Camellia chrysantha flowers are in great market demand as a result of their high ornamental and medicinal values. To induce early flowering in 4-year-old juvenile C. chrysantha seedlings, three levels of paclobutrazol (PBZ) concentration (100, 200, and 300 ppm) were applied to the roots. PBZ is a triazole-type cytochrome P450 inhibitor that was found successful in inducing flowering in juvenile C. chrysantha grafted plants in a prior report. The current study shows that all three PBZ concentrations were equally effective in induction of floral buds, resulting in an average of 20 floral buds per treated plant. In comparison, none of the untreated plants flowered. Although the induced flowers were smaller than the ones from mature trees, PBZ treatment did not affect C. chrysantha flowers’ medical values, because there was no significant change in the content of pharmacologically active compounds (polysaccharide, polyphenols, flavonoids, and saponins). None of the PBZ treatments had a negative effect on the current year’s growth in height and basal diameter, photosynthesis, and levels of water-soluble sugars and nutrients [phosphorus (P), nitrogen (N), potassium (K), and carbon (C)]. It is concluded that PBZ is an effective flowering inducer for juvenile C. chrysantha plants. It was also found that PBZ-treated plants experienced defoliation, and there existed a strong correlation between severity of defoliation and PBZ concentration. This might be attributed by the stress induced by PBZ, as demonstrated by the increased activities of some of the stress-related enzymes [ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD)], and the level of malondialdehyde (MAD). Considering that severe defoliation can cause stunted or malformed plants and reduce aesthetic value, 100 ppm is the optimal PBZ concentration for flowering induction in C. chrysantha seedlings.
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Xiao-Juan Wei, Jinlin Ma, Kun Wang, Xiao-Jing Liang, Jin-Xuan Lan, Yue-Juan Li, Kai-Xiang Li and Haiying Liang
Amir Rezazadeh and Eric T. Stafne
The present study assessed the effect of photoperiod on budbreak of cuttings of three interspecific hybrid grape (Vitis) cultivars that had received different chilling hours. Stem cuttings were collected at 100-hour intervals of chilling (200, 300, 400, 500, 600, 700, and 800 hours) from the vineyard and kept in three growth chambers with daylengths of 8, 16, and 24 hours. Another group of cuttings were maintained in a greenhouse with a natural daylength range of 10.5–13 hours [8 Dec. 2017 to 4 May 2018 (average = 12 hours)]. Chilling requirements, days to budbreak, and budbreak rate were determined after plants were exposed to different chilling hours and daylengths. Results of our study demonstrated that the chilling requirements of all three cultivars were adequately reached at 600 hours or more. Increasing chilling exposure from 600 to 800 hours shortened the time to budbreak in all cultivars. Overall, ‘MidSouth’ had an average budbreak rate of 90% when receiving at least 600 hours chilling. ‘Blanc du bois’ and ‘Lake Emerald’ had 62% and 65% average budbreak, respectively. Longer days (24 hours) reduced time to budbreak by 14, 6, and 8 days, respectively, in ‘Blanc du bois’, ‘Lake Emerald’, and ‘MidSouth’ at 600 hours chilling. A combination of 24-hour photoperiod and chilling of 600 hours resulted in a maximum budbreak rate of 70%, 70%, and 100% in ‘Blanc du bois’, ‘Lake Emerald’, and ‘MidSouth’, respectively. Our results indicate that breaking dormancy may be controlled by both temperature and photoperiod in these three cultivars.
Layla J. Dunlap, Jeremiah R. Pinto and Anthony S. Davis
Water conservation in nursery systems is an ever-increasing focus, yet there is relatively little guidance for growers producing seedlings intended for restoration regarding how practices such as subirrigation influence plant growth in the nursery and after outplanting. Our study investigated red-flowering currant (Ribes sanguineum Pursh) seedling development and early field performance using different fertilizer treatments under a subirrigation regime. Plants were fertilized with 1) incorporated organic fertilizer, 2) incorporated controlled-release fertilizer, 3) top-dressed controlled-release fertilizer, or 4) water-soluble fertilizer. We found that seedlings grown with organic fertilizer used significantly less water than all other treatments. Media electrical conductivity (EC) levels were significantly greater in the organic fertilizer treatment, and EC values in the top portion of the media were significantly greater than the middle or bottom portions for all fertilizer treatments. The remaining subirrigation water at the end of 22 weeks held 17% of applied nitrogen (N) from the water-soluble fertilizer treatment and less than 1% of applied N from the other fertilizer treatments. We observed no differences in plant morphology among fertilizer treatments. Seedlings were subsequently out-planted into low- and high-competition treatments, where myriad factors indicated reduced growth among high-competition compared with low-competition plots, highlighting that competition for soil water limited seedling performance. These results indicate that a variety of fertilizers can be used to grow red-flowering currant under subirrigation and that postplanting growth is enhanced with control of competing vegetation.
