bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Kaolin Particle Film Use and Its Application on Coffee
Authors: Steiman Shawn R. , Bittenbender Harry C. , Idol Travis W.
Published: February 2019

Application of a kaolin-based particle film, Surround WP, was analyzed using glass plates and slides. The kaolin was sprayed on coffee grown in full sun to evaluate physiological responses to this shading technique. Kaolin reduced photosynthetically active radiation and ultraviolet transmission and decreased surface temperatures on glass slides. In the second year of application, photosynthesis of plants sprayed with kaolin was 71% greater than full-sun plants and yields were doubled. Leaf temperature was significantly lower in the kaolin treatment, but stable C isotope ratios, water use efficiency, nodal growth, and specific leaf area were not. The most likely mechanisms for increased yield are increased light transmittance to inner-canopy nodes or greater storage of photosynthate during the first year. Although results from this study suggest there is much promise for improving the performance and yield of coffee with kaolin application, studies with other species have shown inconsistent results. This inconsistency may be linked to variation in application techniques, kaolin coverage and subsequent effects on light transmission, leaf temperature, and physiological function. Thus, reports on physiological performance alone are insufficient to evaluate the use of kaolin application. Detailed information on application techniques combined with measurements of end-product criteria such as yield or quality are recommended to facilitate cross-study comparisons.
End-of-day Lighting with Different Red/Far-red Ratios Using Light-emitting Diodes Affects Plant Growth of Chrysanthemum × morifolium Ramat. ‘Coral Charm’
Authors: Lund Janni Bjerregaard , Blom Theo J. , Aaslyng Jesper Mazanti
Published: February 2019

Controlling plant height without the use of plant growth retardants is one of the goals in future production of potted plants. Light quality with a low red to far-red ratio (R:FR) increases plant height. In this trial, the effects of light quality [R:FR ratio of 0.4, 0.7, and 2.4 (R = 600–700 nm, FR = 700–800 nm)] at the end of day were investigated on potted chrysanthemums using growth chambers. After a 9-h photoperiod, the 30-min end-of-day lighting was provided by light-emitting diodes at low irradiance by maintaining either red = 1 μmol·m−2·s−1 (Rcon) or far-red = 1 μmol·m−2·s−1(FRcon). After 3 weeks of end-of-day lighting, plants given the lowest end-of-day ratios (R:FR of 0.4 or 0.7) were taller than control plants (R:FR = 2.4). For low ratios of R:FR (0.4), the actual intensities of R and FR did not affect plant height, whereas for higher ratios of R:FR (0.7 and 2.4), plant height was greater for FRcon than for Rcon. Leaf area of the lateral side shoots was lower for plants treated with an R:FR of 0.4 compared with those of controls. Dry weight, stem diameter, number of internodes, and number of lateral branches were unaffected by the end-of-day ratio.
Determining Plant-available Water of Woody Ornamentals in Containers In Situ During Production
Authors: Beeson Richard C.
Published: February 2019

In nursery production, small root balls are transplanted into larger containers and grown for sale or further transplanting into still larger containers. When a root ball is smaller than a container, the amount of plant-available water (PAW) is initially limited to that of the original root ball. With growth, roots colonize new substrate and thereby increase the volume of water available to a shoot. Because of hydraulic gradients in container substrates, PAW is not linearly proportional to the volume of substrate occupied by roots. To practice precision irrigation in nursery production, it is important to know the extent of PAW and how it changes with growth. A method is detailed that calculates in situ PAW in containers based on changes in actual evapotranspiration while irrigation is withheld. The method is applied under field conditions and requires only daily mass loss measurements and corresponding reference evapotranspiration. An example of how PAW changes during production from rooted cuttings to marketable size plants is provided.
Identification of Climacteric and Nonclimacteric Phenotypes of Asian Pear Cultivars by CAPS Analysis of 1-Aminocyclopropane-1-Carboxylate Synthase Genes
Authors: Itai Akihiro , Fujita Naoko
Published: February 2019

The maximum level of ethylene production is closely related to fruit ripening and storage potential in Asian pears. In a previous study, we identified two markers (A and B) linked to high and moderate ethylene production during fruit ripening, respectively, by restriction fragment-length polymorphism analysis of two 1-aminocyclopropane-1-carboxylate (ACC) synthase genes (PPACS1 and PPACS2). In this study, a total of 152 cultivars were categorized into four marker types (AB, Ab, aB, and ab); types AB and Ab show high levels, aB a moderate level, and ab a low level of ethylene production during fruit ripening. A large number of ab and aB cultivars but few AB and Ab cultivars were observed. It suggests that there has been a decrease in high ethylene producers by artificial selection because of short shelf life. The ab cultivars are a good genetic resource for production of new cultivars with a long shelf life. Such information on marker types is useful for breeding strategies aimed at improving storage ability in Asian pears.
Effects of Fertilizer Rate on Growth and Fruiting of Containerized Southern Highbush Blueberry
Authors: Wilber Wendy L. , Williamson Jeffrey G.
Published: February 2019

