bluuebunny/crossref_metadata_2025 huggingface dataset:
Late-season `Valencia' Orange Mechanical Harvesting with an Abscission Agent and Low-frequency Harvesting
Authors: Burns Jacqueline K. , Roka Fritz M. , Li Kuo-Tan , Pozo Luis , Buker Richard S.
Published: February 2019

An abscission agent (5-chloro-3-methyl-4-nitro-1H-pyrazole [CMNP]) at 300 mg·L–1 in a volume of 2810 L·ha–1 was applied to Valencia orange trees [Citrus sinensis (L.) Osb.] on 22 May 2004. At this time, immature and mature fruit were present on the tree simultaneously. Three days after application, fruit were mechanically harvested using a trunk-shake-and-catch system. The power to the shaker head was operated at full- or half-throttle (FT or HT, respectively), and the duration of trunk shaking was 2 seconds at FT or 4 seconds at FT and HT. Mature fruit removal percentage and number of immature fruit removed, and fruitlet weight and diameter were determined. Mature fruit removal percentage with 2 seconds at FT or 4 seconds at FT harvesting ±CMNP, or 4 seconds at HT + CMNP was not significantly different and ranged between 89% to 97%. Harvesting at 4 seconds HT without CMNP removed significantly less mature fruit than any treatment. CMNP did not affect immature fruit removal by the trunk shaker. Harvesting at 4 seconds at HT removed significantly less immature fruit than 2 seconds at FT or 4 seconds at FT. No significant difference in fruitlet weight or diameter was measured between any trunk shaker harvest operation and CMNP treatment. Trunk shaking frequency was estimated to be 4.8 and 8.0 Hz at HT and FT, respectively. Yield in 2005 was determined on the same trees used for harvest treatments in 2004. CMNP did not impact yield. No significant difference in yield was seen between the hand-picked control and 4 seconds at HT, whereas yield in the remaining treatments was lower. The results demonstrate that CMNP application combined with low frequency trunk shaker harvesting can achieve high percentage of mature fruit removal with no significant impact on return yield of the following crop.
Hurricane Katrina: Perspective from the Southern Horticultural Laboratory
Authors: Pounders Cecil , Marshall Donna , Posadas Benedict
Published: February 2019

Surviving extremes of climate is a fundamental component of horticultural production and research. The Southern Horticultural Laboratory has weathered many storms including Hurricane Camille and now Hurricane Katrina. The name of the research station has changed twice, both times following massive hurricanes. Before Hurricane Camille in 1969, the station title was the Tung Research Unit. After the devastation of the tung industry by Camille, the research focus changed to blueberries and other small fruit crops with a corresponding name change to Small Fruit Research Unit in 1976. The research objectives expanded to include ornamental research in 2001. Post Hurricane Katrina, the unit was renamed the Thad Cochran Southern Horticultural Laboratory to reflect the station's expanded research mission. This paper chronicles how the station reacted to the devastation of Hurricane Katrina. It also evaluates economic vitality of commodities researched at the station in contrast with storm effects on pecan and the demise of tung production. Katrina produced some temporary interruptions in production but no drastic restructuring of the type experienced with tung production after Camille is anticipated. Hurricanes are inevitable for the Gulf Coast region. Wise planning and implementation of preventative measures to protect horticultural crops and research will determine future success.
Control of Bud Sprouting and Elongation in Colored Zantedeschia Tubers by Low-temperature Storage
Authors: Naor Vered , Kigel Jaime , Ziv Meira
Published: February 2019

The effect of low-temperature (LT) storage at 10 °C on dormancy relaxation and budbreak was studied in tubers of colored Zantedeschia. LT storage for 35 or 64 days enhanced budbreak by about 80 days compared to tubers stored at 20 °C. Primary bud elongation did not occur at 10 °C for 143 days, but took place after the tubers were transferred to 20 °C. Prolonged LT storage enhanced the rate of bud elongation at 20 °C. It is proposed that LT storage enhances dormancy relaxation but, at the same time, inhibits bud elongation in nondormant buds. This dual effect can serve growers in programmed production of year-round forcing of colored calla lily flowers.
Biology and Control of Bacterial Leaf Blight of Cornus mas
Authors: Mmbaga M.T. , Nnodu E.C.
Published: February 2019

Cornelian cherry (Cornus mas L.) has been free of disease and pest problems until recently when a bacterial leaf blight caused by Pseudomonas syringae was reported. Since its first observation in middle Tennessee in 1999, the disease has become endemic in the nursery where it was first discovered. The objective of this study was to assess the disease, evaluate factors that favor disease development, and develop disease management strategies. Cool temperatures of 20 to 24 °C (day) and 10 to 15 °C (night) were most favorable to the disease and young leaves were highly susceptible while mature leaves were resistant to infection. Leaf wounding increased the susceptibility of leaves and mature leaves developed infection at 28 °C, temperature at which nonwounded leaves were completely resistant to infection. Results from this study also showed that plant propagation from seemingly healthy branches of infected plants may have perpetuated the disease at the nursery. Six chemicals—Phyton-27 (copper sulfate), Camelot (copper salt of fatty acids), Agri-Mycin 17 (streptomycin), Kocide 101 (copper hydroxide), Basicop (elemental copper 53%), and, Bordeaux mixture (cupric sulfate + lime) were evaluated for disease control. Phyton-27, and Agri-Mycin—were most effective and reduced disease severity to 10% of foliage showing disease symptoms. Information from this study will be useful in designing effective disease management strategies.
Hot Water Treatment of Postharvest Mei Fruit to Delay Ripening
Authors: Luo Zisheng
Published: February 2019

