bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in Leaf Nutrient Concentrations of Freeman Maple Resulting from Canopy Position, Leaf Age, and Petiole Inclusion
Authors: Mickelbart Michael V.
Published: February 2019

Consistent evaluation of nursery crop nutrient status within and among plots and years requires careful consideration of leaf collection practices. The objectives of this study were to determine the differences and variability among leaf age and cardinal position within the tree. Another objective was to determine if petioles should be included in leaf samples. Leaves were collected from seven trees of the Freeman maple (red–silver maple hybrid) Celebration® (Acer ×freemanii) from two leaf ages (early- and late-season leaves) and four positions (north, south, east, and west). On the south side of each tree, samples were separated into lamina, petiole, or lamina + petiole samples. Leaf traits were not different among positions, except that leaves on the north side of the tree had a lower specific leaf weight (SLW). Leaf nitrogen (N) was slightly lower on the north and west sides of the tree and leaf calcium (Ca) was highest on the south side of the tree, but otherwise position (i.e., side of the tree) had very little effect on leaf nutrient concentrations. Older leaves (leaves produced early in the season) were darker green and had a higher leaf area, longer petiole length, and lower SLW. Older leaves also had higher concentrations (on a mass basis) of all nutrients analyzed. Petiole concentrations of Ca, magnesium, and manganese were higher than lamina concentrations, whereas concentrations of N, sulfur, iron, zinc, boron, copper, and aluminum were all higher in the lamina. These differences, however, did not affect nutrient analyses conducted on samples consisting of lamina + petiole or lamina only. Variation within samples was lowest on the east and south sides for macro- and micronutrients, respectively, in late-season leaves. Based on the relative variation within samples, samples for nutrient analysis of red maple and red maple hybrids should consist of leaves collected from the southeast side of the tree and can consist of samples with or without petioles attached to the lamina.
Use of External Indicators to Predict Maturity of Mini-watermelon Fruit
Authors: Vinson Edgar L. , Woods Floyd M. , Kemble Joseph M. , Perkins-Veazie Penelope , Davis Angela , Kessler J. Raymond
Published: February 2019

Mini-watermelon [Citrullus lanatus (Thunb.)] cultivars Valdoria and Vanessa were evaluated at 20, 30, 40, or 50 days after anthesis to determine maturity at harvest. Fruit circumference, weight, ground spot color, and number of senescent tendrils were measured as external indicators for each watermelon. Soluble solids content (SS), pH, and SS:total acid ratio (SS:TA) of each watermelon were determined to provide an indication of internal maturity. Regression and Akaike Information Criterion fit statistics analyses were performed to determine significant relationships and best predictors for external indicators of internal maturity factors. In this study, external predictors were most closely linked to fruit pH rather than to SS or SS/TA. Of the external indicators tested, fruit weight, circumference, number of senescent tendrils, and International Commission on Illumination (CIE) b* color coordinate values of the ground spot were best related to fruit pH. According to the regression models, two completely senesced tendrils, a circumference of 53 cm, weight of 3 kg, and CIE b* coordinate ground spot value of 40 are each sufficient to predict maturity when pH is used as the internal indicator of maturity under the conditions of this experiment.
Effects of Drying and Extraction Conditions on the Biochemical Activity of Selected Herbs
Authors: Yi Weiguang , Wetzstein Hazel Y.
Published: February 2019

Herbs have been long known to provide health-promoting benefits and are demonstrated to have antioxidant, anti-inflammatory, antibacterial, analgesic, and antitumor activities. This study evaluated the effects of drying conditions and extraction protocols on the biochemical activity of three culinary and medicinal herbs: rosemary (Rosmarinus officinalis), motherwort (Leonurus cardiaca), and peppermint (Mentha piperita). Leaf tissues were dried by sun, oven-dried at 40 °C, or oven-dried at 70 °C and extracted using 80% methanol or 80% ethanol. Total polyphenol (TPP) using the Folin-Ciocalteu reagent method and antioxidant capacity using the Trolox-equivalent antioxidant capacity (TEAC) assay were determined. Both drying and extraction conditions significantly impacted TPP content and TEAC in the three herb species. Sun-dried or 40 °C oven-dried herbs exhibited significantly higher TPP content and TEAC capacity than fresh samples, suggesting low-temperature drying may be a good postharvest means to store medicinal/culinary herbs. Exposure to 70 °C oven-drying caused significant antioxidant loss. In addition, the current study showed that with fresh tissue, 80% ethanol extraction had significantly higher TPP and TEAC than 80% methanol extraction for all three herbs, yet for dried herbs, the efficacy of ethanol/methanol extraction varied with different drying treatments.
Sources of Resistance to Race 2WF Powdery Mildew in U.S. Watermelon Plant Introductions
Authors: Zhang Haiying , Guo Shaogui , Gong Guoyi , Ren Yi , Davis Angela R. , Xu Yong
Published: February 2019

Powdery mildew of cucurbits, incited by Podosphaera xanthii (Castagne) Braun & Shishkoff (syn. Sphaerotheca fuliginea auct. p.p.), is an economically important foliar disease. which is now common in watermelon [Citrullus lanatus (Thunb.) Mastum. & Nakai]. This disease occurs in all watermelon-growing areas and can reduce yields by up to 30%. Finding and breeding for resistance to this disease is important to reduce dependence on fungicides and to use in combination with fungicides to limit the spread of fungicide-resistant P. xanthii. This is the first English report that race 2WF of P. xanthii can infect watermelon. It is the prevalent race of watermelon powdery mildew in Beijing.
Application of Composted Poultry Litter as a Fertilizer for Landscape Bedding Plants
Authors: Marble S. Christopher , Sibley Jeff L. , Gilliam Charles H. , Torbert H. Allen
Published: February 2019

