bluuebunny/crossref_metadata_2025 huggingface dataset:
421 Thermodynamic Analysis on Mechanism of Deep Supercooling of Tissue Water in Winter-hardy Plants
Authors: Shen Fanyi , Gao Rongfu , Liu Wenji , Zhang Wenjie , Zhao Qi
Published: February 2019

It is known that the redistribution of water and the formation of dispersed water units appears to be a prerequisite for deep supercooling. A concentration of the cell solute results from the migration of water during extracelullar freezing and lowers the temperature of homogeneous nucleation, but we are convinced that nucleation of ice within cells may be initiated by a heterogeneous mechanism, except we consider a small spherical cave, the water can freeze on the wall of this cave. We are also convinced that the solid walls of the capillary exert an external potential on the water molecules, causing the shift of the triple point of the confined fluids. Based on Fletcher's work for spherical particle, we have gotten the formula of critical free energy in the process of heterogeneous nucleation of water in a small spherical cave. This presentation introduces the theoretical background and counts the drop of temperature in heterogeneous nucleation. Then, putting two actions (depression of triple point and process of heterogeneous nucleation) together, we have calculated the freezing point. Sometimes it is lower than –38 °C. Some phenomena can be explained by using this theory: 1) Water is at the tension status, which means that it wets plant tissue, so the triple point (melting point) of tissue water can be lowered. 2) The redistribution of water, formation of dispersed water units, and dry region preventing ice from propagating, all allow heterogeneous nucleation, then the two actions can be synthesized and the water would lead to deep supercooling. If the barriers were destroyed, heterogeneous nucleation and deep supercooling would certainly be lost. 3) This theory is only suited to rigid wall of small cave, so we understand why cell wall rigidity has been shown to affect freezing characteristics. Project 39870234 supported by National Nature Science Foundation.
422 Water Uptake Patterns in shrunken-2 Sweet Corn (Zea mays) during Imbibition of Film-coated Seeds
Authors: Wilson Tina , Geneve Robert , Rowell Brent
Published: February 2019

Membrane damage associated with rapid influx of water during imbibition can play a role in the poor emergence and seedling vigor associated with sweet corn germination. Film-coating as a seed treatment has been used to improve germination and vigor in sweet corn and this improvement may not be associated with changes in imbibition rate. Two seed lots of shrunken-2 variety sweet corn, low-vigor `Even Sweeter' and high-vigor `Sugar Bowl', were treated with a hydrophilic polymer film-coating and evaluated for differences in emergence and water uptake. Both cultivars were grown at 19, 21, and 26 °C with no effect on emergence due to film-coating. Imbibition curves were established for untreated and hydrophilic film-coated seeds. Film-coated seeds showed an 18% increase in fresh weight compared to untreated seeds for both cultivars during a 6-h period. Bulk conductivity tests resulted in no significant mean difference between untreated and hydrophilic-treated seeds after 24 h. These seed lots have been treated with a hydrophobic polymer and are currently being evaluated for cold temperature emergence and imbibition rates. Water entry during imbibition will also be compared for untreated sugary (su) and shrunken-2 (sh2) seeds using the fluorescent compound trisodium salt, 8-hydroxypyrene-1, 3,6-trisulfonic acid (HPTS).
423 Tensiometer-controlled Irrigation in Large Container-grown Bald Cypress (Taxodium distichum)
Authors: Thaxton Virginia , Bush Ed , Gray Ann , Wilson Paul
Published: February 2019

Proper irrigation practices are important in the production of container-grown woody ornamentals. When choosing irrigation methods, nurserymen must attempt to maximize production and comply with public policies mandating decreased water usage and runoff. One of these methods schedules irrigation based on plant demand, using tensiometers to measure matric potential of the substrate. While tensiometers have been used successfully with agronomic crops in the field, their effectiveness in irrigation management of large container-grown woody ornamentals has not been extensively tested. The objective of this study was to determine the effect of four irrigation treatments (7 cb tensiometer setting, 14 cb tensiometer setting, 1 time a day application, 4 times a day application) on the production of the ornamental tree Bald Cypress over a 9-month period. Growth differed significantly among treatments. The highest growth index was observed in the 4 times a day and the 7 cb tensiometer treatments, followed by the 1 time a day and 14 cb treatments, respectively. Effluent and leachate (pH, EC, N, P, K) were also measured. Percent effluent volume was highly variable, with maximum volume occurring in June for the 7 cb setting (82%) and in October for the 1 time a day treatment (47%). Higher pH values (7.0 to 8.0) initially occurred in the timed irrigation treatments and higher EC values (2.0–6.0 mmhos) were found in tensiometer treatments; over time, differences among treatments decreased for both variables. Substrate concentrations of N, P and K varied significantly among treatments, while no significant differences were found in the leaf tissue analysis.
425 Comparisons of Mechanical Scarification Techniques for Enhancing Seed Germination in Two Saltgrass (Distichlis spicata) Seed Lots
Authors: Bonnart Remi , Koski Anthony , Hughes Harrison
Published: February 2019