Mei (Prunus mume `Daqinghe') fruit were immersed in 20 °C (control), 47 °C (HWT47), 50 °C (HWT50), or 53°C (HWT53) water for 3 min after harvest, then stored at 20 °C. Firmness, peel color, chlorophyll, chlorophyllase activity, soluble solids content (SSC), titratable acidity (TA), respiration, ethylene production, and pectinmethylesterase (PME) and polygalacturonase (PG) activity were monitored to determine the effects of hot water treatment in delaying fruit ripening. Control fruit displayed a typical climacteric pattern of respiration and ethylene production. Peak CO2 production and ethylene production were observed 6 days after harvest. Fruit softening was accompanied by decreases in hue angle, chlorophyll content, SSC, and TA and increases in chlorophyllase and PME and PG activity. Hot water treatment delayed the onset of the climacteric peaks of CO2 and ethylene production. The delays were associated with delays in fruit softening, consistent with lags in the rise of PME and PG activity; delays in yellowing and chlorophyll breakdown, consistent with lags in the rise of chlorophyllase activity; and delays in loss of SSC and TA. The shelf life of fruit increased by 6 days, or 60%, with HWT47, and by 8 days, or 80%, with HWT50 or HWT53.
Somaclonal Variation of Coreopsis Regenerated from Leaf Explants
Authors: Trader Brian W. , Gruszewski Hope A. , Scoggins Holly L. , Veilleux Richard E.
Published: February 2019

Coreopsis species (tickseed) can be regenerated from leaf segments allowing the possibility to exploit somaclonal variation as a means to develop novel phenotypes. We used true leaf explants from in vitro seedlings of perennial C. grandiflora (A. Gray) Sherff `Domino' and `Sunray' grown on Murashige and Skoog (MS) basal medium. Two of ten seedlings of `Domino' regenerated freely and others were generally recalcitrant. From these two seedlings, designated E2 and H2, shoots were regenerated and acclimatized to the greenhouse. About 175 plants were established and vernalized from which somaclones were selected based on distinct differences in flower orientation and appearance. The selected somaclones were propagated by division and transplanted to the field in August 2001 in a randomized complete block design with three-plant plots and three replications to determine whether novel characteristics persisted through an additional propagation cycle. In the field, plant height, leaf dimension, flowering, and flower dimensions were scored in June and July 2003. Differences were found between somaclones and similarly propagated E2 and H2 for desirable (more petals per flower, greater flowering, shorter plants), undesirable (less flowering, smaller flowers), and neutral (narrower leaves, taller plants) traits. Open-pollinated (OP) seed was collected and germinated and the seedlings from somaclones that differed significantly from E2 and H2 were evaluated. These maternally selected seedlings were overwintered then planted in the field in May 2004. Most traits that differentiated somaclones from E2 and H2 did not persist in the OP seedling population; however variation that was likely introduced through outcrossing resulted in desirable phenotypes with potential for new cultivar development.
In vitro Induction and Characterization of Tetraploid Lychnis senno Siebold et Zucc.
Authors: Chen Li-ping , Wang Yan-ju , Zhao Man
Published: February 2019

In this study, in vitro induction of tetraploid Lychnis senno Siebold et Zucc. and its cytological and morphological characterization were conducted. For polyploid induction, nodal segments with axillary buds from in vitro grown plants were kept for 3 days in MS (Murashige and Skoog, 1962) liquid or solid media added with a series of concentrations of colchicine. Out of total 588 recovered plants, 15 tetraploids and 6 mixoploids determined by flow cytometry analysis were obtained. The tetraploid contained 48 chromosomes, twice the normal diploid number of 24, as observed under light microscope. The tetraploid plants exhibited much larger but less stomata than diploid plants. Moreover, significant differences in stem height and leaf size between the diploid and tetraploid plants were noted. The tetraploid plants were more compact than diploids.
Nutrient Release from Controlled-release Fertilizers in Acid Substrate in a Greenhouse Environment: I. Leachate Electrical Conductivity, pH, and Nitrogen, Phosphorus, and Potassium Concentrations
Authors: Merhaut Donald J. , Blythe Eugene K. , Newman Julie P. , Albano Joseph P.
Published: February 2019

Release characteristics of four types of controlled-release fertilizers (Osmocote, Nutricote, Polyon, and Multicote) were studied during a 47-week simulated plant production cycle. The 2.4-L containers containing a low-fertility, acid-based substrate were placed in an unheated greenhouse and subjected to environmental conditions often used for production of azaleas and camellias. Leachate from containers was collected weekly and monitored for pH, electrical conductivity, and concentrations of NH4+ N, NO3–N, total P and total K. Leachate concentrations of all nutrients were relatively high during the first 10 to 20 weeks of the study, and then gradually decreased during the remaining portion of the experiment. Differences were observed among fertilizer types, with Multicote often resulting in higher concentrations of N, P, and K in leachates compared to the leachates from the other fertilizer types during the first half of the study. Concentrations of NO3– and P from all fertilizer types were often above permissible levels as cited in the federal Clean Water Act.
Bermudagrass Putting Green Performance Influenced by Nitrogen and Trinexapac-ethyl
Authors: McCullough Patrick E. , Liu Haibo , McCarty Lambert B. , Toler Joe E.
Published: February 2019