Each year, over 16 million tons of poultry litter is produced in the United States. Federal and state regulations now limit the amount of poultry litter that can be land-applied, making it difficult to store and dispose of poultry litter. The objective of this study was to evaluate composted poultry litter (CPL) as a fertilizer source for bedding plants at various rates in comparison with commercially available inorganic fertilizers in regard to plant growth and nutrient leaching. Two experiments were conducted to evaluate use of CPL as fertilizer for landscape annual bedding plants. Petunia spp. ‘Celebrity Red’ and Verbena hybrida ‘Quartz Scarlet’ were planted in raised beds simulating an urban landscape. Before planting, 10 inorganic fertilizer or CPL treatments were incorporated into the raised beds, including Peafowl® brand garden-grade fertilizer 13N–5.6P–10.9K (13-13-13) at rates of 4.9 g N/m2 and 9.8 g N/m2, Polyon® 13N–5.6P–10.9K (13-13-13) at rates of 4.9 g N/m2 and 9.8 g N/m2, and CPL at rates of 4.9 g N/m2, 9.8 g N/m2, 19.6 g N/m2, 29.4 g N/m2, 39.2 g N/m2, and 49 g N/m2. Use of CPL incorporated into landscape planting beds as a fertilizer source resulted in plants equal to or larger than plants grown with conventional inorganic fertilizers. Nitrate (NO3) and ammonia (NH4) levels in leachates from plots amended with CPL were comparable with plots amended with commercial inorganic fertilizers and nitrogen (N) levels were in most cases less in plots fertilized with CPL when compared with inorganic fertilizers when the same N rate was applied. Composted poultry litter may not be able to fully replace inorganic fertilizers, but it can reduce inorganic fertilizer requirements and provide an environmentally sound alternative to poultry waste disposal as well as provide beneficial aspects for plant growth in annual bedding plants.
Analysis of the Impact of Climatic Conditions on Floral Transformation in Hydrangea macrophylla ‘Leuchtfeuer’
Authors: Galopin Gilles , Crespel Laurent , Mauget Jean C. , Morel Philippe
Published: February 2019

Hydrangea macrophylla is a horticultural plant of considerable commercial interest that has been widely studied with the aim to more effectively control the different stages of its development during production. However, although floral transformation is a key factor underlying the commercial quality of the product, it remains difficult to control despite these efforts. The floral transformation sequence consists of three successive phases: floral induction (B1), floral evocation (B2), and floral organogenesis (B3). The first is a phase of vegetative organogenesis without elongation leading to the formation of a bud composed of eight phytomer primordia under inductive climatic conditions. This work shows that climatic conditions favorable to floral transformation must be continuously applied without interruption throughout phase B1 to ensure the formation of the floral bud in Hydrangea macrophylla ‘Leuchtfeuer’. In the opposite case, floral transformation is stopped and vegetative growth begins once again.
Determining the Effects of Abscisic Acid Drenches on Evapotranspiration and Leaf Gas Exchange of Tomato
Authors: Astacio Manuel G. , van Iersel Marc W.
Published: February 2019

It is common for plants in the retail market to receive inadequate water and lose aesthetic value within a short period of time. The plant hormone abscisic acid (ABA) is naturally produced in response to drought conditions and reduces transpiration (E) by closing the stomata. Thus, ABA may lengthen shelf life of retail plants by reducing water loss. Two studies were conducted to look at effects of ABA on plant water use and shelf life over a 13-day period and short-term effects of ABA on leaf physiology. The objective of the short-term study was to determine how quickly 100-mL drenches of 250 mg·L−1 ABA solution affect leaf gas exchange of tomatoes (Solanum lycopersicum ‘Supersweet 100’). ABA drenches reduced stomatal conductance (gS), E, and photosynthetic rate (Pn) within 60 min. After 2 h, E, gs, and Pn were reduced by 66%, 72%, and 55% respectively, compared with the control plants. In the13-day study, ABA was applied to tomatoes as a 100-mL drench at concentrations ranging from 0 to 1000 mg·L−1 and ABA effects on water use and time to wilting were quantified. Half of the plants were not watered after ABA application, whereas the other plants were watered as needed. In general, higher ABA concentrations resulted in less water use by both well-watered and unwatered plants. ABA delayed wilting of unwatered plants by 2 to 8 days (dependent on the dose) as compared with control plants. In well-watered plants, ABA reduced daily evapotranspiration (ET) for 5 days, after which there were no further ABA effects. Negative side effects of the ABA application were rate-dependent chlorosis of the lower leaves followed by leaf abscission. These studies demonstrate that ABA drenches rapidly close stomata, limit transpirational water loss, and can extend the shelf life of retail plants by up to 8 days, which exemplifies its potential as a commercially applied plant growth regulator.
Carbon, Nitrogen, and Orthophosphate Leaching from Soil under Single- and Mixed-species Landscapes
Authors: Pannkuk Tim R. , Aitkenhead-Peterson Jacqueline A. , Steinke Kurt , Thomas James C. , Chalmers David R. , White Richard H.
Published: February 2019

