bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrophysical Properties, Moisture Retention, and Drainage Profiles of Wood and Traditional Components for Greenhouse Substrates
Authors: Fields Jeb S. , Fonteno William C. , Jackson Brian E. , Heitman Joshua L. , Owen James S.
Published: February 2019

Pine tree substrates (PTSs) may provide growers with sustainable substrate component options. Improved processing of PTS components has provided new materials with little scientific evaluation or understanding of their hydrophysical behavior and properties. Moisture retention characteristics were developed for two PTSs and four traditional greenhouse components: sphagnum peat, coconut coir, perlite, pine bark, shredded-pine-wood (SPW), and pine-wood-chips (PWC). Mixtures of peat containing 10%, 20%, 30%, 40%, and 50% of perlite, SPW, or PWC were also characterized. Hydrophysical properties were measured, allowing for comparison of the PTS components to the more traditional substrate components (peat, coir, perlite, and pine bark). The SPW was constructed to retain water similarly to peat and pine bark, whereas the PWC was made to increase drainage like perlite. Shredded pine wood had higher total porosity and more easily available water than did PWC components. Total porosities of SPW and PWC were similar to pine bark and coir; air space and drainage were higher than peat and coir because of the lower percentage of fine particles in the PTS components. The two PTS components had a greater influence on water drainage and retention dynamics than did perlite when amended with peat as an aggregate. Water release patterns of SPW or PWC components at low tensions were lower than peat and greater than pine bark; drainage was similar to perlite at higher tensions. Equilibrium capacity variable models predicted similar physical properties (and trends) across multiple container sizes for peat mixes amended with perlite, SPW, or PWC. The impact of PWC on drainage and aeration was similar to perlite in all containers, but these effects were greater in smaller containers.
Characterization of Fragaria virginiana and F. chiloensis in a Minimal-chill, Winter Annual Production System
Authors: Kennedy Colleen , Hasing Tomas N. , Whitaker Vance M.
Published: February 2019

Wild Fragaria supercore accessions from the U.S. Department of Agriculture (USDA) National Plant Germplasm System collection have been evaluated in temperate climates; however, there have been no characterizations of supercore accessions in non-temperate climates or in annualized production systems. Because Florida can serve as a model system for annualized winter and spring production worldwide, the objective of this study was to characterize an elite group of wild strawberry accessions under field and high tunnel production systems for mortality and the phenological responses of flowering and runner production. The wild accessions along with cultivars were planted in open-field and high tunnel production environments in a randomized complete block design within each environment with raised beds serving as blocks. Four replications of five-plant plots were planted in each of two environments in 2 separate years. With the exception of Darrow 72, F. chiloensis accessions did not perform well in the minimum-chill annualized winter production system. The accessions of this species generally did not flower and were prolific instead in runner production. The F. virginiana accessions performed better with F. virginiana subsps. grayana and virginiana accessions appearing more adapted for minimum-chill winter production because they flowered well and had few runners. We conclude that NC 96-48-1 (PI 612324), NC 95-21-1 (PI 612569), Darrow 72 (PI 236579), and RH 30 (PI 612499) would be attractive for inclusion in germplasm development in a minimal-chill, winter annual production system. In addition to producing many flowers and few runners, these accessions had low mortality.
Genetic Variability of Reproductive Traits in Common Carpetgrass
Authors: Ma Long , Kenworthy Kevin E. , Lu Huangjun , Cherry Ronald
Published: February 2019

Common carpetgrass is a warm-season grass species that is commonly used as a pasture grass in Louisiana and as an alternative low-maintenance lawn grass in the southern Unites States. Understanding genetic variation for traits related to seed production is important to determine breeding strategies for improvement. Ten genotypes were analyzed for number of branches per inflorescence, number of spikelets per branch, and percentage seed set under self-pollination and open pollination. The 10 genotypes exhibited a wide range of variation for number of spikelets per branch and seed set but had a narrow range of variation for number of branches per inflorescence. Genotype was more important than year in contributing to number of branches per inflorescence, whereas the year variance component had a greater impact on number of spikelets per branch. The relative importance of genotype and environment for seed set differed between the two modes of pollination. Broad-sense heritability was 0.35 for number of branches per inflorescence and 0.07 for number of spikelets per branch. Heritability of seed set was 0.29 when the inflorescences were selfed and 0.50 when the inflorescences were subjected to open pollination. Average percentage seed set of the 10 genotypes under self-pollination and open pollination was not significantly different. However, two of 10 genotypes had significantly different means for seed set between self-pollination and open pollination. This information should be useful to plant breeders to select appropriate breeding methods for cultivar development of common carpetgrass.
An Evaluation of U.S. Tart and Sweet Cherry Producers Trait Prioritization: Evidence from Audience Surveys
Authors: Yue Chengyan , Gallardo R. Karina , Luby James J. , Rihn Alicia L. , McFerson James R. , McCracken Vicki , Oraguzie Nnadozie , Weebadde Cholani , Sebolt Audrey , Iezzoni Amy
Published: February 2019

