bluuebunny/crossref_metadata_2025 huggingface dataset:
CO2 Assimilation, Carbohydrate Metabolism, Xanthophyll Cycle, and the Antioxidant System of `Honeycrisp' Apple Leaves with Zonal Chlorosis
Authors: Chen Li-Song , Cheng* Lailiang
Published: February 2019

To determine the cause of zonal chlorosis of `Honeycrisp' apple leaves, we compared CO2 assimilation, carbohydrate metabolism, xanthophyll cycle and the antioxidant system between chlorotic leaves and normal leaves. Chlorotic leaves accumulated higher levels of non-structural carbohydrates, particularly starch, sorbitol, sucrose, and fructose at both dusk and predawn, and no difference was found in total non-structural carbohydrates between predawn and dusk. CO2 assimilation and the key enzymes in the Calvin cycle, ribulose 1,5-bisphosphate carboxylase/oxygenase, NADP-glyceraldehyde-3-phosphate dehydrogenase, phosphoribulokinase, stromal fructose-1,6-bisphosphatase, and enzymes in starch and sorbitol synthesis, ADP-glucose pyrophosphorylase, cytosolic fructose-1,6-bisphosphatase, and aldose 6-phosphate reductase were significantly lower in chlorotic leaves than in normal leaves. However, sucrose phosphate synthase activity was higher in chlorotic leaves. Thermal dissipation of excitation energy was enhanced in chlorotic leaves under full sun, lowering the efficiency of excitation energy transfer to PSII reaction centers. This was accompanied by a corresponding increase in both xanthophyll cycle pool size (on a chlorophyll basis) and conversion of violaxanthin to antheraxanthin and zeaxanthin. The antioxidant system was up-regulated in chlorotic leaves in response to the increased generation of reactive oxygen species. These findings support the hypothesis that phloem loading and/or transport is partially or completely blocked in chlorotic leaves, and that excessive accumulation of non-structural carbohydrates may cause feedback suppression of CO2 assimilation via direct interference with chloroplast function and/or indirect repression of photosynthetic enzymes.
Evaluation of Strawberry Genotypes for Tolerance to Black Root Rot
Authors: Drake* Chrislyn A. , Hancock James F.
Published: February 2019

Black root rot is a serious disease of strawberry (Fragaria ×ananassa Duch.) that causes the death of feeder roots, the degradation and blackening of structural roots, and an overall decrease in plant vigor and productivity. The causal organisms of black root rot are Rhizoctonia fragariae, Pythium sp. and Pratylenchus penetrans (the root lesion nematode). Each organism alone can cause extensive damage to strawberry roots, but studies have shown that black root rot may be more severe when all organisms are present, indicating there is an interaction between the fungal organisms and the nematode. The current method of control for black root rot is methyl-bromide fumigation; however, methyl bromide is to be phased out by 2005, and it is not very effective in perennial matted-row systems. The objectives of the study are to measure levels of tolerance to black root rot in 21 strawberry genotypes. The genotypes were planted in four blocks each of methyl-bromide fumigated and non-fumigated soil, and were evaluated for crown, runner, and inflorescence number; yield; average berry weight; and root health. `Cavendish', `Kent', `Midway' and `Winona' showed the highest degree of tolerance, while `Jewel', `Mesabi', and LH50-4 (a F. virginiana genotype) were the poorest performers.
Trench Layering as a Method of Clonally Propagating Pawpaw (Asimina triloba)
Authors: Crabtree* Sheri B. , Pomper Kirk W. , Geneve Robert L.
Published: February 2019

The pawpaw (Asimina triloba) is the largest fruit native to the U.S. and has potential as a new fruit crop. Few methods are available to clonally propagate pawpaw, with grafting or budding onto a seedling rootstock being the only currently feasible method. Developing new options for clonal propagation of pawpaw could help advance this growing industry. Layering has been used to clonally propagate other difficult to root tree species. The objective of this study was to examine trench layering as a method to clonally propagate pawpaw. A randomized factorial experiment was implemented to examine the roles of plant juvenility and auxin concentration on rooting in a greenhouse trench layering system. Seedlings were defoliated, tipped, and transplanted into trench layering beds at 3, 6, and 12 weeks after emergence. Shoots were etiolated, then girdled and treated with three levels of IBA (0, 5000, and 10,000 ppm). The main effects of age and IBA concentration significantly affected the percentage of shoots producing roots. Juvenility enhanced rooting, with 15% of the shoots of the 3-week-old pawpaw seedlings producing roots, compared to only about 5% of the 12-week-old seedlings rooting. Auxin application to shoots also promoted rooting, with 16% of IBA-treated shoots producing roots, compared to the untreated control, with only 2% of shoots producing roots. There was no significant difference in rooting percentage between the two concentrations of IBA. The treatment combination most successful at promoting root initiation was 10,000 ppm IBA applied to shoots of 3-week-old seedlings, with 31% of shoots rooting.
The Influence of Location of Main Stem Segment Origin on Forcing and Rooting of Softwood Shoots of Betula nigra L.
Authors: George* Laurie J. , Preece John E.
Published: February 2019