Effective landscape management practices in urban landscapes must include an awareness of nutrient removal from soil caused by leaching, and these practices should be those least damaging to freshwaters. Annual mean dissolved organic carbon (DOC), dissolved organic nitrogen (DON), nitrate-N, ammonium-N, soluble phosphate, and bicarbonate concentrations and fluxes were quantified in leachate from landscapes planted with different urban horticultural types. Plot vegetation consisted of either a single species or mixed species. The experiment was conducted at two sites in Texas with significantly different irrigation water chemistry. At the two sites, plant species had a significant effect on PO43--P flux, and irrigation chemistry had a significant effect on all nutrient fluxes. There was an interaction between plant species and irrigation chemistry for PO43--P flux (P < 0.05) only. The relationship between bicarbonate and DOC flux at sites was stronger and significant (0.92; P < 0.05) at the site irrigated with Na-HCO3 municipal tap water than at the site irrigated with Ca-HCO3 municipal tap water (R2 = 0.76, P = 0.05). Type of irrigation water chemistry may result in lower plant water uptake resulting in increased nutrients lost to leachate.
Tolerance of Three Warm-season Turfgrasses to Increasing and Prolonged Soil Water Deficit
Authors: Cathey Sarah E. , Kruse Jason K. , Sinclair Thomas R. , Dukes Michael D.
Published: February 2019

Water management and turfgrass breeding efforts focused on water conservation can benefit from a better understanding of drought stress physiology because it relates to visual quality. In a repeated study under controlled conditions, ‘Argentine’ bahiagrass (Paspalum notatum Flugge), ‘Floratam’ st. augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and ‘Empire’ zoysiagrass (Zoysia japonica Steud.) were subjected to drought stress as defined by the normalized transpiration ratio (NTR) of drying to well-watered plants. Differences in total water extracted from the soil as the soil dried to stomatal closure were not different among grasses; however, zoysiagrass had the slowest water use rate and less firing under increasing drought stress than the other grasses. Optical sensing of the normalized difference vegetation index from the turf canopies was not an effective predictor of drought stress for either study. In both studies, severe wilting and some firing occurred in bahiagrass and st. augustinegrass when NTR was 0.3. Zoysiagrass was not severely wilted until 0.1 NTR and exhibited little firing even after drying had continued for an additional 7 days past 0.1 NTR. After 7 days at well-watered status after drought stress to a severity of 0.1 NTR, all grasses were able to recover to an acceptable visual quality rating. This recovery from severe wilt and some canopy firing (except for zoysiagrass), indicating that a return to well-watered soil after severe stress, can result in acceptable turf recovery.
Development of Simple Bayesian Belief and Decision Networks as Interactive Visualization Tools for Determining Optimal In-row Spacing for ‘Beauregard’ Sweetpotato
Authors: Villordon Arthur , Sheffield Ron , Rojas Jose , Chiu Yin-Lin
Published: February 2019

A Bayesian belief network (BBN) model, which we named BxINROW/NET, was developed to represent the relationships among in-row spacing regimes, some agroclimatic variables known to influence storage root initiation, growing degree-days (GDDs) to harvest, and yield grades in ‘Beauregard’ sweetpotato grown in Louisiana. The model was developed from experimental data collected in a subset of years between 1990 and 2010 and assumed that soil moisture, weeds, and chemical injury were not limiting variables during the growing season. The BBN model error rates for storage root yields were 21%, 20%, and 13% for U.S. #1 (US1), canner, and jumbo grades, respectively, as estimated from repeated random partitioning of the modeling data set into training and testing partitions. In comparison, the error rates for a baseline logistic regression model were 56%, 54%, and 53% for US1, canner, and jumbo grades, respectively. The BBN model showed that GDDs to harvest (GDDH) as well as air and soil temperatures during the critical storage root initiation period [20 days after transplanting (DAT)] interacted with in-row spacing regimes to help determine the yield outcomes. Under a uniform irrigation management and minimum to intermediate GDDH (980 to 1495 GDDs), narrow (20 to 22 cm) to intermediate in-row spacing regimes (30 cm) were associated with higher probabilities (56% to 71% of cases) for attaining a high US1 yield (22 to 45 t·ha−1). These outcomes were associated with minimum to intermediate soil and air heat units 20 DAT, representing early to intermediate planting dates. Under similar conditions, wide in-row spacing treatments (38 to 40 cm) were associated with increased probabilities (100% of cases) for achieving a high yield of jumbo or oversized roots if GDDH (1495 to 1710 GDDs) was maximized. BxINROW/NET was also used as the foundation model to construct Bayesian decision networks (BDNs) for fresh market and processing scenarios. The BDNs were constructed by adding a value or gain node associated with each yield grade. Nodes representing price per box and stand deficiency were also added. These nodes allowed the prediction of estimated net return associated with a specific in-row regime given some agroclimatic variables and GDDH. As a result of its reliance on conditions observed in the study, BxINROW/NET is only applicable to a local Louisiana growing area. Further study is necessary to determine the model's applicability in other regions and growing conditions.
Uptake and Distribution of Boron in Coconut and Paurotis Palms
Authors: Broschat Timothy K.
Published: February 2019

Natural distribution patterns of boron (B) among leaves within a canopy, among leaflets within a leaf, and within single leaflets were determined for coconut palm (Cocos nucifera L.) and within leaves for paurotis palm [Acoelorrhaphe wrightii (Griseb. & H. Wendl.) Becc.]. Leaf B concentrations did not vary significantly among leaves within the canopy or among leaflets within a single leaf for coconut palm, but basal leaflets of paurotis palm had higher B concentrations than central leaflets. Boron concentrations were significantly higher toward the tips of individual leaflets in both species. Application of Solubor to the soil significantly increased leaf B concentrations in all leaves of coconut palm after 2 months as well as in new leaves produced up to 6 months later. Application of Solubor as a leaf axil drench was much less effective in increasing foliar B concentrations than soil treatment.
Determining Exercise Intensities of Gardening Tasks as a Physical Activity Using Metabolic Equivalents in Older Adults
Authors: Park Sin-Ae , Lee Kwan-Suk , Son Ki-Cheol
Published: February 2019

