significant challenge to this emerging market. This article reviews the current state of research in cider apple production, including economic feasibility, mechanized management, and cultivar evaluation and improvement.

Open access

Aikaterini N. Martini and Maria Papafotiou

Limoniastrum monopetalum is an evergreen perennial shrub native to Mediterranean coastal sands and salt marshes. It has adapted to a variety of environmental stresses and is used in traditional medicine and as an ornamental plant. In the present study, an efficient micropropagation protocol for this species was developed to facilitate the production of selected genotypes and promote its wider use. Research has focused on the effects of various cytokinin types [benzyladenine (BA), zeatin, 6-furfurylaminopurine (kinetin) or 6-γ-γ-dimethylallilopurine (2iP)] and concentrations (0.0–4.0 mg·L−1) and various NaCl concentrations (0.0–20 g·L−1) during all stages of in vitro culture. For in vitro establishment, Murashige and Skoog (MS) medium supplemented with 0.5 mg·L−1 BA and 0.0 or 5.0 g·L−1 NaCl was most appropriate (100% explant response, 3–4 shoots per explant, 2 cm shoot length). The best results for shoot multiplication (100% response, 9 shoots per explant, 0.8–1.0 cm shoot length) were obtained with low (0.5 mg·L−1) BA or relatively high (2.0 mg·L−1) kinetin concentrations in the medium; however, 0.5 mg·L−1 kinetin should be preferred in the case of production of multiple rooted microshoots during one stage. The addition of NaCl at relatively low concentrations (2.5 or 5.0 g·L−1) in a medium supplemented with 0.5 mg·L−1 BA doubled shoot multiplication but did not improve shoot elongation (100% explant response, 16 shoots per explant, 0.8 cm shoot length). For in vitro rooting, half-strength MS medium supplemented with 1.0 mg·L−1 IBA was most appropriate (97% rooting, 9.4 roots per microshoot, 1.2 cm root length). Regarding the effects of NaCl on in vitro rooting, microshoots were relatively tolerant to NaCl concentrations up to 10.0 g·L−1. The effects of NaCl depend on the micropropagation stage; they are synergistic during shoot multiplication and tolerant during rooting. However, explants responded satisfactorily in its absence, indicating that NaCl was not necessary as a medium component. Ex vitro acclimatization and establishment of plantlets was 100% successful in a mixture of peat:perlite 1:1 or 2:1 (v/v).

Open access

D. Michael Jackson, Howard F. Harrison, Robert L. Jarret and Phillip A. Wadl

During 2012–14, 737 sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), plant introduction (PI) accessions from the U.S. Department of Agriculture, Agricultural Research Service (USDA, ARS) sweetpotato germplasm collection were evaluated for several phenotypic leaf and plant characteristics, and a photographic record of each accession was made. Data were prepared for placement in the USDA, ARS Germplasm Resources Information Network (GRIN) database and the sweetpotato ontology. The parameters recorded for each genotype were canopy coverage, vine length, general leaf outline, leaf lobing, shape of the central leaf lobe, number of leaf points, leaf petiole length, leaf width, leaf length, leaf width × length, and leaf width/length (aspect ratio). The data indicate that there is wide genetic diversity for vegetative phenotypic characteristics within the USDA, ARS sweetpotato germplasm collection. This study provides important phenotype information for the USDA, ARS sweetpotato collection that has been lacking and can be used for curation of the collection and by researchers and breeders working with this important global food crop.

Open access

Margarita Velandia, Karen L. DeLong, Annette Wszelaki, Susan Schexnayder, Christopher Clark and Kimberly Jensen

Polyethylene (PE) mulch provides significant benefits to fruit and vegetable producers because it has the potential to improve crop quality and increase yield. However, the use of PE mulch generates plastic pollution, posing challenges to the sustainability of fruit and vegetable production. Plastic biodegradable mulches (BDMs) are a sustainable alternative to PE mulch because they are designed to decompose into water, carbon dioxide, and microbial biomass. We surveyed Tennessee fruit and vegetable growers to assess their use of PE mulch, BDM, or both; the differences in the characteristics of BDM users and nonusers; and their interest in using BDM. Our results indicate a large percentage of fruit and vegetable growers have used PE mulch compared with BDM. In general, BDM users tend to have more acres in fruit and vegetable production, have used dumping and burying as PE mulch disposal methods, and have spent more hours removing and disposing of PE mulch. Results indicate that even at prices higher than the current average market price for BDM, there is a percentage of Tennessee fruit and vegetable growers interested in using BDM.