The objective of this study was to investigate the effects of the position on the main stem that large stem segments were harvested from on forcing and subsequent rooting of Betula nigra L. (river birch) softwood shoots. The main trunks of eight adult-phase native trees (four trees per run of the experiment) were cut into 50-cm long segments from the ground up. The segments placed in horizontally in 52 × 25 × 6.5 cm (l × w × h) flats containing perlite and were positioned so the bottom one-third of the stem was within the medium. Shoots were forced under natural photoperiod and intermittent mist. This experiment was conducted twice. Data were collected weekly for fourteen weeks on the number of softwood shoots each segment produced, shoot length, number of rootable shoots (>6 cm long), the length of time that the stem segments produced rootable shoots, and the rootability of these shoots treated with 3000 ppm IBA in talc. The number of harvested shoots was greater in Run 1, with the basal segments producing the most harvestable shoots. However, the upper segments in Run 2 produced the most harvestable shoots. Softwood shoots that rooted were placed under intermittent mist. Out of the 540 harvested shoots for both runs, 82.4% rooted, with the majority of those from Run 1. Shoots harvested from this run began producing roots about 6 weeks after harvest, and continued until the end of the experiment. Run 2 shoots began root initiation about 3 weeks after harvest and ended about 2 weeks before the end of the experiment. Run 1 had an mean of 8.3 roots per shoot and Run 2 had an mean of 6.2 roots. The relationship between juvenility and shoot forcing and subsequent rooting will be discussed.
Growth and Development of Lingonberry Cultivars as Affected by In Vitro and Ex Vitro Culture Methods and Source Propagule
Authors: Debnath* Samir
Published: February 2019

The morphological development of lingonberry (Vaccinium vitis-idaea L.) plants propagated either by conventional softwood cuttings or by in vitro shoot proliferation from nodal explants or by shoot regeneration from excised leaves of micropropagated shoots, was studied in cultivars `Regal', `Splendor', and `Erntedank'. Significant differences were observed between the treatments. In vitro-derived plants produced more shoots branches and rhizomes in contrast to conventional cuttings which rarely produced rhizomes. Plants propagated from cuttings had a lower number but vigorous shoots and thicker rhizomes than in vitro-derived plants. Source propagule had significant effect on multiplication rate. Another experiment evaluated the effect of indole-3-butyric acid (IBA) application to softwood cuttings on subsequent rooting, shoot development, and rhizome production. Treating cuttings with IBA did not significantly improve rhizome formation and elongation. In vitro culture on nutrient medium apparently induces the juvenile branching characteristics that favored rhizome production. The advantage of rhizome production of in vitro-derived plants over stem cuttings varied among genotypes.
Leaf Area Response of Lantana camara L. subsp. camara to Plant Growth Regulators under Different Photosynthetic Flux Conditions
Authors: Matsoukis Aristidis S. , Tsiros Ioannis , Kamoutsis Athanasios
Published: February 2019

The effect of various plant growth regulators on leaf area development of Lantana camara L. subsp. camara was investigated under three photosynthetic photon flux (PPF) conditions (100%, 72%, and 34% light transmittance). The triazole compounds paclobutrazol (0, 50, 100, 200, and 500 mg·L-1) and triapenthenol (175, 350, 700, and 1400 mg·L-1), as well as the onium-type compounds mepiquat chloride (125, 250, 500, and 1000 mg·L-1) and chlormequat chloride (750, 1500, 3000, and 6000 mg·L-1), were applied as foliar spray solutions in each PPF level after pinching the plants. Leaf area, in general, decreased logarithmically as the concentrations of paclobutrazol and triapenthenol increased at all PPF levels. On the other hand, PPF reduction was found to increase leaf area of lantana plants treated with all concentrations of each regulator. Leaf area reduction of the paclobutrazol and triapenthenol treated plants at all PPF levels exceeded 60% compared with that of nontreated plants. However, the corresponding reduction was 22%, up to 51% for the plants treated with mepiquat chloride and chlormequat chloride. These results indicate that the triazole compounds have a greater effect on the reduction of lantana leaf area than the onium-type compounds. Chemical names used: (2RS, 3RS)-1-(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1, 2, 4-triazol-1-yl) pentan-3-ol (paclobutrazol); (E)-(RS)-1-cyclohexyl-4,4-dimethyl-2-(1H-1, 2, 4-triazol-1-yl) pent-1-en-1-ol (triapenthenol); 1,1-dimethyl-piperidinium chloride (mepiquat chloride); (2-chloroethyl) trimethylammonium chloride (chlormequat chloride).
Gypsum Effects on Growth and Macroelement Uptake of Field-grown Asimina triloba (Pawpaw) Irrigated with Low-saline, Sodic Water
Authors: Picchioni G.A. , Graham C.J. , Ulery A.L.
Published: February 2019

Asimina triloba (L.) Dunal is an underused tree species with demonstrated potential as a new fruit crop and landscape ornamental plant. Best management practices for A. triloba are not adequately defined, particularly for field establishment in high-Na conditions characteristic of numerous southern U.S. production areas. We evaluated the growth and net macroelement uptake of field-grown A. triloba seedlings on soil amended with a single addition of gypsum at 0, 7.5, or 15.0 t·ha-1 and later receiving a regular supply of Na-affected but nonsaline irrigation water [sodium adsorption ratio (SAR) of 15.5 and electrical conductivity (EC) at 0.4 dS·m-1]. Over two growing seasons, the soil saturation extract Ca concentration increased while the soil saturation extract SAR decreased with increasing gypsum rate. Amending the soil with gypsum increased total lateral branch extension per tree by 60% to 73% and trunk cross-sectional area (TCSA) per tree by 68% to 87% above a non-gypsum-amended control treatment. Total dry matter accumulation and the net uptake of N, P, and K per tree were over 100% greater following gypsum application as compared to controls. The growth and mineral uptake-enhancing effects of gypsum were likely related to functions of Ca at the root level and on soil physical properties that should be considered in establishing young A. triloba trees with irrigation water containing high sodicity but relatively low total salinity.
Optical Sensing of Turfgrass Chlorophyll Content and Tissue Nitrogen
Authors: Bell G.E. , Howell B.M. , Johnson G.V. , Raun W.R. , Solie J.B. , Stone M.L.
Published: February 2019