The effects of fertilizer rate and composition on growth and fruiting of ‘Misty’ and ‘Star’ southern highbush blueberry were evaluated in a containerized production system using pine bark medium. Two fertilizer analyses (12N–1.8P–46.6K and 12N–5.2P–9.9K) and three fertilizer rates were used. Plant growth and fruiting were unaffected by fertilizer analysis. Growth and fruit yield of ‘Star’ increased linearly with increasing fertilizer rate. For ‘Misty’, plant growth and yield were reduced at the highest fertilizer rate as a result of a high incidence of blueberry stem blight associated with that treatment. Flower bud density was highest for the ‘Misty’ plants receiving the high fertilizer rate and this may have resulted in excessive fruit set leading to stress-induced blueberry stem blight. Optimum fertilizer rates for young southern highbush blueberry plants grown in containerized pine bark systems appear to be cultivar-specific and similar to fertilizer requirements in soil culture.
Growing Degree-day Requirements for Scheduling Flowering of Scadoxus multiflorus subsp. katharinae (Baker) Friis & Nordal
Authors: Funnell Keith A.
Published: February 2019

Containerized plants of Scadoxus multiflorus subsp. katharinae (Baker) Friis & Nordal were forced to anthesis under three environments of contrasting temperature. Flowering performance, growing degree-days (GDD) requirements for timing of anthesis, and the influence of cold storage (12 °C for 4 weeks) before forcing were evaluated. Total forcing time from the beginning of the experiment until anthesis decreased with warmer forcing environment, ranging between 129 and 86 days. Across all forcing environments, use of GDD was readily able to explain differences in time to anthesis resulting from both cold storage and forcing. Using a base temperature of 5 °C, GDD requirements between beginning of the experiment and anthesis was 1166 ± 124 GDD, emergence of the vegetative shoot and anthesis 1075 ± 118 GDD, and appearance of the tips of the leaf lamina and anthesis 883 ± 91 GDD. Using a base temperature of 11.5 °C, GDD requirements between appearance of tip of the involucre and anthesis was 180 ± 44 GDD, and the whole involucre being visible and anthesis 144 ± 42 GDD. In the next year, validation of the GDD requirements was achieved by subsequently forcing a second population of plants to anthesis for a specific date.
Stability of Resistance to Root-knot Nematodes in ‘Charleston Belle’ and ‘Carolina Wonder’ Bell Peppers in a Sub-tropical Environment
Authors: Thies Judy A. , Dickson Don W. , Fery Richard L.
Published: February 2019

Two root-knot nematode-resistant bell pepper cultivars, ‘Charleston Belle’ and ‘Carolina Wonder’ (Capsicum annuum L. var. annuum], and their susceptible parents, ‘Keystone Resistant Giant’ and ‘Yolo Wonder B’, were compared for managing the southern root-knot nematode [Meloidogyne incognita (Chitwood) Kofoid and White] in fall and spring tests at Citra, FL. In the fall test, ‘Charleston Belle’ and ‘Carolina Wonder’ exhibited minimal root galling and nematode reproduction, and ‘Keystone Resistant Giant’ and ‘Yolo Wonder B’ exhibited severe root galling and high nematode reproduction. Fruit yield of ‘Charleston Belle’ was 97% greater than yields of the two susceptible cultivars (P ≤ 0.006). In the spring test, one-half of the plots were treated with methyl bromide/chloropicrin before planting the same four bell pepper cultivars. ‘Keystone Resistant Giant’ and ‘Yolo Wonder B’ grown in untreated control plots exhibited severe root galling and high nematode reproduction, but the other six cultivar × methyl bromide combinations exhibited minimal root galling and nematode reproduction. Although soil temperatures (10-cm depth) were greater than 30 °C on 78 days and 57 days during the Fall 2002 and Spring 2003 trials, respectively, resistance did not break in ‘Charleston Belle’ and ‘Carolina Wonder’ in either test. These results demonstrate that root-knot nematode-resistant cultivars such as Charleston Belle and Carolina Wonder are viable alternatives to methyl bromide for managing southern root-knot nematode in bell pepper in sub-tropical environments.
Silicon Supplements Affect Horticultural Traits of Greenhouse-produced Ornamental Sunflowers
Authors: Kamenidou Sophia , Cavins Todd J. , Marek Stephen
Published: February 2019

In greenhouse production, most floricultural crops are cultivated in soilless substrates, which often supply limited amounts of plant-available silicon (Si). The goal of this study was to determine the effects of Si supplementation on greenhouse-produced ornamental sunflower (Helianthus annuus L. ‘Ring of Fire’). Potassium silicate (KSiO3) substrate incorporation or weekly substrate drenches, sodium silicate (NaSiO3) foliar applications, and rice husk ash substrate incorporation were used as Si supplements. Silicon content of Si-treated plants increased compared with untreated controls. Depending on the source and concentration of silicon supplied, several horticultural traits were improved as a result of Si supplementation. Thick, straight stems, increased flower and stem diameters, and increased height were observed in some of the treatments, upgrading sunflower quality compared with untreated controls. However, growth abnormalities were observed when concentrations of 100 and 200 mg·L−1 Si were supplied as KSiO3 substrate drenches. In these treatments, plants appeared stunted with deformed flowers and were delayed in flowering. Consequently, Si supplementation effects on greenhouse-produced sunflowers can vary from beneficial to detrimental depending on the applied source and concentration.
The Role of Micropropagation in Producing Specific Pathogen-tested Plants
Authors: Dale Adam , Hughes Becky R. , Donnelly Danielle
Published: February 2019

