bluuebunny/crossref_metadata_2025 huggingface dataset:
H-mutant Bacteriophages as a Potential Biocontrol of Bacterial Blight of Geranium
Authors: Flaherty J.E. , Harbaugh B.K. , Jones J.B. , Somodi G.C. , Jackson L.E.
Published: February 2019

Bacteriophages specific to Xanthomonas campestris pv. pelargonii (Xcp), the causal agent of bacterial blight of geranium, Pelargonium ×hortorum L.H. Bailey, were isolated from soil and sludge samples from Florida, California, Minnesota, and Utah. Sixteen phages were evaluated for their potential to lyse 21 Xcp strains collected from around the world. The Xcp strains varied in their susceptibility to the phage isolates with 4 to 14 phages producing a lytic or highly virulent reaction. A mixture of five h-mutants was developed from phages that exhibited the broadest host-ranges and tested against the same Xcp strains. The h-mutant phage mixture lysed all 21 Xcp strains. Three experiments were designed to determine the efficacy of using a mixture of four h-mutant phages to control the spread of the bacterial blight pathogen on potted and seedling geraniums under greenhouse conditions. Plants surrounding diseased inoculated plants were treated with a phage mixture at 5 × 108 pfu/mL daily, biweekly, or triweekly, or treated with Phyton-27®, at 2.0 mL·L-1 every 10 or 14 days. In potted geraniums, daily foliar sprays of the phage mixture had reduced disease incidence and severity by 50% and 75%, respectively, relative to control plants after 6 weeks. In two plug experiments, the phage mixture applied daily also had reduced disease incidence and severity by 69% and 86%, and 85% and 92%, respectively, when compared with controls after 5 weeks. In all three experiments, disease incidence and severity were less for plants treated daily with phages than for those treated less frequently with phages or with Phyton-27®. Chemical name used: copper sulfate pentahydrate (Phyton-27®).
Distribution of 15N-Labeled Fertilizer Applied to Pecan: A Case Study
Authors: Kraimer Rebecca A. , Lindemann William C. , Herrera Esteban A.
Published: February 2019

From March through June 1996, 15N-labeled fertilizer was applied to mature pecan trees [Carya illinoinensis (Wangehn.) K. Koch] in a commercial orchard to determine the fate of fertilizer-N in the tree and in the soil directly surrounding the tree. The concentrations of 15N and total N were determined within various tissue components and within the soil profile to a depth of 270 cm. By Nov. 1996, elevated levels of 15N were greatest at depths just above the water table (280 cm), suggesting a substantial loss of fertilizer-N to leaching. Recoveries of 15N from tissue and soil at the end of 1996 were 19.5% and 35.4%, respectively. Harvest removed 4.0% of the fertilizer-N applied, while 6.5% was recycled with leaf and shuck drop. In 1997, with no additional application of labeled fertilizer, the tissue components continued to exhibit 15N enrichment. By the end of the 1997 growing season, 15N levels decreased throughout the soil profile, with the most pronounced reduction at depths immediately above the water table. Estimated recoveries of 15N from pecan tissue (excluding root) and soil at the end of 1997 were 8.4% and 12.5%, respectively. In 1996 and 1997, 15N determinations indicated an accumulation of fertilizer-N in the tissues and a loss of fertilizer-N to the groundwater. Early spring growth, flowering, and embryo development used fertilizer-N applied the previous year, as well as that applied during the current year.
Photodegradation of FeDTPA in Nutrient Solutions. I. Effects of Irradiance, Wavelength, and Temperature
Authors: Albano Joseph P. , Miller William B.
Published: February 2019

Irradiation of FeDTPA-containing nutrient solutions by a fluorescent plus incandescent light source resulted in the loss of both Fe-chelate and soluble Fe, the formation of a precipitate that was composed mostly of Fe, and a rise in pH. The rate of Fe-chelate photodegradation in solution increased with irradiance intensity and with solution temperature under irradiation, but irradiance had the greater effect. Fe-chelates absorb in the blue and UV regions of the spectrum. Removal of these wavelengths with a spectral filter eliminated photodegradation. Chemical name used: ferric diethylenetriaminepentaacetic acid (FeDTPA).
Photodegradation of FeDTPA in Nutrient Solutions. II. Effects on Root Physiology and Foliar Fe and Mn Levels in Marigold
Authors: Albano Joseph P. , Miller William B.
Published: February 2019

Marigold (Tagetes erecta L.) grown hydroponically in an irradiated nutrient solution containing FeDTPA had root ferric reductase activity 120% greater, foliar Fe level 33% less, and foliar Mn level 90% greater than did plants grown in an identical, nonirradiated solution, indicating that the plants growing in the irradiated solution were responding to Fe-deficiency stress with physiological reactions associated with Fe efficiency. The youngest leaves of plants grown in the irradiated solution had symptoms of Mn toxicity (interveinal chlorosis, shiny-bronze necrotic spots, and leaf deformation). Plants grown in irradiated solution in which the precipitated Fe was replaced with fresh Fechelate were, in general, no different from those grown in the nonirradiated solution. Chemical name used: ferric diethylenetriaminepentaacetic acid (FeDTPA).
Aminoethoxyvinylglycine, Combined with Ethephon, Can Enhance Red Color Development without Over-ripening Apples
Authors: Wang Zhenyong , Dilley David R.
Published: February 2019