Differences in soil microenvironment affect the availability of N in small areas of large turfgrass stands. Optical sensing may provide a method for assessing plant N needs among these small areas and could help improve turfgrass uniformity. The purpose of this study was to determine if optical sensing was useful for measuring turfgrass responses stimulated by N fertilization. Areas of `U3' bermudagrass [Cynodon dactylon (L.) Pers.], `Midfield' bermudagrass [C. dactylon (L.) Pers. × C. transvaalensis Burtt-Davy], and `SR1020' creeping bentgrass (Agrostis palustris Huds.) were divided into randomized complete blocks and fertilized with different N rates. A spectrometer was used to measure energy reflected from the turfgrass within the experimental units at 350 to1100 nm wavelengths. This spectral information was used to calculate normalized difference vegetation index (NDVI) and green normalized difference vegetation index (GNDVI). These spectral indices were regressed with tissue N and chlorophyll content determined from turfgrass clippings collected immediately following optical sensing. The coefficients of determination for NDVI and GNDVI regressed with tissue N averaged r2 = 0.76 and r2 = 0.81, respectively. The coefficients of determination for NDVI and GNDVI regressed with chlorophyll averaged r2 = 0.70 and r2 = 0.75, respectively. Optical sensing was equally effective for estimating turfgrass responses to N fertilization as more commonly used evaluations such as shoot growth rate (SGR regressed with tissue N; r2 = 0.81) and visual color evaluation (color regressed with chlorophyll; r2 = 0.64).
Salinity Tolerance of Seashore Paspalum Ecotypes: Shoot Growth Responses and Criteria
Authors: Lee Geungjoo , Duncan Ronny R. , Carrow Robert N.
Published: February 2019

Evaluation of turfgrass salt tolerance is a basic strategy for selecting grasses that can be grown in areas with salt-affected water or soils. Our objectives were to determine the relative salinity tolerances of 32 grasses and to evaluate potential shoot-based criteria for assessing salinity tolerance. Shoot growth responses to salinity of 28 seashore paspalums (Paspalum vaginatum Swartz) and four bermudagrass [Cynodon dactylon (L.) × C. transvalensis Burtt-Davy] cultivars were investigated under solution/sand culture in a greenhouse. Turfgrasses were grown in a sea-salt amended nutrient solution. Salinity ranges were 1.1 to 41.1 dS·m-1 based on electrical conductivity of the solution (ECw). Selection criteria to assess salt tolerance were absolute growth at 1.1 (ECw0), 24.8 (ECw24), 33.1 (ECw32), and 41.1 dS·m-1 (ECw40); threshold ECw; ECw for 25% and 50% growth reduction based on ECw0 growth; and leaf firing (LF) at ECw0 and ECw40 (LF0 and LF40, respectively). Significant variations among 32 entries were observed for all shoot responses except threshold ECw. Ranges of values for shoot parameters were: inherent growth at ECw0 = 0.10 to 0.98 g dry weight (10-fold difference); growth at 24.8 dS·m-1 = 0.11 to 0.64 g; growth at 33.1 dS·m-1 = 0.09 to 0.54 g; growth at 41.4 dS·m-1 = 0.06 to 0.35 g; threshold ECW = 3.9 to 12.3 dS·m-1; ECw25 % = 14 to 38 dS·m-1; ECw50% = 22 to 43 dS·m-1; and LF40 = 7% to 41%. Results in this study indicated substantial genetic-based variation in salt tolerance within seashore paspalums. When evaluation of salt tolerance based on shoot responses is attempted at wide salinity levels up to 40 dS·m-1, all seven criteria exhibiting a significant F test can be used. Five entries (SI 92, SI 93-1, SI 91, SI 93-2, SI 89) were ranked in the top statistical grouping for all seven-growth parameters, followed by SI 90 ranked in six out of seven, and three paspalums (SI 94-1, `Sea Isle 1', and `Taliaferro') were ranked in five out of seven categories.
The Genes of Watermelon
Authors: Guner Nihat , Wehner Todd C.
Published: February 2019

Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is a major vegetable crop in the world, accounting for 6.8% of the world area devoted to vegetable crops. Watermelon is a useful vegetable crop for genetic research because of its small genome size, and the many available gene mutants. The watermelon genes were originally organized and summarized in 1944, and have been expanded and updated periodically. However, the action of some watermelon genes has not been described clearly in some cases. Also, the interaction of multiple gene loci that control similar traits needs to be described more clearly. Finally, it is necessary to identify the inbred lines having each published gene mutant, for use as type lines in studies of gene action, allelism, and linkage. The objective of this work was to update the gene list, identify the cultivar or line having each gene mutant, and collect seeds of the lines for use by interested researchers. In addition, the gene descriptions were expanded and clarified, information on gene interactions was added, and errors in naming or citing previously described genes were corrected. New genes that have not previously been described (cr, Ctr, dw-3, ms-2, Ti, ts and zym-FL) were added to the list, for a total of 163 watermelon gene mutants.
Evaluation of Common Bean Accessions for Resistance to Pythium ultimum
Authors: Lucas Bruno , Griffiths Phillip D.
Published: February 2019