Native turfgrasses have received greater attention in recent years because of their usefulness in growing in areas where many other grasses cannot. Saltgrass (Distichlis spicata) has good salt tolerance, but the natural germination rate for the seed is low. This is most likely due to the thickness of the seed coat inhibiting normal imbibition of water. Previous research in our laboratory has demonstrated increased germination with hand-scarification. The purpose of this research was to compare germination rates of machine-scarified, hand-scarified, and nonscarified seed. Scarifying the seeds by hand results in greater uniformity, but the operation is tedious and time-consuming. Machine scarification is quick, but the seeds have reduced uniformity. Two seed lots, one designated “Modoc” and one designated “Granite,” were compared in laboratory and field germination tests. Preliminary observations have shown that “Granite” seed had somewhat higher viability and vigor than the “Modoc” seed. Significantly greater germination occurred with scarification when seeds were germinated at 14 h of light at 30 °C and 10 h of darkness at 20 °C in the laboratory. Although scarification treatments were similar with the “Granite” seeds, near 80% germination, there were significant differences between hand and machine scarification with the”Modoc” seeds; hand scarified seed had greater germination. The field germination experiment had similar results to the laboratory experiments with “Granite” seed. However, scarification did not aid germination of “Modoc” seed. This is thought to be due to low vigor and associated death of seedlings prior to emergence. Preliminary data confirm the low vigor of the “Modoc” seed as compared to “Granite” seed.
431 Seasonal Changes in Nitrogen Uptake Efficiency in a Woody Ornamental (Tilia cordata Mill. `Greenspire')
Authors: Rose Mary Ann , Rose Mark , Wang Hao
Published: February 2019

Fertilizer recommendations for woody ornamentals suggest applying nutrients in early spring at budbreak, and in fall at the time of leaf coloration or leaf abscission. Because plants lack functional leaves at those times, there would be minimal contributions from photosynthesis to active ion absorption or from transpiration to mass flow of ions in soil towards roots. Thus, we hypothesized that fertilizer efficiency also would be low at those times. To estimate N uptake efficiency, 15N-enriched fertilizer was applied to container linden trees at one of five times during the 1998 season: at budbreak, during active growth, after terminal bud-set, before leaf abscission, and during leaf abscission. Half of the plants received 15N-nitrate-enriched ammonium nitrate on each date, and half received 15N-ammonium-enriched ammonium nitrate. Treated plants were harvested 10 days after enriched fertilizer application (29 May, 6 July, 17 Aug., 28 Sept., and 16 Nov.). Patterns of uptake were not different between plants treated with 15N-ammonium- or 15N-nitrate-enriched fertilizer. In both cases, nitrogen recovery efficiencies at budbreak and leaf abscission were much lower than at other application times. Whole-plant recovery efficiency of 15N-nitrate-enriched ammonium nitrate was 10% at budbreak, 13% at leaf abscission, and ranged from 58% to 71% for the intervening times. Recovery of 15N-ammonium-enriched ammonium nitrate was 6% at budbreak, 24% at leaf abscission, and 42% to 56% for intervening times.
433 Phosphorous and Potassium Fertilizers Influence Establishment of Bermudagrass
Authors: Miller G.L. , McCarty L.B. , Rodriguez I.R.
Published: February 2019

Establishment of an acceptable turfgrass quality on sand-based golf putting greens presents major agronomic and environmental challenges to turfgrass managers. The objective of this study was to evaluate of five N:P:K fertilizer ratios to aid in the establishment of bermudagrass on sand-peat (85:15 v/v). `Floradwarf' and `Tifdwarf' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burt-Davy] were sprigged in Aug. 1996 at the Envirogreen in Gainesville, Fla. `Tifeagle' and `Tifway' bermudagrass were sprigged in May 1999 at Clemson Univ. research green in Clemson, S.C. Treatments consisted of N:P2O5:K2O ratios of 1:0:1, 1:0:2, 1:1:1, 1:2:1, and 1:3:1 applied based on an N rate of 49 kg/ha per week. Treatments were applied weekly for 7 weeks. In Gainesville, the best growth rate was achieved from the 1:1:1 ratio of N:P2O5:K2O. While the 1:2:1 and 1:3:1 plots filled in well, they did not experience the same coverage rates as plots fertilized with the 1:1:1 ratio. In Clemson, similar growth was achieved with the 1:1:1, 1:2:1, and 1:3:1 treatments. The 1:0:1 and 1:0:2 plots were slow to establish at both locations. In general there were no differences in root and shoot dry weights of grasses grown in Clemson; whereas these weights were positively correlated to growth rates in Gainesville. These studies indicate that turf will respond to P fertilizer when it is grown in a P-deficit situation and that N or K cannot substitute for balanced nutrition.
439 Cultivar Variation in Response to 1-Methylcyclopropene Application to Apple Fruit in Air and Controlled-atmosphere Storage
Authors: Watkins C.B. , Nock J.F.
Published: February 2019

The inhibitor of ethylene binding, 1-methylcyclopropene (1-MCP) has been applied to `Gala', `Cortland', `McIntosh', `Empire', `Delicious', `Jonagold', and `Law Rome' apples under air and/or controlled atmosphere (CA) storage conditions. 1-MCP gas concentrations ranged from 0 to 2 mL·L–1. Effects of 1-MCP were greater in CA than air storage. A dose response of internal ethylene concentrations and flesh firmness to 1-MCP was found in cultivars such as `McIntosh' and `Law Rome', whereas in others, such as `Delicious' and `Empire', ripening was generally prevented by all 1-MCP concentrations. We have further investigated the effects of 1-MCP on `McIntosh' by increasing rates of the chemical to 50 mL·L–1, and confirming that fruit of this cultivar respond poorly if fruit have entered the climacteric prior to 1-MCP application. Efficacy of 1-MCP is affected by cultivar and storage conditions, and that successful commercial utilization of the chemical will require understanding of these relationships.
440 Effects of UV-B Irradiance on Postharvest Quality and Storability of Hand-picked Rabbiteye Blueberry as Related to Maturity Stage and Harvest Time
Authors: Basiouny Fouad M.
Published: February 2019

