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Jayesh B. Samtani, Curt R. Rom, Heather Friedrich, Steven A. Fennimore, Chad E. Finn, Andrew Petran, Russell W. Wallace, Marvin P. Pritts, Gina Fernandez, Carlene A. Chase, Chieri Kubota and Brad Bergefurd

Strawberry (Fragaria ×ananassa) production practices followed by growers in the United States vary by region. Understanding the challenges, needs, and opportunities in each region is essential to guide research, policy, and marketing strategies for the strawberry industry across the country, and to enable the development of general and region-specific educational and production tools. This review divided the United States into eight distinct geographic regions and an indoor controlled or protected environment production system. Current production systems, markets, cultivars, trends, and future directions for each region are discussed. A common trend across all regions is the increasing use of protected culture strawberry production with both day-neutral and short-day cultivars for season extension to meet consumer demand for year-round availability. All regions experience challenges with pests and obtaining adequate harvest labor. Increasing consumer demand for berries, climate change-induced weather variability, high pesticide use, labor and immigration policies, and land availability impact regional production, thus facilitating the adoption of new technologies such as robotics and network communications to assist with strawberry harvesting in open-field production and production under controlled-environment agriculture and protected culture.

Open access

James R. Schupp, H. Edwin Winzeler and Melanie A. Schupp

Renewal of limbs by pruning to leave a short, angled, upward-facing stub is common practice for spindle-type apple (Malus ×domestica) training systems. A short, beveled stub cut is thought to stimulate renewal growth from latent buds present underneath the base of the excised branch, and to stimulate smaller, more fruitful renewal limbs with wide crotch angles. We conducted trials over the course of 2 years that involved dormant pruning of ‘Buckeye Gala’ with renewal cuts to compare two stub lengths, 0.5 and 2 cm, and three stub orientations, upward facing, downward facing, and vertical facing, to determine the effects on renewal shoot number, position, angle, and length. We found no clear advantages with either stub length that we evaluated, and there was no improvement in renewal shoot quality with a bevel cut at any orientation. Stub length and stub angle did not influence limb renewal and may be unimportant for training orchard-pruning crews and for machine-learning and robotic pruning.

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Allison Hurt, Roberto G. Lopez and Joshua K. Craver

In northern latitudes, the photosynthetic daily light integral can be less than 5 mol·m–2·d–1, necessitating the use of supplemental lighting (SL) to reduce bedding plant seedling production time and increase quality. Our objectives were 1) to quantify seedling quality and production time under continuous 16-h or instantaneous threshold SL, continuous low-intensity photoperiodic lighting (PL) for 16 or 24 hours with and without far-red light, or no electric lighting; and 2) to determine whether the described lighting treatments during propagation impact finished plant quality or flowering. Seeds of begonia (Begonia ×semperflorens) ‘Bada Bing Scarlet’, gerbera (Gerbera jamesonii) ‘Jaguar Deep Orange’, impatiens (Impatiens walleriana) ‘Accent Premium Salmon’, petunia (Petunia ×hybrida) ‘Ramblin Peach Glo’, and tuberous begonia (Begonia ×tuberosa) ‘Nonstop Rose Petticoat’ were sown in 128-cell trays and grown under either SL, PL, or no electric lighting (control). SL treatments consisted of high-intensity light-emitting diode (LED) or high-pressure sodium (HPS) lamps providing a photosynthetic photon flux density (PPFD) of either 70 µmol·m–2·s–1 on continuously for 16 h·d–1 or 90 µmol·m–2·s–1 based on an instantaneous threshold. PL treatments consisted of low-intensity red:white (R:W) or red:white:far-red (R:W:FR) lamps for 16 h·d–1 or R:W:FR lamps for 24 h·d–1. Seedlings of gerbera, impatiens, and petunia from each treatment were subsequently transplanted and finished in a common greenhouse environment. The highest quality seedlings were grown under SL compared with PL or control conditions. When comparing SL treatments, seedlings produced under HPS or LED SL using an instantaneous threshold were of equal or greater quality compared with those under continuous SL with a 16-h photoperiod. Although the greater leaf area and internode elongation under PL may give growers the perception that seedling production time is reduced, PL did not increase biomass accumulation and seedling quality. Petunia seedlings propagated under HPS lamps using an instantaneous threshold flowered 4 to 11 days earlier compared with the other SL treatments. In addition, petunia propagated under R:W:FR PL for 16 h·d–1 flowered 5 to 7 days earlier compared with LED SL and the other PL treatments.