Common bean accessions were evaluated to identify white- or light-seeded beans with resistance to Pythium ultimum Trow. In total, 568 common bean (Phaseolus vulgaris L.) accessions were inoculated with a hyphal suspension of P. ultimum under greenhouse conditions. The bean accessions included represented the Andean-Middle American core collections (406 accessions) and 162 additional white- or cream-seeded accessions. The accessions were categorized into 12 groups according to seedcoat color. Accessions with light seedcoats exhibited higher levels of disease symptoms, with white-seeded bean accessions being the most susceptible class. No symptomless white-seeded accessions were identified. The most resistant white-seeded accessions were PI 430207, PI 527803, PI 290996, PI 299021, PI 194574, and PI 304110. Cream-seeded beans exhibited higher levels of resistance, with nine accessions rated as symptomless out of 188 cream and white accessions tested. Of 568 accessions, 48 tested were symptomless, whereas disease ratings of the other accessions ranged from resistant to highly susceptible.
Typing European Chestnut (Castanea sativa Mill.) Cultivars Using Oak Simple Sequence Repeat Markers
Authors: Boccacci P. , Akkak A. , Marinoni D. Torello , Bounous G. , Botta R.
Published: February 2019

Microsatellite or simple sequence repeat (SSR) markers show many characteristics of the ideal molecular marker, and recent studies have shown that loci developed in one species may allow analysis in taxonomically related species. In this study, 52 primer pairs developed in two oak species—Quercus robur L. and Quercus petraea (Matt.) Lieb.—were used to amplify DNA of 5 chestnut cultivars; 28 of them yielded amplicons and 12 polymorphic loci were selected and used to fingerprint 12 european chestnut (Castanea sativa Mill.) cultivars grown in the Piedmont region of northwestern Italy. The number of alleles per locus ranged from 3 to 8, mean expected heterozygosity was 0.592 (range: 0.288 to 0.868), and mean observed heterozygosity was 0.667 (range: 0.333 to 1.000). The results demonstrate the usefulness of some SSR markers isolated in Quercus for the fingerprinting and genetic mapping of Castanea cultivars.
Identification of A Heath-leaved Cypress Cultivar Based on Sequences of Nuclear Ribosomal DNA
Authors: Li Jianhua , Ledger Jeremy , Del Tredici Peter , Zhang Donglin
Published: February 2019

The identity of heath-leaved cypress is controversial. In this study nucleotide sequences of nuclear ribosomal DNA were used to identify heath-leaved cypress (Chamaecyparis `Ericoides') species. Sixteen individuals were sampled representing the five species of Chamaecyparis, `Ericoides', and four other genera of Cupressaceae (Cupressus, Fokienia, Juniperus, and Thuja). The results placed `Ericoides' unequivocally to Chamaecyparis thyoides, supporting a conclusion derived from wood anatomy. This study supports the usefulness and integrity of using molecular data to identify the genetic affinity of cultivars that are morphologically different from the parent species.
Response of Container-grown Grapevines to Soil Compaction
Authors: Ferree D.C. , Streeter J.G.
Published: February 2019

Container-grown `Chambourcin' grapevines were exposed to soil compaction created by changing soil bulk density to determine the effect of levels of compaction, rootstocks and moisture stress on mineral nutrition, leaf gas exchange and foliar carbohydrate levels. Shoot growth, leaf area, number of inflorescences and leaf dry weight decreased linearly as soil bulk density increased with the effects being significant above 1.4 g·cm-3. The early season leaf area was reduced 40% in the second season, but later leaves were unaffected by a soil bulk density of 1.5 g·cm-3. Net photosynthesis (Pn) and transpiration (E) increased linearly with increasing soil bulk density the first year, but the second year a nonlinear pattern was observed with highest rates at 1.3 and 1.4 g·cm-3. Soil bulk density of 1.5 g·cm-3 reduced number of leaves, leaf area and shoot length and advanced bloom 16 days on `Chambourcin' vines on six rootstocks with no interaction of rootstock and soil compaction. Withholding water for 8 days reduced Pn and E in all treatments, with no effect on shoot length, leaf, stem and total dry weights. Moisture stress in the noncompacted soil caused a reduction in leaf concentration of fructose, glucose and myo-inositol, but moisture stress had no effect in the compacted soil. Moisture stress caused a reduction in sucrose in both compacted and noncompacted soil. Compacting soil to a bulk density of 1.5 g·cm-3 was associated with an increase in leaf N, Ca, Mg, Al, Fe, Mn, Na, and Zn and a decrease in P, K, B, and Mo.
Cover Crop Management and Weed Suppression in No-tillage Sweet Corn Production
Authors: Carrera Lidia M. , Abdul-Baki Aref A. , Teasdale John R.
Published: February 2019

Cover crops combined with conservation tillage practices can minimize chemical inputs and improve soil quality, soil water-holding capacity, weed suppression and crop yields. No-tillage production of sweet corn (Zea mays var. `Silver Queen') was studied for 2 years at the USDA Beltsville Agricultural Research Center, Md., to determine cover crop management practices that maximize yield and suppress weeds. Cover crop treatments were hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and hairy vetch mixture, and bare soil (no cover crop). There were three cover crop killing methods: mowing, rolling or contact herbicide paraquat. All plots were treated with or without atrazine and metolachlor after planting. There was a 23% reduction in sweet corn plant population in the rye-hairy vetch mixture compared to bare soil. Averaged over both years, sweet corn yield in hairy vetch treatments was 43% greater than in bare soil, whereas yield in the rye-hairy vetch mixture was 30% greater than in bare soil. There were no significant main effects of kill method or significant interactions between kill method and cover crop on yield. Sweet corn yields were not different for hairy vetch or rye-hairy vetch treatments with or without atrazine and metolachlor. However, yield in bare soil without the herbicides atrazine and metolachor were reduced by 63% compared to bare soil with these herbicides. When no atrazine and metolachlor were applied, weed biomass was reduced in cover crops compared to the bare soil. Regression analysis showed greater yield loss per unit of weed biomass for bare soil than for the vetch or rye-hairy vetch mixture. This analysis suggests that cover crops increased sweet corn yield in the absence of atrazine and metolachlor not only by reducing weed biomass, but also by increasing the competitiveness of corn to weeds at any given biomass.
Light Intensity and Fertilizer Concentration: I. Estimating Optimal Fertilizer Concentrations from Water-use Efficiency of Wax Begonia
Authors: Nemali Krishna S. , van Iersel Marc W.
Published: February 2019