The objective of this study was to determine the exercise intensities of 15 gardening tasks in older adults using a portable indirect calorimeter. Twenty older Korean adults (16 females, four males) older than 65 years of age (average 67.3 ± 2.7 years) were recruited from the community of Gwangjin-gu, Seoul, South Korea. The subjects visited a garden created for the study at Konkuk University, Seoul, South Korea, three times and performed a total 15 gardening tasks. Subjects wore a portable calorimetric monitoring system (Cosmed K4b2) with telemetry that allowed measurement of oxygen consumption as they conducted each gardening task over a 5-min period and during a subsequent 5-min rest period while seated on a chair between each task. Their heart rate was also continuously measured using radiotelemetry (Polar T 31) during the test. The gardening tasks performed were of low to moderate intensity physical activities [1.7–4.5 metabolic equivalents (METs)]. Tasks using both upper and lower body (e.g., digging, fertilizing, weeding, raking, tying plants to stakes) required moderate-intensity physical activity (3–4.5 METs); those using the upper body while standing or squatting (e.g., pruning, mixing soil, planting seedlings, sowing, watering using a watering can or hose, harvesting) were low-intensity physical activities (1.7–2.9 METs); and tasks requiring limited use of the upper body while standing (e.g., filling containers with soil, washing harvested produce) were the least demanding physical activities of the gardening tasks tested. The results will allow more precise tailoring of gardening activities of older individuals to achieve appropriate levels of activity for good health.
Selection for Resistance to Verticillium Wilt Caused by Race 2 Isolates of Verticillium dahliae in Accessions of Lettuce (Lactuca sativa L.)
Authors: Hayes Ryan J. , Maruthachalam Karunakaran , Vallad Gary E. , Klosterman Steven J. , Subbarao Krishna V.
Published: February 2019

Verticillium wilt of lettuce caused by Verticillium dahliae can cause severe economic damage to lettuce producers. The pathogen exists as two races (Races 1 and 2) in lettuce, and complete resistance to Race 1 is known. Resistance to Race 2 isolates has not been reported, and production of Race 1-resistant cultivars will likely increase the frequency of Race 2 strains. The objective of this research was to select lettuce accessions for resistance to Race 2 isolates of V. dahliae. Two independent populations totaling 314 randomly sampled PIs were evaluated for Verticillium wilt disease incidence (DI) caused by V. dahliae isolate VdLs17 in one unreplicated and two replicated greenhouse experiments. Selection for PIs with reduced DI was conducted between each experiment and plant stems were plated on semiselective media to identify colonized plants that remained non-symptomatic. No accession with complete resistance was identified, although accessions with partial resistance were selected. Genetic variation for the frequency of V. dahliae-colonized plants that remain symptomless was detected. Four PIs (169511, 171674, 204707, and 226641) were selected for further testing in three replicated greenhouse experiments and demonstrated significantly lower disease incidence than the susceptible control cultivars. The results indicate that lettuce has genetic variation for partial resistance to a Race 2 isolate of V. dahliae. The resistant PIs selected in this research are morphologically diverse, and no dependence between rate of bolting and resistance was found. PIs with partial resistance may be useful for breeding lettuce cultivars with resistance to Race 2 isolates of V. dahliae.
Apple Δ13C Discrimination Is Related to Shoot Ash Content
Authors: Glenn D. Michael , Bassett Carole
Published: February 2019

Plant ash content has been highly correlated with plant water use efficiency (WUE) and Δ13C (Δ) in field crops and grassland species and proposed as a selection criteria for WUE. δ18O (δ) has also been correlated with transpiration in herbaceous plants. The objectives of the study were to 1) evaluate the relationship of shoot ash (ASH) with Δ and δ in ‘Empire’ apple over a 3-year period; 2) determine if yearly variation significantly affected the relationship of ASH with Δ and δ; and 3) evaluate the value of the relationship between ASH content with Δ and δ for a population of Malus sieversii. ‘Empire’ leaf area index (LAI) was negatively correlated with ASH content and positively correlated with Δ. Δ was negatively correlated with ‘Empire’ ASH. There were no yearly effects at a site. Within the Malus sieversii accessions, there was a grouping based on ASH that could be identified and this outlier group also had the lowest δ of the accessions. There were no correlations of leaf area, number, length, width, or stomata number with δ, Δ, or ASH for the Malus sieversii accessions. Rather than a substitute for Δ measurement in assessing WUE, ash content analysis adds an additional dimension to understanding the dynamics of WUE in apple. This work has identified a unique population of Malus meriting further study.
Photosynthetic Daily Light Integral during Propagation of Tecoma stans Influences Seedling Rooting and Growth
Authors: Torres Ariana P. , Lopez Roberto G.
Published: February 2019

Current market trends indicate an increasing demand for unique and exotic flowering crops, including tropical plants. Tecoma stans (L. Juss. Kunth) ‘Mayan Gold’ is a tropical plant that was selected as a potential new greenhouse crop for its physical appearance and drought and heat tolerance. However, in winter and early spring, when propagation occurs, outdoor photosynthetic daily light integral (DLI) can be relatively low. The objective of this study was to quantify the effects of DLI during propagation of Tecoma and to determine optimum DLI levels for seed propagation. Seeds were propagated under 13 mean DLIs ranging from 0.75 to 25.2 mol·m−2·d−1 created by the combination of high-pressure sodium lamps (HPS) and fixed woven shadecloths of varying densities. Thirty-five days after sowing, height, stem diameter, node number, relative leaf chlorophyll content, leaf fresh weight, leaf number, total leaf area, individual leaf area, leaf area ratio, shoot and root dry mass increased as DLI increased. Average internode elongation and specific leaf area decreased at a quadratic and linear rate, respectively, as DLI increased from 0.75 to 25.2 mol·m−2·d−1. These experiments indicate that high-quality Tecoma seedlings were obtained when DLI was 14 to 16 mol·m−2·d−1 during propagation.
Elevated Air Temperatures Cause Foliar Bleaching of Ivy Geranium ‘Beach’ and ‘Butterfly’
Authors: Dhir Ritu , Harkess Richard L. , Bi Guihong
Published: February 2019