Micropropagation of strawberries is an extremely effective tool to rid strawberry plants of Colletotrichum infections. The continued health of these plants depends on a vigorous sanitation program throughout the nursery system in North America. Propagating healthy strawberry plants requires a series of steps: plants are micropropagated, virus-tested, screened for fungal and bacterial pathogens, and finally grown under strict guidelines for two growing seasons in propagator's fields. In the propagator's fields, the plants are inspected for visual symptoms of diseases and checked for trueness-to-type. This paper reviews the protocols used to develop specific pathogen-tested strawberry plants in Ontario and, where appropriate, discusses alternate techniques.
A Brief History of 1-Methylcyclopropene
Authors: Reid Michael S. , Staby George L.
Published: February 2019

Research that led to the discovery of 1-methylcyclopropene (1-MCP) started with efforts to understand the effects of controlled atmosphere storage and continued with studies that examined the nature of the ethylene binding site. Although some researchers focused on the use of silver ion for inhibiting ethylene action, Sisler and his colleagues focused on analogs of olefins that had a similar effect. Efforts to tag the binding site using activation tagging with diazocyclopentadiene led to the discovery of the dramatic effects of cyclopropenes, which were identified as products of its photooxidation. The story is a testament to the value of fundamental research and the collegiality and unique intellectual and technical abilities of the primary inventor, Edward C. Sisler.
Freeze Risk and Protection Measures of Satsuma Mandarins Grown in the Southeastern United States
Authors: Ebel Robert C. , Nesbitt Monte , Dozier William A. , Dane Fenny
Published: February 2019

The northern fringe of the Gulf of Mexico has an excellent climate for growing high-quality satsumas that are available in U.S. retail chain stores before most other citrus. In part because of high fruit quality, satsuma mandarin production grew into a major industry in Alabama, Louisiana, Mississippi, and the panhandle of Florida in the early 1900s. Freeze protection measures were not sufficient to prevent devastation of the industry by severe freezes. For the period encompassing the late 1900s, freeze risk was estimated using a mathematical approach that determined killing temperature based on air temperature. Freeze injury was determined to occur 1 out of every 4 years on average, although the freezes tended to come in clusters that have as yet not been correlated with long-term climate patterns. Within-tree microsprinkler irrigation, which was not available in the early 1900s, has been shown to reduce the severity of injury. Within-tree microsprinkler irrigation allows full production the year after the freeze, whereas unprotected trees must be grown from the base or replanted. The northerly geographical limit in the southeastern United States whereby satsumas can be successfully grown commercially is currently not known. Methods of protecting the entire tree, including overtree microsprinkler irrigation plus windbreaks and high tunnel houses, are being evaluated. More cold-tolerant satsuma cultivars have been selected, but they reduce freeze risk by at most 2 °C in this region compared with current commercial cultivars. Genetic modification is one possible mechanism for improving cold tolerance sufficiently to reduce freeze risk similar to that of the citrus industry in Florida.
Response of Young Pecan Trees to Trunk and Foliar Applications of Glyphosate
Authors: Foshee Wheeler G. , Blythe Eugene K. , Goff William D. , Faircloth Wilson H. , Patterson Michael G.
Published: February 2019

A field experiment was conducted from 1995 to 1999 in central Alabama to determine the effect of repeated applications of glyphosate herbicide on young ‘Sumner’ pecan trees. Herbicide treatments were applied on ‘Sumner’ pecan trees varying in age from newly established (first growing season) to established fourth-year growing season trees. Measurements taken included tree mortality, trunk cross-sectional area, nut yield, and nut quality in the third and fourth years of the study. Glyphosate applications were targeted at the lowest 5 to 8 cm of the tree trunk (“standard” treatment), a percentage (lowest 33%, 67%, or 100%) of the tree trunk below the first scaffold limb, or a percentage (lowest 25%, 50%, 75%, or 100%) of tree foliage to simulate situations ranging from minor spray drift to major misapplication. No adverse effects were detected when glyphosate was applied to trunks, regardless of tree age. However, repeated application of glyphosate to 75% to 100% of tree foliage resulted in a significant reduction of growth and, in some cases, tree death. Results indicate that limited contact of glyphosate with the lowest 5 to 8 cm of the trunk of the young pecan tree, which usually occurs during conventional orchard weed management, is unlikely to result in adverse effects on young pecan trees.
High Irrigation Frequency and Brief Water Stress Before Harvest Enhances Essential Oil Yield of Rose-scented Geranium (Pelargonium capitatum × P. radens)
Authors: Eiasu Bahlebi K. , Soundy Puffy , Steyn J. Martin
Published: February 2019

Pot experiments were conducted to investigate the effects of irrigation frequency and withholding irrigation during the week before harvesting on rose-scented geranium herbage yield and essential oil yield and composition. A factorial experiment with three irrigation frequencies (twice a day, once a day, and every second day) and two growth media (silica sand and sandy clay soil) were conducted in a tunnel. One week before harvest, irrigation was withheld for half of the pots in each treatment combination. In a glasshouse, sandy clay soil was used as growing medium, and five irrigation frequencies (everyday, everyday with 1-week irrigation withholding period, every second day, every third day, and every fourth day irrigation to pot capacity) were applied as treatments. Results showed that essential oil content (percent oil on fresh herbage weight basis) increased as the irrigation frequency decreased. Both herbage yield and essential oil yield positively responded to frequent irrigation. Thus, higher herbage and essential oil yields were obtained from the highest irrigation frequency. A 1-week stress period significantly increased total essential oil yield as well as oil content per fresh herbage weight. The results highlighted that conditions of high soil water availability followed by brief water stress just before harvesting would maximize rose-scented geranium essential oil yield. Citronellol and citronellyl formate tended to increase with an increase in the stress level, but the reverse was true for geraniol and geranyl formate. Other major essential oil components were unaffected by water stress.
Prohexadione-Ca Affects Vegetative Growth of the Rejuvenated Shoots in Walnut Trees
Authors: Solar Anita , Jakopič Jerneja , Veberič Robert , Štampar Franci
Published: February 2019