Blueberry fruits (Vaccinium ashie Read) of two cultivars, `Delite' and `Woodard', were hand-picked twice during the growing season (15 June and 1 July) to study the benefits of UV-B irradiance on postharvest fruit quality. After precooling, healthy, disease-free, uniform fruits were selected and exposed to UV-B irradiance (180 to 310 nm) for 24 h under cold conditions. The fruits were then kept at 2–3 °C and 90% to 95% relative humidity for 2 weeks before determining their quality parameters. Irradiated fruits were softer, wrinkled, and non-marketable compared to non-irradiated berries. UV-B had no beneficial effects on fruit quality or storability.
441 Nondestructive Quality Evaluation in Strawberries by Means of Chlorophyll Fluorescence
Authors: Hakim Abdul , Austin Max E. , Batal Dean , Khatoon Mohfeza
Published: February 2019

The possibility of using chlorophyll fluorescence for detecting internal quality of strawberry has been investigated. The mature fruit were marked and stored at 0 and 5 °C for 5, 10, and 15 days. After storage they were placed in the dark for 20 min and fluorescence measurement then was taken at the marked place with a fluorescence probe with a light intensity of 20 μmol·m–2·s–1. Samples were also taken from the marked place for laboratory analysis to determine chlorophyll and total soluble solute content. Firmenss was detected by an Instron Universal Testing Machine taking measurement at the marked section of the fruit. Rot was detected visually. Multiple regression and simple correlation were detected between fluorescence and laboratory-analyzed data. Multiple correlation coefficient (R) ranged from 0.80 to 0.97. Simple correlation (r) ranged from 0.44 to 0.89. The results of this study indicated that chlorophyll fluorescence is capable of detecting internal quality of strawberry and may potentially extend to other fruits. Feasible applications of the method include packinghouse, sorting of fruits, and parent and progeny quality assessment in a strawberry breeding program.
449 Cucurbit Viruses in Southern Illinois
Authors: Walters S. Alan , Kindhart Jeff D. , Hobbs Houston A. , Eastburn Darin M.
Published: February 2019

Cucurbit viruses are a major hindrance to cucurbit production in southern Illinois, often rendering cucumber and summer squash fruit unmarketable. Specific viruses infecting cucurbits in the region need to be determined since this would enable growers to make better decisions on virus disease management. Leaf samples of various cucurbit vegetables that had symptoms of viral infection were collected from grower fields during the 1998 and 1999 growing seasons to determine the predominant cucurbit viruses present. Samples were assayed for the presence of five individual viruses: cucumber mosaic virus (CMV), papaya ringspot virus (PRSV, formerly watermelon mosaic virus-1), squash mosaic virus (SqMV), watermelon mosaic virus (WMV, formerly watermelon mosaic virus-2), and zucchini yellow mosaic virus (ZYMV). Results from the two years indicated that WMV was the most prevalent virus in southern Illinois. Cucumber mosaic virus was found both years, but only in a low percentage of samples collected each year. Two cucurbit viruses, PRSV and ZYMV, were each identified only in one sample during the 1998 growing season, and neither were found in any of the samples collected during 1999. Squash mosaic virus was not identified in any of the samples collected during 1998; however, for the 1999 growing season, SqMV was identified in 19% of the samples collected, primarily from those samples of transgenic squash that were showing symptoms of virus infection.
454 Effect of Tuber Cutting and Planting Dates on Growth and Yield of Some Potato Cultivars
Authors: Abdalla M.M.A. , Butt A.M.A. , El-Damarany A.M. , Mckhaiel S.M.A.
Published: February 2019

This work was performed at the Experimental Farm of the Faculty of Agriculture Assiut Univ. during two fall seasons (1995–1996 and 1996–1997) to study the effect of planting date, cultivar, and seed cutting on the growth and yield of potato. A factorial experiment was designed. All data was subjected to statistical analysis. The results indicate that there is a significant effect for all the studied factors on the growth and yield of potato. The data also indicate that planting on 1 Oct. or 1 Nov. showed higher emergence percentage, total yield, final plant stand, rate of emergence, and height and number of stems. `Spunta' produced the highest stem length, fresh weight per plant, and total yield. Whole tubers gave higher stem length, plant fresh weight, tuber weight, and tuber number per hill.
456 Measuring the Intensity of School Gardening Programs and the Impact on Positive Youth Development
Authors: Skelly S.M. , Bradley J.C.
Published: February 2019