Bleaching of the youngest leaves of actively growing ivy geranium (Pelargonium peltatum L.) develops as the temperature increases from late spring to summer in the southeastern United States. Heat stress-induced iron deficiency has been suspected as causing this disorder. Ivy geranium ‘Beach’ (bleaching-resistant) and ‘Butterfly’ (bleaching-susceptible) were grown for 8 weeks at 24 or 31 °C average root-zone temperature and iron chelate (Fe-EDDHA, 6% Fe) was applied at 0 mg Fe (control), 0.54 mg Fe foliar spray, 1.08 mg Fe foliar spray, 54 mg Fe drench, or 108 mg Fe drench per plant at 30-day intervals. In a second experiment, ivy geranium ‘Beach’ and ‘Butterfly’ plants were grown for 6 weeks at 28 °C day/16 °C night or 36 °C day/22 °C night average air temperatures and iron chelate (Fe-EDDHA, 6% Fe) was applied at 0 mg (control) or 27 mg Fe soil drench per pot at 15-day intervals. No bleaching was observed as a result of elevated root-zone temperatures. High levels of Fe-chelate suppressed growth reducing fresh weight, dry weight, and fresh-to-dry-weight ratio in ‘Butterfly’. Elevated air temperatures severely reduced plant growth, leaf area, fresh weight, and dry weight in both cultivars. Elevated air temperature reduced chlorophyll a, carotenoids, and pheophytins in ‘Butterfly’ but not in ‘Beach’. Fe-chelate application had no effect at ambient temperature but increased chlorophyll to carotenoids ratio (Chl:Caro) at elevated air temperatures in ‘Butterfly’. Therefore, elevated air temperatures were determined to be the cause of bleaching in ivy geranium.
Photoperiod and Temperature Influence Flowering Responses and Morphology of Tecoma stans
Authors: Torres Ariana P. , Lopez Roberto G.
Published: February 2019

Tecoma stans (L. Juss. Kunth) ‘Mayan Gold’ is a tropical flowering plant that was selected as a potential new greenhouse crop for its physical appearance and drought and heat tolerance. The objective of this study was to quantify how temperature during the finishing stage and photoperiod during propagation and finishing stages influence growth, flowering, and quality. In Expt. 1, plants were propagated from seed under four photoperiods (9, 12, 14, or 16 h) for 35 days. Under long-day (LD) photoperiods (14 h or greater), seedlings were 3.0 to 3.7 cm taller than those propagated under 9-h photoperiods. During the finishing stage, days to first open flower, shoot dry mass, and number of nodes below the terminal inflorescence were reduced when plants were grown under LD photoperiods. In addition, number of open flowers and branches increased under LD photoperiods. Few plants developed visible buds when grown under short-day (SD) photoperiods (12 h or less). In Expt. 2, plants were forced at average daily temperatures of 19, 20, or 22 °C after transplant. Time to first open flower was reduced by 7 days as temperature increased. Inversely, number of visible buds increased by 57 as temperature increased from 19 to 22 °C. Under the experimental conditions tested, the most rapid, complete, and uniform flowering of Tecoma occurred when plants were propagated and finished under LD photoperiods and forced at 22 °C.
Asymbiotic Seed Germination, Induction of Calli and Protocorm-like Bodies, and In Vitro Seedling Development of the Rare and Endangered Nothodoritis zhejiangensis Chinese Orchid
Authors: Zeng Song-jun , Chen Zhi-lin , Wu Kun-lin , Zhang Jian-xia , Bai Cheng-ke , Teixeira da Silva Jaime A. , Duan Jun
Published: February 2019

Nothodoritis zhejiangensis Z. H. Tsi is a rare and endangered epiphytic orchid restricted to a narrow distribution in China. The species is threatened with extinction as a result of loss of suitable habitats. An efficient propagation system is part of this species’ conservation plan. Seed germination reached 64.7% on Knudson's C (KC) medium containing 1.0 mg·L−1 α-naphthaleneacetic acid (NAA), 10% coconut water, and 0.1% activated charcoal. After 50 days culture, most callus (71.3%) from seed-derived protocorms formed on KC medium with 1.0 mg·L−1 2,4-dichlorophenoxyacetic acid and 10% coconut water. Callus could be subcultured 12 times during ≈2 years with more than a 3.0-fold increase from the third to the twelfth subculture. Furthermore, 84% of callus from the tenth sub-culture on KC media supplemented with 1.0 mg·L−1 NAA, 5% coconut water, and 0.1% activated charcoal formed protocorm-like bodies (PLBs). Many (57%) protocorms on KC medium containing 1.0 mg·L−1 6-benzylaminopurine and 10% coconut water formed PLBs. Both callus and PLBs formed simultaneously from different protocorms on KC medium containing 0.01 to 1.0 mg·L−1 thidiazuron and 10% coconut water. PLBs were incubated 12 times during ≈2 years with an approximate 2.4-fold increase per sub-culture. Both callus and PLBs maintained their competence to regenerate plantlets. Hyponex N026 medium supplemented with 1.0 mg·L−1 NAA, 50 g·L−1 banana homogenate, and 0.1% activated charcoal was suitable for plantlet formation and growth of 95.5% of plantlets that developed from PLBs. The roots of plantlets 2 cm in height or taller were wrapped in Chilean sphagnum moss and fixed to a fir bark block; 69.3% of plantlets survived after 180 days in a greenhouse. This protocol is an efficient means for the large-scale propagation of this endangered orchid.
Changes in ‘Riviera’ Bermudagrass [Cynodon dactylon (L.) Pers.] Carotenoid Pigments after Treatment with Three p-Hydroxyphenylpyruvate Dioxygenase-inhibiting Herbicides
Authors: Brosnan James T. , Kopsell Dean A. , Elmore Matthew T. , Breeden Gregory K. , Armel Gregory R.
Published: February 2019