Prohexadione-calcium (ProCa), formulated as Regalis, was tested as a vegetative growth inhibitor in rejuvenated annual shoots of 14-year-old mother trees in the ‘Franquette’ walnut cultivar. ProCa was applied three times during growing seasons in 2005 (Y5) and 2006 (Y6). This was during the second half of spring growth flush, the resting phase between the first and second growth flushes, and in the middle of summer growth flush. As a result, treated shoots in the upper part of the canopy were shorter than untreated ones during the whole growing season in both years. In Y5, two treatments of ProCa (250 mg·L−1), applied until the middle of June, inhibited shoot elongation during summer growth, which was the main purpose of the experiment. The reduction of shoot elongation was between 18% [lower shoots in the canopy (LS)] and 33% [upper shoots (US)]. After three ProCa applications, also the final length of the shoots was reduced by 5% (US) and 18% (LS). In Y6, when 100 mg·L−1 of ProCa had been used, strong reduction (24%) was observed only in US after two treatments. Summer growth was not reduced, probably as a result of an interaction between lower concentration of ProCa and stress caused by a water deficit and extremely high temperatures during the summer. On the base of the shoots, three treatments of ProCa (100 mg·L−1) in Y6 increased the ratio between wood and pith and, consequently, increased the quality and uniformity of the scion wood. Further research into additional cultivars and ProCa concentrations is recommended to optimize the terms of application.
Assessing Yield Potential of Cowpea Genotypes Grown Under Virus Pressure
Authors: Goenaga Ricardo , Quiles Adolfo , Gillaspie A. Graves
Published: February 2019

Cowpea or Southernpea [Vigna unguiculata (L.) Walp.] is an important grain legume in many parts of the tropics. However, viral diseases, particularly Cucumber mosaic virus (CMV) and Blackeye cowpea mosaic virus (BlCMV), can be a limiting factor in cowpea production. We evaluated in replicated field plots and under virus pressure nine PIs (441919, 441925, 441917, 147071, 146618, 180014, 180355, 194208, 612607) and three commercial cultivars (Coronet, KnuckleHull-VNR, Pinkeye Purplehull), some of which had shown absence of symptoms for CMV and BlCMV in unreplicated, seed regeneration plots of the U.S. cowpea collection. Only 3% of all plots had plants infected with both CMV and BlCMV in 2003 and 2004. This percentage increased to 47% in 2005. The accession PI 441917 had the highest 3-year mean for grain yield. However, PI 147071, PI 180014, and ‘KnuckleHull-VNR’ had higher seed protein concentration than other genotypes, but their grain yield was significantly lower than that of PI 441917. The cultivar Coronet and PI 180355 attained midbloom and maturity earlier than the other genotypes. Overall, PI 441917 outperformed all other genotypes for grain yield, including virus-resistant PI 612607 and the cultivar KnuckleHull-VNR. This accession is in the process of being released as a virus-tolerant genotype and should be useful in cowpea breeding programs to help control yield losses by CMV and BlCMV.
Husk Softening and Kernel Characteristics of Three Black Walnut Cultivars at Successive Harvest Dates
Authors: Brawner Scott A. , Warmund Michele R.
Published: February 2019

Eastern black walnuts (Juglans nigra L.) were collected weekly in September and October to identify a method to determine the optimal harvest date and to develop a quantifiable color classification system for kernels. Husk hardness, measured by a durometer, decreased over a 5-week period. During the collection periods, the greatest percent kernel for ‘Emma K’, ‘Kwik Krop’, and ‘Sparrow’ was recorded when durometer values (i.e., force measurements) of husks were 5.2, 5.5, and 3.4 N, respectively. Husk softening was also detected using the denting method, but the perception of denting did not consistently correspond with a specific husk hardness value. Of the three cultivars, ‘Kwik Krop’ kernels were the most difficult to visually sort into light, medium, and dark colors. Kernel LCH sum (L* + chroma + hue angle values), measured by a handheld spectrophotometer, provided a reliable color classification for all black walnut cultivars in which light kernels had LCH sums ≥150, medium kernels had sums of 149 to 126, and dark kernels had values ≤125.
Estimating the Economic Impact of the U.S. Golf Course Industry: Challenges and Solutions
Authors: Haydu John J. , Hodges Alan. W. , Hall Charles R.
Published: February 2019