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Cibele Mantovani, Jonas Pereira de Souza Júnior, Renato de Mello Prado and Kathia Fernandes Lopes Pivetta

Salicylic acid (SA) may induce toxicity in orchids depending on its concentration and the plant species, but there is no information about the effect of this substance on orchids cultivated in vitro. The objective of the present study was to evaluate the effects of different concentrations of SA on Cymbidium atropurpureo and Phalaenopsis Golden Peoker cultivated in vitro to verify the biological losses caused by the substance’s toxicity. The orchids Cymbidium atropurpureo and Phalaenopsis Golden Peoker were sown in vitro in a Murashige and Skoog (MS)-growth medium and transferred to a medium of the same type containing SA 90 days after sowing. The studied SA concentrations were 0, 50, 100, 200, 300, 400, 500, and 1000 µmol·L−1, and the plants were kept in this medium for 210 days. The treatments were distributed into a completely randomized design with four replications. Biometric variables of the seedlings and electrolyte leakage were evaluated 300 days after sowing. The results indicate that the addition of SA interfered with the in vitro growth and development of seedlings of Cymbidium atropurpureo and Phalaenopsis Golden Peoker, given that it caused all the examined variables to show reduced values and triggered electrolyte leakage, consequently inducing toxicity.

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Chandra S. Thammina, Christopher von Kohn and Margaret R. Pooler

The genus Magnolia (Magnoliaceae) comprises more than 130 species distributed predominantly in temperate and tropical regions in Southeast Asia and is valued worldwide for its ornamental traits as well as for timber and medicinal products, and in trade. Despite their favored status, many species of Magnolia are faced with threats from logging, agricultural land use, development, and collection, and are at risk of extinction. Conservation of these species through habitat preservation and in ex situ collections is needed to prevent extinction. To provide a tool for conservation of Magnolia species, microsatellite markers developed previously for Magnolia ashei were tested in 10 other species of Magnolia to determine their transferability across species. Of the 64 primer pairs tested, 21 amplified alleles in the expected size range in all samples; 11 primer pairs amplified clean products in most, but not all, species; 18 primer pairs consistently amplified a polymerase chain reaction (PCR) product in most species, but had either low peak height or other amplification issues; and 14 primers showed excessive stutter, nonspecific amplification, or no amplification. Cluster analysis using the 129 alleles amplified by these 21 simple sequence repeat (SSR) primer pairs generated groups that corresponded to the known taxonomic relationships in this genus.

Open access

Dewayne L. Ingram, Charles R. Hall and Joshua Knight

Understanding carbon footprint (CF) terminology and the science underlying its determination is important to minimizing the negative impacts of new product development and assessing positive or negative cradle-to-grave life-cycle impacts. Life cycle assessment has been used to characterize representative field-grown and container-grown landscape plants. The dominant contributor to the CF and variable costs of field-grown trees is equipment use, or more specifically, the combustion of fossil fuels. Most of that impact is at harvest when heavy equipment is used to dig and move individual trees. Transport of these trees to customers and the subsequent transplant in the landscape are also carbon-intensive activities. Field-grown shrubs are typically dug by hand and have much smaller CFs than trees. Plastics are the major contributor to CF of container-grown plants. Greenhouse heating also can be impactful on the CF of plants depending on the location of the greenhouse or nursery and the length and season(s) of production. Knowing the input products and activities that contribute most toward CF and costs during plant production allows nursery and greenhouse managers to consider protocol modifications that are most impactful on profit potential and environmental impact. Marketers of landscape plants need information about the economic and environmental life-cycle benefits of these products, as they market to environmentally conscious consumers.

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Sabrina J. Ruis, Humberto Blanco-Canqui, Ellen T. Paparozzi and Russ Zeeck

Processed corn (Zea mays L.) stover (PCS), defined as finely ground stover with or without additions, could be a potential alternative to peat in greenhouse mixes. However, this option has not yet been examined. We performed two split-plot experiments (1 and 2) with tomatoes (Solanum lycopersicum L.) and marigolds (Tagetes patula L.) as main plots. Expt. 1 involved five stover rates (0%, 25%, 50%, 75%, and 100% by volume) mixed with peat as subplots. Expt. 2 involved 0% stover mixed with peat, 25% distillers grain, and 50% quick compost (mechanically processed to accelerate compost process) stover with and without CaO, and 75% quick compost stover without CaO, as subplots. We measured growth parameters (height, dry weight, and flower number) and properties of the mixes. During Expt. 1, across both species, the addition of stover at rates >50% reduced relative greenness by 40%, vegetative biomass yield by 74%, and reproductive biomass yield by 73% compared to mixes with 0% and 25% stover. As the stover rate increased, available water content in the mixes decreased (r = −0.34; P < 0.001). Mixes with 0% and 25% stover had 34% more available water than mixes with 100% stover, which probably reduced plant growth in the 100% stover treatment. As the stover rate increased, plant tissue N and P concentrations decreased. Mixes with 0% stover generally had greater N and P concentrations than mixes with stover. During Expt. 2, for marigolds, the addition of 50% quick compost stover+CaO and 75% quick compost stover-CaO reduced relative greenness by 19% and vegetative biomass by 66% compared to mixes with 25% distillers grain or 0% stover. For tomatoes, the addition of 50% quick compost stover+CaO and 75% quick compost stover-CaO reduced biomass yield by 64%, which may be due to the higher pH and electrical conductivity (EC) of both treatments. Plant tissue N and P concentrations were greater in the mix with 25% distillers grain compared to most treatments, but N and P concentrations in the other mixes varied. Overall, the 25% distillers grain (3 peat: 1 distiller grain: 4 perlite) and 25% stover (3 peat: 1 stover: 4 perlite) treatments showed the most promise as additives in a peat-based mix.