The number of school garden programs in America is growing. With interest in school gardens rising, research exploring the benefits of school gardens is important to establish the value of horticulture and gardening in primary education to help schools develop, promote, and use gardens for a variety of purposes. The goals of this research project were 1) to develop a typology, or matrix, of school garden program intensity and 2) to determine if variables related to positive youth development varied within the intensity typology. Twenty elementary schools in Florida participated in the research project accounting for ≈20 teachers and 400 third-grade students. This presentation will include how the typology was developed using three levels of intensity (high, medium, and low) and three types of gardens (vegetable, flower, and combination). The dependent variables examined for this study were the student developmental assets of responsibility, school engagement, achievement motivation, and interpersonal competence. Additional dependent variables included students' environmental attitudes and attitudes toward science. Discussion of school garden program intensity and the influence it may have on positive youth development will be the focus of this presentation.
457 Postharvest Research and Training: A Powerful Development Tool in Developing Countries
Authors: Pèrez-Brennan Rufino
Published: February 2019

During the past 30 years, numerous studies undertaken in developing countries, such as the region of the Caribbean, have consistently demonstrated that the returns on agricultural research investments are superior to any other alternate use of resources in agriculture. It has been reported that investment in agricultural research has contributed to an increase in productivity of ≈40% in pilot areas. In spite of this figure, countries such those in the Caribbean region still do not consider research as a development tool that could be used to solve problems such as postharvest losses of perishable crops. During the past decade, international cooperation organizations have been supporting research and training activities to help developing countries to be able to compete economically and access international markets. The main idea of these cooperation programs is to make agribusinesses understand that investing in research and training activities in areas such as postharvest and food distribution is one of the most powerful development tools that would help these countries to access better and more markets. It is hard to see a continuous and progressive increase in productivity and competitiveness without the corresponding technological development that would make products fulfill international standards.
459 New Ideas for Recruiting Horticultural Undergraduate Students
Authors: Childers Norman F.
Published: February 2019

For about 65 years, I have tried many ideas for recruiting horticultural students. Each has been effective to a limited extent, often involving much time in contacting vocational–agricultural schools and high school career advisors, making movies and slides, printing and distributing brochures, and designing and distributing displays at meetings. These continuing efforts are worthwhile and needed; however, I have found it easier, perhaps less expensive, and more effective, to recruit students already on campus. On college campuses, there are always a wealth of students still undecided on a major or minor, even in their senior year. The problem is to find a way to attract these students to stimulating experiences in horticulture and, at the same time, gain administrative credit for more undergraduates in departmental classes. Since 1990, the Univ. of Florida has been offering a 1-h credit “snack” course titled “Growing Fruits for Fun and Profit” at the noon hour two days a week in the spring and summer semesters. We serve the students a few fresh strawberries in that fruit is the topic, a big cookie or two, and a fruit drink. Enrollment has grown to a limited 300 students in spring and 80 students in summers—with a waiting list! We cover most fruits grown in Florida, with help of extension personnel specializing in the respective fruit and with the leader (Rebecca Darnell or me) offering a few of the 15 lectures. One session is a tour of the Univ. of Florida fruit plantings. Students are required to be present (given one absence) and keep a notebook. There are no exams. Students are graded on their attendance, notebooks, and attentiveness. One lecture from vegetables or ornamental faculty may be invited during the course. Most students get an A or B. For further attraction, 12 to 15 scholarships of $500 to $1500 are offered. We have been able to capture a few majors each year from students coming from across the campus.
460 Using Critical Thinking Exercises to Increase Environmental Awareness of Undergraduate Horticulture Students
Authors: Tignor Milton E. , Wilson Sandra B.
Published: February 2019

Information is more accessible to students than ever before. Gone are the days of a single instructor being the ultimate authority on a specific scientific discipline. Search engines, online journals, virtual libraries, and the development of Internet II will continue to drive the increase in availability of information. With basic computer skills, the average college student can put their hands on more subject data than they could possibly read during the time frame of a semester-long course. Therefore, it is more critical than ever to give students the logical tools to evaluate information and construct intelligent arguments. One particular area of interest to the horticulture industry is the impact of environmental regulations and public concern over common horticultural production practices such as irrigation, land development, application of pesticides, and developmental manipulation using growth regulators. South Florida is a mosaic of pristine natural areas, major agricultural production regions, densely populated urban areas, and regions of rapid suburban growth. As a result, there is heightened public awareness of environmental issues, which often leads to spirited conflicts among people with diverse professional backgrounds and personal interests. This catalyzed the development of a new course entitled “South Florida Flora and Ecosystems” that uses several different types of critical thinking exercises to help relate course content information into the cultural and political framework of South Florida. Techniques such as role playing, utilizing guest speakers with opposite opinions on the same topic, and active evaluation of data were used to enhance student learning, increase environmental awareness, and place undergraduate horticultural students one step closer to becoming “society-ready” graduates.
465 Carotenoid and Anthocyanin Content in High Pigment and Heirloom Tomato Germplasm as Measured by a Rapid HPLC Method
Authors: Jones Carl M. , Myers James R.
Published: February 2019

