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Asmita Paudel, Ji Jhong Chen, Youping Sun, Yuxiang Wang and Richard Anderson

Sego SupremeTM is a designated plant breeding and introduction program at the Utah State University Botanical Center and the Center for Water Efficient Landscaping. This plant selection program introduces native and adapted plants to the arid West for aesthetic landscaping and water conservation. The plants are evaluated for characteristics such as color, flowering, ease of propagation, market demand, disease/pest resistance, and drought tolerance. However, salt tolerance has not been considered during the evaluation processes. Four Sego SupremeTM plants [Aquilegia barnebyi (oil shale columbine), Clematis fruticosa (Mongolian gold clematis), Epilobium septentrionale (northern willowherb), and Tetraneuris acaulis var. arizonica (Arizona four-nerve daisy)] were evaluated for salt tolerance in a greenhouse. Uniform plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.25 dS·m−1 as control or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 for 8 weeks. After 8 weeks of irrigation, A. barnebyi irrigated with saline solution at an EC of 5.0 dS·m−1 had slight foliar salt damage with an average visual score of 3.7 (0 = dead; 5 = excellent), and more than 50% of the plants were dead when irrigated with saline solutions at an EC of 7.5 and 10.0 dS·m−1. However, C. fruticosa, E. septentrionale, and T. acaulis had no or minimal foliar salt damage with visual scores of 4.2, 4.1, and 4.3, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. As the salinity levels of treatment solutions increased, plant height, leaf area, and shoot dry weight of C. fruticosa and T. acaulis decreased linearly; plant height of A. barnebyi and E. septentrionale also declined linearly, but their leaf area and shoot dry weight decreased quadratically. Compared with the control, the shoot dry weights of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis decreased by 71.3%, 56.3%, 69.7%, and 48.1%, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. Aquilegia barnebyi and C. fruticosa did not bloom during the experiment at all treatments. Elevated salinity reduced the number of flowers in E. septentrionale and T. acaulis. Elevated salinity also reduced the number of shoots in all four species. Among the four species, sodium (Na+) and chloride (Cl) concentration increased the most in A. barnebyi by 53 and 48 times, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. In this study, C. fruticosa and T. acaulis had minimal foliar salt damage and less reduction in shoot dry weight, indicating that they are more tolerant to salinity. Epilobium septentrionale was moderately tolerant to saline solution irrigation with less foliar damage, although it had more reduction in shoot dry weight. On the other hand, A. barnebyi was the least tolerant with severe foliar damage, more reduction in shoot dry weight, and a greater concentration of Na+ and Cl.

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Debalina Saha, S. Christopher Marble, Brian Pearson, Héctor Pérez, Gregory MacDonald and D. Calvin Odero

The objective of this research was to determine how mulch type affects adsorption and efficacy of commonly used preemergence herbicides in nurseries and landscapes. Nursery containers were filled with standard potting media and mulched with either pine bark (PB) mini-nuggets (mixed Pinus sp.), pine straw (PS; mixed Pinus sp.), or shredded eucalyptus hardwood (HW; Eucalyptus sp.) at a 2-inch depth. Herbicides including dimethenamid-P + pendimethalin (applied as a tank mix), prodiamine, and indaziflam were applied to mulched containers, watered in, and the mulch was subsequently removed 3 days later. Seeds of garden spurge (Euphorbia hirta), large crabgrass (Digitaria sanguinalis), and eclipta (Eclipta prostrata) were then seeded and used as bioassay species for dimethenamid-P + pendimethalin, prodiamine, and indaziflam, respectively. Chemical assays were also performed using a separate set of pots mulched with PB at 2 inches and treated with the same herbicides. Results from the bioassay experiment showed PS was the only mulch type that did not significantly decrease efficacy of any applied herbicide. Chemical assays showed only 34% of the applied dimethenamid-P reached the soil surface as evidenced by chemical assay, but more dimethenamid-P moved through PB than did pendimethalin (12%) or prodiamine (17%), which adsorbed more strongly. Overall results suggest preemergence herbicides will be strongly adsorbed to organic mulch. However, as mulch is typically more effective on weeds that germinate below the mulch layer, this does not automatically result in reduced efficacy from herbicide + mulch combinations, and the addition of a preemergence herbicide may be effective in reducing weed germination within or on top of the mulch layer.