AVG, as ReTain™, an inhibitor of ethylene biosynthesis, was used alone or with a subsequent application of ethephon (Ethrel™), an ethylene-releasing chemical, to determine if red color development could be enhanced without over-ripening `Gala' and `Jonagold' apples. Treatments included: 1) AVG alone; 2) AVG followed by ethephon; 3) ethephon alone; and 4) control. Silwet L-77 surfactant was included in all treatments. Application of AVG delayed the onset of the ethylene climacteric and red color development of both cultivars. Application of AVG followed by ethephon similarly delayed the onset of the ethylene climacteric, but red color development at the commercial harvest date was only marginally reduced or not affected. The results were similar in both 1998 and 1999, although environmental stress during the growing seasons differed (1998—heat; 1999—moderate temperatures). The delay of fruit maturation and ripening observed at harvest following AVG +/- ethephon treatments improved storability of fruit in controlled atmosphere (CA) storage, as demonstrated by low internal ethylene levels after storage, and high retention of flesh firmness and shelf-life, while control fruit and those treated only with ethephon entered the ethylene climacteric during storage, and flesh firmness subsequently declined during shelf-life evaluation. Chemical name used: aminoethoxyvinylglycine (AVG).
Inheritance of Powdery Mildew Resistance in Sweet Cherry
Authors: Olmstead James W. , Lang Gregory A. , Grove Gary G.
Published: February 2019

Most sweet cherry (Prunus avium L.) cultivars grown commercially in the Pacific Northwestern states of the United States are susceptible to powdery mildew, caused by the fungus Podosphaera clandestina (Wall.:Fr.) Lev. The disease is prevalent in the irrigated arid region east of the Cascade Mountains in Washington State. Little is known about genetic resistance to powdery mildew in sweet cherry, although a selection (PMR-1) was identified at Washington State Univ.'s Irrigated Agriculture Research and Extension Center that exhibits apparent foliar immunity to the disease. The objective of this research was to determine the inheritance of powdery mildew resistance from PMR-1. Reciprocal crosses were made between PMR-1 and three high-quality, widely-grown susceptible cultivars (`Bing', `Rainier', and `Van'). Resultant progenies were screened for reaction to powdery mildew colonization using a laboratory leaf disk assay. Assay results were verified by natural spread of powdery mildew among the progeny in a greenhouse and later by placing them among infected trees in a cherry orchard. Segregation within the progenies for powdery mildew reaction fit a 1 resistant: 1 susceptible segregation ratio (P ≤ 0.05), indicating that resistance to powdery mildew derived from PMR-1 was conferred by a single gene.
Salinity Tolerance of 35 Bentgrass Cultivars
Authors: Marcum Kenneth B.
Published: February 2019

Relative salinity tolerance of 33 creeping bentgrass (Agrostis palustris Huds), one colonial bentgrass (A. capillaris L.), and one velvet bentgrass (A. canina L.) cultivars were determined via hydroponics in a controlled-environment greenhouse. After gradual acclimation, grasses were exposed to moderate salinity stress (8 dS·m-1) for 10 weeks to determine tolerance to chronic salinity stress. Relative dry weight of leaf clippings (RLW), percentage of green leaf area (GL), root dry weight (RW), and root length (RL) were all effective parameters for predicting salinity tolerance. Following 10 weeks of salinity stress, RLW was correlated with GL (r = 0.72), with RW (r = 0.71), and with RL (r = 0.66). The range of salinity tolerance among cultivars was substantial. `Mariner', `Grand Prix', `Seaside', and `Seaside II' were salt-tolerant, `L-93', `Penn G-2', `18th Green', and `Syn 96-1' were moderately salt tolerant, and `Avalon', `Ambrosia', `SR1119', `Regent', `Putter', `Penncross', and `Penn G-6' were salt sensitive.
Nitrogen Nutrition of Spathiphyllum 'Sensation' Grown in Sphagnum Peat- and Coir-based Media with Two Irrigation Methods
Authors: Mak Albert T.Y. , Yeh D.M.
Published: February 2019

Effects of nitrogen application on growth, stomatal conductance, transpiration, and chlorophyll content were studied in Spathiphyllum Schott 'Sensation' grown in sphagnum peat (SP)- and coir dust (CD)-based media with top-irrigation or subirrigation. Maximum shoot dry weight occurred at 8 mM N in plants grown in SP-based medium under top-irrigation and subirrigation, and in CD-based medium under subirrigation. For plants in CD-based medium under top-irrigation, maximum shoot dry weight was obtained at 16 mm N. In SP- or CD-based medium, shoot dry weight was greater at 4 and 8 mm N under subirrigation than under top-irrigation. Stomatal conductance and transpiration were reduced by nitrogen deficiency (0 N), greatly enhanced by 4 mm N, and decreased gradually at higher N levels. Chlorophyll content increased with increasing N concentration up to 8 mm. The percentage of maximum total dry weight increased quadratically as leaf N content increased from 1.5% to 3.5%. Nitrogen at 16 and 32 mm increased the number of leaves with marginal necrosis. Reduced growth and more leaves with marginal necrosis occurred in SP- or CD-based media with EC > 1.25 dS·m-1 in the middle and bottom layers.
Stability of Provenance Differences during Development of Hard Maple Seedlings Irrigated at Two Frequencies
Authors: Hilaire Rolston St. , Graves William R.
Published: February 2019