Continued and mounting evidence of the health benefits provided by carotenoid and anthocyanin pigments has increased public interest in dietary sources of these important phytonutrients. Tomatoes (Lycopersicon esculentum) are the primary dietary contributor of lycopene and an important source of beta-carotene. A collection of tomatoes containing the genes hp-1, dg, ogc, Ip, B and Af that are known to affect carotenoid and anthocyanin levels have been analyzed using HPLC. Levels of lycopene, beta-carotene, phytoene, and phytofluene have been determined in these accessions. Accession LA 3005, containing the dg gene, had the highest lycopene levels of the accessions analyzed (14 mg/100 g fresh wt.). A rapid HPLC method for quantitation of carotenoid levels from tomato fruit has been developed. “Heirloom” black and purple tomatoes have also been included in the accessions analyzed and have carotenoid levels comparable to cultivated red tomatoes. Anthocyanin presence has been confirmed only in the accessions LA 1996 (Af) and in some fruit of segregating plants from LA 3668 (Abg). Total monomeric anthocyanin content of LA 1996 as measured by the pH differential method is estimated to be 5.6 mg/100 g in the outer pericarp tissues and 18.6 mg/100 g in the skin tissue.
471 Defining the East African Highland Banana (I AAA) Ideotype and Breeding Objectives
Authors: Hartman J.B. , Vuylsteke D. , Makumbi D. , Ssebulibe R.N. , Karamura D.A.
Published: February 2019

The East African highland bananas are a sub-group of the Musa AAA group and are unique to the mid-altitude and highlands of Eastern Africa. In much of the area where they are grown, highland bananas are the main staple crop for both rural and urban populations. Yields of highland bananas have fallen precipitously in many areas and production deficits have been met by shifting highland banana production into new areas. Yield reductions have been attributed to a number of factors, including plant parasitic nematodes, the banana weevil (Cosmopolites sordidus), and black Sigatoka leaf streak (Mycosphaerella fijiensis). A program to breed improved highland bananas was established at the International Institute of Tropical Agriculture's Eastern and Southern Africa Regional Center (IITA-ESARC) in collaboration with the National Banana Program of Uganda in 1994. Following preliminary studies of fertility, breeding began in 1997. The breeding program has taken as its model IITA's successful plantain-breeding program. The plantain-breeding program has used an ideotype breeding approach to selection of improved plantain hybrids. The unique features, culture, and end-use of highland bananas have necessitated the definition of a new ideotype. Results of studies during the past 2 years have identified traits unique to highland bananas and a highland banana ideotype has emerged.
476 Reducing Midday Irradiance Increases Net CO2 Assimilation in Citrus Leaves
Authors: Jifon John L. , Syvertsen Jim
Published: February 2019

Maximum CO2 assimilation rates (ACO2) in citrus are not realized in environments with high irradiance, high temperatures, and high leaf-to-air vapor pressure differences (D). We hypothesized that moderate shading would reduce leaf temperature and D, thereby increasing stomatal conductance (gs) and ACO2. A 61% reduction in irradiance under aluminum net shade screens reduced midday leaf temperatures by 8 °C and D by 62%. This effect was prominent on clear days when average midday air temperature and vapor pressure deficits exceeded 30 °C and 3 kPa. ACO2 and gs increased 42% and 104%, respectively, in response to shading. Although shaded leaves had higher gs, their transpiration rates were only 7% higher and not significantly different from sunlit leaves. Leaf water use efficiency (WUE) was significantly improved in shaded leaves (39%) compared to sunlit leaves due to the increase in ACO2. Early in the morning and late afternoon when irradiance and air temperatures were low, shading had no beneficial effect on ACO2 or other gas exchange characteristics. On cloudy days or when the maximum daytime temperature and atmospheric vapor pressure deficits were less than 30 °C and 2 kPa, respectively, shading had little effect on leaf gas exchange properties. The results are consistent with the hypothesis that the beneficial effect of radiation load reduction on ACO2 is related to improved stomatal conductance in response to lowered D.
477 Sources of Supplemental Pollen and Their Contribution to Yield in Almonds
Authors: Ferrari Thomas E.
Published: February 2019

Almond flowers are self-incompatible and require cross-pollination for nut set. Commercial production requires pollinizers be planted within an orchard and the presence of honeybee colonies during bloom. External pollen sources are also available when “nearby” orchards produce flowers simultaneously, and when growers apply “extra” precollected pollen to foragers. The latter cultural practice is performed to improve cross-pollination under adverse bloom conditions. Paternity tests on nuts detected these two sources of supplemental pollen and measured what percent (%) each contributed to fertilization and crop production. Polymorphic enzymes were analyzed following electrophoresis of extracts from 42,000 embryos sampled over an 8-year period from orchards throughout California. A J-shaped frequency histogram was produced by “nearby” pollen sources (n = 30), with 0% to 0.2% being the most common class. The histogram from “extra” pollen (n = 70) was strongly right-skewed and bimodal (m1= 2.0% to 2.5%, m2=15.0% to 17.5%). Both sample populations possessed significantly different (P < 0.001) means, medians, and variances. Nut production by pollen from nearby orchards ranged from 0% to 5% (mean 0.97%, median, 0.45%, SD = 1.455); and production by extra pollen applied to honey bees ranged from 0% to 55% (mean 12.51%, median 7.9%, SD = 12.09). Evidence suggests pollen applied to honeybees contributed from 13- to 18-times more to yield than pollen transferred, naturally, from orchard to orchard.
480 Screening for Fire Blight Resistance in Apple Rootstock Breeding
Authors: Johnson W.C. , Aldwinckle H.S. , Norelli J.L. , Holleran H.T.
Published: February 2019