Developing new cherry cultivars requires breeders to be aware of existing and emerging needs throughout the supply chain, from producer to consumer. Because breeding programs in perennial crop plants like sweet and tart cherries require both extended time and extensive resources, understanding and targeting priority traits is critical to improve the efficiency of breeding programs. This study investigated the relative importance of fruit and tree traits to sweet and tart cherry producers using ordered probit models. Tart cherry producers considered productivity and fruit firmness to be the most important traits, whereas sweet cherry producers regarded fruit size, fruit flavor, fruit firmness, freedom from pitting, and powdery mildew resistance as important traits. The location of producers’ orchards and their demographic backgrounds influenced their perceptions of the importance of traits. Our findings provide a quantitative basis to reinforce existing priorities of breeding programs or suggest new targets.
Irrigation Frequency during Container Production Alters Rhododendron Growth, Nutrient Uptake, and Flowering after Transplanting into a Landscape
Authors: Scagel Carolyn F. , Bi Guihong , Bryla David R. , Fuchigami Leslie H. , Regan Richard P.
Published: February 2019

One deciduous cultivar of Rhododendron L., Gibraltar (AZ), and two evergreen cultivars, P.J.M. Compact (PJM) and English Roseum (ER), were grown in containers for 1 year to determine the effects of irrigation frequency during container production on plant performance the next spring when the plants were transplanted into the landscape. While in the containers, each cultivar was irrigated once or twice daily, using the same amount of water per day, and fertilized with complete nutrient solutions containing 0, 35, 70, or 140 mg·L−1 nitrogen (N). Three months after transplanting into the landscape, nutrient uptake, growth, and flowering were evaluated. In general, the effects of irrigation frequency in containers on performance in the landscape differed between the deciduous cultivar and the evergreen cultivars. In AZ, less frequent irrigation in containers had a pre-conditioning effect that resulted in greater vegetative growth in the landscape but less reproductive growth. In contrast, less frequent irrigation reduced vegetative growth of evergreen cultivars in the landscape and improved flowering. Different growth responses to irrigation frequency between deciduous and evergreen cultivars appeared to be related to differences in timing of nutrient uptake and mobilization. In the deciduous cultivar, less frequent irrigation increased nutrient reserves and improved the ability of the plants to absorb and use nutrients after transplanting, but in the evergreen cultivars, it generally decreased nutrient uptake after transplanting. Less frequent irrigation also altered plant attributes that are important to consumers, including developing a sparser canopy in ER and a fuller canopy in PJM, and producing more but smaller inflorescences in both cultivars. Landscape performance was related to plant nutrition in containers; however, irrigation frequency in containers disrupted relationships between nutrition and performance in all three cultivars. Our results indicate that irrigation frequency during container production of Rhododendron results in a tradeoff between vegetative and reproductive growth the next spring when the plants are in the landscape.
Interactions of Heterotrophic Bacteria from Recycled Greenhouse Irrigation Water with Plant Pathogenic Pythium
Authors: Burgos-Garay Maria L. , Hong Chuanxue , Moorman Gary W.
Published: February 2019

Heterotrophic bacteria present in recycled greenhouse irrigation water (RIW) were characterized and then evaluated for their effect on Pythium aphanidermatum, P. cryptoirregulare, and P. irregulare. Nutrient agar (NA) and R2A agar were used to isolate copiotrophic and oligotrophic bacteria. Bacterial isolates recovered from RIW were categorized according to whether they inhibited Pythium growth, attached to hyphae, or enhanced Pythium growth in the three Pythium species used. Three bacterial isolates were selected to determine whether their in vitro interactions with Pythium aphanidermatum, the most pathogenic of the three species used, influenced disease development in the greenhouse. An isolate of Sphingobium sp. that inhibited Pythium, Pseudomonas sp. that attached to hyphae, and Cupriavidus sp. that enhanced the growth of P. aphanidermatum in vitro were used in greenhouse experiments to examine their effects on disease development in geranium (Pelargonium ×hortorum ‘White Orbit’) grown in pasteurized potting mix in ebb and flood irrigation systems. Disease progress curves evaluating the effect of each bacterium indicate that they did not suppress or enhance disease development (P = 0.05). Thus, the effects that the bacterial isolates had in vitro differed from their effects under greenhouse conditions.
Photosynthetic Characteristics of Four Wild Dendrobium Species in China
Authors: Wu Gang-Yi , Hui Jun-Ai , Wang Zai-Hua , Li Jie , Ye Qing-Sheng
Published: February 2019

Photosynthetic physiology of Dendrobium nobile, Dendrobium pendulum, Dendrobium chrysotoxum, and Dendrobium densiflorum was studied. A bimodal diurnal variation of the net photosynthetic rate (Pn) was observed in the four Dendrobium species with the first peak [5.09 to 6.06 μmol (CO2) per m−2·s−1] ≈1100 hr and the second peak [3.83 to 4.58 μmol (CO2) per m−2·s−1] at 1500 hr. No CO2 fixation was observed at night. For all four Dendrobium species, the light compensation point (LCP) was 5 to 10 μmol·m−2·s−1, light saturation point (LSP) ranged from 800 to 1000 μmol·m−2·s−1, apparent quantum yield (AQY) was 0.02, and CO2 compensation points (CCP) and saturation point (CSP) were 60 to 85 μmol·mol−1 and 800 to 1000 μmol·mol−1, respectively. Carboxylation efficiency (CE) values ranged from 0.011 to 0.020. The optimum temperature for photosynthesis was between 26 and 30 °C. The measurement of Pn seasonal variation indicated that July to August had the higher Pn for Dendrobium species. Additionally, the chlorophyll a/b (Chl a/b) ratios of the leaves were 2.77 to 2.89. Measurement of key enzymes in the photosynthetic pathway indicated relatively high Ribulose-1,5-bisphosphate carboxylase (RuBPCase) and glycolate oxidase (GO) activities but very low phosphoenolpyruvate carboxylase (PEPCase) activities. It suggested that these four Dendrobium species are typical semishade C3 plants.
Validation of a Fertilizer Potential Acidity Model to Predict the Effects of Water-soluble Fertilizer on Substrate pH
Authors: Fisher Paul R. , Argo William R. , Biernbaum John A.
Published: February 2019