Environmental conditions and incorporation of nutrients into the growing medium can affect the fertilizer needs of bedding plants. To evaluate the effects of photosynthetic photon flux (PPF) and starter fertilizer on the fertilizer requirements of subirrigated plants, we grew wax begonias (Begonia semperflorens-cultorum Hort.) under three PPF levels (averaging 4.4, 6.2, and 9.9 mol·m-2·d-1) and four fertilizer concentrations [electrical conductivity (EC) of 0.15, 0.33, 0.86, and 1.4 dS·m-1] in a normal (with starter fertilizer, EC = 2.1 dS·m-1) and heavily leached (with little starter fertilizer, EC = 0.9 dS·m-1) growing medium. Except for shoot dry mass, we did not find any significant interactions between PPF and fertilizer concentration on any of the growth parameters. There was an interactive effect of fertilizer concentration and starter fertilizer on all growth parameters (shoot dry mass, leaf area, plant height, and number of flowers). When the growing medium contained a starter fertilizer, fertilizer concentration had little effect on growth. When the growing medium was leached before transplanting, growth was best with a fertilizer EC of 0.86 or 1.4 dS·m-1. Water-use efficiency (WUE) was calculated from 24-hour carbon exchange and evapotranspiration measurements, and used to estimate the required [N] in the fertilizer solution to achieve a target tissue N concentration of 45 mg·g-1. Increasing PPF increased WUE and the required [N] (from 157 to 203 mg·L-1 at PPF levels of 4.4 and 9.9 mol·m-2·d-1, respectively). The PPF effect on the required [N] appeared to be too small to be of practical significance, since dry mass data did not confirm that plants grown at high light needed higher fertilizer concentrations. Thus, fertilizer concentrations need not be adjusted based on PPF.
Effects of Prohexadione-Calcium on Fruit Size and Return Bloom in Pear
Authors: Sugar David , Elfving Don C. , Mielke Eugene A.
Published: February 2019

The effects of prohexadione-calcium (P-Ca) on fruit size and return bloom in three pear cultivars were evaluated in Medford and Hood River, Ore., and in Cashmere, Wash. A variety of treatment dosages and timings was applied to 4- and 5-year-old trees in 2 years of study. Fruit weight of `Bosc' and `Red Anjou' pears was not affected by P-Ca treatments at any location in either year. However, decreased weight of `Bartlett' pear fruit was associated with all P-Ca treatments in 1999 in Medford except for 83 ppm applied at 2.5 to 6.0 cm shoot growth (first treatment) plus 2, 4, 6, and 8 weeks after first treatment (WAFT) and 125 ppm applied at 2.5 to 6.0 cm growth plus 4 WAFT. `Bartlett' fruit weight was reduced in Medford in 2000 by all treatments except 125 ppm applied at 2.5 to 6.0 cm growth plus 4, 8, and 12 WAFT. In Cashmere in 2000, mean weight of `Bartlett' and `d'Anjou' fruit was reduced by treatments with 83 or 125 ppm applied at 2.5 to 6.0 cm growth plus 2, 4, and 6 WAFT and of `Bosc' pear by all treatments that included more than a single application of P-Ca. Crop load was not significantly different among treatments at any location. Return bloom in the year following P-Ca treatment was reduced in `Bosc' pears by some to most treatments at all locations in both years. In contrast, return bloom was reduced in `Bartlett' and `Anjou' pears only in Hood River in 1999.
Economic Return in Production of Lettuce and Cantaloupe Is Affected by Cropping System and Management Practice
Authors: Ogbuchiekwe Edmund J. , McGiffen Milton E. , Ngouajio Mathieu
Published: February 2019

Economic analysis compared the returns of cropping systems and management practices for production of fall lettuce (Lactuca sativa L.) and spring cantaloupe (Cucumis melo) following summer cover crops. The cover crop treatments included: cowpea [Vigna unguiculata (L.) Walp.] incorporated into the soil in the fall, cowpea used as mulch in the fall, sorghum sudangrass [Sorghum bicolor (L.) Moench] incorporated into the soil in the fall, and a bare ground control. Lettuce and cantaloupe were managed using conventional, integrated, and organic practices. The effect of each cropping system and management practice on crop yield, cost of production and net return was determined. In 1999 and 2000, yield and net return were greatest for cantaloupe and lettuce when the cowpea cover crop was incorporated into the soil before planting. The effect of crop management practice varied with type of cover crop. When lettuce was planted into cowpea-incorporated treatment in 1999, conventional management had the highest cash return followed by integrated crop management. In 2000, organically-grown lettuce after cowpea incorporated had the highest net return followed by integrated crop management grown under cowpea incorporated treatments. In 1999 and 2000, integrated cantaloupe following cowpea-incorporated treatment had the highest yield and cash-return. A 20% price premium for organic produce increased the net returns for the organic-grown lettuce and cantaloupe. Organic lettuce following cowpea-incorporated treatments produced a high net of $2,516/ha in 1999 and $5,971/ha in 2000. The net returns due to 20% organic premium price varied between 1999 and 2000 in cantaloupe production. They were highest for organic cantaloupe after bareground with a net return of $4,395 in 1999 and $3,148 in 2000 for organic cantaloupe after sudangrass.
Peptide Biocides for Engineering Bacterial Blight Tolerance and Susceptibility in Cut-flower Anthurium
Authors: Kuehnle A.R. , Fujii T. , Chen F.C. , Alvarez A. , Sugii N. , Fukui R. , Aragon S.L. , Jaynes J.M.
Published: February 2019