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Kelly Nascimento-Silva, Luis Roca-Castillo, María Benlloch-González and Ricardo Fernández-Escobar

Silicon (Si) is the second most abundant element in the Earth’s crust. It is a nonessential element for plant growth, but it is considered beneficial because it can prevent biotic and abiotic stresses. Because nothing is known about the effects of Si in the olive, two experiments were performed with young plants of ‘Arbequina’ and ‘Picual’ cultivars to evaluate the effect of continuous Si applications on the incidence of olive leaf spot, the main foliar disease affecting this crop. Plants were grown in pots containing a mixture of washed sand and peat. In the first experiment, Si was foliar sprayed (foliar treatment) or applied to the soil through irrigation water (soil treatment) at the concentrations of 0, 2.5, 5, and 10 or 0, 1.25, 2.5, and 5 mg·L−1, respectively. The treatments were arranged in a completely randomized design for each cultivar. In the second experiment, the experimental design was a randomized complete block design in a 2 × 4 factorial arrangement, consisting of two forms of Si application (foliar vs. soil) and four concentrations (0, 5, 10, or 20 mg·L−1). Leaf Si concentration significantly increased with the amount of Si applied. After 5 months of treatments, plants were inoculated with a conidial suspension of the pathogen, and the disease index (DSI) was calculated. Shoot growth only increased in ‘Picual’ after Si application. The DSI showed a significant reduction in both cultivars treated with Si when compared with control plants, although differences between cultivars were observed.

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Kate A. Ivancic, Matthew D. Ruark, Francisco J. Arriaga and Erin M. Silva

Spring-planted green manure cover crops may provide a nitrogen (N) benefit to a subsequent sweet corn (Zea mays L.) crop, but spring growth and lack of consistent benefits documented in previous studies provide limitations to adoption. Berseem clover (BC; Trifolium alexandrinum) and chickling vetch (CV; Lathyrus sativus L.) are two legumes that could be beneficial when spring-seeded, but they have not been well studied in this context. The objectives of this study were to measure spring-seeded cover crop biomass and N yield, and the subsequent effects on sweet corn yield and response to N fertilizer. The study was conducted in 2014 and 2015, and the experimental design was a randomized complete block split-plot design with cover crop as whole-plot treatments [CV, BC, berseem clover and oat (Avena sativa) mixture (BC + O), oats, and no cover crop] and N rate as split-plot treatments. Cover crop growth and effects on sweet corn production varied greatly between years, with both cover crop and sweet corn biomass greater in 2015, although BC produced very little biomass (<0.7 Mg·ha–1) and thus is not recommended for spring seeding. In 2014, CV resulted in the lowest agronomically optimum N rates (AONRs) compared with no cover crop, suggesting a potential N credit when only having an N yield of 11.6 kg·ha–1, but this effect was not seen in 2015. There was also no evidence that oat would supply N to the subsequent crop. Overall, evidence is lacking that any spring-seeded cover crop will provide a consistent N benefit on sandy soil, and limitations to spring growth may preclude widespread adoption.

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Keun H. Cho, Joo Young Kim, Maria I. Alvarez, Veronica Y. Laux, Lauren K. Valad, Joshua M. Tester, Thomas A. Colquhoun and David G. Clark

Fluorescent proteins (FT) have become essential, biological research tools. Many novel genes have been cloned from a variety of species and modified for effective, stable, and strong expression in transgenic organisms. Although there are many applications, FT expression has been employed most commonly at the cellular level in plants. To investigate FT expression at the whole-plant level, particularly in flowers, petunia ‘Mitchell Diploid’ [MD (Petunia ×hybrida)] was genetically transformed with seven genes encoding FTs: DsRed2, E2Crimson, TurboRFP, ZsGreen1, ZsYellow1, rpulFKz1, or aeCP597. Each gene was cloned into a pHK-DEST-OE vector harboring constitutive figwort mosaic virus 35S promoter and NOS-terminator. These plasmids were individually introduced into the genome of MD by Agrobacterium tumefaciens–mediated transformation. Shoot regeneration efficiency from the cocultured explants ranged from 8.3% to 20.3%. Various intensities of red, green, and yellow fluorescence were detected from TurboRFP, ZsGreen1, and ZsYellow1-transgenic flowers, respectively, under ultraviolet light for specific excitation and emission filters. More than 70% of plants established from the regenerated shoots were confirmed as transgenic plants. Transgenic ZsGreen1 petunia generated strong, green fluorescence in all flower organs of T0 plants including petals, stigmas, styles, anthers, and filaments. Most of the chromophores were localized to the cytoplasm but also went into the nuclei of petal cells. There was a positive linear relationship (R 2 = 0.88) between the transgene expression levels and the relative fluorescent intensities of the ZsGreen1-transgenic flowers. No fluorescence was detected from the flowers of DsRed2-, E2Crimson-, rpulFKz1-, or aeCP597-transgenic petunias even though their gene transcripts were confirmed through semiquantitative reverse transcriptase-polymerase chain reaction. T1 generation ZsGreen1 plants showed green fluorescence emission from the cotyledons, hypocotyls, and radicles, which indicated stable FT expression was heritable. Four homozygous T2 inbred lines were finally selected. Throughout this study, we demonstrated that ZsGreen1 was most suitable for generating visible fluorescence in MD flowers among the seven genes tested. Thus, ZsGreen1 may have excellent potential for better utility as a sensitive selectable marker.