Compared with more traditional sectors of U.S. agriculture, little economic information is available on the turfgrass industry, of which golf courses are an integral part. As a result, over the past 30 years individual states have conducted over 60 individual studies that describe in detail the economic importance of their industry. To date, no such information exists at the national level primarily due to the high cost of collecting primary data. To ameliorate this situation, the authors used secondary data from various sources and developed a composite of the turfgrass industry for the entire United States. This report focuses on the golf course industry in particular. Golf represents a very high value amenity use of horticultural products and services, is a major form of development, and uses large amounts of land and water. Results indicate the golf sector is the largest component of the turfgrass industry, accounting for a 44% share. The nearly 16,000 golf courses generated $33.2 billion (B) in (gross) output impacts, contributed $20.6 B in value added or net income, and generated 483,649 jobs nationwide. Economic impacts were also examined for each state, with “top 10” states highlighted. States falling in the top 10 category varied somewhat depending on the variables being examined. The exception were the top four states—Florida, California, Texas, and Illinois—that remained in the top four irrespective of variable type. In general, the top 10 states accounted for 55% to 60% of economic impacts for the entire United States while the top four alone contributed 40% of the total.
Relationship of Trunk Size to Selected Canopy Size Parameters for Native Pecan Trees
Authors: Smith Michael W.
Published: February 2019

Trees in a native pecan [Carya illinoinensis (Wangenh.) C. Koch.] grove vary in size, age, and genotype and tree spacing pattern is not uniform. This presents some problems for managing tree density, calibrating pesticide sprayers, and other management tasks. Trunk and canopy diameters and tree height of diverse sizes of native pecan trees in managed groves were measured and the relationships of cross-sectional trunk area with canopy footprint, surface area, and volume were determined. The canopy footprint, surface area, and volume per hectare were then calculated for the recommended stocking density of 6.9 m2·ha−1 of cross-sectional trunk area. Cross-sectional trunk area was strongly correlated with canopy footprint, surface area, and volume. Groves with an average tree size between 0.02 and 0.75 m2·ha−1 cross-sectional trunk had ≈50% canopy cover per unit land area and 3 ha·ha−1 bearing surface per unit land area at the recommended stocking density.
Restricted Water Availability During Lettuce Seed Production Decreases Seed Yield per Plant but Increases Seed Size and Water Productivity
Authors: Contreras Samuel , Bennett Mark A. , Tay David
Published: February 2019

Lettuce (Lactuca sativa) is an important vegetable crop worldwide, and its seed is commercially produced mainly under irrigation in arid and semiarid regions. The objective of this study was to determine how water availability during seed development affects lettuce seed productivity and quality. Three experiments were performed in the greenhouse and growth chambers using lettuce (cv. Tango) cultivated in pots. When watering volume was restricted (dry treatment) from bolting to seed harvest to 54% of the well-watered control (wet treatment), plants were shorter, had reduced dry weight, and produced fewer and heavier seeds. Water productivity (seed yield/watering volume) was nearly 50% higher in the dry treatment. Seeds from the dry treatment had a modest improvement in seed vigor (assessed by seedling growth) and decreased germinability (higher sensitivity to exogenous abscisic acid and water potential) compared with the wet treatment. In another experiment, water stress was applied abruptly to well-hydrated lettuce plants with developing seeds. Seeds that were at one-third and two-thirds of physiological maturity when water was withheld had lower germinability and greater storability than seeds with no water restriction. These results provide information that may be used for improvement of irrigation practices for lettuce seed production.
The Flavr Savr Tomato, an Early Example of RNAi Technology
Authors: Krieger Elysia K. , Allen Edwards , Gilbertson Larry A. , Roberts James K. , Hiatt William , Sanders Rick A.
Published: February 2019

The Flavr Savr tomato was introduced as the first genetically engineered whole food in 1994. The commercial event, resulting from transformation with an antisense expression cassette of the endogenous polygalacturonase gene, was sequenced and found to contain two contiguous, linked, transfer DNA insertions. We found polygalacturonase suppression correlates with accumulation of ≈21-nt small interfering RNAs, the hallmark of an RNA interference-mediated suppression mechanism.
Screening Fruit Loosening Agents for Black Ripe Processed Table Olives
Authors: Burns Jacqueline K. , Ferguson Louise , Glozer Kitren , Krueger William H. , Rosecrance Richard C.
Published: February 2019

The California table olive (Olea europaea L.) industry relies exclusively on hand harvesting of its primary Manzanillo cultivar. Increased harvesting costs have intensified industry interest in identifying an abscission agent that can be used with developing mechanical harvesting technologies to increase removal rates. Table olives are harvested immature green at horticultural maturity but before physiological maturity. The goal of this research was to reevaluate the potential of ethylene-releasing compounds (ERCs) as olive-loosening agents and to screen additional candidates previously shown to accelerate citrus fruit abscission. Eleven compounds were screened at two separate table olive-growing sites (Fresno and Tehama counties) in California in September until Nov. 2006. Compounds were applied at various concentrations alone or in combination. Fruit detachment force (FDF) and percent fruit drop were measured and leaf loss assessed. Of the compounds evaluated, the ERC ethephon (2-chloroethyl phosphonic acid) and 1-aminocyclopropane-1-carboxylic acid were the most efficacious. In whole tree applications, concentrations of ethephon or 1-aminocyclopropane-1-carboxylic acid above 1000 mg·L−1 reduced FDF to less than 50% of the untreated control within 17 days, but leaf drop increased with increasing concentrations. Addition of 1-methylcyclopropene reduced efficacy of ethephon and delayed leaf drop. Monopotassium phosphate + ethephon (4% and 1000 mg·L−1, respectively) reduced FDF and leaf loss was equivalent to the ethephon alone treatment. Compounds such as methyl jasmonate, coronatine, dikegulac, MAXCEL, traumatic acid, and 5-chloro-3-methyl-4-nitro-1H-pyrazole were not efficacious.
Using Infrared Thermography to Study Freezing in Plants
Authors: Wisniewski Michael , Michael Glenn D. , Gusta Lawrence , Fuller Michael P.
Published: February 2019