Mesotrione, topramezone, and tembotrione are inhibitors of the enzyme p-hydroxyphenylpyruvate dioxygenase (HPPD), which impacts the carotenoid biosynthetic pathway. An experiment was conducted to determine the effects of mesotrione, topramezone, and tembotrione on carotenoid pigment concentrations in common bermudagrass [Cynodon dactylon (L.) Pers.; cv. Riviera] leaf tissues. Bermudagrass plants were treated with three rates of mesotrione (0.28, 0.35, and 0.42 kg·ha−1), topramezone (0.018, 0.025, and 0.038 kg·ha−1), and tembotrione (0.092, 0.184, and 0.276 kg·ha−1). The lowest rate of each herbicide represented the maximum labeled use rate for a single application. Percent visual bleaching was measured at 3, 7, 14, 21, 28, and 35 days after application (DAA). Leaf tissues were sampled on the same dates and assayed for carotenoids. Topramezone and tembotrione bleached bermudagrass leaf tissues to a greater degree than mesotrione. Concomitantly, topramezone and tembotrione also reduced total chlorophyll (chlorophyll a + b), β-carotene, lutein, and total xanthophyll cycle pigment concentrations (zeaxanthin + antheraxanthin + violaxanthin) more than mesotrione. Increases in visual bleaching resulting from application rate were accompanied by linear reductions in lutein, β-carotene, and violaxanthin for all herbicides. Topramezone and tembotrione increased the percentage of zeaxanthin + antheraxanthin in the total xanthophyll pigment pool (ZA/ZAV) 7 days after peak visual bleaching was observed at 14 DAA. Reductions in ZA/ZAV were reported after 21 DAA. This response indicates that sequential applications of topramezone and tembotrione should be applied on 14- to 21-day intervals, because stress induced by these herbicides is greatest at these timings. Increases in photoprotective xanthophyll cycle pigments (ZA/ZAV) at 14 to 21 DAA may be a mechanism allowing bermudagrass to recover from HPPD-inhibiting herbicide injury, because bermudagrass recovered from all treatments by 35 DAA. Data in the current study will allow turf managers to design physiologically validated bermudagrass control programs with HPPD-inhibiting herbicides. Chemical names: mesotrione [2-(4-methysulfonyl-2-nitrobenzoyl)-1,3-cyclohexanedione], tembotrione {2-[2-chloro-4-(methylsulfonyl)-3-[(2,2,2-(trifluoroethoxy)methyl]benzoyl]-1,3-cyclohexanedione}, topramezone {[3-(4,5-dihydro-3-isoxazolyl)-2-methyl-4-(methylsulfonyl)phenyl](5-hydroxy-1-nethyl-1H-pyrazol-4-yl)methanone}.
The Influence of Day and Night Temperature Fluctuations on Growth and Flowering of Annual Bedding Plants and Greenhouse Heating Cost Predictions
Authors: Blanchard Matthew G. , Runkle Erik S.
Published: February 2019

Volatile energy costs and lower profit margins have motivated many greenhouse growers in temperate climates to improve the energy efficiency of crop production. We performed experiments with dahlia (Dahlia ×hybrida Cav. ‘Figaro Mix’), French marigold (Tagetes patula L. ‘Janie Flame’), and zinnia (Zinnia elegans Jacq. ‘Magellan Pink’) to quantify the effects of constant and fluctuating temperatures on growth and flowering during the finish stage. Plants were grown in glass-glazed greenhouses with a day/night (16 h/8 h) temperature of 20/14, 18/18, 16/22 (means of 18 °C), 24/18, 22/22, or 20/26 °C (means of 22 °C) with a 16-h photoperiod and under a photosynthetic daily light integral of 11 to 19 mol·m−2·d−1. Flowering times of dahlia, French marigold, and zinnia (Year 2 only) were similar among treatments with the same mean daily air temperature (MDT). All species grown at 20/14 °C were 10% to 41% taller than those grown at 16/22 °C. Crop timing data and computer software that estimates energy consumption for heating (Virtual Grower) were then used to estimate energy consumption for greenhouse heating on a per-crop basis. Energy costs to produce these crops in Charlotte, NC, Grand Rapids, MI, and Minneapolis, MN, for a finish date of 15 Apr. or 15 May and grown at the same MDT were estimated to be 3% to 42% lower at a +6 °C day/night temperature difference (DIF) compared with a 0 °C DIF and 2% to 90% higher at a −6 °C DIF versus a 0 °C DIF. This information could be used by greenhouse growers to reduce energy inputs for heating on a per-crop basis.
Investigating Consumer Preference for Organic, Local, or Sustainable Plants
Authors: Yue Chengyan , Dennis Jennifer H. , Behe Bridget K. , Hall Charles R. , Campbell Benjamin L. , Lopez Roberto G.
Published: February 2019