Whitney J. Garton, Mark Mazzola, Nairanjana Dasgupta, Travis R. Alexander and Carol A. Miles
This study was designed to determine the efficacy of canker excision (CE) followed by a subsequent application of cauterization (CAU) and/or fungicide treatment to the excised area for the management of anthracnose canker (caused by Neofabraea malicorticis) on cider apple (Malus ×domestica) trees. Three experiments were conducted from 2015 to 2017, with one experiment each year, in an experimental cider apple orchard in western Washington where trees were naturally infested with N. malicorticis. Treatments were applied once in December and data were collected January through March. Treatments in the 2015 experiment were CE + CAU, CE + CAU + copper hydroxide, CE + 0.5% sodium hypochlorite, Bordeaux mixture (BM) only, and CE + copper hydroxide (control). The 2016 experiment included the same treatments as in 2015 plus one additional treatment, CE + BM. In 2017, one additional treatment was added, CE only, and CAU treatments were removed as they caused significant injury to the trees. Canker size was measured pretreatment, and the treated canker or excised area was measured posttreatment every 2 weeks for 13–15 weeks. Compared with pretreatment, cankers treated with BM did not increase in size, while the excised area treated with CAU increased 28-fold in size on average, and the excised area treated with 0.5% sodium hypochlorite or copper hydroxide increased up to 4-fold in size. Each year new cankers developed in all treatments 13–15 weeks after treatment application, at a time of year when there should not be any spores present to cause new infections. Dark brown streaking, indicative of the disease, was observed in the tissue below the intact or excised cankers 15 months after treatment application all years. Although N. malicorticis was not isolated from symptomatic tissue, symptoms were observed in all treatments including where cankers had not been excised and there was no wounding of the cambium tissue. Findings from this study indicate that of the treatments evaluated, the application of copper hydroxide after CE was the most effective for limiting the number of new cankers, but it did not limit expansion of the excised area. Additional physical and fungicidal strategies need to be tested for effective management of anthracnose canker.
A-Young Lee, Seon-Ok Kim and Sin-Ae Park
This study aimed to investigate elementary school students’ needs and preferences regarding urban agriculture. In total, 1268 students in grades 4 to 6 at four elementary schools in Seoul, South Korea, participated in the study. A 21-item questionnaire was developed and distributed in each school by trained researchers for 3 weeks in Oct. 2017. More than 73.7% of the students reported having an awareness of and need for urban agriculture, and 86.8% (N = 1048) indicated their participation intention. Students noted needing urban agriculture for scientific inquiry and recommended including a learning activity in urban agriculture (35.4%, N = 400) for psychological stability and stress reduction (20.9%, N = 236), and for leisure and hobby purposes (16.2%, N = 183). Students reported participating in urban agriculture activities in indoor and outdoor spaces (33.8%, N = 423) for more than 30 minutes and less than 60 minutes (42.0%, N = 525) twice per week (40.2%, N = 501) with friends (72.9%, N = 818). Preferred urban agriculture indoor activities were planting plants (21.8%, N = 822), arranging flowers (20.9%, N = 788), and making craftwork using plants (18.9%, N = 714). Harvesting (20.8%, N = 790), watering (15.1%, N = 570), and planting transplants (13.1%, N = 493) were preferred outdoor activities. Other preferred activities included playing with livestock (22.4%, N = 884), cooking with the harvested crops (21.3%, N = 805), and feeding livestock (17.2%, N = 650). The female students demonstrated greater perception, experience, awareness of the necessity, and willingness to participate in urban agriculture compared with male students (P = 0.01). The lower the grade, the more students perceived the necessity of urban agriculture (P < 0.001). The results of this study can provide basic data for the practical development of urban agriculture programs for elementary school students.