A primary focus of the apple rootstock breeding and evaluation program at USDA-ARS/Cornell Univ. has been to develop screening protocols to identify genotypes resistant to the fire blight bacterium (Erwinia amylovora). Direct inoculation is a simple technique, but does not represent the only mode by which rootstocks become infected in the orchard. Selection based on direct inoculation screens may, however, enrich the population for resistant genotypes. Large breeding populations from controlled crosses are shoot-tip inoculated with E. amylovora, and the fraction showing the highest levels of resistance are retained for further evaluations. These survivors are again screened through direct inoculation in the field, and the less-resistant genotypes are discarded. Following selection for other pathogen tolerance and horticultural characters, elite genotypes are multiplied through asexual propagation. Replicated tests using direct inoculation with multiple strains of E. amylovora are then used to estimate the level of fire blight resistance of elite genotypes. A final screen utilizes mature, grafted orchard trees to verify that the resistance of rootstock genotypes to fire blight is maintained under conditions simulating natural infection. Direct inoculation screening and selection have resulted in a high frequency of strong resistance to severe fire blight epidemics in recent orchard inoculation trials.
481 Performance of Macadamia Varieties in Three Agroecological Zones
Authors: Wasilwa Lusike A. , Watani Grace W. , Ondabu N. , Nyaga A. , Kagiri B. , Kiiru S.
Published: February 2019

Although macadamia was introduced to Kenya in 1946, it was not until the 1960s that commercial cutlivation commenced in the central, eastern, and western highlands. In the 1970s, 300 macadamia trees in the Central and Eastern highlands were selected based on nut yield and tree characteristics. In 1981, a subset of 25 of the most outstanding macadamia clones were planted (1979–1987) and evaluated at the National Horticulture Research Centre in Thika. Trial orchards, consisting seven to 15 clones (EMB-1, EMB-2, EMB-H, KMB-1, KMB-3, KMB-4, KRG-1, KRG-3, KRG-4, KRG-15, MRG-1, MRG-20, MRG-24, MRU-25, and TTW-2), were established in 1982, 1986, and 1989. The trials were set up as RCBD with five blocks and three to eight plants of each clone per block. Results from trial orchards show that macadamia hybrids (a natural hybrid between M. integrifolia and M. tetraphylla) EMB-H, KMB-3, and KMB-4 perform well at the higher elevations (>1700 m). The most outstanding clones of M. integrifolia with wide adaptability (1400 to 1750 m) were EMB-1, KRG-15, and MRG-20. Three distinct nut-bearing patterns [single peak (most varieties), bimodal peak, and ever-bearing] were observed. Nut clusters contain an average of 10 nuts (M. integrifolia) or 25 nuts (macadamia hybrid). Ten-year-old trees yield between 30 to 60 kg of nuts a year with kernel recovery of 28% to 41%.
482 In Vivo Micrografts in Almond (Prunus dulcis)
Authors: Martinez-Gomez Pedro , Thorpe Mary Ann , Gradziel Thomas M
Published: February 2019

Micrografts have proven a very useful technique when the early propagation of plant material is desired either to invigorate weak material, multiply selected genotypes, or obtained virus-free shoots. This is the situation with the recovery of haploid almond embryos, which occur at low frequency with sexual embryos in twin seeds (i.e., multiple embryos within the same seedcoat). Often these haploid plants show weak growth due to their haploid condition and their poorly developed state within twin seeds. Very little information is presently available, however, concerning the effectiveness of different micrografting techniques for almond. In this work, we examine the success of in vivo micrografting of `Nonpareil' almond seedlings under different conditions. Variables included type of micro-scion, the rootstock genotype, and the growth stage of the rootstock. Microscions tested included small (3 mm) micro-wedges from either unsprouted or recently sprouted buds. Rootstocks evaluated included the `Hanson' (peach × almond) hybrid, and Nemared and Nemaguard peach rootstocks. Rootstocks were grafted after either ≈3 weeks of growth, when the tissue was still herbaceous, or after ≈3 months of growth, when the tissue had become woody. Results show significant differences between the treatments. Findings will be discussed both in terms of effectiveness of different approaches and the advantages and disadvantages of their use in breeding programs.
486 Expression of β-glucuronidase Gene in Aspen under Control of CaMV35S, Heat Shock and RolC Promoters
Authors: Dai Wenhao , Cheng Zong-Ming , Sargent Wayne
Published: February 2019

Transgenic hybrid aspens (Populus tremuloides × P. tremula) were produced by Agrobacterium-mediated transformation and confirmed by polymerase chain reaction. Three promoters (CaMV 35S, Heat shock, and Rol C) were used to drive transcription of chimeric genes -glucuronidase (GUS), npt-II, and rol B. Stem sections in ≈100 mm thick, leaf blades, and root tips of transgenic aspen were treated with X-Gluc solution for 2 to 12 h in a 37 °C incubator and fixed in a solution containing 5% formaldehyde, 5% acetic acid, and 20% ethanol (FAA) for 10 min. After washing with 50% ethanol twice and clearing with absolute ethanol until free of chlorophyll, the GUS expression (localization and intensity of blue staining) in leaf, stem, and root at different growth stages were evaluated and photographed under the light microscope. When CaMV35S and rol C were used as promoters, the GUS gene was expressed in all parts of mature stem except pith, with the strongest activity in phloem. The heat shock promoter gave rise to very strong expression only in epidermis and phloem. In the young stem, GUS activity was detected in epidermis, parenchyma, vascular cambium, and primary xylem in CaMV35S-GUS transformed aspen shoots. The rol C promoter produced GUS gene expression in all stem tissues. When the heat shock promoter was used, the GUS gene expressed in a more tissue-specific manner, especially in mature stems, with activity mainly in parenchyma. In young leaf tissues, the GUS activity was primarily located in veins and mesophyll. In the mature leaves, no blue staining was found in the main vein. In root tip, the GUS gene driven by CaMV35S and heat shock promoters were expressed in the columella, vascular, and root apical meristem with very strong expression in the root apical meristem. Aspen plants transformed by rol C-Gus construct showed less or no expression in the columella.
489 Using Plant Nutrition Experiments as Models for Exploring Multiple Factor Interactions
Authors: Paparozzi Ellen T. , Stroup Walter W. , Conley M. Elizabeth , Landes Reid D.
Published: February 2019