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Cristián Vela-Hinojosa, Héctor B. Escalona-Buendía, José A. Mendoza-Espinoza, Juan M. Villa-Hernández, Ricardo Lobato-Ortíz, Juan E. Rodríguez-Pérez and Laura J. Pérez-Flores

Antioxidants, antioxidant capacity, and the expression of isoprenoid metabolism–related genes and two pigmentation-related transcription factors were studied in four native and four hybrid tomato (Solanum lycopersicum) genotypes with different-colored fruit. Red fruit genotypes were associated with greater lycopene, β-carotene, lipophilic antioxidant capacity, and greater chromoplast-specific lycopene β-cyclase (CYC-B) transcript levels. Orange fruit genotypes had greater concentrations of tocopherols and greater transcript levels of homogentisate phytyl transferase (VTE-2), 1-deoxy-D-xylulose phosphate synthase (DXS), and 4-hydroxyphenylpyruvate dioxygenase (HPPD). The yellow fruit genotype was greater in total polyphenol and hydrophilic antioxidant capacity with greater expression of geranylgeranyl reductase (GGDR), phytol kinase (VTE-5), phytoene synthase (PSY) 2, lycopene β-cyclase (LCY-B), SlNAC1, and SINAC4. Greater levels of individual antioxidants were associated with specific coloration of tomato fruit. Moreover, the negative correlations between the expression of PSY1 and VTE-5, and between lycopene and chlorophyll, suggest a balance between carotenoids, tocopherols, and chlorophylls. The results of this study support either the direct commercialization of tomatoes with different color fruit or use of their genotypes in breeding programs to increase antioxidant levels among existing cultivars.

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Robert L. Jarret, Gloria E. Barboza, Fabiane Rabelo da Costa Batista, Terry Berke, Yu-Yu Chou, Amanda Hulse-Kemp, Neftali Ochoa-Alejo, Pasquale Tripodi, Aniko Veres, Carolina Carrizo Garcia, Gabor Csillery, Yung-Kuang Huang, Erzsebet Kiss, Zsofia Kovacs, Mihaly Kondrak, Magda Lisette Arce-Rodriguez, Marisel A. Scaldaferro and Antal Szoke

Pepper (Capsicum L.) is a major vegetable and spice crop worldwide. Global production of both fresh and dried fruit continues to increase steadily in terms of area harvested and yield. Various topics are addressed in this review, including recent additions to and clarification of Capsicum taxonomy, genetic resources of Capsicum, cytogenetic studies, the current status of our understanding of the mechanisms affecting the biosynthesis of capsaicinoids, the use of gene mutations to elucidate carotenoid biosynthetic pathways and their regulation, and recent advances in whole-genome sequencing and assembly.

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Moritz Knoche, Eckhard Grimm, Andreas Winkler, Merianne Alkio and Jürgen Lorenz

Neck shrivel is a physiological disorder of european plum (Prunus ×domestica L.) fruit, characterized by a shriveled pedicel end and a turgescent stylar end. Affected fruit are perceived as of poor quality. Little is known of the mechanistic basis of neck shrivel, but microcracking of the cuticle has been implicated. The objective of our study was to quantify transpiration through the skin surfaces of european plums with and without symptoms of neck shrivel. Cumulative transpiration increased linearly with time and was greater in the susceptible european plum cultivar Hauszwetsche Wolff with neck shrivel, compared with fruit of the same cultivar but without neck shrivel and compared with fruit of the nonsusceptible unnamed clone P5-112. Cumulative transpiration of epidermal skin segments (ES) excised from symptomatic ‘Hauszwetsche Wolff’ from near the pedicel end exceeded that from ES excised from near the stylar end. The permeance of ES from near the pedicel end of ‘Hauszwetsche Wolff’ with neck shrivel (12.4 ± 2.6 × 10−4 m·s−1) exceeded that of ES from near the stylar end (2.9 ± 0.4 × 10−4 m·s−1) 4.3-fold. However, in the clone P5-112, the same difference was only 1.6-fold (1.3 ± 0.8 × 10−4 m·s−1 vs. 0.8 ± 0.3 × 10−4 m·s−1). Microscopy revealed numerous microcracks near the pedicel end of symptomatic ‘Hauszwetsche Wolff’ fruit but markedly fewer microcracks near the stylar end. The microcracks near the pedicel end were oriented parallel to the pedicel/style axis, whereas those near the stylar end were randomly oriented. Juices extracted from near the pedicel end of susceptible cultivars had consistently more negative osmotic potentials [ψS (e.g., for Doppelte Hauszwetsche −5.1 ± 0.1 MPa)] than those from near the stylar end (e.g., for Doppelte Hauszwetsche −4.0 ± 0.1 MPa) or that from fruit without symptoms of neck shrivel (e.g., for pedicel end and stylar scar regions of Doppelte Hauszwetsche −3.8 ± 0.1 vs. −3.3 ± 0.1 MPa, respectively). Our results indicate that increased transpiration through microcracks near the pedicel end may contribute to neck shrivel but that the causes of neck shrivel are likely more complex.