Kellie J. Walters and Roberto G. Lopez
The plant growth regulator (PGR) ethephon [(2-chloroethyl) phosphonic acid; ETH] can be sprayed on floriculture crops to inhibit internode elongation, hinder apical dominance, increase lateral branching, and abort flower buds and flowers. However, the efficacy of ETH can be reduced as the pH of the carrier water used to mix the spray solution or temperature increase. Therefore, our objective was to quantify how the efficacy of ethephon sprays is influenced by carrier water alkalinity (CaCO3; ALK) and the air temperature at application (TEMP). Young plants of verbena (Verbena peruviana) ‘Aztec Blue Velvet’, ivy geranium (Pelargonium ×peltatum) ‘Precision Pink’, and petunia (Petunia ×hybrida) ‘Easy Wave Neon Rose’ were transplanted into 11-cm-diameter containers and grown in a greenhouse with an average daily air temperature (ADT) set point of 21 °C. Before the ETH spray application(s), the ADT in each greenhouse compartment was changed from a set point of 21 °C to 14, 17, 20, 23, or 26 °C for ≈24 hours. Plants were sprayed with 0, 250, 500, or 750 mg·L−1 ETH mixed with carrier water containing ≈50, 150, or 300 mg·L−1 CaCO3 2 and 3 weeks (Expt. 1) or 1 or 2 weeks (Expt. 2) after transplant. Generally, high ALK had a negative effect on spray efficacy. For example, an increase in ALK from 50 to 300 mg·L−1 CaCO3 resulted in one and five fewer ivy geranium and verbena branches, respectively. In addition, as application TEMP increased above 23 °C, chemical efficacy generally decreased in all species. For instance, as ETH increased from 0 to 750 mg·L−1 across ALKs, inflorescence number of ivy geraniums increased from 7 to 18 at a TEMP of 23 °C, but was unaffected at 26 °C. Based on our results, we can conclude that both ALK and TEMP influence ETH efficacy and are additional factors for greenhouse growers to consider when making applications.
Nastaran Basiri Jahromi, Amy Fulcher, Forbes Walker, James Altland, Wesley Wright and Neal Eash
Controlling irrigation using timers or manually operated systems is the most common irrigation scheduling method in outdoor container production systems. Improving irrigation efficiency can be achieved by scheduling irrigation based on plant water needs and the appropriate use of sensors rather than relying on periodically adjusting irrigation volume based on perceived water needs. Substrate amendments such as biochar, a carbon (C)-rich by-product of pyrolysis or gasification, can increase the amount of available water and improve irrigation efficiency and plant growth. Previous work examined two on-demand irrigation schedules in controlled indoor (greenhouse) environments. The goal of this study was to evaluate the impact of these on-demand irrigation schedules and hardwood biochar on water use and biomass gain of container-grown Hydrangea paniculata ‘Silver Dollar’ in a typical outdoor nursery production environment. Eighteen independently controlled irrigation zones were designed to test three irrigation schedules on ‘Silver Dollar’ hydrangea grown in pine bark amended with 0% or 25% hardwood biochar. The three irrigation schedules were conventional irrigation and two on-demand schedules, which were based on substrate physical properties or plant physiology. Conventional irrigation delivered 1.8 cm water in one event each day. The scheduling of substrate-based irrigation was based on the soilless substrate moisture characteristic curve, applying water whenever the substrate water content corresponding to a substrate water potential of –10 kPa was reached. The plant-based irrigation schedule was based on a specific substrate moisture content derived from a previously defined relationship between substrate moisture content and photosynthetic rate, maintaining the volumetric water content (VWC) to support photosynthesis at 90% of the maximum predicted photosynthetic rate. Total water use for the substrate-based irrigation was the same as for the conventional system; the plant-based system used significantly less water. However, plant dry weight was 22% and 15% greater, water use efficiency (WUE) was 40% and 40% greater, and total leachate volume was 25% and 30% less for the substrate-based and plant-based irrigation scheduling systems, respectively, than for conventional irrigation. The 25% biochar amendment rate reduced leachate volume per irrigation event, and leaching fraction, but did not affect total water use or plant dry weight. This research demonstrated that on-demand irrigation scheduling that is plant based or substrate based could be an effective approach to increase WUE for container-grown nursery crops without affecting plant growth negatively.