Traits associated with drought resistance vary with provenance of hard maples (Acer sp.), but the stability of differences ex situ and over time is unknown. We compared growth, dry-matter partitioning, leaf anatomy, and water relations of seedlings from central Iowa, eastern Iowa, and the northeastern United States over 2 years. Some seedlings from each of the three provenances were used as well-irrigated controls. The remaining seedlings were drought-stressed and irrigated based on evapotranspiration. Across irrigation treatments, plants from Iowa had shorter stems and higher specific weight of lamina, root: shoot dry-weight ratios, and root: lamina dry-weight ratios than did plants from the northeastern United States when treatments began. Biomass partitioning did not differ based on provenance after irrigation treatment for 2 years, but leaves from central Iowa had a higher specific weight, and their abaxial surfaces had more stomates and trichomes, than did leaves from the Northeast. Drought stress reduced conductance only in plants from central Iowa. Across provenances, drought stress reduced stomatal frequency, surface area of laminae, and dry weights of laminae and roots, and increased root: shoot dry-weight ratio. Leaf water potential of plants subjected to drought was lower at predawn and higher at midday than that of control plants. Drought did not cause osmotic adjustment in leaves. We conclude that the stability of foliar differences among provenances of hard maples validates using these traits as criteria for selecting ecotypes for use in managed landscapes prone to drought.
Crop Injury from Sublethal Rates of Herbicide. I. Tomato
Authors: Gilreath James P. , Chase Carlene A. , Locascio Salvadore J.
Published: February 2019

Drift from pesticides can kill or damage nontarget organisms. In these studies, the effects of sublethal rates of the herbicide glyphosate applied prebloom, at bloom, and postbloom of the first flower cluster were evaluated in tomato (Lycopersicon esculentum Mill.). As rates increased from 1 to 100 g·ha-1, foliar injury and flower and fruit number per plant varied with the stage of development at the time of exposure and the time of evaluation after treatment. Plants treated with 60 and 100 g·ha-1 glyphosate prebloom and at bloom had developed moderate to severe foliar injury by 14 days after treatment, but phytotoxicity to plants treated postbloom was only mild to moderate. Blooms abscised from plants treated with 60 and 100 g·ha-1 glyphosate for several weeks after application and fruit set was reduced. Greatest yield losses occurred following treatment prebloom (just prior to bloom) and at bloom. Plants treated before emergence of flower buds, and more mature plants exposed when first cluster fruit were sizing, yielded better than did those treated just prior to bloom and at bloom. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).
Stale Seedbed Practices for Vegetable Production
Authors: Caldwell Brian , Mohler Charles L.
Published: February 2019

Effects of several stale seedbed procedures on weed density and biomass were evaluated on a silt loam soil in central New York. After an initial rotary tillage, weeds were allowed to emerge and either single or multiple applications of glyphosate, propane flame, spring tine weeder, springtooth harrow, or rotary tiller were used to kill the weeds over a 4-week period. The last (or only) application occurred immediately prior to simulated seeding of a crop performed by passing an empty seeder through the plots. These stale seedbed treatments were compared with a control consisting of a single rotary tillage just before simulated planting. Flaming or glyphosate stale seedbed techniques significantly reduced density and biomass of the principal broadleaf species, common purslane (Portulaca oleracea L.) and common chickweed [Stellaria media (L.) Cyrillo], in most cases. A single delayed flame or glyphosate stale seedbed treatment was usually as effective as multiple treatments. None of the stale seedbed techniques was effective against yellow nutsedge (Cyperus esculentus L.). A flexible tine weeder was not effective as a stale seedbed weed-killing treatment in this study because of poor penetration of crusted soil. Penetration was better with a springtooth harrow, but this failed to reduce weed density. None of the stale seedbed treatments fully controlled weeds. However, glyphosate or flaming a stale seedbed could be incorporated into integrated weed management programs to improve control and reduce the need for herbicides. Broadleaf weed density within 3.8 cm of the center of the seeder wheel track was greater than elsewhere in the plot. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).
Resistance to Common Bacterial Blight of Bean Introgressed from Phaseolus coccineus
Authors: Welsh M.M. , Grafton K.F.
Published: February 2019

Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Smith) Dye, is a major bacterial disease of dry bean (Phaseolus vulgaris L.). Resistance to common bacterial blight has been identified in other Phaseolus species and resistance genes have been introgressed into P. vulgaris. The objective of this study was to characterize in dry bean the inheritance pattern of common bacterial blight-resistance genes derived from P. coccineus. Two common, bacterial blight-susceptible, dry bean cultivars were crossed with different common, bacterial blight-resistant dry bean lines with resistance derived from P. coccineus. F2 progeny were inoculated with Xanthomonas campestris pv. phaseoli strain F19-W and were scored for disease reaction. The ratio of resistant to susceptible plants for F2 populations did not differ significantly from a 1 resistant: 3 susceptible ratio. The F3 segregation was obtained for only one cross and did not differ significantly from a 1 resistant: 2 heterozygous: 1 susceptible ratio, suggesting that the resistance introgressed from P. coccineus into dry bean was controlled by one recessive gene. Additionally, the range of symptom expression within the susceptible class provided evidence of other genes modifying the expression of resistance.
Use of Random Amplified Polymorphic DNA Markers for Cultivar Identification in Mint
Authors: Fenwick A.L. , Ward S.M.
Published: February 2019

Seventeen mint accessions representing the three species grown for commercial oil production in the United States were characterized using randomly amplified polymorphic DNA (RAPD) analysis. The RAPD profiles readily identified the different Mentha species; calculation of genetic distance, based on the number of shared bands, indicated that M. spicata L. is more closely related to M. × gracilis than to M. × piperita. The RAPD profiles also distinguished among eight peppermint accessions of different geographical origin. However, only limited polymorphism was observed among the most widely grown peppermint and Scotch spearmint cultivars. These results indicate a potential lack of genetic diversity in mint cultivars grown for oil in the United States.
Summer Cultivation Increases Field Infiltration Rates of Water and Reduces Soil Electrical Conductivity on Annual Bluegrass Golf Greens
Authors: Green Robert L. , Wu Laosheng , Klein Grant J.
Published: February 2019