Dwarf-type bermudagrass (Cynodon dactylon Pers. × C. transvaalensis Burtt-Davy) putting greens tolerate long-term mowing heights of 3.2 mm but require heavy nitrogen (N) fertilizations that increase ball roll resistance. Applying a plant growth regulator, such as trinexapac-ethyl (TE), could reduce uneven shoot growth from high N fertility and improve putting green ball roll distances. Field experiments were conducted from April to August 2003 and 2004 in Clemson, SC to investigate effects of ammonium nitrate applied at 6, 12, 18, or 24 kg N/ha per week with TE applied at 0 or 0.05 kg a.i. per ha every 3 weeks on `TifEagle' bermudagrass ball roll distances (BRD). BRD were measured weekly with a 38-cm stimpmeter in the morning (900 to 1100 hr) and evening (>1700 hr) beginning 1 wk after initial TE treatments. Interactions were not detected among N, TE, or time of day. TE increased BRD about 15% from non-TE treated. BRD was reduced with increased N rate and from am to pm; however, bermudagrass treated with TE averaged 10% longer PM BRD than am distances of non-TE treated. Overall, increased N fertility and diurnal shoot growth may reduce BRD but TE will be an effective tool for mitigating these effects on bermudagrass putting greens. Chemical name used: [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (trinexapac-ethyl).
Dissimilatory Reduction of Sulfate in Black Layer
Authors: Berndt W.L. , Vargas Joseph M.
Published: February 2019

Black layer has been associated with a severe decline in the quality of turf on putting greens. It was suggested that the black layer results from dissimilatory sulfate (SO42–) reduction. This study was done to determine if SO42– reduction occurs in an existing black layer. Radioactive 35SO42– was used to calculate the rate of SO42– reduction in intact soil cores taken from an existing black layer in a `Penncross' creeping bentgrass (Agrostis palustris Huds. `Penncross') putting green. When 10–3 M 35SO42– with a specific activity of 1.554 × 105 Bq·mg–1 SO42– was injected into a core it reduced to sulfide (35S2–) at a mean rate of 7.1 nmol sulfur (S)/cm3 soil/d. Injecting azide (N3–) or molybdate (MoO42–) at 10% w/v with the label reduced the rate of SO42– reduction to 0.03 and 0.01 nmol S/cm3 soil/d, respectively. The effect of N3– confirmed that reduction of SO42– was biological, while the effect of MoO42– confirmed that the entities responsible for the reductive cycling were sulfate-reducing bacteria (SRBs). This was the first proof that biological reduction of SO42– produces S2– in a black layer from a creeping bentgrass putting green. It was concluded that the respiration of indigenous SRBs was linked to development of this black layer. Thus, a key to successfully controlling black layer in putting greens must involve regulating the respiratory activities of SRBs.
Comparing Cultivars of Three Cool-season Turfgrasses for Nitrogen Recovery in Clippings
Authors: Liu Haibo , Hull Richard J.
Published: February 2019

Economic and environmental concerns over nitrogen (N) fertilization of turfgrasses are prompting serious considerations of how to best use various N pools in turf-soil ecosystems. Nitrogen in clippings is receiving special consideration but information on how large and variable this N source might be for different turfgrasses is limited. Therefore, a field study investigated growth of and N recovery in clippings from 10 cultivars each of kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.) turf at the University of Rhode Island Turfgrass Research Station, Kingston, during 1990 and 1991 growing seasons. All turf had been established in 1985, 1986 or 1987 on an Enfield silt loam (Coarse loamy over sandy skeletal, mixed, mesic, Typic Dystrochrepts) and maintained under N fertilization rate of 147 kg N ha/year. Daily clipping growth rate (DCG), leaf blade N concentration (NC), and daily N recovery rate (DNR) in clippings were compared across species and cultivars. Seasonal clipping yields ranged from 5152 kg dry weight/ha for tall fescue to 3680 kg·ha–1 for perennial ryegrass. Significant species differences in the amount and seasonal pattern of N recovery were identified. Cultivar differences in N recovery were greatest for kentucky bluegrass but much less for perennial ryegrass and tall fescue. Total N recovery in clippings ranged from 260 to 111 kg N/ha/year generally exceeded N supplied as fertilizer, thus emphasizing potential importance of clipping N in turf management.
Genetic Variation and Relationships among Frangipani Cultivars
Authors: Meerow Alan W. , Criley Richard , Schnell Raymond J.
Published: February 2019

Plumeria is a small genus of succulent trees and shrubs in the Apocynaceae native to tropical America. It is favored as a landscape ornamental in tropical and tropical regions due to its tolerance of hot, dry conditions, ease of propagation, and long season of bloom. Flowers of certain varieties are important components of leis in Hawaii. Numerous cultivars have been developed, chiefly from either seedling selections of P. rubra, a Mexican species, and P. obtusa, broadly distributed in the Caribbean basin, or hybrids between these species and among older cultivars. Little is known of the breeding behavior of the species in nature or cultivations, but very few of the cultivars set an abundant number of fruits. We used 21 microsatellite DNA (SSR) loci developed in our lab from Plumeria rubra to investigate the genetic relationships of 83 cultivars of Plumeria from a germplasm collection at the University of Hawaii, now duplicated in Miami. All 21 loci were highly polymorphic, with three to 15 alleles observed across the cultivar population. Six of the 21 loci exhibit heterozygote excess across the cultivars; the majority of the remaining 15 have an excess of homozygotes, suggesting that the cultivars are largely inbred. Clustering with Bayesian analysis suggests that there are five main groups represented among the cultivars, with varying degrees of admixture among the five. The data also suggest that identical genotypes have received different cultivar names at times. We are also analyzing seedling populations from fruits spontaneously set on several cultivars to determine if they are predominantly the result of self-pollination or out-crossing.
Determination of Seed Germination Requirements in Nolana sp.
Authors: Douglas Amy , Freyre Rosanna
Published: February 2019