Michelle M. Moyer, Jaqueline King and Gary Moulton
The Puget Sound American Viticulture Area (AVA), located west of the Cascade Mountain Range in Washington State, is a large and uniquely situated area with diverse topography and mesoclimates. Given the young age of the AVA, little formal information exists on the appropriate rootstock–scion combination in wine grapes (Vitis vinifera) for the region. This project reports on a series of rootstock trials from 2003 to 2007, which evaluated the influence of ‘420A Millardet et de Grasset’, ‘3309 Couderc’, ‘101-14 Millardet et de Grasset’ (all Vitis hybrids), and a self-rooted control on basic harvest metrics of the wine grape scion ‘Pinot noir clone 02A’. At the warmer site in Everson, WA, rootstocks had no effect on final juice harvest metrics measured by soluble solids, titratable acidity (TA), and pH. At the cooler site in Mount Vernon, WA, the use of rootstocks did not always influence soluble solids or pH but did reduce final harvest TA, a desired effect for the region that is typified by low sugar–high TA wines. Even with a reduction in TA in some rootstock–scion combinations, overall, TA remained at the upper end or above the range typically desired for many wine styles.
Guirong Zhang, Mohammad Babadoost, Alan De Young, Eric T. Johnson and David A. Schisler
Basil downy mildew (Peronospora belbahrii) is a destructive disease that occurs in sweet basil (Ocimum basilicum). Foliar fungicide treatments could reduce infection and the severity of foliar symptoms over the course of the growing season. Multiple fungicides in variable combinations, application rates, and sequences were applied to basil foliage weekly over the course of a field season in Illinois (14 July to 8 Sept. 2014), and the treatment effects on basil downy mildew were evaluated three times. The evaluated treatments included mixtures and different rotations of azoxystrobin, potassium phosphite, mandipropamid, cyazofamid, oxathiapiprolin, experimental compound A18269SE, dimethomorph, zoxamide + mancozeb, fluazinam, fluopicolide, mefenoxam + copper hydroxide, fenamidone, mancozeb, and ametoctradin + dimethomorph. Potassium phosphite, which is known to be effective against other downy mildew pathogens, was included in combination with other fungicides or in fungicide application sequences. Disease severity was rated in fungicide-treated plots (0% to 20%) and compared with the control (73% to 80%) at each evaluation time. All fungicide treatments significantly reduced the area under the disease progress curve values compared with the untreated control. Adding a nonionic surfactant did not improve the efficacy of any of the chemical treatments evaluated for reducing downy mildew. Organic basil growers need novel, effective products to minimize damage from basil downy mildew. To aid organic basil growers, two novel, effective biocontrol agents were evaluated, Bacillus amyloliquefaciens AS 43.3 and Papiliotrema flavescens OH 182.9 3C (formerly Cryptococcus flavescens). Greenhouse experiments were conducted with the fungicides quinoxyfen and azoxystrobin serving as negative and positive fungicide treatment controls, respectively. Azoxystrobin reduced downy mildew according to the greenhouse tests, but neither quinoxyfen nor the biocontrol agents reduced downy mildew severity compared with the untreated control. This study identified 13 fungicide regimens that resulted in less than 10% basil downy mildew disease severity. More studies are needed to identify effective control products for basil downy mildew on organic basil.
Guo-Liang Jiang, Laban K. Rutto and Shuxin Ren
Edamame is a vegetable or specialty soybean (Glycine max (L.) Merr.) with high nutrition and market value. The market demand for edamame has significantly increased in the United States since its health and nutritional benefits became recognized. However, there are a limited number of domestically developed or improved edamame cultivars in the United States, and the knowledge of edamame is very limited. In this study, 86 breeding lines and cultivars of maturity group (MG) V and VI developed in the United States were evaluated in replicated field trials for edamame yield and agronomic traits in Virginia in 2015 and 2016. The results indicated that there were significant differences among the genotypes and between years in all the traits investigated (plant height, fresh biomass, pod yield, pod ratio, fresh seed yield, seed ratio, and 100-seed weights), but the yearly differences for dried 100-seed weight and dried-to-fresh ratio of seeds were insignificant. Genotype-by-year interaction effects were not significant in most cases. Estimates of the broad sense heritability varied with traits, from 23% to 88%. Coefficients of phenotypic and genotypic correlation were mostly low, but fresh pod and seed yields were highly correlated. Fresh biomass exhibited a positive phenotypic correlation with pod and seed yields, but the genotypic correlation coefficients were not significant. Twelve breeding lines were preliminarily identified to have greater edamame yield and desired traits. The information generated in this study will be helpful for edamame breeding and commercial production.