Summer decline of annual bluegrass (Poa annua L.) putting greens is a major concern of golf course superintendents. Low soil water infiltration rates and high concentrations of salts in the root zone are contributing factors. This study was conducted to determine the effects of summer cultivation treatments on field infiltration rates of water, soil salinity, oxygen diffusion rates (ODR), bulk density, total and air-filled porosity, and root weight density. This research was conducted during two summer seasons (1996 and 1997) on a practice putting green located at Industry Hills Golf Courses, City of Industry, Calif. The green was constructed to U.S. Golf Association (USGA) specifications in 1978. Cultivation treatments consisted of: 1-3) water injection cultivation (WIC) applied with a Toro HydroJect every 21 d (raised position), and every 14 or 21 d (lowered position); 4) solid tine cultivation (STC) applied every 14 d; and 5) no cultivation (check). Results showed WIC and STC significantly increased field infiltration rates of water and lowered overall soil electrical conductivity of the extract (ECe) at depths of 2.5 to 7.5 cm and 7.5 to 15.0 cm in the root zone. The effects of WIC, raised position, did not differ significantly from those of STC, but infiltration rates of water were greater on all rating dates. Cultivation treatments had no significant effects on overall soil ODR, bulk density, and porosity or on overall root weight density.
Consumer Preference for Edible-flower Color, Container Size, and Price
Authors: Kelley Kathleen M. , Behe Bridget K. , Biernbaum John A. , Poff Kenneth L.
Published: February 2019

Two surveys were conducted to determine characteristics important in containerized edible flowers that could be sold in retail outlets. Self-selected participants at Bloomfest at Cobo Hall, Detroit, were assigned to one group that rated the importance of attributes such as color of pansy (Viola ×wittrockiana Gams. `Accord Banner Clear Mixture'), color combinations, container size, and price. Participants assigned to a second group rated color, color combinations, and container size. Flower color was allocated the most points in the purchasing decision (63% for the first group and 95% for the second), with a mixture of all three colors (blue, yellow, and orange) being the most desirable. Responses were subjected to Cluster Analysis (SPSS Inc., Chicago), which resulted in the formation of three distinct groups. The groups were labeled “Likely Buyer” (those who had eaten and purchased edible flowers before and rated characteristics of edible flowers favorably); “Unlikely Consumer” (those who had eaten edible flowers before and had rated characteristics of edible flowers unfavorably); and “Persuadable Garnishers” (those who had not eaten edible flowers before, but were very likely to purchase edible flowers for a meal's garnish).
Leaf Gas Exchange Response of 'Arapaho' Blackberry and Six Red Raspberry Cultivars to Moderate and High Temperatures
Authors: Stafne Eric T. , Clark John R. , Rom Curt R.
Published: February 2019

Leaf gas exchange of six red raspberry (Rubus idaeus L.) and one blackberry (Rubus L. subgenus Rubus Watson) genotypes growing in 12-L containers was measured at four temperatures (20, 25, 30, and 35 °C) once a month for 3 months in growth chambers by infrared gas analysis. Measurements were taken on three successive leaves on the same primocane between the third and seventh nodes (≈75% to 85% of full leaf expansion). The plants were grown in ambient (field) conditions except when measurements were taken. Maximum daily ambient temperatures rose as high as ≈37 °C during this period. Net CO2 assimilation (A), evapotranspiration (ET), and stomatal conductance (gs) were measured during June, July, and August. Significant differences (P ≤ 0.01) in A were found among the seven genotypes. 'Arapaho' blackberry displayed the highest mean A rate at all temperatures. Only in the raspberry cultivars Nova and Reveille did the rate of A drop significantly when temperature increased from 20 to 30 °C. 'Reveille' was also the only cultivar in which A significantly declined between 30 and 35 °C. The ET increased significantly over the four temperatures in four cultivars ('Arapaho', 'Heritage', 'Nova', and 'Southland'). The ET rate at 35 °C was higher for 'Arapaho' than for all other cultivars. 'Autumn Bliss', 'Dormanred', and 'Reveille' did not change significantly as the temperature rose from 20 to 35 °C. Stomatal conductance of 'Heritage' and 'Arapaho' did not change significantly between 20 and 35 °C, whereas that of 'Autumn Bliss' and 'Reveille' declined almost 50% when temperature increased to 30 or 35 °C.
Narrow Row Spacing Does Not Affect Lima Bean Yield or Management of Weeds and Other Pests
Authors: Sankula Sujatha , VanGessel Mark J. , Kee Walter E. , Beste C. Edward , Everts Kathryne L.
Published: February 2019

Potential increases in the yield of agronomic crops through enhanced light interception have led many growers to consider using narrow rows in lima bean (Phaseolus lunatus L.). However, no information is available on how narrow row spacing affects weed management or fits into an integrated pest management strategy. To address this, field studies were conducted in Delaware and Maryland in 1996 and 1997 to evaluate the effects of row spacing (38 vs. 76 cm) on weed control, and on yield and quality of lima bean. Weed management inputs were also evaluated with labeled or reduced pre-emergence rates of metolachlor plus imazethapyr applied broadcast or banded. Only 76-cm rows were cultivated according to the standard practice for this production system. In general, row spacing, herbicide rate, and herbicide application method had no effect on lima bean biomass or yield, on weed density, control, or biomass production, or on economic return. However, weed control consistency was improved when wide rows were used, even with reduced herbicide rates, possibly because of cultivation. Using reduced herbicide rates and band applications resulted in 84% less herbicide applied without affecting weed control. Chemical names used: 3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (bentazon); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl-4-(1-methylethyl)-5-oxo-1Himidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid (imazethapyr); 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 2-[1-(ethoxyimino)butyl]-5-[2-ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim).
Leonardite and Fertilizer Levels Influence Tomato Seedling Growth
Authors: Pertuit A.J. , Dudley Jerry B. , Toler Joe E.
Published: February 2019