Nolana is a diverse genus native to coastal deserts of Peru and Chile, with great potential for developing new ornamental cultivars. Low germination has been an obstacle to breeding efforts at the University of New Hampshire (UNH). Nolana fruits are comprised of unusual sclerified mericarps, each containing one or more embryos. Germination occurs with opening of funicular plugs on the mericarps. Under normal greenhouse conditions at UNH, germination success in eight Nolana species (N. adansonii, N. aticoana, N. humifusa, N. laxa, N. ivaniana, N. plicata, N. elegans, and N. rupicola) ranged from 0 to 0.05 seedlings/mericarp. We analyzed mericarp morphology, imbibition, and the effect of chemical and environmental germination treatments. SEM showed that soaking treatments create physical changes in mericarp morphology, exposing tracheid tubes in the funicular plugs. Mericarps were soaked in dye to track imbibition, confirming that this occurs through the tracheid tubes, and that additional scarification is not required. The following chemical treatments were unsuccessful in increasing germination: 0.1 N HNO3, 0.2 KNO3, conc. H2SO4, 10 mM or 1 μM ethephon. Gibberellic acid (1000 ppm) effectively increased germination in some species (up to 0.47 seedlings/mericarp). Mericarps stored dry for 2 years had significantly higher germination than fresh mericarps (0.55 seedlings/mericarp). Mericarps of N. aticoana were subjected to after-ripening treatments. Mericarps stored for 7 weeks at 35 °C and 75% RH showed significantly higher germination (0.36 seedlings/mericarp) than mericarps stored dry, or stored moist for 1-6 or 8-12 weeks. Our findings facilitate development of larger hybrid populations, thus increasing the efficiency of Nolana breeding programs.
Fritillaria Species Are at Risk of Extinction in Iran: Study on Effective Factors and Necessity of International Attention
Authors: Ebrahimie Esmaeil , Mohammadi-Dehcheshmeh Manijeh , Sardari Manoochehr
Published: February 2019

The fascinating Fritillaria genus includes 100 species, of which 14 species are native to Iran. Iran is center of origin and genetic diversity of important species like F. imperialis and F. persica. Unfortunately, in recent years wild populations of these valuable plants, which have commercial value, are at risk of extinction in Iran. Effective factors on extinction of F. imperialis and F. persica were investigated in 2 years (2003 and 2004). The important factors were: 1) irregular grazing of Fritillaria stands (provenances); 2) in Iran, there is no protecting rule for saving Fritillaria from extinction; 3) changing of pastures to dry farms; 4) pest overflows that are related to destruction of pastures; and 5) Fritillaria are not commercially cultivated in Iran. Because of poverty, native people eradicate Fritillaria with their bulbs and transfer them to florists' shops. Prevention of this tragedy and conservation of Fritillaria require international attention. Because of these factors, Fritillaria will be removed rapidly from their place of origin.
Virtual Field Trips for Improving Undergraduate Education in Greenhouse Management
Authors: Evans Michael R. , Cavins Todd J. , Kuehny Jeff S. , Harkess Richard L. , Lane Greer R.
Published: February 2019

Economics and logistics have greatly reduced or eliminated the ability of horticulture instructors to use field trips or on-site visits as educational tools. This is especially problematic in the field of greenhouse management and controlled environment agriculture, since the facilities and technologies used are essential to the discipline. To address this problem, we developed 15 DVD-based virtual field trips (VFT's) that instructors may use to demonstrate to students the most up-to-date facilities, technologies, and management strategies used in greenhouse management (ornamental and food crops) and controlled environment agriculture (GCEA). Each VFT included a preface with background information about the company, a tour organized by subject chapters, self-examination, and a teacher's guide with additional information and case studies. Each land-grant institution with an instructional program in greenhouse management of controlled-environment agriculture will be provided a free copy of each VFT, which will benefit all instructors of GCEA in the United States.
Food and Nutrition Security and Horticulture
Authors: Nath Prem
Published: February 2019

The world produces adequate food for everyone, but unequal distribution has created a gap between the countries that produce more food than they consume and those countries with deficit production. About 815 million people suffer from hunger and malnutrition, mostly in the developing world. By 2020, the developing world is expected to face the overwhelming challenge of a 97.5% increase in population; moreover, developing countries will face serious challenges with the trend of a major shift in population from rural to urban areas, where 52% of the people will live in megacities—all asking for more food, land, and infrastructure. According to the World Health Organization, an estimated 334 million children in developing countries are malnourished. In 2020, one out of every four children in these countries will still be malnourished. It is recognized that modern agriculture must diversify production and achieve sustainable higher output to supplement food security. In order to reduce pressure on cereals as well as to improve human nutrition through the consumption of other nutritious crops, diversification in cropping patterns can provide better options. The increased production and consumption of fruits and vegetables, with their wide adaptation and providers of important nutrients (especially vitamins and minerals), offer promise for the future. Fruits and vegetables as food and diet supplements are gaining momentum in most countries. In addition, recent experimental evidence has shown the growing importance of fruits and vegetables in the prevention of noncommunicable diseases. Further, horticulture would play an important role in urban and peri-urban agriculture and development.
Effect of Provenance on Alkalinity Tolerance of Baldcypress
Authors: Denny Geoffrey , Arnold Michael A. , Bryan Donita
Published: February 2019