Two experiments were run to validate a “Nitrogen Calcium Carbonate Equivalence (CCE)” model that predicts potential fertilizer basicity or acidity based on nitrogen (N) form and concentration for floriculture crops grown with water-soluble fertilizer in containers with minimal leaching. In one experiment, nine bedding plant species were grown for 28 days in a peat-based substrate using one of three nutrient solutions (FS) composed of three commercially available water-soluble fertilizers that varied in ammonium to nitrate (NH4+:NO3–) ratio (40:60, 25:75, or 4:96) mixed with well water with 130 mg·L−1 calcium carbonate (CaCO3) alkalinity. Both the ammonium-nitrogen (NH4-N) content of the FS and plant species affected substrate pH. Predicted acidity or basicity of the FS for Impatiens walleriana Hook.f. (impatiens), Petunia ×hybrida E. Vilm. (petunia), and Pelargonium hortorum L.H. Bailey (pelargonium) from the Nitrogen CCE model was similar to observed pH change with an adjusted R2 of 0.849. In a second experiment, water alkalinity (0 or 135.5 mg·L−1 CaCO3), NH4+:NO3– ratio (75:25 or 3:97), and N concentration (50, 100, or 200 mg·L−1 N) in the FS were varied with impatiens. As predicted by the N CCE model, substrate pH decreased as NH4+ concentration increased and alkalinity decreased with an adjusted R2 of 0.763. Results provide confidence in the N CCE model as a tool for fertilizer selection to maintain stable substrate pH over time. The limited scope of these experiments emphasizes the need for more research on plant species effects on substrate pH and interactions with other factors such as residual limestone and substrate components to predict pH dynamics of containerized plants over time.
Application of Marker-assisted Selection in Persimmon Breeding of PCNA Offspring Using SCAR Markers among the Population from the Cross between Non-PCNA ‘Taigetsu’ and PCNA ‘Kanshu’
Authors: Mitani Nobuhito , Kono Atsushi , Yamada Masahiko , Sato Akihiko , Kobayashi Shozo , Ban Yusuke , Ueno Toshihito , Shiraishi Mikio , Kanzaki Shinya , Tsujimoto Tomoyuki , Yonemori Keizo
Published: February 2019

Persimmon (Diospyros kaki Thunb) is hexaploid, and the pollination-constant, non-astringent (PCNA)/non-PCNA trait of Japanese origin is qualitatively controlled by the AST/ast alleles at a single locus and the PCNA trait is recessive to the non-PCNA trait. To avoid inbreeding depression led by repeated crosses among PCNA genotypes, non-PCNA genotypes should be used as cross parents. The marker-assisted selection system has been developed for the selection of PCNA offspring in the progeny derived from the cross of non-PCNA ‘Taigetsu’ (non-PCNA ‘Kurokuma’ × PCNA ‘Taishu’) to PCNA ‘Kanshu’. The primer pairs E8.5/E9r and 7H9F/AST-R were used for detecting the molecular markers A1 and A3, respectively, which link AST alleles. Complete agreement was found between the sequence-characterized amplified region (SCAR) marker genotype and fruit astringency phenotype of the 48 offspring. The result confirmed that the marker-assisted selection using those markers was highly practical. In a larger offspring population (522 offspring) from the same cross, offspring segregated into 100 with both markers, 162 with only A1, 179 with A3, and 81 with neither, and this segregation ratio was significantly different from 2:3:3:2, which is the segregation ratio of random chromosome assortment in autohexaploid. The percentage of offspring expected to be PCNA was 15.5% (81 of 522), which was slightly lower than 20%.
Soil Solarization in High Tunnels in the Semiarid Southwestern United States
Authors: Hanson Kristen , Mahato Tilak , Schuch Ursula K.
Published: February 2019

High tunnels are unheated structures covered with polyethylene (PE) glazing to protect high-value crops from adverse weather. The objective of this study was to raise soil temperatures to determine the efficacy of soil solarization using clear mulch on the soil surface and glazing or no glazing on a high tunnel during the hottest months of the year in the semiarid southwestern United States. Solarization trials were conducted in May and June 2013 in two high tunnels in southern Arizona. Highest soil temperatures were reached with the combination of a high tunnel covered with glazing and the soil covered with PE mulch. Average daily soil temperatures were 48 and 47 °C and average degree hours (DH) per day (base temperature 45 °C) were over 14 at soil depths of 5 and 15 cm. The average daily maximum soil temperature at 5- and 15-cm depth was 63.4 and 52 °C, respectively. The second highest soil temperatures were reached when the soil was covered with PE mulch without high tunnel glazing, which resulted per day in 5.2 DH above 45 °C at 5 cm and less than one DH at 15-cm depth. Glazing on the high tunnel without covering the soil surface raised soil temperatures only at the 5-cm depth above 45 °C, but not further down. High tunnel producers in the low desert areas in the southwestern United States can complete solarization in less than 1 week, depending on the organism to be controlled, when the soil is fallow during the summer months with glazing on the high tunnel and on the soil surface.
Determining the Effect of Carrier Water pH and Bicarbonate Concentration on Final pH of Plant Growth Regulator Solutions
Authors: Camberato Diane M. , Camberato James J. , Lopez Roberto G.
Published: February 2019