Two cultivars of Anthurium andraeanum Hort. hybrids, `Paradise Pink' and `Tropic Flame', were transformed by Agrobacterium to contain gene sequences for Shiva-1, a cecropin-based lytic peptide. The antibacterial gene was driven by a 35-35S cauliflower mosaic viral (35-35S CaMV) promoter and the construct included the secretory signal sequence for pathogenesis-related protein 1b (PR1b). Blight tolerance of regenerated plants was tested by inoculation with a virulent strain of Xanthomonas axonopodis (formerly campestris) pv. dieffenbachiae (Xad) that is bioluminescent to allow detection of symptomless infections in Shiva-1 transformants. Primary regenerants for two Shiva-1 transgenic lines of `Paradise Pink' displayed significantly enhanced tolerance to bacterial blight over blight susceptible `Rudolph' and even the blight tolerant `Kalapana'. Two Shiva-1 transgenic lines of `Tropic Flame' showed no improved resistance when compared to the control at the mean percent leaf infection level. One Shiva-1 transgenic line of `Tropic Flame' was unexpectedly more susceptible to blight than the nontransgenic control. Low expression of Shiva-1 observed in this line is hypothesized to be the cause of its increased susceptibility to Xad.
1-Methylcyclopropene (1-MCP) for Maintaining Texture Quality of Fresh-cut Tomato
Authors: Jeong Jiwon , Brecht Jeffrey K. , Huber Donald J. , Sargent Steven A.
Published: February 2019

A study was conducted to determine the effect of 1-methylcyclopropene (1-MCP) on textural changes in fresh-cut tomato (Lycopersicon esculentum, Mill.) slices during storage at 5 °C. The relationship between fruit developmental stage and tissue watersoaking development was also determined. Fresh-cut tomato slices prepared from light-red fruit that had been exposed to 1-MCP (1 μL·L-1 for 24 h at 5 °C) retained significantly higher pericarp firmness during storage at 5 °C for 10 d than slices from nontreated fruit or slices stored at 10 or 15 °C and they also had a significantly higher ethylene production maximum. 1-MCP (1 or 10 μL·L-1 for 24 h at 5 °C) had no affect on the firmness of fresh-cut, red tomato slices at 5 °C or on slices prepared from 5 °C-stored, intact red tomatoes. Nor did 1-MCP treatment have a significant effect on electrolyte leakage of tomato slices or intact fruit stored at 5 °C. Slices from fruit of the same developmental stage but with higher initial firmness values had less watersoaking development and responded better to 1-MCP treatment during 8 d storage at 5 °C. 1-MCP (1 μL·L-1) was more effective in reducing watersoaking in light red stage tomato slices when applied at 5 °C for 24 h compared with 1-MCP applied at 10 or 15 °C. Watersoaking development was also more rapid in fresh-cut tomato slices as initial fruit ripeness advanced from breaker to red stage. Our results suggest that watersoaking development in fresh-cut tomato slices is an ethylene-mediated symptom of senescence and not a symptom of chilling injury as had previously been proposed.
Optimum Potassium Concentrations in Recirculating Subirrigation for Selected Greenhouse Crops
Authors: Haley Trisha Blessington , Reed David Wm.
Published: February 2019

Two experiments were conducted to investigate the effect of K fertilizer rates on growth of New Guinea impatiens (Impatiens Hawkeri Bull.), vinca (Catharanthus roseus (L.) G. Don) and petunia (Petunia ×hybrida Hort. Vilm.-Andr.) in a recirculating subirrigation system. Based on a variety of growth parameters, a broad range of K concentrations allowed maximum growth, notably 1 to 6 mM for New Guinea impatiens `Ovation Salmon Pink Swirl', 2 mm for New Guinea impatiens `Cameo' and `Illusion', 2 to 8 mm for vinca `Pacifica Apricot', and 2 to 16 mm for petunia `Trailing Wave Misty Lilac'. Thus, the lowest concentration that allowed maximum growth was 1 to 2 mm K. A third experiment compared the optimum K concentration and K balance of vinca grown with recirculating subirrigation versus top-watering. Based on a variety of growth parameters of vinca `Pacifica Red', the lowest concentration that allowed maximum growth was 2 mm K with recirculating subirrigation and 4 mm K with top-watering. The K balance demonstrated that subirrigated plants were twice as efficient in K use compared to the top-watered plants. Leachate loss was the major contributor to inefficiency in top-watered plants. Electrical conductivity (EC) of the growing medium remained below the recommended level of 1.2 dS·m-1 in both irrigation methods at K concentrations of 16 mm and below in the bottom layer and 8 mm and below in the middle layer. In the top layer of the growing medium, EC was above the recommended level at all K concentrations tested in subirrigation at all concentrations, and in top-watering at 16 mm and above.
Ultraviolet-B Radiation Damage on Kentucky Bluegrass. I. Antioxidant and Colorant Effects
Authors: Ervin Erik H. , Zhang Xunzhong , Fike John H.
Published: February 2019