New Mexico-mined raw leonardite was characterized by comparing it with the International Humic Substances Society's Standard Leonardite. In the first experiment, adding as little as 1/64 leonardite (v/v) to a sand medium increased tomato [Lycopersicon esculentum (L.) Mill. `Mountain Pride'] root and shoot growth compared with plants produced with fertilizer alone. Growth increased linearly with increasing leonardite levels, from 0% to 25%; however, 50% leonardite inhibited growth. In a second experiment, leonardite alone had no effect on plant height, shoot or root fresh and dry weight, or total leaf area, but stimulated growth when combined with a complete fertilizer. Adding 1/3 leonardite (v/v) (the highest level) and a complete fertilizer increased plant height 40%, total leaf area 160%, shoot fresh weight 134%, root fresh weight 82%, shoot dry weight 133%, and root dry weight 400%.
Soil pH Affects Nutrient Balance in Cherry Rootstock Leaves
Authors: Melakeberhan H. , Bird G.W. , Jones A.L.
Published: February 2019

This study was conducted as part of a stone fruit decline project to determine the effects of soil pH (3.9 to 7.0) on soil and plant nutrient imbalance and mortality of standard (Mazzard and Maheleb) and new (GI148-1 and GI148-8) rootstocks. Seedling mortality and soil Ca in all rootstocks and soil K and leaf Ca, K, Al, and Mn contents in all rootstocks but GI148-8 were higher at below optimum than at optimum soil pH. The nutrient imbalance suggests that the adaptation of these rootstocks to biotic and abiotic factors needs to be considered.
Prohexadione-Ca (Apogee®): Growth Regulation and Reduced Fire Blight Incidence in Pear
Authors: Costa Guglielmo , Andreotti Carlo , Bucchi Fabrizio , Sabatini Emidio , Bazzi Carlo , Malaguti Sabrina , Rademacher Wilhelm
Published: February 2019

Prohexadione-Ca (Apogee®) was tested as a growth retardant and fire-blight control agent in the pear (Pyrus communis L. cv. Abbé Fétel) on both bearing trees in the orchard and on 1-year-old scions under greenhouse conditions. Four sprays of 50 and 100 mg·L-1 of the chemical were applied to trees in the orchard at 2-week intervals starting at petal fall, when terminal growth was 4 cm (mid-April). Scions received a single application (250 mg·L-1) and were transferred 2 weeks later to a greenhouse where the shoots were inoculated with a local, virulent strain of Erwinia amylovora (Burrill) Winslow et al. In the orchard, the higher prohexadione-Ca concentration was more effective in reducing shoot growth, enhancing fruit weight and controlling fire blight incidence and severity. Similar effects on growth parameters and disease progression were observed under greenhouse conditions. Chemical name used: calcium 3-oxido-4-propionyl-5-oxo-3-cyclohexene carboxylate (prohexadione-Ca)
Trehalose plus Chloramphenicol Prolong the Vase Life of Tulip Flowers
Authors: Iwaya-Inoue Mari , Takata Mutsumi
Published: February 2019

The tepals of cut tulips (Tulipa gesneriana L. cv. Ile de France) kept at 20 °C had severely wilted 7 days after flower opening. Suppression of abscission and undesirable growth of tepals is required to extend vase life. Treatment with 50 mm trehalose in combination with 50 μm chloramphenicol (CAP) delayed abscission by 4 days compared with stems placed in distilled water or CAP without trehalose. Only 4% of trehalose+CAP-treated flowers exhibited tepal abscission 7 days after harvest, while 82% and 60% of flowers held in distilled water and CAP, respectively, did so; the tepals of trehalose+CAP-treated flower stems contained 50% more water than did those treated with CAP alone. Further, trehalose did not promote elongation of epidermal parenchyma cells in tepal tissues, but maintained radial enlargement of the cells. Thus, trehalose+CAP treatment is effective in prolonging vase life without abscission, water loss, or elongation of cells in tulip tepals, but slight wilting occurs in leaves.
Resistance to Blighting by Monilinia vaccinii-corymbosi in Diploid and Polyploid Vaccinium Species
Authors: Ehlenfeldt M.K. , Stretch A.W.
Published: February 2019

Resistance to blighting by Monilinia vaccinii-corymbosi (Reade) Honey was evaluated under greenhouse conditions in multiple populations of the diploid species Vaccinium boreale Hall & Aalders, V. corymbosum L., V. darrowi Camp, V. elliottii Chapm., V. myrtilloides Michx., V. myrtillus L., V. pallidum Ait., and V. tenellum Ait., as well as in accessions of the polyploid species 4x V. hirsutum Buckley and 6x V. corymbosum f. amoenum Aiton. Significant species differences were found in mean blighting levels averaged over 2 years, with values ranging from 3.5% for V. boreale to 49.2% for 2x V. corymbosum, compared with 27.5% for the resistant 4x V. corymbosum check, `Bluejay', and 64.3% for the susceptible 4x V. corymbosum check, `Blueray'. Wild Vaccinium species may serve as new sources of resistance to blighting, if resistance can be transferred easily and horticultural type recovered.
Inheritance of Resistance to the NL-8 Strain of Bean Common Mosaic Necrosis Virus in Bean
Authors: Provvidenti R.
Published: February 2019