Chemical plant growth regulators (PGRs) are important tools in greenhouse ornamental crop production because growers must increasingly meet specifications for plant shipping and marketability. However, the role of water quality parameters such as pH or alkalinity (bicarbonate in this study) on final PGR solution pH is not well documented and could impact efficacy. We assessed the interaction of PGR type and concentration on the final spray solution pH when combined with carrier water of varying pH and bicarbonate concentration. Eleven PGRs commonly used in floriculture (ancymidol, benzyladenine, chlormequat chloride, daminozide, dikegulac-sodium, ethephon, flurprimidol, gibberellic acid, gibberellic acid/benzyladenine, paclobutrazol, and uniconazole) at three concentrations (low, medium, and high recommended rates for each product) were added to reverse osmosis (RO) carrier water adjusted to four pH (5.3, 6.2, 7.2, 8.2) levels or added to tap carrier water adjusted to four bicarbonate concentrations (40, 86, 142, 293 mg·L−1 of CaCO3). Resultant solution pH levels were measured. Plant growth regulators were categorized as acidic, neutral, or basic in reaction based on the change of the carrier water pH on their addition. Benzyladenine, chlormequat chloride, gibberellic acid, and gibberellic acid/benzyladenine acted as weak acids when added to RO water, whereas daminozide, ethephon, and uniconazole reduced final solution pH from 1.25 to 5.75 pH units. Flurprimidol and paclobutrazol were neutral in reaction with final solution pH being similar to that of the RO carrier water before their addition. Ancymidol and dikegulac-sodium were basic in reaction, increasing final solution pH in RO carrier water up to 2.3 units. There was an interaction between chlormequat chloride concentration and RO carrier water pH on change in pH. When added to tap carrier water, final solution pH increased for all except the stronger acids, daminozide, ethephon, and uniconazole, where it decreased up to 3.5 units, and benzyladenine, where it decreased 0.35 units at 40 mg·L−1 bicarbonate. There was an interaction between PGR concentration and bicarbonate concentration in tap carrier water for daminozide and ethephon. The magnitude of change in pH (final solution pH minus initial carrier water pH) with the addition of each PGR was greater for RO than for tap water containing 40 to 293 mg·L−1 bicarbonate for all 11 PGRs tested.
Vermicompost Leachate Reduces Temperature and Water Stress Effects in Tomato Seedlings
Authors: Chinsamy Mayashree , Kulkarni Manoj G. , Van Staden Johannes
Published: February 2019

Abiotic stresses negatively affect the rate of nutrient mobilization in soils resulting in poor crop performance. Vermicompost-leachate (VCL) is an organic liquid produced from earthworm-digested material. It improves soil fertility as a result of the presence of proteins, vitamins, and micro- and macroelements. However, the effects of VCL on plant growth under temperature and water stress are not yet fully studied. To assess the growth performance under low, optimum, and high temperatures, 1-month-old well established tomato seedlings were treated with and without VCL (1:10 v/v) under various temperature regimes (10, 15, 20, 25, and 30 °C). In the second trial, tomato seedlings were tested in a greenhouse with and without VCL (1:10 v/v) at different watering regimes (15, 30, and 45 mL of Hoagland’s nutrient solution) to evaluate the effect of water stress. In comparison with the control seedlings, VCL treatment significantly improved stem thickness, leaf area, and shoot/root both fresh and dry weight of seedlings at 30 °C. At this temperature, VCL-treated seedlings showed a significant increase for all examined physiological parameters (total chlorophyll, total sugars, and proline). Number of leaves, stem thickness, and shoot/root length and fresh weight of VCL-treated tomato seedlings irrigated under a low watering regime were significantly greater than the control. Total chlorophyll, total sugars, and proline content were significantly elevated at the high watering regime but declined in the low watering regime with VCL treatment. Both increasing and decreasing trends of compatible solutes and photosynthetic pigments indicated osmotic adjustment to stress conditions. VCL can be a suitable soil amendment product to improve overall soil fertility and, more importantly, growth of tomato plants even under temperature and water stress conditions.
Salt Tolerance of Three Tree Species Differing in Native Habitats and Leaf Traits
Authors: Leksungnoen Nisa , Kjelgren Roger K. , Beeson Richard C. , Johnson Paul G. , Cardon Grant E. , Hawks Austin
Published: February 2019