High ultraviolet-B (UV-B; 290-320nm wavelength) may significantly contribute to kentucky bluegrass (Poa pratensis L.) sod death at harvest and transplanting. As terrestrial UV-B levels continue to increase due to a depletion of the stratospheric ozone layer this problem may worsen. Epidermal attenuation from pigments and detoxification of reactive oxygen species by antioxidant metabolites and enzymes are involved in plant defense against oxidative stress caused by UV-B. Our objective was to determine whether the attenuation and detoxification systems of kentucky bluegrass could be artificially boosted by exogenous applications of ascorbic acid (AA), alpha-tocopherol (AT), or a colorant before exposure to high levels of UV-B. Ascorbic acid, AT, and the colorant Green Lawnger (GL), were applied to plugs of mature kentucky bluegrass alone or in combination, and then subjected to artificial, continuous UV-B exposure (70 μmol·m-2·s-1); three greenhouse experiments were conducted. By 3 to 5 days after UV-B initiation, visual quality and photochemical efficiency, as measured by chlorophyll fluorescence were significantly reduced. However, in Expt. 1, AA alleviated decline of visual quality, delayed loss of photochemical efficiency, and increased recovery relative to the control. In Expt. 3, decreased endogenous AT and antioxidant enzyme activities were measured due to UV-B stress. Application of AA, AA + AT, or GL partially alleviated photochemical efficiency decline from 4 to 12 days after initiation of UV-B. In addition, application of the chemical treatments increased leaf tissue AT concentrations by 32% to 42%, increased SOD activity by 30% to 33% and increased catalase activity by 37% to 59%, relative to the control as measured 10 days after UV-B initiation. Greater AT concentration and SOD and catalase activities were associated with greater visual quality under UV-B stress. The results of these studies indicate that kentucky bluegrass UV-B tolerance may be increased by supplementing its pigment and antioxidant defense systems with foliar applications of AA, AT or GL.
Performance of Component Species in Three Apple-Berry Polyculture Systems
Authors: Rivera Tina M. , Quigley Martin F. , Scheerens Joseph C.
Published: February 2019

The commercial and ornamental potential of three apple-berry polyculture systems was ascertained by monitoring the above-ground performance of component species in plots of `GoldRush' apple (Malus ×domestica Borkh.) trees on M.7 rootstock cropped with either blackberry (Rubus spp. L. `Navaho'), edible honeysuckle (Lonicera caerulea L. `Blue Belle' and `Blue Velvet'), or jostaberry (Ribes nidigrolaria Bauer `Josta') as understory plants. Polyculture plots and corresponding monoculture controls were established in 1999, with berry plants at recommended (R) or close [(C), half-recommended] spacings. Blackberries and jostaberries planted in monoculture at recommended spacings [i.e., control (R) plots] amassed dry weights >1 kg/plant by Fall 2001; the dry weight of edible honeysuckle from comparable plots was slightly >0.3 kg/plant. In 2001, blackberry yield (3.1 kg/plant) and fruit weight (3.4 g) were typical of `Navaho' plantings of similar age, whereas jostaberry was only moderately productive (yield = 286 g/plant; fruit weight = 1.4 g). Edible honeysuckle productivity (yield = 13 g/plant, fruit weight = 0.5 g) was minimal, due to disparate flowering phenology between cultivars. `GoldRush' apple growth and productivity (yield = 25 kg/tree; fruit weight = 158 g) was consistent with values expected for trees of similar age. Blackberry plant dry weights were reduced by 20% to 33% when planted at close spacing, whereas blackberry yields were reduced 35% to 38% when grown in polyculture with apple. Both polyculture and plant spacing significantly reduced jostaberry dry weights (i.e., 12% and 24%, respectively) relative to the control, but neither significantly affected jostaberry yield. Conversely, both close-spaced planting and the presence of an apple tree improved the yield of edible honeysuckle. Apple performance was not affected by the presence of an edible honeysuckle understory, but apple growth factors were reduced in blackberry and jostaberry polycultures by as much as 65%. Apple bloom, fruit set, and yield were also significantly reduced in apple-blackberry and apple-jostaberry plots, with fruit numbers/tree averaging <5 in all except the apple-blackberry (C) treatment. None of the polyculture treatments studied were suitable for profitable fruit production. However, each of the polyculture constituents exhibited unique, beneficial attributes with respect to their use as components within an edible landscape.
Plant Population and Nitrogen Fertilization for Subsurface Drip-irrigated Onion
Authors: Shock Clinton C. , Feibert Erik B. G. , Saunders Lamont D.
Published: February 2019

Onion (Allium cepa L.) production in the Treasure Valley of eastern Oregon and southwestern Idaho has been based on furrow irrigation with 318 kg·ha-1 N fertilizer and average yields of 70 Mg·ha-1, but these practices have been implicated in nitrate contamination of groundwater. Drip irrigation, introduced in the early 1990s, has several advantages, including reduced leaching losses. Since onion plant populations and N fertilizer rates can affect economic returns, studies were conducted in 1999, 2000, and 2001 to determine optimum plant populations and N fertilizer rates for subsurface drip-irrigated onion. Long-day onion (`Vision') was subjected to a combination of seven nitrogen fertilization rates (0 to 336 kg·ha-1 in 56-kg increments applied between late May and early July) and four plant populations (185, 250, 300, and 370 thousand plants/ha). Onion was grown on silt loam in two double rows spaced 0.56 m apart on 1.1 m beds with a drip tape buried 13 cm deep in the bed center. Soil water potential was maintained nearly constant at -20 kPa by automated irrigations based on soil water potential measurements at a 0.2-m depth. Onion bulbs were evaluated for yield and grade after 70 days of storage. Onion yield and grade were highly responsive to plant population. Onion marketable yield increased, and bulb diameter decreased with increasing plant population. Within the range of plant populations tested, gross returns were not always responsive to plant population. Returns were increased by the increase in marketable yield obtained with higher plant population, but higher plant population also reduced the production of the largest sized bulbs which had the highest value per weight. Onion yielded 95 Mg·ha-1 with no applied N fertilizer, averaged over plant populations and years. Onion yield and grade were not responsive to N fertilizer rate or interaction of N fertilizer rate with plant population. Preplant soil available N, N mineralization, and N in irrigation water all contributed N to the crop. Onion N uptake did not increase with increasing N fertilizer rate.
(170) Scion Bud Removal Delays Leaf Development, But Decreases Graft Success in Pecan Four-flap Graft
Authors: Conner Patrick
Published: February 2019