Factors that determine when and to what extent a plant will freeze are complex. Although thermocouples have served as the main method of monitoring the freezing process in plants, infrared (IR) thermography offers distinct advantages and the use of this latter technology has provided new insights on the processes of ice nucleation and propagation. This technology is based on the fact that freezing is an exothermic event. The temperature and spatial resolution of a high-resolution IR camera has enabled researchers to clearly define initial sites of nucleation as well as monitor the ice front as it spreads into surrounding tissues. Ice nucleation is induced by both extrinsic and intrinsic nucleators. Ice nucleation-active bacteria and moisture are two major extrinsic agents. In herbaceous plants, the influence of extrinsic ice nucleators on ice nucleation can be moderated by thick cuticles or the application of synthetic hydrophobic barriers. The situation in woody plants, however, is different. Woody plants appear to possess native, intrinsic nucleating agents that are as active as many extrinsic agents. However, the identity of the intrinsic nucleating agents in woody plants is not known. Despite the presence of intrinsic nucleating agents, barriers exist in woody plants that inhibit growth of ice from older stems into primary, lateral appendages. This is important because many tissues in woody plants that are frost-sensitive are flowers and primary, elongating shoot tissues that arise from buds attached to older stems. Pictures derived from video segments of the freezing process and data on the ability to block nucleation through the use of hydrophobic kaolin are provided.
Genetic Studies of Flower Color in Anagallis monelli L.
Authors: Quintana Andrea , Freyre Rosanna , Davis Thomas M. , Griesbach Robert J.
Published: February 2019

Wild Anagallis monelli exhibits blue or orange flower colors in geographically isolated populations. A new red flower color was developed through breeding, and a three-gene model was proposed for the inheritance of flower color in this species. In this study, blue and orange wild diploid accessions were used as parents to develop six F2 populations (n = 19 to 64). Sexual compatibility between blue and orange wild individuals was low with only 29% of the hybridizations producing F1 individuals. Six of 14 cross combinations between F1 siblings produced fruits, and fruiting success ranged from 55% to 90%. The number of seeds per fruit averaged 14.1 and germination rates for the F2s were low (16.8% to 30.7%). In three of six F2 populations obtained, flower color segregation ratios for orange, blue, and red were not significantly different from the expected ratios under a previously proposed three-gene model. White flower color was obtained as a fourth color variant in two of the remaining F2 populations. For one of these populations, segregation ratios were not significantly different from expected ratios for an expanded four-gene model. White flowers did not contain anthocyanidins, suggesting that there was a mutation in the early stage of the anthocyanin pathway. Orange flower color was found to be primarily the result of pelargonidin, blue to malvidin, and red to delphinidin. These three pigments may be present simultaneously, and their ratios play a significant role in determining flower color. Other factors such as copigments, metal ions, or a different molecular conformation of the anthocyanin could also be involved in flower color determination.
Comparative Canopy Damage among Provenances of Baldcypress Associated with the Presence of Cercosporidium sequoiae (Ellis and Everth.) W.A. Baker and Partridge
Authors: McDonald Garry Vernon , Denny Geoffrey C. , Arnold Michael A. , Bryan Donita L. , Barnes Larry
Published: February 2019

Seeds of Taxodium distichum (L.) Rich. were collected, germinated, and grown from native stands ranging from Mexico, Texas, Louisiana, Mississippi, and Alabama. Twenty-two provenance selections were planted in Summer 2004 in College Station, TX, in 36 replicated single-plant replications per block for a total of 792 trees. Below-average midsummer temperatures and above-average number of rainfall events were conducive to the development of a leaf blight associated with the presence of Cercosporidium sequoiae (Ellis and Everh.) W.A. Baker and Partridge. A survey conducted in Oct. 2007 rated differential defoliation responses among provenances. Selections of Taxodium distichum var. mexicanum (Gordon) from Mexico and south Texas showed defoliation rates from 89% to 96%, whereas T. distichum var. distichum from central Texas had defoliation ratings from 79% to 99%. With the exception of one family collected from the Sabinal River in Texas, the central Texas selections had similar defoliation compared with those from south Texas. Selections of T. distichum var. distichum and one selection of T. distichum var. imbricarium (Nutt.) Croom from southeastern regions (Alabama, Louisiana, Mississippi, and east Texas) showed greater tolerance to the presence of the leaf blight with 52% to 80% mean defoliation. A few individuals within these families exhibited little or no symptoms of the leaf blight. In general, those selections from high-rainfall, high-humidity areas had less defoliation associated with the presence of the leaf blight fungus, although defoliation was variable among provenances within all geographical regions. These results suggest that tolerance to defoliation from C. sequoiae could be included in selection criteria when choosing possible germplasm releases from Taxodium distichum.
Variation in Chilling Sensitivity among Eight Dieffenbachia Cultivars
Authors: Li Qiansheng , Chen Jianjun , Stamps Robert H. , Parsons Lawrence R.
Published: February 2019