Organically and locally grown food products have become increasingly popular in recent years. However, unlike food products, consumers purchase most outdoor plants for their aesthetic value rather than their nutritional value. Many of the health concerns related to food products might not be applicable to ornamental plants, so the demand for organic non-food plants is unknown. Using a survey with 834 participants from four states, we investigated consumer preference for ornamentals, vegetable transplants, and herbs grown: 1) organically, locally, and sustainably; 2) in energy-efficient greenhouses; and 3) in biodegradable, compostable, and recyclable containers. Our study found that consumers are not enthusiastic about plants or their fertilizers being “organic.” However, consumers are very interested in plants being produced locally, similar to the public's ever-increasing interest in local food products. Consumers are also interested in purchasing plants in containers that are more sustainable. Among the different types of containers, biodegradable and compostable pots are more desirable than recycled pots.
Identification of Markers Linked to Seedlessness in Citrus kinokuni hort. ex Tanaka and Its Progeny Using Bulked Segregant Analysis
Authors: Chavez Dario J. , Chaparro José X.
Published: February 2019

Citrus kinokuni ‘Mukaku kishu’ PI539530 and its progeny were studied to identify random amplified polymorphic DNA (RAPD) primers associated with seedlessness. Ninety-one F1 [(Robinson op) × C. kinokuni] individuals showed a 1:1 segregation ratio between seedless and seeded phenotypes with seedless as a single dominant gene. Bulked segregant analysis was used to identify markers associated with the seedless locus. Eighteen RAPD primers were mapped into a partial linkage group (≈55.8 cM length) with four RAPD primers flanking the seedless locus: OPAI11-0.8 at 8.7 cM, OPAJ19-1.0 at 8.4 cM, OPM06r-0.85 at 4.3 cM, and OPAJ04r-0.6 at 6.4 cM. The identification of molecular markers linked to C. kinokuni Fs seedless locus constitutes an important and major tool for citrus breeding and selection.
Impact of Different Cover Crops and Types of Transplanter Mounted Subsoiler Shanks on Tomato Yield
Authors: Kornecki Ted S. , Arriaga Francisco J.
Published: February 2019

A 4-year experiment with different tillage practices for tomatoes was conducted in Cullman, AL, to determine the impact of plastic mulch (control), rye and crimson clover cover crops, and different subsoiler shanks (no shank, slim 13 mm thick and wide 20 mm thick) on tomato yield. Overall, during 2007 and 2008 growing seasons, total tomato yields (between 58,905 and 60,115 kg·ha−1) and marketable tomato yields (between 48,331 and 49,873 kg·ha−1) were significantly higher than in 2005 and 2006 (between 49,656 and 50,151 kg·ha−1 and from 40,581 to 41,194 kg·ha−1) for total and marketable tomato yields, respectively. During the 2006 and 2008 growing seasons, plastic cover provided higher yield (60,921 and 73,718 kg·ha−1) compared with rye and crimson clover overall shank treatments. In 2007, higher yield was produced following rye without shank (70,577 kg·ha−1) compared with plastic mulch and crimson clover treatments. Across years, tomato yield after crimson clover was lower compared with rye and plastic. Percent of marketable fruit yield to total yield exceeded 80% in all treatments, including the plastic control. Cover crops and shank treatments did not affect percentage of marketable tomato yield compared with total tomato yield. Cover crops, especially rye, can provide an alternative in tomato production for those producers not wanting to use plastic mulches.
Low-input Performance of Zoysiagrass (Zoysia spp.) Cultivars Maintained under Dense Tree Shade
Authors: Wherley B.G. , Skulkaew P. , Chandra A. , Genovesi A.D. , Engelke M.C.
Published: February 2019

A 3-year study was conducted to evaluate the comparative performance of zoysiagrass (Zoysia spp.) cultivars for shaded environments in which inputs are minimized. Included in the study were commercial cultivars Diamond, Cavalier, Royal, Shadow Turf, Zorro, Zeon, Jamur, Crowne, Palisades, and Meyer. In July 2006, grass plugs were planted in a shade nursery comprised of live oak trees providing 89% shade. From 2007 to 2009, turf plots were periodically evaluated for quality, density, color, vertical canopy height, and extent of lateral spread. Overall turfgrass quality was noticeably reduced by the heavily shaded environment; however, some cultivars attained acceptable levels during midsummer periods. A turf performance index (TPI) was generated for ranking the cultivars that represented the number of times an entry occurred in the top statistical group across all parameters and rating dates. ‘Royal’, ‘Zorro’, and ‘Shadow Turf’ were the cultivars ranking in the top statistical grouping most often throughout the study. The results suggest that Z. matrellas may be better adapted than Z. japonicas for heavily shaded environments where inputs are conserved.
Mapping Genes Governing Flower and Seedcoat Color in Asparagus Bean (Vigna unguiculata ssp. sesquipedalis) Based on Single Nucleotide Polymorphism and Simple Sequence Repeat Markers
Authors: Xu Pei , Hu Tingting , Yang Yuejian , Wu Xiaohua , Wang Baogen , Liu Yonghua , Qin Dehui , Ehlers Jeffrey , Close Timothy , Lu Zhongfu , Li Guojing
Published: February 2019

Colors of flower and seedcoat are interesting traits of asparagus bean, a cultivated subspecies of cowpea grown throughout Asia for its tender, long green pods. Little is known about the inheritance of these traits including their genome location. We report here the genetic analysis and mapping of the genes governing flower and seedcoat color in asparagus bean based on single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers. Analysis of the F1 and F7:8 generation of recombinant inbred lines (RILs) population showed a monogenetic inheritance of both traits. Purple flower and brown seedcoat are dominant over white flower and cream seedcoat, respectively. We further show that genes governing flower color and seedcoat color are tightly linked on LG8, ≈0.4 cM apart. Synteny analysis showed that the gene controlling seedcoat color in our study is syntenic to the soybean T locus. The use of the mapping information in asparagus bean breeding is discussed.
Frost Dehardening and Rehardening of Hydrangea macrophylla Stems and Buds
Authors: Pagter Majken , Williams Michelle
Published: February 2019