Horticulturists are often interested in evaluating the effect of several treatment factors on plant growth in order to determine optimal growing conditions. Factors could include three or more nutrient elements, or types and rates of irrigation, pesticides or growth regulators, possibly in combination with one another. Two problems with such experiments are how to characterize plant response to treatment combinations and how to design such experiments so that they are manageable. The standard statistical approach is to use linear and quadratic (a.k.a. response surface) regression to characterize treatment effects and to use response surface designs, e.g., central-composite designs. However, these often do a poor job characterizing plant response to treatments. Hence the need for more generally applicable methods. While our goal is to be able to analyze three and higher factor experiments, we started by tweaking two-factor nutrient analysis data. The result was a hybrid model which allows for a given factor to respond linearly or non-linearly. We will show how this was done and our current “in progress” model and analysis for analyzing three quantitative factors.
490 Effects of Rye–Vetch No-till and Habitat Strips and Black Plastic Mulch on Insect Densities, Weed Control, and Freshmarket Cucumber Growth and Yield
Authors: Caldwell John , Ogutu Maurice
Published: February 2019

Greater plant diversity is associated with reduced insect pest pressure, but field-scale vegetable production systems incorporating plant diversity have been lacking. Cucumber was grown in 1998 and 1999 at the Virginia Tech Kentland experimental farm, by direct seeding or transplanting into rye/vetch mixture rolled to make a no-till mulch alternating with strips of vetch left to flower as a habitat for beneficial insects between cucumber rows, or direct-seeded into black plastic mulch between habitat strips or with bare soil between rows. Rye and hairy vetch were seeded at 56 kg·ha–1 each the preceding fall; only rye was planted in plots without habitats. A rippled coulter, cutting shank, and daisy wheels mounted on a tractor-drawn toolbar enabled a belt-driven seeder to seed cucumbers without pulling the no-till mulch. One hand weeding in cucumber rows at 3 weeks after planting (WAP) provided weed control equivalent to pre-emergence herbicide. At 3 WAP, no-till transplanted cucumbers had higher above-ground plant dry weights than no-till direct seeded cucumbers in both years, but, at 6 WAP, cucumber above-ground plant dry weights were equal (1999) or higher (1998) in direct seeded no-till than in transplanted no-till or black plastic mulch on bare soil. In 1999, Pennsylvania leatherwings, Chauliognathus pennsylvanicus DeG. (Coleoptera: Cantharidae), a cucumber beetle predator, had higher densities and cucumber beetles lower densities in no-till plots than in black plastic mulch plots, and bacterial wilt incidence was reduced in plots with habitat strips and no insecticide application compared to plots without habitat strips and four insecticide applications. Cumulative marketable yields in no-till were 59% higher in 1998 and 23% higher in 1999 compared to yields on black plastic mulch.
491 Intercropping of Spring-planted Sugarcane with Sweetpotato and Cowpea Under Conditions of Middle Egypt
Authors: Abdalla M.M.A. , El-Gergawi A.S.S.
Published: February 2019

Sugarcane, cowpea, and sweetpotato were grown in sole and intercrop systems at Experimental Station, Mallawi, Egypt (lat. 28°N) in the two spring seasons in 1996 and 1997 to determine the effects of cropping system on yield and yield components. The soil texture of the experimental site was loamy with a pH of 8.2. Results showed significant differences in yield and yield components of cane, cowpea, and sweetpotato due to intercropping treatments. Sugarcane intercropping caused signficant reduction in yield of sweetpotato and cowpea. The average yields of both sweetpotato and cowpea in the intercrop system were about 19.8 % and 29.9 %, respectively, of those of sole crop yields. Moreover, sweetpotato was more competitive than cowpea when intercropped. Furthermore, the magnitude of differences in sugarcane was low between sole and intercropped system as compared to sweet potato or cowpea. All yield attributes of cowpea and sweetpotato were better for the sole planted as compared to those for intrecrop treatments. Intercropping of one cowpea row sown at 15-cm hill spacing, between two sugarcane rows produced the maximum Land Equivalent Ratio (LER). This work suggests that the best cash return could be obtained when a single cowpea row planted at 30-cm hill spacing, is intercropped between two springplanted sugarcane rows.
493 The University Horticultural Department as an Introducer of New Ornamental Crops, Without a Plant Breeder—Is It Possible?
Authors: Armitage Allan M.
Published: February 2019