Seedlings from 15 open-pollinated families of Taxodium distichum (L.) Rich. native to the Gulf Coast, central and south Texas, and Mexico, were evaluated for growth and foliar chlorosis development on field sites in Texas with acidic to alkaline soils. Forty seedlings per family were rated for level of chlorosis, height, and trunk diameter after two growing seasons in the field. Families grown on acidic soils did not differ in chlorosis ratings. Families from Mexico and south Texas had the lowest levels of chlorosis in the field, followed by those from central Texas, and then those from the Gulf Coast. Additionally, eight of the families were subjected to a greenhouse screening experiment with four levels of KHCO3 (0, 4, 8, 12 mM). These were evaluated for height, trunk diameter, shoot and root dry mass, and level of chlorosis and leaf necrosis. Family differences were less apparent during greenhouse screening experiments than in the field. Mexican families were significantly less chlorotic than other families at higher levels of alkalinity in the greenhouse. There was also a trend for height and shoot dry masses of western populations to be less adversely affect by higher alkalinity levels than more eastern populations.
Mid-season Pruning Affects Cold Tolerance of Abelia Cultivars in Central Georgia
Authors: Chappell Matthew , Robacker Carol
Published: February 2019

While the recommended time to prune abelia is before spring growth initiates, the actual pruning time is often variable and dependent upon labor and plant appearance. As abelia suffers from freeze damage north of zone 8A, pruning may have an impact on the level of freeze damage. Six Abelia genotypes were established in replicated field plots in Griffin, Ga., in 1999. On 3–4 July 2003, half the individuals of each genotype were severely pruned (75% of growth removed). Subsequently, 80 uniform-sized stem tips were randomly collected from plants of each genotype–treatment combination once per month from Oct. 2003 through Apr. 2004. Stem sections were exposed to predetermined temperatures ranging from –3 °C to –27 °C in a temperature bath. The number of stem sections killed in each of two replications out of four possible stem sections was recorded (0 = none dead; 4 = all dead). Data were analyzed with SAS using the Genmod procedure to acquire seasonal results as well as with PROC GLM and means separation to acquire monthly results. Using the Genmod procedure, all genotypes with the exception of `Canyon Creek' were significantly more cold tolerant in unpruned compared to pruned treatments. In this study, Dec. 2003 was the first month with temperatures below freezing at the test site. Proc GLM analysis indicated a significant difference between the pruned and unpruned treatments in Dec. 2003–Feb. 2004. Results of the Proc GLM analysis for the months of Oct. and Nov. 2003 as well as Mar. and Apr. 2004 were nonsignificant (P < 0.05) due to an absence of cold acclimation. These results indicate that mid-season pruning of Abelia genotypes can significantly reduce cold hardiness and lead to serious stem dieback in pruned plants.
Genetics of the Star Mutation in Petunia ×hybrida
Authors: Griesbach Robert , Beck Ron
Published: February 2019

Differences in structural gene expression are responsible for a wide range of responses from human cancer to patterned flowers. Gene silencing is one of the ways in which gene expression is controlled. We have developed a model system to study gene silencing using a gene silencing mutation in Petunia ×hybrida (Star mutation) and the ability of certain viruses to reverse the silencing mutation. This model system was used to characterize how the Star flower color pattern was controlled.
Yield of Citrus Trees with Foliar Urea as the Only N Source
Authors: Albrigo L. Gene , Syvertsen James P.
Published: February 2019

In order to evaluate possible reduced nitrate leaching while maintaining yield, `Hamlin' orange and `Flame' grapefruit trees on `Carrizo' or `Swingle Citrumelo' rootstocks were grown from planting using only foliar urea or soil-applied nitrate or ammonium N. An intermediate treatment of foliar and ground N was included also. From the 4th year, yields were recorded for 3 years. As previously reported, canopy growth was greater for the foliar urea treatment for the first 3 years. For 2 of the next 3 bearing years, the grapefruit trees in the foliar urea N treatment produced significantly less yield than the soil-applied treatment and the intermediate treatment was intermediate. The orange trees in the foliar urea treatment produced significantly less fruit than the soil N treatment in only 1 of 3 years, but the yields were numerically less every year. Results for fruit quality and nitrate leaching will be reported also. Foliar urea application alone was more costly and less productive than a soil N program.
Drought Stress and Recovery in Green Ash
Authors: Litus Greg , Klett James
Published: February 2019