Open access

Natalie Yoder and Jessica G. Davis

Selecting supplemental nitrogen (N) fertilizer for use on certified organic farms can be difficult and confusing. There are many options commercially available to farmers with similar N concentrations but widely different ingredients. Experiments were conducted in a certified organic field and high tunnels near Fort Collins, CO in 2013 and 2014 to evaluate the impact of organic fertilizers on yield and nutrient concentrations of three kale (Brassica oleracea and Brassica napus) cultivars. This study includes an organic fertilizer (cyano-fertilizer), which is produced on-farm by growing N-fixing cyanobacteria (Anabaena cylindrica) in raceway ponds. The three fertilizer treatments were hydrolyzed fish emulsion, alfalfa (Medicago sativa) meal, and cyano-fertilizer. These were applied at rates calculated by subtracting soil nitrate concentration from a target 50 mg·kg−1 to the depth of 6 inches of soil. Cyano-fertilizer and hydrolyzed fish emulsion were applied in liquid form, while the alfalfa meal was incorporated dry into the soil before planting. Biweekly measurements of plant height were taken on three cultivars of kale: Dinosaur, Red Russian, and Winterbor. Leaf weight, leaf area, and N, iron (Fe), and zinc (Zn) concentrations were measured during three to four monthly harvests each year. Organized in a split-plot experimental design, there were three treatment replications with subplots of different kale cultivars. Fertilizer treatment did not significantly affect plant height, leaf weight, leaf area, or plant N, Fe, and Zn concentrations. However, there were cultivar differences in plant height, leaf area, and yield. Kale cultivar choice had a larger impact on yield and plant nutrient concentrations than fertilizer choice, because fertilizers were applied at similar N rates.

Open access

Santiago García-Martínez, Adrián Grau, Aranzazu Alonso, Pedro Carbonell, Juan F. Salinas, José A. Cabrera and Juan J. Ruiz

Open access

Shana G. Brown and James E. Klett

Stock plant productivity is an important concern for growers of ‘Snow Angel’ coral bells (Heuchera sanguinea) because this variety produces a limited number of basal cuttings. The objective of the study was to determine the best growth substrate and container size combination to maximize productivity of stock plants. A secondary objective was to determine if the stock plant treatments influenced the rooting of vegetative cuttings. The study used three different container sizes (2.8, 11.4, and 14.6 L) and four commercial soilless substrates that were primarily composed of the following: bark, peat, and perlite (substrate 1); bark, peat, and vermiculite (substrate 2); bark, peat, and coarse perlite (substrate 3); and peat (substrate 4). Two stock plant experiments were conducted using the same 12 treatment combinations, and a subset of those stock plants was randomly selected for the rooting studies that immediately followed each stock plant experiment. Stock plants responded to substrate treatments differently depending on the batch of substrate in which they were grown. The most successful stock plants, which produced more cuttings per plant and per square foot, as well as larger cuttings, were those grown in substrate 3 (Expt. 1) and substrate 2 (Expt. 2). Regardless of the substrate, the highest number of cuttings per square foot was obtained from stock plants grown in 2.8-L containers, indicating that the smaller containers allow for the most efficient use of space when growing ‘Snow Angel’ stock plants for 6 to 8 months. The rooting of vegetative cuttings was successful (98% to 100% of cuttings rooted after 4 weeks under mist) for all treatment combinations, although higher numbers of visible roots were produced during the second study and may be due to larger fresh weights of cuttings.