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Beiquan Mou

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Yu Wang, Haobo Yang, Shuai Zhong, Xin Liu, Tong Li and Chengwen Zong

Sugar and organic acid contents as well as sugar-to-acid ratio of fruit are important factors affecting fruit quality and processing. In this study, we compared sugar and organic acid contents of Vaccinium uliginosum (bog bilberry) fruit harvested from 100 plants across 10 wild populations growing in the Changbai Mountains of China. Correlation of sugar and acid contents with the spatial distribution of these populations was accessed. Germplasm with high sugar and low acid with potential for use in future breeding was also identified. Results showed that sugar and organic acid contents varied among different V. uliginosum populations in the Changbai Mountains. Fructose (18.60–38.54 mg·g−1) and glucose (15.77–35.08 mg·g−1) were the main sugars, whereas quinic (16.06–20.97 mg·g−1), citric (10.39–14.96 mg·g−1), and malic (4.28–7.47 mg·g−1) acids were the main organic acids in V. uliginosum. The first population collected in the Dongfanghong forest farm (lat. 42°00′N, long. 128°03′E) showed the highest average sugar content and sugar-to-acid ratio among the sampled populations. Moreover, total sugar content and sugar-to-acid ratio of Sample 7—Population 1, which is located at Manjiang forest farm (lat. 41°09′N, long. 127°05′E) was much higher than the other 99 samples, making this sample representative of important germplasm for breeding. Altitude and latitude were important environmental factors affecting sugar and organic acid contents. Fructose, glucose, and total sugar contents were positively correlated with altitude and negatively correlated with latitude. Oxalic acid content and sugar-to-acid ratio were positively correlated with altitude, and there was no significant correlation between organic acid contents and latitude.

Open access

Erin J. Yafuso, Paul R. Fisher, Ana C. Bohórquez and James E. Altland

Greenhouse propagation of unrooted plant cuttings is characterized by short container cell height and high irrigation frequency. These conditions can result in high moisture level and low air content in soilless container substrates (“substrates”), causing delayed growth of adventitious roots and favoring root disease. The objective of this study was to quantify and compare substrate water and air relations for three propagation substrates (peat, rockwool, and phenolic foam) that varied widely in physical characteristics using four methods: 1) evaporation method with a tensiometer, 2) frozen column method, 3) gravimetric analysis, and 4) X-ray computed tomography (CT) analysis. Moisture retention curves based on evaporation (1) and the frozen column (2) resulted in differences for peat, but similar curves for rockwool and foam. The frozen column method was simple and low cost, but was constrained by column height for peat, which had a higher water potential compared with the other two substrates. Substrate porosity analysis at container capacity by gravimetric or CT methods were similar for volumetric water and air content (VWC and VAC) in rockwool and foam, but differed for peat for VWC and VAC. Gravimetric analysis was simple, rapid, and low cost for whole-cell analysis, but CT further quantified spatial water and air relations within the cell and allowed visualization of complex water and air relations in an image. All substrates had high water content at container capacity ranging from 67% to 91% VWC with 5% to 11% VAC in the short propagation cells, emphasizing the need for careful irrigation management.

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Zhenyu Huang, Lehan Xia, Long Chen, Zexuan Cui, Shuai Ren, Yibin Feng and Yuling Chen