This study evaluated chilling sensitivity of eight popular Dieffenbachia cultivars. Tissue culture liners were potted in 15-cm diameter pots using Vergro Container Mix A and grown in a shaded greenhouse under maximum photosynthetically active radiation of 285 μmol·m−2·s−1 for 5 months. After determining growth indices, the plants were chilled in walk-in coolers at 2, 7, or 12 °C for 6, 12, or 24 h. Chilled plants were placed back in the shaded greenhouse for chilling injury and growth evaluation. Visible symptoms of injury included chlorosis, necrosis, water-soaked patches on leaves, or complete wilting. In addition to leaf injury, stems of some cultivars chilled at 2 °C for 24 h became water-soaked at the base, which resulted in the death of either entire shoots or entire plants depending on cultivars. Leaf injury occurred in all cultivars chilled at 2 °C, except for ‘Panther’; and the longer the exposure at this temperature, the greater the injury. No visual injury was observed among plants chilled at 7 and 12 °C except ‘Tropic Honey’ that had 26% of leaves injured at 7 °C. Based on the percentage of injured leaves 12 days after chilling at 2 °C for 24 h, the sensitivity of the eight cultivars ranked as follows: Tropic Honey > Sterling > Carina ≥ Octopus > Camille > Camouflage > Star Bright > Panther. In addition to visual injury, plant growth was also affected by chilling during the subsequent 3 months of growth. All ‘Tropic Honey’ chilled at 2 °C died regardless of the tested chilling duration. Growth indices of all other cultivars except for ‘Panther’ chilled at 2 °C for 24 h significantly decreased compared with those of controls. ‘Camille’, ‘Camouflage’, ‘Carina’, and ‘Sterling’ also exhibited significant growth reduction after chilling at 2 °C for 12 h. This study showed that genetic variation in chilling sensitivity exists among cultivated Dieffenbachia. The identified chilling-tolerant cultivars could be used for breeding of new chilling-tolerant cultivars. The use of chilling-tolerant cultivars in production may reduce the chance of injury during heating outages and shipment.
Effects of Cooling Temperature and Duration on Flowering of the Nobile Dendrobium Orchid
Authors: Yung-Ting Yen Christine , Starman Terri W. , Wang Yin-Tung , Niu Genhua
Published: February 2019

The effects of cooling temperature [constant (10, 13, 15, or 18 °C, or 15, 18, or 21 °C)] and duration (2, 3, 4, 5, or 6 weeks, or 3, 4, 5, 6, or 7 weeks) at two separate locations (College Station and Weslaco, TX) on growth and flowering of Dendrobium Sea Mary ‘Snow King’, a Dendrobium nobile Lindl. hybrid, were investigated and the cooling requirement for flowering was quantified. Interactions between temperature and cooling duration were significant on time required to reach anthesis from either the beginning or completion of cooling, average flower number per flowering node, and percentage of nodes with aborted buds. Increasing cooling duration from 2 to 6 or 3 to 7 weeks resulted in less time to reach anthesis after the completion of cooling. However, the increased cooling durations extended the time needed for producing a flowering crop. Plants cooled at a relatively higher temperature among 10, 13, and 15 °C required less time to reach anthesis after the completion of cooling. Plants had more flowering nodes and total flowers when cooled at 10, 13, or 15 °C than at 18 °C in College Station or at 15 or 18 °C than at 21 °C in Weslaco. The results suggest that 3 weeks at 13 °C has saturated the cooling requirement, and 3 weeks at 13 or 15 °C is a recommended cooling treatment that saves production cost without retarding flower development.
Integration of Cover Crop, Conservation Tillage, and Low Herbicide Rate for Machine-harvested Pickling Cucumbers
Authors: Wang Guangyao , Ngouajio Mathieu
Published: February 2019

The effects of two cover crops [cereal rye (Secale cereale L.) and oat (Avena sativa L.)], four tillage systems [no tillage (NT), strip tillage (ST), conventional tillage with cover crops incorporated (CTC), and conventional tillage without cover crop (CTN)], and three pre-emergence herbicide rates (full rate, half rate, and no herbicide) on pickling cucumber (Cucumis sativus L.) growth and production, weed populations, and the incidence of pythium fruit rot were studied. Weed infestations, cucumber establishment, and cucumber leaf chlorophyll content were similar between the rye and oat treatments. However, the oat treatment had higher cucumber fruit number and weight and a lower percentage of cucumber fruit infected with Pythium spp. compared with the rye treatment. The NT and CTC systems reduced cucumber stand and leaf chlorophyll content, but had equivalent cucumber fruit number and weight compared with CTN. The NT and ST had lower weed biomass and weed density than CTN and CTC. The NT also reduced the percentage of cucumber fruit affected with pythium compared with CTN and CTC. Reducing the pre-emergence herbicide rate by half did not affect weed control or cucumber fruit yield compared with the full rate. However, weeds escaping herbicide application were larger in the half-rate treatment. The experiments indicate that with the integration of cover crops and conservation tillage, it is possible to maintain cucumber yield while reducing both herbicide inputs (by 50%) and the incidence of fruit rot caused by Pythium spp. (by 32% to 60%).
Using Digital Images to Characterize Canopy Coverage and Light Interception in a Processing Tomato Crop
Authors: Campillo C. , Prieto M.H. , Daza C. , Moñino M.J. , García M.I.
Published: February 2019