Hydrangea macrophylla is a popular and commercially important flowering shrub, but frost injury of buds and current-year shoots is a common problem in some of its cultivars. As a result of climate warming, temperate winters are becoming progressively milder, and temperature patterns are becoming increasingly irregular with an increased frequency of warm spells. Warm spells may induce premature dehardening, increasing the risk of subsequent freezing injuries. This study investigated cold-hardiness of stems and buds of Hydrangea macrophylla ssp. macrophylla (Thunb.) Ser. ‘Alma’ during dehardening in response to simulated warm spells and subsequent rehardening in January and early March. Plants were acclimated in the field and dehardened in the greenhouse at controlled warm temperatures for various durations. Dehardened plants were rehardened for up to 12 days in an unheated greenhouse (January) or in the field (March). Buds of H. macrophylla were slightly less cold-hardy than stems. In both stems and buds, the dehardening resistance and the rate of dehardening were influenced by temperature, but buds appeared to be less resistant to dehardening and dehardened faster than stems. In stems, dehardening proceeded faster in March than in January, and the capacity of the stems to reharden seemed reduced, indicating that both dehardening and rehardening were influenced by the progression of winter. Results of this study indicate that buds of H. macrophylla are more sensitive to frost injury than stems and the vulnerability of stems to frost injuries, caused by an unstable temperature regime, changes during the winter season.
Correlation of Three Salinity Tolerance Screening Methods for Cool-season Turfgrasses
Authors: Koch Matthew J. , Bonos Stacy A.
Published: February 2019

The identification of turfgrasses with salinity tolerance will be important for the successful implementation of saline irrigation water use on turfgrass sites. Salinity tolerance in turfgrasses has been evaluated using different techniques, including hydroponic and overhead irrigation methods. This study compared turfgrass response and efficiency of three different salinity screening methods: hydroponic, an overhead irrigation greenhouse method, and a field screening method. There was a significant correlation among all three methods for percent green ratings and a significant correlation between the two greenhouse techniques for dry clipping weights, dry shoot weights, and dry root weights. A difference in magnitude was observed between methods. The overhead-irrigated greenhouse and field methods had lower percent green value ratings than the hydroponic method. However, similar rankings among perennial ryegrass clones were found between methods indicating that numerous methods can be used to screen turfgrass germplasm for salinity tolerance with similar results. The cost, time, and available area required and reliability varied depending on the method with the field screening requiring the most area (929 cm2 per plant) and cost ($23.18 per plant) and the hydroponic method requiring the most time (48.3 min per plant). However, these results indicate any of these methods should be sufficient to screen germplasm for salinity tolerance. This information will be useful to plant breeding programs choosing selection methods for germplasm screening.
Screening the USDA Watermelon Germplasm Collection for Drought Tolerance at the Seedling Stage
Authors: Zhang Haiying , Gong Guoyi , Guo Shaogui , Ren Yi , Xu Yong , Ling Kai-Shu
Published: February 2019

Because of the growing threat of global warming, drought stress could severely affect the normal growth and development of crop plants. To alleviate such an adverse effect, there is a need to screen watermelon germplasm collections to identify genetic sources for potential drought tolerance. In the present study, 820 accessions of USDA's Citrullus PIs and 246 watermelon breeding lines were evaluated for their drought tolerance at the seedling stage under extreme water stress conditions in a greenhouse. Significant variations in drought tolerance were observed in the Citrullus germplasm collections. Using fast clustering analysis, the tested watermelon materials could be assigned into four groups, including tolerant, intermediate tolerant, moderately sensitive, and sensitive, respectively. The most drought-tolerant Citrullus germplasm, including 13 Citrullus lanatus var. lanatus and 12 C. lanatus var. citroides accessions, were originated from Africa. These genetic materials could be used for rootstock breeding or for developing drought-tolerant watermelon cultivars.
Genotypic Variation in Senescence and Water Relations in Cut Flowers of Anthurium andraeanum (Hort.)
Authors: Farrell Aidan D. , Evelyn Sarah , Lennon Adrian M. , Umaharan Pathmanathan
Published: February 2019

The role of water status in determining vase life was investigated in three Anthurium andraeanum Hort. cultivars: Spirit, Success, and Honduras. The cultivars were selected based on their vase life in previous studies and designated as ‘Vshort’, ‘Vmed’ and ‘Vlong’ respectively. A timeline experiment observing spadix necrosis (bloom degradation) under controlled conditions determined end of vase life as 15, 18, and 36 days for Vshort, Vmed and Vlong respectively. Spathe relative water content (RWC) was closely associated with bloom degradation with all three cultivars reaching end of vase life at ≈75% spathe RWC. Membrane integrity of the spathe showed no association with bloom degradation before the end of vase life with increased ion leakage found only after spadix necrosis was visible, indicating that bloom degradation was driven by spathe water status rather than senescence induced by other factors. RWC of the peduncle base and apex showed no association with bloom degradation in any of the cultivars. In fact, base and apex RWC remained high throughout the experiment despite the consistent loss of spathe RWC. This suggests that the reduced water content of the spathe was not induced by reduced hydraulic conductance of the peduncle. Stomatal conductance (gS) was highest in Vshort (approximately twice that of Vlong) and likely contributed to the rapid loss of spathe RWC in this cultivar. However, Vmed and Vlong had similar gS rates and water uptake rates despite large differences in spathe RWC. Thus, the two cultivars differed in their ability to retain water within the spathe tissue. In all three cultivars, end of vase life was determined by spathe water status. Genotypic variation in vase life was not driven by differences in the hydraulic conductance of the peduncle as previously thought. Differences in spathe water status were partially explained by differences in gS but other factors were also involved.