We investigated if salt tolerance can be inferred from observable cues based on a woody species’ native habitat and leaf traits. Such inferences could improve species selection for urban landscapes constrained by soils irrigated with reclaimed water. We studied the C3 tree species Acer grandidentatum Nutt. (canyon maple; xeric-non-saline habitat) that was hypothesized to have some degree of salt tolerance based on its semiarid but non-saline native habitat. We compared it with A. macrophyllum Pursh. (bigleaf maple) from mesic/riparian-non-saline habitats with much larger leaves and Eucalyptus camaldulensis Dehnh. (eucalyptus/red gum) from mesic-saline habitats with schlerophyllous evergreen leaves. Five levels of increasing salt concentrations (non-saline control to 12 dS·m−1) were applied over 5 weeks to container-grown seedling trees in two separate studies, one in summer and the other in fall. We monitored leaf damage, gas exchange, and hydric behavior as measures of tree performance for 3 weeks after target salinity levels were reached. Eucalyptus was the most salt-tolerant among the species. At all elevated salinity levels, eucalyptus excluded salt from its root zone, unlike either maple species. Eucalyptus maintained intact, undamaged leaves with no effect on photosynthesis but with minor reductions in stomatal conductance (gS). Conversely, bigleaf maple suffered increasing leaf damage, nearly defoliated at the highest levels, with decreasing gas exchange as salt concentration increased. Canyon maple leaves were not damaged and gas exchange was minimally affected at 3 dS·m−1 but showed increasing damage at higher salt concentration. Salt-tolerant eucalyptus and riparian bigleaf maple framed canyon maple’s moderate salt tolerance up to 3 dS·m−1 that appears related to seasonal soil drying in its semiarid native habitat. These results highlight the potential to infer a degree of salt tolerance from either native habitat or known drought tolerance in selecting plant species for urban landscapes limited by soil salinity or brackish irrigation water. Observable cues such as xeri-morphic leaf traits may also provide visual evidence of salt tolerance.
Effects of Biosolids on Root Growth and Nitrogen Metabolism in Kentucky Bluegrass under Drought Stress
Authors: Chang Zhihui , Zhuo Laiqiang , Yu Fangfang , Zhang Xunzhong
Published: February 2019

Biosolids are valued as a source of plant nutrients, soil organic matter, and biologically active substances. This greenhouse study was designed to examine if application of biosolids can improve plant drought tolerance by affecting nitrogen (N) and hormone metabolism as well as root growth in kentucky bluegrass (Poa pratensis L.; KBG). The three treatments, which provided N rates equivalent to 75 mg plant-available N/kg soil, included: 1) biosolids at 1× agronomic (Ag) N rate (75 mg N/kg soil completely provided with biosolids); 2) biosolids at 0.5× Ag N rate (37.5 mg N/kg soil provided with biosolids and 37.5 mg N/kg soil provided with NH4NO3); and 3) control (75 mg N/kg soil completely provided with NH4NO3). The treated KBG was grown under either well-watered (90% container capacity) or drought stress (≈25% container capacity) conditions. Biosolids application improved turf quality and delayed leaf wilting under drought stress. The grass treated with biosolids at 1× N rate had higher leaf proline and amino acid content and greater nitrate reductase activity than the control under drought stress. Biosolids treatments also increased leaf and soil indole-3-acetic acid (IAA) content. Moreover, biosolids at 1× N rate increased root length density by 23% compared with the control under drought stress. The results of this study suggest that biosolids may enhance plant drought tolerance by improving N and hormone metabolism and root growth in KBG.
Springtime Dandelion (Taraxacum officinale) Control with Seven Postemergence Herbicides Applied at Three Anthesis Stages
Authors: Raudenbush Zane , Keeley Steven J.
Published: February 2019

Although spring is not considered the optimal time for herbicidal control of most cool-season broadleaf weeds in turfgrass, spring applications are often required. Most new postemergence broadleaf herbicides combine several active ingredients, possibly resulting in synergistic, antagonistic, or additive effects. Therefore, as new herbicides become available, information is needed about their performance when applied in the spring. The objective of our study was to determine the effect of spring application timing on dandelion control with seven commercially available postemergence herbicides. Products were applied at their lowest labeled rate for dandelion control at three spring application timings, which coincided with dandelion anthesis stages (pre-, peak-, or post-bloom). A grid was used to determine percent dandelion control at several rating dates. The 2010 site had a denser turfgrass stand with smaller dandelions and was irrigated more frequently compared with the 2011 site. In 2010, all herbicides gave 98% or greater control at 30 days after treatment (DAT) when applied post-bloom; when applied pre- or peak-bloom, control was 80% or greater for all herbicides except for two products applied peak-bloom. At pre- and peak-bloom, products combining a protoporphyrinogen oxidase (PPO) inhibitor with a 2,4-D ester formulation were superior to most other herbicides. When evaluated at the end of the growing season in 2010, all herbicides provided 89% or greater control at all three timings. In 2011, with a less dense turfgrass stand, larger dandelions, and less frequent irrigation, control was more variable and shorter-lived among herbicides. When applied pre-bloom, all products containing 2,4-D provided 87% or greater control 60 DAT. Post-bloom application generally gave similar control to the pre-bloom timing. Peak-bloom application resulted in the poorest overall control at 60 DAT, but products combining a PPO inhibitor with a 2,4-D ester formulation performed better than most other herbicides. By the end of the season, dandelion regrowth caused reduced overall control at all timings, but overall control was poorest when applied at peak-bloom. In summary, peak-bloom applications should be avoided, especially if dandelion pressure is high. Products combining PPO inhibitors with ester forms of 2,4-D were most effective across all spring application timings. Products containing amine forms of 2,4-D may provide effective control if applied pre- or post-bloom.
The Germination Responses of Five Bermudagrass Cultivars to Seedcoating and Temperature
Authors: Munshaw Gregg C. , Layton John M. , Stewart Barry R. , Philley H. Wayne , Beasley Jeffrey S. , Lemus Rocky W.
Published: February 2019