Bean common mosaic necrosis virus (BCMNV) includes four African strains, BCMNV-NL3, -NL-5, -NL8, and -TN1, previously considered to be members of the bean common mosaic virus (BCMV) group. Many bean cultivars resistant to BCMNV-NL8 were found to be susceptible to the other strains of the virus. `California Light Red Kidney' (CLRK) and `Carbon', resistant to BCMNV-NL8, were crossed with the susceptible cultivars Sanilac or Black Turtle 2 (BT-2). In plants of F1, F2, and reciprocal backcross populations involving CLRK × `Sanilac' or BT-2 × `Carbon', the resistance to BCMVN-NL8 was determined to be conferred by a single dominant factor. The same factor was detected in BCMNV-NL8-resistant `Great Northern 1140' and `IVT-7214, when crossed with the susceptible cultivar Stringless Refugee or BT-2.
Chlorophyll Fluorescence and Vegetative Propagation of Taxus
Authors: Bruce Sarah E. , Rowe D. Bradley , Flore James A.
Published: February 2019

Chlorophyll fluorescence over the course of stem cutting propagation was examined in 10 cultivars of Taxus ×media (Taxus baccata L. × T. cuspidata Sieb. & Zucc.), including `Brownii', `Dark Green Pyramidalis', `Dark Green Spreader', `Densiformis', `Densiformis Gem', `Hicksii', `L.C. Bobbink', `Runyan', `Tauntoni', and `Wardii'. The fluorescence value measured was the ratio of variable over maximum chlorophyll fluorescence (Fv/Fm). This value reflects the maximum dark-adapted photochemical efficiency of photosystem II (PSII) reaction centers involved in photosynthesis and is an indirect measure of plant stress. The objective of this study was to examine Fv/Fm as a method for stock plant selection and for monitoring rooting progress of various cultivars. Fv/Fm varied significantly (P ≤ 0.05) among cultivars, initially and over time. However, there was significant overlap among some cultivars. The Fv/Fm decreased dramatically during cold storage, but usually returned to original levels after several weeks in the propagation beds. This appeared to be a reflection of the reduction of water stress as the cuttings formed roots. Initial stock plant Fv/Fm was not correlated (P ≤ 0.05) with rooting percentage, root number, root dry weight, or root length, indicating that Fv/Fm is not a reliable indicator of stock plant rooting potential. Visual assessment is just as reliable.
Elevated Temperature Affects Axillary Meristem Development in Dendranthema ×grandiflorum 'Improved Mefo'
Authors: Schoellhorn Richard K. , Barrett James E. , Bartuska Carolyn A. , Nell Terril
Published: February 2019

Effects of heat stress on viable and nonviable axillary meristem development and subsequent lateral branching in 'Improved Mefo' chrysanthemum [Dendranthema ×grandiflorum Ramat. (Kitamura)] were studied. Plants grown at 33 °C day/27 °C night produced more nonviable buds than did plants grown at 23 °C day/18 °C night. A negative linear relationship {y = 28.7 + [-0.66 (x days)], r2 = 0.70} between timing of exposure to high temperatures and the number of nonviable buds was observed. Histological examination 28 days after exposure to 33 °C/27 °C revealed that plants showed both normal and abnormal bud development. Abnormal bud development occurred as a consequence of premature differentiation of axillary meristematic tissue into nonmeristematic parenchyma tissue immediately after separation of axillary from apical meristems.
Evaluation of Polyolefin-coated Urea for Potato Production on a Sandy Soil
Authors: Zvomuya Francis , Rosen Carl J.
Published: February 2019

Field studies were conducted on a Hubbard loamy sand (sandy, mixed, frigid Entic Hapludoll) during 1996 and 1997 at Becker, Minn., to evaluate the effect of a polyolefin-coated urea (POCU) fertilizer (Meister, Chisso Co., Japan) on yield and quality of irrigated `Russet Burbank' potatoes (Solanum tuberosum L.). The POCU was a 3:1 mixture of 70-day and 50-day release formulations, respectively, based on historical soil temperatures at the site. The study compared five banded nitrogen (N) rates (110, 155, 200, 245, and 290 kg·ha-1 N) as a split application of urea applied at emergence and hilling, vs. POCU applied at planting. All plants received an additional 30 kg·ha-1 N as monoammonium phosphate band-applied at planting. Yields were higher in 1996 because of cooler temperatures and poor tuber set in 1997. Total and marketable yields averaged, respectively, 3.9 and 3.3 Mg·ha-1 higher with POCU than with urea. Total yield was not affected by rate of N application regardless of source, but marketable yield increased linearly with N rate. The yield of marketable tubers larger than 170 g increased linearly with N rate in both years. Gross return was 10% higher with POCU than with urea, but estimated net return showed a significant sourc × N rate interaction. The net return increased by $3.13 per kg of urea-N applied, but there was no significant change across POCU application rates.
Low Genetic Diversity Indicates the Need to Broaden the Genetic Base of Cultivated Watermelon
Authors: Levi Amnon , Thomas Claude E. , Wehner Todd C. , Zhang Xingping
Published: February 2019

Genetic diversity and relatedness were assessed among 46 American cultivars of watermelon (Citrullus lanatus var. lanatus), and 12 U.S. Plant Introduction accessions (PIs) of Citrullus sp. using 25 randomly amplified polymorphic DNA (RAPD) primers. These primers produced 288 distinct reproducible bands that could be scored with high confidence among cultivars and PIs. Based on the RAPD data, genetic similarity coefficients were calculated and a dendrogram was constructed using the unweighted pair-group method with arithmetic average (UPGMA). The cultivars and C. lanatus var. lanatus PIs differentiated at the level of 92% to 99.6% and 88% to 95% genetic similarity, respectively. In contrast, the C. lanatus var. citroides, and C. colocynthis PIs were more divergent and differentiated at the level of 65% to 82.5% and 70.5% genetic similarity, respectively. The low genetic diversity among watermelon cultivars in this study emphasizes the need to expand the genetic base of cultivated watermelon.
Pear Seeds Retain Viability after Liquid Nitrogen Immersion
Authors: Reed Barbara M. , Schwanke Sara , Shala Rebecca
Published: February 2019