During Summer 2005, green ash (Fraxinus pennsylvanica `Patmore') trees planted at the Colorado State University Agricultural Research Development and Education Center in 1996 were exposed to simulated drought by restricting irrigation for 33 to 41 days. During this period, predawn leaf water potentials in drought-stressed trees progressively dropped to a low of –2.04 MPa, while the control plot was maintained with full irrigation such that predawn leaf water potentials did not fall below –0.5 MPa. On 24 Aug. 2005, 31 days into this drought cycle, mid-day leaf water potentials and stomatal conductance were measured at –3.0 MPa and 22.63 mmol·m-2·s-1, respectively. Measurements in control trees collected at about the same time were –2.0 MPa and 169 mmol·m-2·s-1. The dramatic reduction in stomatal conductance in the drought-stressed trees began at about 10:30 a.m. and continued into the evening. Once irrigation was resumed, drought stressed trees rebounded from depressed predawn leaf water potentials and mid-day leaf water potentials and stomatal conductance and reached levels similar to control trees in 2 to 5 days. Stem flow gauges indicate that, during this period, fully hydrated control trees used about 250 liters/day.
Mechanism of Up-regulation of Starch Synthesis in Mature Leaves of Transgenic Apple Trees with Decreased Sorbitol Synthesis
Authors: Zhou Rui , Cheng Lailiang , Dandekar Abhaya
Published: February 2019

The reaction catalyzed by ADP-glucose pyrophosphorylase (AGPase) to form ADP-glucose is a regulatory and rate-limiting step in starch synthesis in plants. In response to decreased sorbitol synthesis, starch synthesis was up-regulated in the transgenic apple plants. In this study, we examined both redox and metabolite regulation of AGPase to understand the mechanism responsible for the up-regulation of starch synthesis. No difference in the monomerization/dimerization of apple leaf AGPase small subunits was observed between the transgenic plants and the untransformed control. NADP-dependent malate dehydrogenase, indicative of chloroplastic redox status, did not show significant change in the transgenic plants either. Determination of key metabolites with nonaqueous fractionation indicated that concentrations of hexose phosphates (mainly glucose-6-phosphate and fructose-6-phosphate) were higher in both the cytosol and chloroplasts of the transgenic plants than in the control, whereas 3-phosphoglycerate (PGA) concentration in the chloroplast was not higher in the transgenic plants. We conclude that accumulation of hexose-phosphates results in a decrease in inorganic phosphate (Pi) concentration and an increase in PGA/Pi ratio in the chloroplast, leading to up-regulation of starch synthesis via activating AGPase.
Observations on the Relationship Between Crop Load and Return Bloom in `Honeycrisp' Apple
Authors: Schwallier Philip G. , Sabbatini Paolo , Bukovac Martin J.
Published: February 2019

The `Honeycrisp' apple has unique characteristics favored by consumers that has provided exceptional return to growers. This cultivar also has some traits that challenge plant management. There appears to be a strong inhibitory effect of crop load on flower initiation and thus annual cropping. We studied the relationship between fruit load, established by post-bloom hand and chemical thinning, and effect of ethephon and gibberellin (GA4+7) on flower initiation and thereby annual cropping. Initially, return bloom (RB) was related to previous season's crop load in three thinning studies on 3- and 9-year-old `Honeycrisp'/M 9, Pajam 1 trees. The RB density was rated 1–10 on trees (n=172), which produced 0-60 kg of fruit/tree. Return bloom ratings (RBR) on the 3-year-old trees ranged from 0–9. Percentage of trees with RBR >5 for previous season's yield of <5 kg, 5–10, 10–15, and 15–20 was 70, 9, 2.5, and 0, respectively. There was dramatic inhibition of flowering at a crop load of >5 kg/tree. In the second study (9-year-old trees), crop load ranged from 15–60 kg/tree (n=24). RBR for trees in the 30–40 kg/tree class ranged from 0–8 with high variability. Thirty-one percent of trees with crop load between 20–30 kg had RBR of 5–8, and 26% between 0–5. Twenty-one percent of trees in the 30–40 kg/tree class flowered and all but one had a RBR of 5 or less. Yields ranged from 22–81 kg/tree in the third study (n=60); crop load was normally distributed among trees. Flower initiation was almost completely inhibited. Fifty percent of the trees did not flower; the remainder had a RBR of <1, i.e. <10%. In the ethephon/GA study, RBR ranged 8–10 on trees producing <12 kg/tree, then decreased rapidly to <2 for yields of 25–50; greatest variation at 20–40 kg.
Effect of Varying Crop Load on Leaf Photosynthesis and Carbon Isotope Discrimination of `Imperial Gala' Apple Tree
Authors: Sabbatini Paolo , Flore James
Published: February 2019

Crop load (CL) is a critical regulator of production and quality on apple. It affects leaf photosynthetic rate and usually an increase is detected in leaves close to developing sinks. The objective of this work was to test if 13C discrimination during photosynthesis could be an indicator of carbon sink limitation. The natural plant carbon isotope composition (13C/12C ratio: d13C) is an indicator of water use efficiency and it is an effective tool to study environmental stresses in plants. Seven-year-old trees of Imperial Gala/Bud 9 (n=30), field-grown at the Clarksville Horticultural Research Station in Michigan, were hand-thinned to five levels of CL manipulating the leaf to fruit ratio (LFR: 4, 8, 16, 32, 64) after June drop. Net photosynthetic rate (A) of leaves was monitored daily during the season and elevated rates were observed in low LFR. The A was inhibited in low CL trees (LFR 32 and 64) more in the afternoon (from 20% to 42% in relation to normal CL: LFR 16) than in the morning (from 5% to 20%), and stomatal conductance declined over the afternoon. Shoot and fruit growth were affected (fruit size –11/+11%, shoot length –13/+18% from normal CL; LFR 16). Variations of the stable carbon isotope composition of leaves show a significant reduction of 13C discrimination in low CL trees (–3.2%: d13C –25.82) and an increase of 13C discrimination (+2.7%: d13C –27.38) in relation to normal CL trees (LFR 15.63). The results were similar to those reported in 2004, which imply isotopic discrimination in relation to source limitation. This is the opposite of what you would expect under water stress conditions. Although trees were well-watered during the season, the effect of water stress on apple trees and its interaction with source limitation will be discussed.
Pre-plant Dipping of Strawberry Transplants for Control of Colletotrichum acutatum
Authors: Daugovish Oleg , Gubler Doug
Published: February 2019