As turfgrass quality of seeded bermudagrass (SB) [Cynodon dactylon (L.) Pers.] cultivars has increased over the past 20 years, so has their use. Improved SB cultivars offer ease of establishment and convenience of storage while providing an economic advantage over vegetative propagation. Currently, most improved seeded cultivars are marketed with a seedcoating unique to each seed company. However, germination of some of the new cultivars is not ideal. The objectives of this study were to determine commercial coating effects on germination, compare germination among cultivars, and evaluate the effect of temperature on germination of five bermudagrass cultivars. ‘Princess-77’, ‘Riviera’, ‘Transcontinental’, and ‘Yukon’ were selected for a series of 21-day germination studies with ‘Arizona Common’ included as a standard cultivar. The study compared two seed lots of coated and uncoated samples of the five cultivars for germination response to six temperature regimes. Cumulative count intervals occurred on Day 7, Day 14, and Day 21. Overall, commercial seedcoating did not significantly affect SB germination. However, both temperature regime and cultivar were significant factors. Germination percentage was greatest with either the 35/25 °C or the 30/20 °C temperature regimes. ‘Riviera’ exhibited the lowest overall germination, whereas ‘Transcontinental’ and ‘Arizona Common’ exhibited the highest.
Growth and Physiological Responses of Rangpur Lime Seedlings Irrigated by a Prototype Subirrigation Tray
Authors: Garcia Barreto Carlos Vinicius , Ferrarezi Rhuanito Soranz , Arruda Flávio Bussmeyer , Testezlaf Roberto
Published: February 2019

Citrus rootstock production in Brazil commonly uses manual overhead irrigation systems to water plants. Manual irrigation systems present low efficiency, apply more water than needed, and result in release of nutrients and pesticides into the soil with a potential to contaminate groundwater. Closed irrigation systems that avoid the disposal of nutrient solutions like subirrigation can be used to increase production efficiency and reduce the environmental contamination. Our objective was to evaluate the effect of subirrigation applied by a prototype tray on plant growth and morphological and physiological responses of Rangpur lime (Citrus limonia Osbeck ‘Limeira’) seedlings subjected to different water levels in conic containers filled with pine bark substrate. We tested three treatments: T1) subirrigation with water reaching two-thirds of the container height (8 cm); T2) subirrigation with water reaching one-third of the container height (4 cm); and T3) control with manual overhead irrigation. Subirrigation resulted in higher plant growth of Rangpur lime seedlings. At 90 days after sowing (DAS), we observed significant effects of T1 over the other treatments on plant growth, as indicated by higher total dry mass (P = 0.0057), shoot/root ratio (P = 0.0089), shoot height (P = 0.0004), leaf area (P = 0.0005), and root length (P = 0.0333). The number of bifurcations was 400% higher in T3 than at the subirrigated treatments, which can lead to an increase in the labor costs for pruning. Seedlings grown under T1 presented leaf water potential 13% higher compared with T3 at predawn, which was the time of highest stomatal efficiency, presenting the lowest water loss, maximum stomatal closure, and higher transpiration at lower stomatal resistance. T2 plants displayed intermediate water status with a water potential 5% higher than T3. T3 plants showed a higher transpiration rate under maximum stomatal closure, reducing leaf water potential. The subirrigated treatment with water level of two-thirds of container height (8 cm) induced higher plant growth and shortened the crop cycle, anticipating the transplanting to the next phase (grafting) with the possibility of reducing production costs in the nursery.
Identification of the Appropriate Leaf Sampling Period for Nutrient Analysis in ‘Hass’ Avocado
Authors: Salazar-García Samuel , González-Durán Isidro J.L. , Ibarra-Estrada Martha E.
Published: February 2019

This research was carried out from 2004 to 2005 in two commercial ‘Hass’ avocado orchards cultivated under rainfed conditions in a hot subhumid climate of the state of Nayarit, Mexico. The objectives of this study were to: 1) establish the patterns in nutrient concentrations during the lifespan of winter and summer vegetative flush leaves; and 2) validate a methodology based on mathematical functions to identify the appropriate period for leaf sampling to diagnose plant nutrition in avocado considering its two major vegetative flushes. Leaf samples were taken monthly for each vegetative flush, starting when leaf length was 5 cm or greater and concluding at leaf abscission. Starting at vegetative budbreak, winter and summer leaves lived 12.5 and 7.8 months, respectively. Summer flush leaves grew faster and attained greater length than winter leaves. A mathematical model based on the concentration of macro- and micronutrients through the lifespan of avocado leaves was evaluated. This model was used to determine the period when nutrient concentrations became stable and, consequently, to identify the proper leaf sampling period. For the ‘Hass’ avocado in Nayarit, the period for sampling winter flush leaves corresponded to 6.6- to 7.9-month-old leaves (4 Sept. to 13 Oct.). For summer leaves the optimum period was shorter and occurred when leaves were 3.9 to 4.9 months old (5 Dec. to 5 Jan.). The procedure and sampling time obtained here should be tested in other regions.
Genetic Resources of Almond Species in the Former USSR
Authors: Zaurov David E. , Eisenman Sasha W. , Ford Timothy , Khokhlov Sergei , Kenjebaev Sovetbek , Shalpykov Kaiyrkul T. , Funk C. Reed
Published: February 2019