Canopy light interception (LI) is a determining factor for crop growth and yield. Crop yield depends on a canopy's capacity to intercept incident solar radiation, which in turn depends on the available leaf area, its structure, and its efficiency in converting the energy captured by the plant into biomass. Digital images offer a series of advantages over other methods of LI estimation, including the possibility to directly process images by computer for which free software is available. The objectives of this work were to develop a simple, economical method for determining LI in low-lying crops such as processing tomato using digital images obtained with a standard, commercial camera and free software and to evaluate the influence of different types of soil coverage (bare soil and plastic mulch) on LI. Photographs of the selected areas were taken using a digital camera at a distance of 160 cm above the center of each area. The resulting digital images were then analyzed with the free software GIMP 2.2 and IMAGE J. Three methods [area (SA), contour (SC). and reclassification (SR)] were used to quantify the percentage of groundcover (PGC). They were applied to the same images and compared with LI as measured with a line quantum sensor at solar noon. There was a close relationship between LI and estimated PGC with all three methods and for different soil cover regimes. In all cases, there was a linear adjustment with a significant correlation coefficient (P < 0.01) and an r
2 of greater than 0.88. The adjustment with RI was narrowest when the SR method was used to estimate PGC (r
2 = 0.93) followed by SC (r
2 = 0.92) and SA (r
2 = 0.88). Measurements of LI based on digital images offered practical advantages with respect to the use of photosynthetically active radiation bars because the latter must be used at solar noon. In contrast, measurements obtained with a digital camera can be taken at any time of day and bright sunshine is not necessary. Different correlations were obtained for bare soil and plastic mulch conditions, so it was necessary to use a different equation to estimate LI under each condition.
Characterizing the Interaction between NAA and BA on Apple Fruit Abscission and Development
Authors: Bukovac Martin J. , Sabbatini Paolo , Schwallier Philip G. , Schroeder Michael
Published: February 2019

NAA and BA are important compounds for regulating crop load in apples (Malus domestica Borkh.). When used for fruit thinning, both induce abscission, but at an equivalent crop load NAA tends to reduce and BA to increase fruit size. There is a strong interaction between NAA and BA when used together on ‘Delicious’ and ‘Fuji’, leading to excessive development of pygmy and small fruit (<65 mm diameter). The combination of BA (as Promalin, 1:1 BA + GA4+7) applied at king bloom (KB) and NAAm (amide) at petal fall increased the percentage of small fruit by 3.3- or 5.1-fold compared with BA or NAAm alone. Similar results were obtained with BA (Promalin) at KB oversprayed with NAA at 10 to 12 mm king fruit diameter (KFD). When NAA was oversprayed with BA during fruitlet development, i.e., 5 to 6 mm, 10 to 12 mm, and ≈18 mm KFD, the greatest inhibition of fruit growth occurred at the 10- to 12-mm KFD stage, and there was no significant effect at 18 mm KFD. Inhibition by treatment at the 5- to 6-mm stage was intermediate and trees were overthinned. NAA + BA inhibition of fruit growth in ‘Delicious’ and ‘Fuji’ was not crop load-dependent. In all experiments, crop load (wt basis) of trees treated with NAA + BA was similar or less than of those treated with NAA or BA alone, but they produced 2.5- to 5-fold more small fruit. NAA + BA increased the number of fruit per cluster, many of which failed to fully develop. Increasing the ratio of BA to NAA from 25:15 to 125:15 mg·L−1 increased small fruit formation. The presence of GA4+7 in commercial formulations of BA (0:100, Maxcel; 10:100, Accel; 50:50, Promalin) did not significantly affect the NAA + BA response. Fruit growth was not inhibited by the NAA + BA combination in large-fruited ‘Golden Delicious’ and ‘Jonagold’ and was increased in small-fruited ‘Elstar’ and ‘Gala’ compared with the nontreated control.
Morphogenetic Response of Lilium michiganense to Four Auxin-type Plant Growth Regulators In Vitro
Authors: Ault James Robert , Siqueira Sandy S.
Published: February 2019

Shoot, root, and callus induction were examined in the North American lily Lilium michiganense in response to treatment with four auxin-type plant growth regulators (PGR). Seed from controlled crosses were aseptically excised from slightly immature capsules and cultured in vitro on Murashige and Skoog basal medium and vitamins with 30 g·L−1 sucrose, 7.0 g·L−1 agar, and a pH = 5.7. Seed were maintained at 20 °C with a 14-h photoperiod. After 5.0 to 5.5 months, leaves and roots were removed from seedlings, the bulbs transversely sectioned, then the bulb sections cultured cut-surface down on the identical medium supplemented with 0.0, 1.0, 2.0, 4.0, or 8.0 μm dicamba, picloram, K-NAA, or 2,4-D. Morphogenetic response was tabulated 4 months after treatment. Shoot formation was promoted by treatment with dicamba, picloram, and K-NAA in comparison with the control (2.5 shoots/explant). Shoot formation varied significantly in response to individual dicamba, picloram, and 2,4-D concentrations. A maximum of 7.9 shoots per explant was promoted by 4.0 μm K-NAA and 1.0 μm dicamba, respectively. Root and callus formation also varied significantly between PGR treatments. Root formation was inhibited by dicamba, picloram, and 2,4-D treatments in comparison with the control (100% rooting); callus formation was promoted by dicamba, picloram, and K-NAA treatments in comparison with the control (15% callusing).