Strawberry anthracnose caused by Colletotrichum acutatum may kill strawberry plants or reduce plant vigor and marketable yield, resulting in multimillion dollar losses to strawberry industry. The fungus is often carried with transplants from nurseries to production fields undetected. The studies in one summer and two winter seasons near Oxnard, Calif., evaluated 30-second pre-plant dipping in ten fungicide solutions or water washing of transplants inoculated with C. acutatum as a means of reducing infection and improving fruit yield. In summer-planted `Baeza,' the pathogen caused severe die-back and reduced marketable fruit yield 89% in inoculated, untreated controls compared to non-inoculated plants while plants dipped in Switch (cyprodynil + fludioxynil) at 0.38 g/L had 33% yield reduction. Other fungicides provided even less protection, resulting in 53% to 89% yield losses. During cooler winter seasons the pathogen remained latent and lesions appeared on `Camarosa' when the day-night air temperatures reached 16 °C or more, 7–14 days after rain. None of the treatments reduced fruit lesion development, however, among plants dipped in strobilurin fungicides only 3% had C. acutatum symptoms (including early die-back) as opposed to 26% in inoculated, untreated controls. Plants dipped in Switch, Quadris (azoxystrobin), or Pristine (pyraclostrobin + boscalid) yielded similar to non-inoculated, untreated controls in 2003 and 10% to 12% more in 2005. These studies showed that strobilurin fungicides did not prevent fruit infection (indicating need for foliar in-season control) but improved marketable yield compared to the inoculated, untreated plants. Temperatures over 16 °C and precipitation may significantly increase disease development.
(134) Effect of Seed Source and Organic Management on Agronomic Performance of Three Species of Echinacea
Authors: Romero Fredy R. , Delate Kathleen , Hannapel David
Published: February 2019

Consumption of Echinacea, one of the most popular botanical supplements, continues to expand in the United States. In addition, organic herbal products have captured a large share of the botanical supplement market. We evaluated commercial organic production of the three most-important medicinal species of Echinacea, E. angustifolia DC, E. purpurea (L) Moench., and E. pallida (Nutt.) from two seed sources. Plants were grown in the field for 3 consecutive years. We found that, during the first year, screen cages were associated with enhanced post-transplanting establishment. Growth of E. angustifolia was not affected by either production system or seed source after 3 years, and yields were equivalent for years 2 and 3 for this species. Growth of E. purpurea was affected by production system, but not by seed source, during the first 2 years. In year 3, neither seed source nor production system affected growth of E. purpurea. Yield of E. pallida was greater in the open field the first year; no difference between production systems was found during the second; and, by the third year, plants growing in screened cages produced more than plants growing in the open field. Production system affected yield of E. purpurea only during year 2, and yield was greater in the open field than in screened cages. Echinacea plants in the open field, however, were more affected by aster yellows disease, with an infection rate of 17% for E. purpurea in the open field compared to 3% under screen cages. Based on these results, in areas of aster yellows incidence, excellent Echinacea root yields can be obtained under screen cages using organic seeds.
(3) Comparability of Nutrient and Water Management Strategies for Seepage-irrigated Watermelon in South Florida
Authors: Cushman Kent , Shukla Sanjay , Hendricks Gregory , Obreza Thomas , Roka Fritz , McAvoy Eugene
Published: February 2019

Florida is one of the leading states in the United States in watermelon production, and on-farm management of nutrients and water is an important issue in the state. A management strategy using higher-than-recommended rates was compared to two strategies using recommended rates. A systems approach was used to define treatments: (HR) high rate of 265 pounds per acre (lb/ac) N, 170 lb/ac P2O5, 459 lb/ac K2O, and soil moisture content of 16% to 20% via seepage irrigation, (RR) recommended rate of 150 lb/ac N, 100 lb/ac P2O5, 150 lb/ac K2O, and soil moisture content of 8% to 12% via seepage irrigation, and (RR-S) equal to RR but irrigation provided by subsurface drip tubing. Large quarter-acre plots were used for each experimental unit. `Tri-X 313' was interplanted with `Mardi Gras' during Spring 2004 and with `SP-1' during Spring 2005 in a RCB design with two replications at the SWFREC in Immokalee. Leaf tissue analyses, petiole sap, and biomass accumulation were recorded each season. Watermelons were harvested at least twice each year and fruit were counted and weighed individually from three subplots within each plot. At least five fruit from each subplot were cut open for internal evaluation. Leaf nitrogen and potassium content for HR was consistently greater than that of RR or RR-S. Yields of HR were 41% to 50% greater than the two RR treatments. Yield was 1089, 704, and 775 hundred-pound units per acre (cwt/ac) in 2004 and 801, 541, and 533 cwt/ac in 2005 for HR, RR, and RR-S, respectively. Soluble solids content and hollowheart incidence were not affected by treatment. Our results indicate HR was more productive than RR or RR-S and may justify the higher inputs associated with this management strategy.
(9) Cucurbitaceous Crops in Asia
Authors: Nath Prem , Velu Sundari
Published: February 2019