Prunus dulcis (Mill.) D.A. Webb. is grown as an economically valuable crop in a number of countries worldwide, but large-scale cultivation has been primarily restricted to semiarid and arid regions with mild, temperate climates. Considering the species’ wide native range and inherent genetic, morphologic, and phenologic diversity, almond remains quite underused in areas outside those currently in cultivation. The area comprising the former USSR represents an extremely large and diverse region and is a center of genetic diversity for P. dulcis and related species. Much of this region, which is the center of origin and/or diversity of many important crops, has been inaccessible to the Western world for centuries, and much of the scientific literature produced there has not been widely disseminated in the English language. Since the breakup of the USSR, this region has become increasingly open and opportunities for reciprocal germplasm collection, exchange, and scientific collaborations are growing. To bring increased attention to the valuable P. dulcis genetic resources endemic to this region, and to promote better use, management, and preservation of these important resources, the wild distribution of almond and closely related species, and extensive germplasm holdings of institutions across the former USSR, are herein described. Recent and ongoing collection and breeding activities in the U.S. Intermountain West are also discussed.
Effects of Timing and Intensity of Summer Pruning on Vegetative Traits of Two Southern Highbush Blueberry Cultivars
Authors: Kovaleski Alisson P. , Williamson Jeffrey G. , Casamali Bruno , Darnell Rebecca L.
Published: February 2019

Pruning is a recommended practice for blueberry (Vaccinium spp.) production and is usually done in the summer in warm subtropical climates with long growing seasons. Summer pruning promotes healthy vegetative growth during the remainder of the growing season; however, research-based recommendations for summer pruning strategies are lacking. The objective of this study was to determine effects of summer pruning timing and intensity on vegetative growth in ‘Jewel’ and ‘Emerald’ southern highbush blueberry (V. corymbosum-interspecific hybrid), two cultivars of the primary species grown in subtropical areas. To determine effects of pruning time, 30% of the canopy was removed in June or July. To determine pruning intensity effects, either 30% or 60% of the canopy was removed in June, both followed by shoot tipping in July. Both timing and intensity treatments were compared with a non-pruned control. Lack of pruning in the first year had no negative effects on growth; however, lack of pruning for two or more seasons decreased regrowth volume and shoot length of both cultivars. By the third season, canopy regrowth volume in both cultivars decreased in the non-pruned control compared with the 30% and 60% pruning treatments and compared with the June pruning treatment. Disease infection in ‘Jewel’ was also increased in the non-pruned control compared with these pruning treatments. Summer pruning, regardless of timing or intensity, generally increased vigor of vegetative growth for both cultivars and decreased incidence of leaf disease in ‘Jewel’.
Effect of Foliar Nitrogen and Optical Sensor Sampling Method and Location for Determining Ornamental Cabbage Fertility Status
Authors: Dunn Bruce L. , Goad Carla
Published: February 2019

Leaf nitrogen (N) and contact optical sensor sampling methods vary in the literature. Thus, the objective of this study was to determine the best sampling procedure for correlating leaf N concentration to contact optical sensor readings. To investigate this, fertilizer rates of 0, 5, 10, or 15 g of 16N–9P–12K were applied as a topdress application on ornamental cabbage (Brassica oleracea L.) ‘Tokyo Red’. Soil plant analysis development (SPAD) and atLEAF chlorophyll meters were used every week for 5 weeks starting 30 days after planting. For each pot, SPAD and atLEAF measurements were taken from a single mature leaf from the middle to upper level of the plant at the leaf tip, blade, or base of the leaf not including the midrib. Weekly leaf foliar analysis consisted of collecting either fully developed leaves from a single plant, five plants, or 10 plants per, using only the tip, blade, or base of three leaves for total leaf N concentration per treatment. A significant position affect was seen in both SPAD and atLEAF sensors. For SPAD, sensor readings taken from the tip and blade of a leaf were not significantly different from each other but were significantly different from the base of the leaf. All three positions for atLEAF were significantly different from each other. This indicates that sensor sampling location within a leaf will affect readings. A significant difference was observed among leaf sampling methods. Taking leaf samples from the tip and base had the highest leaf N concentrations and were not significantly different from each other but were significantly different from all other sampling methods, which were not significantly different from each other. Significant correlations were seen among all combinations of sensor positions and leaf N sampling methods except SPAD readings taken from the tip and leaf sampling from a single plant. Highest correlations (r = 0.7 to 0.8) were seen when SPAD readings were taken from the base of the leaf irrespective of leaf sampling method. Based on this experiment, either sensor could be used for correlating leaf N; however, growers should consistently collect sensor readings from the same location on a leaf to achieve consistent values and correlations.
Automated Irrigation Control for Improved Growth and Quality of Gardenia jasminoides ‘Radicans’ and ‘August Beauty’
Authors: Bayer Amanda , Ruter John , van Iersel Marc W.
Published: February 2019