Cryopreservation in liquid nitrogen (LN) is relatively routine for many small, desiccation-tolerant (orthodox) seeds. Seeds of Pyrus species are considered orthodox but have not been evaluated for LN storage. Seeds of freshly collected P. communis L. (`Bosc') were evaluated for germinability and by TZ staining after exposure to four LN treatments: 1) direct immersion and direct removal; 2) direct immersion and 1 minute in LN vapor phase before removal; 3) 2 minutes in vapor phase before immersion and direct removal; and 4) 2 minutes in vapor phase before immersion and 1 minute in vapor phase before removal. Fresh `Bosc' seed viability evaluated by TZ and greenhouse germination tests remained high (83% to 100%) following four types of LN treatments, compared to the controls (77% to 87%). Differences in `Bosc' seed viability were small and TZ results showed no significant differences among the LN treatments. Direct LN immersion and removal resulted in significantly more greenhouse-germinated `Bosc' seeds than the other treatments and fewer control seeds germinated than any LN treated seeds. Fresh `Bosc' seed cryopreserved at 7.9% moisture exhibited high germinability by both TZ and germination tests. LN exposure caused no physical damage to the seeds. Chemical name used: 2,3,5-triphenyltetrazolium chloride (TZ).
Brown Bead of Broccoli. I. Response of the Physiological Disorder to Management Practices
Authors: Jenni Sylvie , Dutilleul Pierre , Yamasaki Stephen , Tremblay Nicolas
Published: February 2019

To investigate whether brown bead can be reduced by various cultural practices, a 3-year field study was conducted on a 600-acre broccoli (Brassica oleracea L., Italica group) farm in southwestern Quebec. Factors studied included N fertilization, soil series, previous crop, season of bed forming, or planting method. Four N treatments were randomly applied to two blocks in 41 fields of `Everest' broccoli: 85-0-0, 85-54-0, 85-54-54, and 85-54-108; the first number indicating N (kg·ha-1) applied before planting; the second, N applied 5 weeks after planting; and the last, N applied 7 weeks after planting. Over the 3-year study, brown bead affected 11% of the broccoli heads and accounted for one-third of the rejects. Brown bead severity on individual heads was described on a 0-8 scale. Plots with greater N applications (i.e., 85-54-54, 85-54-108) had significantly (P < 0.001) lower proportions of plants with brown bead compared with plots with lower N applications. Brown bead incidence reacted similarly from year to year to N fertilization and soil type. However, fertilization interacted with soil type. The less N was applied, the more soil effect was important. Soil effect was maximum at a low N level (85-0-0) with 2.5 times more plants showing brown bead in the Saint Blaise series than in the Sainte Rosalie series. Bed type, previous crop, or planting type did not affect the incidence of brown bead.
Nitrogen Nutrition of Greenhouse Pepper. I. Effects of Nitrogen Concentration and NO3: NH4 Ratio on Yield, Fruit Shape, and the Incidence of Blossom-end Rot in Relation to Plant Mineral Composition
Authors: Bar-Tal A. , Aloni B. , Karni L. , Oserovitz J. , Hazan A. , Itach M. , Gantz S. , Avidan A. , Posalski I. , Tratkovski N. , Rosenberg R.
Published: February 2019

Blossom-end rot (BER) is one of the major physiological disorders of green-house bell pepper (Capsicum annuum L.). The objective of the present work was to study the effects of the solution N concentration and N-NO3: N-NH4 ratio on fruit yield and the incidence of BER and other fruit-quality traits of greenhouse-grown bell pepper in a Mediterranean climate. Three experiments were conducted: Expt. 1 included five total N concentrations (0.25 to 14 mmol·L-1, with a constant N-NO3: N-NH4 ratio of 4); Expt. 2 included five treatments of different NO3: NH4 molar ratios (0.25 to 4, with a constant N concentration of 7 mmol·L-1); and Expt. 3 included three treatments of different NO3: NH4 molar ratios (1.0, 3.0 and 9.0, with a constant N concentration of 7 mmol·L-1). Plants were grown in an aero-hydroponics system in Expts. 1 and 2 and in tuff medium in Expt. 3, in greenhouses in Israel. The optimal values of N concentration for total fruit yield and for high fruit quality (marketable) were 9.3 and 8.3 mmol·L-1, respectively. The total and high-quality fruit yields both increased with increasing N-NO3: N-NH4 ratio in the range studied. The total and high-quality fruit yields both decreased sharply as the NH4 concentration in the solution increased above 2 mmol·L-1. The increase in the NH4 concentration in the solution is the main cause of the suppression of Ca concentration in the leaves and fruits and the increased incidence of BER. The occurrence of flat fruits also increased with increasing NH4 concentration in the solution.
Efficacy and Economic Value of Weed Control for Drip and Sprinkler Irrigated Celery
Authors: Ogbuchiekwe Edmund J. , McGiffen Milton E.
Published: February 2019