Among the vegetables, the cucurbitaceous crops form one of the largest groups with their wide adaptation from arid climates to the humid tropics. In Asia, about 23 edible major and minor cucurbits are grown and consumed. Though the data on cucurbits alone are not easily available, the production of watermelon was reported to be 69.7 million tons in Asia, 9.0 million tons in the Near East, 2.7 million tons in North and Central America, and 2.4 million tons in Latin America and the Caribbean (2003). Cucurbits demonstrate wide adaptability, which allows the crops to grow in varied agroclimatic conditions. Among food crops, cucurbits are the largest producers of biological water and are easily digestible. The cucurbits contain 80% to 95% water and also contain nutritive elements, such as carbohydrates, protein, vitamins A and C, calcium, lycopene, phosphorus, potassium, and other properties, in addition to medicinal values. They are common crops in rural, urban, and peri-urban areas, and are accessible to both rich and poor. Even with the gradual increase in production and consumption, the production of cucurbits is plagued by the occurrence of diseases and insect pests, inadequate availability of quality seeds, lack of maintenance of genetic varieties and of naturally occurring biodiversities, and the lack of knowledge on the international standard of quality production and postharvest handling. The thrust areas of development, as identified, are: harnessing new sciences; diversification in cropping patterns; utilization of available genetic diversities; reversal of postharvest losses; and value addition in food products. Cucurbits hold promise as supplementary food for the common masses.
(181) 1-Methylcyclopropene Pretreatment of Roma-Type Tomato Ameliorates Effects of Physical Impact
Authors: Lee Eunkyung , Sargent Steven A. , Huber Donald J.
Published: February 2019

Roma tomatoes (`Sunoma') were hand-harvested at the mature-green color stage and treated with 100 μL·L-1 ethylene for 60 h at 20 °C and 90% RH. Tomatoes at breaker ripeness stage (<10% red coloration) were sorted by weight (about 100 g) and half of the fruits were treated with 1-methylcyclopropene (1-MCP; 1 μL·L-1 for 24 h at 22 °C). After 1-MCP treatment, individual fruits were subjected to double impacts over the marked locular surface with force equivalent to a 40-cm height drop using a pendulum impactor. In non-1-MCP treated fruit, impacts increased the maximum respiration rate by 27% (to 39.1 mL·kg-1 per h) and ethylene production by 24% (to 5.5 μL·kg-1 per h). Treatment with 1-MCP decreased relative production of both CO2 (56%) and ethylene (54%) over non-1-MCP treated fruit, while the ripening period (as measured by softening and color development) was extended 2.5 times, to about 8 d. Fruits treated with 1-MCP had increased TTA (about 40%; 0.58% citric acid equivalent), decreased pH (5%), and no difference in soluble solids content (3.7 °Brix); double impacts did not affect these values. Double impacts accelerated the onset of polygalacturonase (PG) activity by about 100% (to 99.8 mol·kg-1 per min*10-5 D-galacturonic acid) at day 6 over non-impacted control fruit. 1-MCP treatment delayed the onset of increased PG activity by 10 d over non-1-MCP treated fruit. Although 1-MCP alleviated the impact-induced increase in PG activity, PG activity recovered to rates similar to those of non-1-MCP treated fruit during the final 4 d of ripening.
(183) Quality and Shelf Life of Greenhouse Tomatoes Exposed to 1-Methylcyclopropene
Authors: Stephenson Sarah , DeEll Jennifer , Murr Dennis , Yada Rickey
Published: February 2019

The objectives of this research were to determine if 1-methylcyclopropene (1-MCP) improves fruit quality and extends shelf life of Ontario greenhouse tomatoes. `Beefsteak' tomatoes between breaker and turning maturity stages were harvested from commercial growers in Leamington, Ontario, and randomly sorted into uniform lots for 1-MCP treatment. Application of 1-MCP concentrations from 0 to 1200 nL/L was done at 22 °C for 12 hours in sealed bags. After treatment, fruit were held at 22 °C. Color change, fruit firmness, and production rates of CO2 and ethylene were followed for a period of 2 weeks. Significant differences (P ≤ 0.05) were found in color, ethylene, and CO2 production rates between treatments. However, there were few significant differences among cultivars and growers. This suggests that different tomato cultivars respond similarly to 1-MCP, and that commercial growing conditions and practices may not affect its efficacy. Over the 2-week ripening period, fruit from treatments of less than 300 nL/L 1-MCP exhibited similar color changes while treatments of more than 600 nL/L resulted in blotchy ripening, causing fruit to be unmarketable. 1-MCP treatment led to an increase in the rates of ethylene and CO2 production, two processes correlated with the onset of fruit ripening. This increase was unexpected and other studies showed that 1-MCP delayed the onset of these processes in tomatoes, and inhibited them in other fruits. Tomatoes treated at a maturity between breaker and turning did not respond well to 1-MCP, perhaps due to the ripening process having already begun. This implies that maturity stages earlier than breaker to turning may respond better to 1-MCP, and it may be more beneficial to target greenhouse tomatoes at an earlier maturity.