Pecan is a highly heterozygous outcrossing species that is normally propagated by grafting or budding onto seedling rootstocks. The four-flap or banana graft is commonly used by growers or researchers because of its high percentage of success, especially when employed by novice grafters. We removed scion buds before grafting in an attempt to delay budbreak, thus providing more time for vascular connections to form before leaf development and its associated demand for water takes place. Removal of buds from the scion wood was successful in delaying bud and leaf development, but did not increase graft success, and in one treatment actually lowered graft success.
(171) Auxin Affects Adventitious Rooting of Snowbells (Styrax L.)
Authors: Griffin Jason J. , Lasseigne F. Todd
Published: February 2019

The snowbells (Styrax L.) are a group of flowering shrubs and trees distributed throughout the warm-temperate regions of the northern hemisphere. In all, there are about 120 species, of which only Styrax japonicus Sieb. & Zucc. (Japanese snowbell) and its cultivars are currently of commercial significance. Other species may also posses desirable horticultural traits that could be valuable on their own merit, or used in plant improvement programs. Currently there is little information regarding asexual propagation of the lesser known species. The results herein show that propagation of a diverse collection of Styrax(15 taxa) is possible by stem cuttings. However, species and cultivars within a species do not respond to auxin treatment similarly. The percentage of rooting of many taxa was improved when cuttings were treated with 3000 or 8000 ppm (0.3% or 0.8%) of the potassium salt of indolebutyric acid (K-IBA). However, rooting was unaffected by K-IBA treatment in some taxa, while rooting was negatively affected by K-IBA in others. Additionally, the number of roots produced per rooted cutting were affected by K-IBA treatment. In some instances, K-IBA increased the number of roots per rooted cutting. However, in most of the taxa, root number was unaffected.
(241) Genotyping of Ornamental Flowering Cherry Germplasm (Prunus species) using SSR Technology
Authors: Ma Hongmei , Pooler Margaret
Published: February 2019

Ornamental flowering cherry trees (Prunus species) are popular landscape plants that are used in residential and commercial landscapes throughout most temperate regions of the world. Most of the flowering cherry trees planted in the United States represent relatively few species. The U.S. National Arboretum has an ongoing breeding program aimed at broadening this base by developing new cultivars of ornamental cherry with disease and pest resistance, tolerance to environmental stresses, and superior ornamental characteristics. Knowledge of the genetic relationships among species would be useful in breeding and germplasm conservation efforts. However, the taxonomy of flowering cherry species and cultivars is complicated by differences in ploidy levels and intercrossing among species. We have used simple sequence repeat (SSR) markers developed for other Prunus species to screen a diverse collection of over 200 ornamental cherry genotypes representing 70 taxa in order to determine the genetic relationships among species, cultivars, and accessions. Data were generated from 9–12 primer pairs using an automated DNA genetic analyzer (ABI3770), and subjected to UPGMA cluster analysis. Extremely high levels of polymorphism were exhibited among the materials studied, thus indicating that ornamental flowering cherry germplasm has substantial inherent genetic diversity. This information, combined with traditional morphological characteristics, will be useful in determining genetic relationships among accessions in our collection and for predicting crossability of taxa.
(163) Influence of Single or Mixed Cover Crops on Biomass Production and Fruit Yields of Eggplant Grown with or without Synthetic Nitrogen
Authors: Whitehead Wayne F. , Singh Bharat P.
Published: February 2019

The purpose of this study was to evaluate how leguminous and non-leguminous cover crops alone or in mixture with synthetic nitrogen rates affect aboveground biomass, fruit number, and yield of eggplant. The following fall–spring fertility treatments were applied using randomized complete-block design with three replications: 1) fall-0 N, fallow; spring-0 N; 2) fall-0 N, abruzzi rye; spring-0 N; 3) fall-0 N, hairy vetch; spring-0 N; 4) fall-0 N, abruzzi rye+hairy vetch; spring-0 N; 5) fall-0 N, fallow; spring-70 kg×ha–1 N; 6) fall-0 N, abruzzi rye; spring-70 kg×ha–1 N; 7) fall-0 N, hairy vetch; spring-70 kg×ha–1 N; 8) fall-0 N, abruzzi rye+hairy vetch; spring-70 kg×ha–1 Na; 9) fall-0 N, fallow; spring-140 kg×ha–1 N, 10) fall-0 N, abruzzi rye; spring-140 kg×ha–1 N; 11) fall-0 N, hairy vetch; spring-140 kg×ha–1 N; and 12) fall-0 N, abruzzi rye+hairy vetch; spring-140 kg×ha–1 N. In Spring 2004, `Megal' eggplant seedlings were transplanted. Total yield and fruit number were compiled over 7 weeks, while total vegetative dry matter was measured at final harvest. Maximum aboveground biomass (227.6 g/plant), total yield (28.7 Mg×ha–1) and fruit number (13/plant) were produced by fall-0 N, hairy vetch; spring-70 kg×ha–1 N. Minimum aboveground biomass (53.0 g/plant) was produced by fall-0 N, abruzzi rye; spring-0 N, while minimum total yield (7.8 Mg×ha–1) and fruit number (5/plant) were produced by fall-0 N, fallow; spring-0 N. Results imply that hairy vetch supplemented with N at 70 kg×ha–1 is most effective in supporting fruit number and yield of eggplant.