Economic analyses compared the returns of weed control methods for drip and sprinkler irrigated celery (Apium graveolens L. `Sonora'). The nine treatments included an untreated control, cultivation as needed for weed control, a pre-emergent herbicide (trifluralin), and six post-emergent herbicides. The effect of each treatment on weed control, yield, crop value, cost of control, costs for additional hand-weeding, net return, and dollar investment (marginal rate of return) was determined. The treatments that reduced weed populations under drip and sprinkler irrigation also increased yield, net returns, and rate of returns. Effective weed control reduced the additional costs of hand-hoeing the weeds not killed by herbicides, resulting in greater net return. The net returns of weed control were even greater when celery was drip irrigated than when sprinklers were used. In 1998, the sprinkler irrigated field returned $1148 to $3921/ha, compared with -$5984 for the untreated control. Net returns for drip irrigation were much higher, ranging from $3904 to $9187/ha compared with -$8320 for the untreated control. Net returns were also higher in 1999, ranging from $2466 to $5389 when weeds were controlled compared with a net loss of $5710 for the untreated control in the sprinkler irrigated field. The returns on the drip-irrigated field were much higher, from $6481 to $8920 when weeds were controlled, compared with -$8046 for the untreated control. The associated returns for every dollar invested (marginal rate of return) in the non-dominated treatment (more return and lower cost) ranged from 52% to 156% for sprinkler irrigation, and 59% to 144% for drip irrigation in 1998. In 1999, the rate of return for each dollar invested ranged from 104% to 324% for sprinkler and 2.4% to 321% for drip irrigated fields.
Allelopathic Effect of Glucosinolate-containing Plant Green Manure on Pythium sp. and Total Fungal Population in Soil
Authors: Lazzeri Luca , Manici Luisa M.
Published: February 2019

Two Brassicaceae (Iberis amara L. selection ISCI14 and Rapistrum rugosum All. selection ISCI4) and a Capparidacea (Cleome hassleriana L. selection ISCI2) possessing glucosinolates whose degradation products exhibit high fungitoxic activity in vitro were assayed as biocidal plants in a green manure simulation. The trials were carried out in pots, using aboveground fresh plant tissues incorporated at a realistic field rate into soil naturally infected by Pythium sp. The effect of these plant tissues on total fungal populations and Pythium sp. were compared with Crambe abyssinica H. cv. Mario, a Brassicacea containing glucosinolates whose degradation products exhibit low fungitoxic activity in vitro, and a plant (Helianthus annuus L.) not containing glucosinolates. All green manure treatments induced increases in total fungi over a 10-week period, showing an enhanced microflora level compared with untreated soil. Pythium sp. was strongly suppressed by the C. hassleriana, I. amara, and R. rugosum selections, while sunflower and crambe treatments increased Pythium sp. in a manner similar to that observed for total fungal population. These findings indicate that the green manures assayed suppress Pythium sp. and also induced an increase in total soil microbial activity.
CPPU Influences Fruit Quality and Fruit Abscission of 'McIntosh' Apples
Authors: Greene Duane W.
Published: February 2019

A range of concentrations and timings of CPPU application were evaluated in attempt to identify situations in which fruit size, flesh firmness, and soluble solids could be increased while minimizing increased incidence of fruit asymmetry and reductions in flower bud formation and fruit surface red color on 'McIntosh' apples (Malus×domestica Borkh.). The greatest response to CPPU for most attributes evaluated occurred when it was applied at fruit size between 6 mm and 16 mm. The conclusion from this series of experiments is that differential response to CPPU could not be established by altering the time of application. The response to CPPU is linear with increasing concentration. Results suggested that use of 4 to 6 mg·L-1 CPPU on apples to increase fruit size was the maximum and appropriate range to use without causing fruit asymmetry. Chemical name used: N-(2-chloro-4-pyridyl)-N′-phenyl urea (CPPU)
Genetic Diversity and Relatedness Among Cultivars of Stokes Aster
Authors: Gettys Lyn A. , Werner Dennis J.
Published: February 2019

Stokes aster is a herbaceous perennial native to the southeastern United States. Stokesia is a monotypic genus belonging to the tribe Vernonieae Cass. (family Asteraceae Dumont). The level of genetic diversity within the genus is unknown. The goal of this study was to determine the level of genetic diversity and relatedness among cultivars of stokes aster. The genetic relatedness among 10 cultivars of stokes aster, one accession of Vernonia crinita Raf. (syn. V. arkansana DC.), and one accession of Rudbeckia fulgida Ait. var. sullivantii (Beadle et Boynton) Cronq. `Goldsturm' was estimated using 74 randomly amplified polymorphic DNA (RAPD) primers. Similarity indices suggest that cultivars of stokes aster are very closely related, with values for all pairwise comparisons of cultivars of stokes aster ranging from 0.92 to 0.68. One cultivar, `Omega Skyrocket', had markedly lower similarity indices from the other cultivars, ranging from 0.72 to 0.68. Similarity indices between stokes aster and Vernonia and between stokes aster and Rudbeckia were 0.44 and 0.50, respectively.
Variation in TaqI-digested DNA of Sugar and Black Maples Is Independent of Taxon and Plant Origin
Authors: Hilaire Rolston St. , Graves William R. , Small Randall L.
Published: February 2019

Morphological distinctions between sugar maples and black maples are not consistently evident, and molecular assessment of genetic diversity is lacking for these taxa. We examined restriction-site polymorphisms in the ndhA intron of the chloroplast DNA (cpDNA) in populations of sugar maples and black maples representing their zones of allopatry and sympatry in eastern North America. Restriction-site analysis of the ndhA intron after digestion with HinfI and Sau3AI yielded no polymorphisms. Restriction digestion of the ndhA intron with TaqI revealed two cpDNA haplotypes that were neither geographically localized nor taxon specific. Although testing additional accessions of sugar maples and black maples for cpDNA variation will further elucidate patterns of genetic variation, our initial results suggest that the taxa are either exchanging genes or share an ancestral cpDNA polymorphism.