Sustainable use of water resources is of increasing importance in container plant production as a result of decreasing water availability and an increasing number of laws and regulations regarding nursery runoff. Soil moisture sensor-controlled, automated irrigation can be used to irrigate when substrate volumetric water content (θ) drops below a threshold, improving irrigation efficiency by applying water only as needed. We compared growth of two Gardenia jasminoides cultivars, slow-growing and challenging ‘Radicans’ and easier, fast-growing ‘August Beauty’, at various θ thresholds. Our objective was to determine how irrigation can be applied more efficiently without negatively affecting plant quality, allowing for cultivar-specific guidelines. Soil moisture sensor-controlled, automated irrigation was used to maintain θ thresholds of 0.20, 0.30, 0.40, or 0.50 m3·m−3. Growth of both cultivars was related to θ threshold, and patterns of growth were similar in both Watkinsville and Tifton, GA. High mortality was observed at the 0.20-m3·m−3 threshold with poor root establishment resulting from the low irrigation volume. Height, width, shoot dry weight, root dry weight, and leaf size were greater for the 0.40 and 0.50 m3·m−3 than the 0.20 and 0.30-m3·m−3 θ thresholds. Irrigation volume increased with increasing θ thresholds for both cultivars. For ‘August Beauty’, cumulative irrigation volume ranged from 0.96 to 63.21 L/plant in Tifton and 1.89 to 87.9 L/plant in Watkinsville. For ‘Radicans’, cumulative irrigation volume ranged from 1.32 to 126 L/plant in Tifton and from 1.38 to 261 L/plant in Watkinsville. There was a large irrigation volume difference between the 0.40 and 0.50-m3·m−3 θ thresholds with little additional growth, suggesting that the additional irrigation applied led to overirrigation and leaching. Bud and flower number of ‘Radicans’ were greatest for the 0.40-m3·m−3 θ threshold, indicating that overirrigation can reduce flowering. The results of this study show that growth of the different G. jasminoides cultivars responded similarly to θ threshold at both locations. Similarities in growth and differences in irrigation volume at the 0.40 and 0.50-m3·m−3 θ thresholds show that more efficient irrigation can be used without negatively impacting growth.
Diurnal Effects on Mentha canadensis Oil Concentration and Composition at Two Different Harvests
Authors: Shiwakoti Santosh , Sintim Henry Y. , Poudyal Shital , Bufalo Jennifer , Cantrell Charles L. , Astatkie Tess , Jeliazkova Ekaterina , Ciampa Lyn , Zheljazkov Valtcho D.
Published: February 2019

Japanese cornmint, also known as menthol mint (Mentha canadensis L. syn M. arvensis L.), is an essential oil crop cultivated in several countries in Asia and South America. The plant is currently the only commercially viable source for natural menthol as a result of the high concentration of menthol in the oil compared with other crops. The hypothesis of this study was that harvesting at regular intervals within a 24-hour period would have an effect on essential oil concentration and composition of Japanese cornmint grown at high altitude in northern Wyoming. Flowering plants were harvested every 2 hours on 7 to 8 Aug. and on 14 to 15 Aug. and the essential oil was extracted by steam distillation and analyzed by gas chromatography–mass spectroscopy (GC-MS). The effects of harvest date (Harvest 1 and Harvest 2) and harvest time (12 times within a 24-hour period) were significant on oil concentration and yield of menthol, but only harvest date was significant on the concentration of menthol in the oil. The interaction effect of harvest date and harvest time was significant on water content and on the concentrations of menthol and menthofuran in the oil and on the yield of limonene, menthol, and menthofuran. Overall, the oil concentration in grams per 100 g dried material for the two harvests (1.26 and 1.45, respectively), the concentration of menthol in the oil (67.2% and 72.9%, respectively), and menthol yield (1066 to 849 mg/100 g dried biomass) were higher in plants at Harvest 2 as compared with plants at Harvest 1. The oil concentration was higher in plants harvested at 1100 hr or at 1300 hr and lowest in the plants harvested at 1500 hr. Menthol yield was the highest in plants harvested at 1300 hr and lowest in the plants harvested at 0700 hr, 1900 hr, or at 0300 hr. This study demonstrated that harvesting time within a 24-hour period and harvest date (maturity of the crop) may affect essential oil concentration and composition of Japanese cornmint grown at high altitude in northern Wyoming.
Influence of Citrullus lanatus var. citroides Rootstocks and Their F1 Hybrids on Yield and Response to Root-knot Nematode, Meloidogyne incognita, in Grafted Watermelon
Authors: Thies Judy A. , Buckner Sharon , Horry Matthew , Hassell Richard , Levi Amnon
Published: February 2019

Southern root-knot nematodes (Meloidogyne incognita) are an important re-emerging pest of watermelon in the United States and worldwide. The re-emergence of root-knot nematodes (RKNs) in watermelon and other cucurbits is largely the result of the intensive cultivation of vegetable crops on limited agricultural lands coupled with the loss of methyl bromide for pre-plant soil fumigation, which has been the primary method for control of RKNs and many soilborne diseases of cucurbits and other vegetable crops for several decades. One alternative for managing RKN in watermelon is the use of resistant rootstocks for grafted watermelon. We have developed several RKN-resistant Citrullus lanatus var. citroides lines (designated RKVL for Root-Knot Vegetable Laboratory), which have shown promise as rootstocks for grafted watermelon. In 2011 and 2012, we demonstrated that F1 hybrids derived from our selected RKVL lines exhibited resistance to RKN that was equal to or greater than that of the parental RKVL lines when grown in fields highly infested with M. incognita. In 2011, although significant differences were not observed among rootstocks, the F1 hybrids produced slightly higher yields compared with the selected parental lines. Among the selected parental lines, RKVL 318 produced high yields in both years. In 2011, three of four RKVL parental lines and all four of their F1 hybrids produced greater (P < 0.05) fruit yields than self-grafted ‘Tri-X 313’, ‘Emphasis’ bottle gourd, and ‘Strong Tosa’ squash hybrid. In 2012, three RKVL F1 hybrid lines produced higher yields than the selected parents. Overall, these F1 hybrids were vigorous and should provide useful genetic material for selection and development of robust RKN-resistant C. lanatus var. citroides rootstock lines.