The New Crop Program at the Univ. of Georgia has introduced about a dozen crops new to the floriculture and ornamental plant industry. None of the selections arose from controlled crosses or traditional plant breeding, but were due to discovery, natural plant mutation, and plant donations from interested individuals. All successful introductions benefitted from feedback from the industry, evaluation, research, and promotion of the taxa. No marketing was done by the university. Less than 10% of plants trialed were introduced to the industry, and not all introductions were equally satisfactory. The keys to new crop introduction are feedback from the industry, an industry willing to experiment with new material and to be as highly selective as possible in choosing the crops to be introduced. The disadvantages and benefits of establishing a New Crop Program will be discussed.
495 Public Preferences for Poinsettia Cultivars
Authors: Barrett J.E. , Bradley J.C. , Bartuska C.A. , Nell T.A. , Clark D.C.
Published: February 2019

More than 60 new poinsettia cultivars have been introduced in the past 3 years, and many of these have nontraditional bract color or plant form. About 75% of all poinsettias sold are red and `Freedom' represents more than 50% of the red poinsettia market in the United States In Fall 1999, 212 individuals were surveyed and asked to indicate their favorite 10 cultivars out of the 89 in a cultivar trial. The top choices were `Plum Pudding', `Winter Rose Dark Red', `Cranberry Punch', and `Monet Twilight', which were selected by 48%; 38%; 32%, and 31% of the participants, respectively. These cultivars are all nontraditional in appearance. The top red cultivars were `Freedom', `Orion', and `Red Velvet', which were selected by 27%, 26%, and 23%, respectively. The participants were then asked to rate on a 1 to 10 (most favorable) scale 15 plants that represented different poinsettia forms and colors. Five of these plants were cultivars with different shades of red that the industry easily separates. However, the participants' ratings of these were not significantly different, which indicates the shade of red in bract color may be more important to the industry than it is to the public. These results also indicate that there are strong differences in individual preferences for poinsettias. Each of the 15 plants received both high and low ratings. Also, of the participants that included `Freedom Red' in their top 10 selection, only 13% of those selected `Plum Pudding', which has purple bracts, and only 11% selected `Winter Rose Dark Red', which has a nontraditional plant form.
499 Postharvest Care and Handling Practices for Cut Poinsettia cv. `Winter Rose Dark Red'
Authors: Leonard Ria T. , Nell Terril A. , Barrett Jim E. , Clark David G.
Published: February 2019

The traditional use of poinsettias has been as potted plants. A new poinsettia variety, `Winter Rose Dark Red', is performing well as a cut flower, lasting 2 to 3 weeks. Various postharvest handling procedures were examined, including stem processing methods at harvest, storage and transit conditions, as well as handling practices at the wholesale, retail, and consumer levels, to determine the best handling practices to maximize quality and longevity. At harvest, traditional latex controlling techniques, such as dipping stems in 95% ethanol for 10 min and burning or boiling stem tips were tested. Stems wilted faster when dipped in ethanol or burned. The woody nature of the stem contains little latex compared to traditional varieties; thus, no latex-controlling methods are needed or beneficial. After harvest, there was no benefit found in hydrating stems in a commercial hydration solution compared to plain water. Transport and/or storage conditions between 10 to 15 °C for 3 to 4 days maximized longevity. Chilling injury occurred when transported at 4 °C. Leaves and bracts wilted when stored dry in a box, but recovered within 12 to 24 h when stored for 2 days. Leaves abscised after exposure to short-term wilting but no bract abscission occurred. Storing stems in a 10% bleach solution prevented wilting and reduced bacterial growth. Bracts were sensitive to mechanical injury during transit, resulting in bruising lesions on the bracts, which increased sensitivity to bract edge burn. Stems declined faster when maintained in a floral preservative compared to water during the consumer phase.
501 Summary of Leaf Potassium Status in `French' Prune Suggests Overfertilization
Authors: Glozer Kitren , Southwick Stephen , Olson Bill , Buchner Rick , Kreuger Bill , Sibbett Steve , Reil Wilbur , Yeager Jim
Published: February 2019

Prune (Prunus domestica) producers have an increased incentive to produce larger fruit. Potassium is thought to be critical in prune production and the fruit utilize large amounts of K. Growers have been fertilizing heavily with K to maximize fruit size. We conducted a survey of 16 `French' prune orchards in 1998 and 1999 growing seasons. Low (≈1.0% mid-July) leaf K concentration is associated with leaf chlorosis, early leaf drop and shoot dieback, with symptoms pronounced in the upper canopy, particularly with heavy cropping. The survey orchards were chosen to represent a range of leaf K within and among orchards, and among counties. At harvest, fruit drying ratio, dry yield per tree, and dried fruit size were determined in order to develop relationships between fruit quality and yield, and leaf K over the growing season. To date we have determined the following: 1) spring (May 1998 and April–May 1999) leaf K concentration is correlated with mid-summer (mid-July 1998) and early summer (late June 1999) leaf K concentration, respectively; 2) mid-April to mid-May leaf K concentration is being maintained by growers due to thinning and fertilizing, and to light cropping in 1998, at adequate to above adequate levels (2%) that increase through the growing season; 3) no beneficial relationship between fruit size, drying ratio or dry yield has been found with spring or summer (June or mid-July) leaf K concentration above 2%, either when evaluating all surveyed orchards together or as individual orchards.