bluuebunny/crossref_metadata_2025 huggingface dataset:
Gradients in Susceptibility and Resistance Mechanisms of Buddleia L. Taxa to the Two-spotted Spider Mite (Tetranychus urticae Koch)
Authors: Gillman Jeffrey H. , Dirr Michael A. , Braman S. Kristine
Published: January 2019

Buddleia taxa were assessed for two-spotted spider mite (Tetranychus urticae Koch) resistance using a leaf disk bioassay, a novel shell vial bioassay and a field trial. Leaf pubescence and chemistry were examined for their role in two-spotted spider mite resistance. Results from bioassays and field sampling identified highly resistant taxa including B. fallowiana Balif. `Alba' and B. davidii × B. fallowiana Franch. `Cornwall Blue' as well as susceptible taxa including B. davidii Franch. `African Queen' and B. lindleyana Fort. ex Lindl. `Gloster'. The shell vial bioassay was an accurate predictor of field resistance to spider mite. Leaf pubescence was quantified by calculating the collective length of trichome branches per square millimeter of leaf surface area [effective branch length (EBL)]. EBL values ranged from 39 to 162 mm·mm-2 of leaf surface area among Buddleia taxa. Resistance was positively correlated with increased pubescence. Removal of pubescence by peeling resulted in increased oviposition of two-spotted spider mites. Exposing female two-spotted spider mites to a methylene chloride extract of B. davidii × B. fallowiana `Cornwall Blue' using a modified shell vial bioassay resulted in reduced oviposition and a methylene chloride extract of B. davidii `African Queen' resulted in no difference in oviposition when compared with a control. While pubescence is the best indicator of resistance to the two-spotted spider mite in Buddleia taxa, it is possible that defensive compounds are involved.
Thermoperiodicity in Shoot Elongation of Purple Nutsedge
Authors: Sun Wen-Hao , Nishimoto Roy K.
Published: January 2019

The effect of single and daily alternating temperature cycles on elongation of emerged buds of purple nutsedge (Cyperus rotundus L.) was characterized to determine whether shoot elongation responded to alternating temperature as a thermoperiodic function. Glasshouse-grown tubers with emerged buds of 2 to 5 mm in length were used in experiments. Shoot extension increased at 35 °C after 7 days, but no significant shoot extension occurred at all other constant temperatures of 20, 25, 30, 40, and 45 °C. However, 2- to 8-fold increases in shoot extension occurred at alternating temperatures of 25/15, 30/20, 35/25, 40/30, 41/35, 42/38, and 45/35 °C (12/12 hours) as compared to the respective mean constant temperatures. Daily temperature differences of 2 and 4 °C did not stimulate shoot elongation, while temperature differences of 8 and 12 °C caused an 8-fold shoot stimulation when compared to the 24 °C constant temperature. Shoot elongation increased with increasing numbers of alternating temperature cycles. The optimal duration of the lower and upper temperature phases differed depending on temperature regimes; at 40/30 °C, maximal elongation occurred with daily exposures of 40 °C for 1 to 3 hours and 30 °C for 23 to 21 hours respectively, while at 30/20 °C, maximal elongation occurred with daily exposures of 30 °C for 15 hours and 20 °C for 9 hours. These results suggest that elongation of purple nutsedge tuber buds responds to alternating temperature as a thermoperiodic function.
Changes in the S-alk(en)yl Cysteine Sulfoxides and their Biosynthetic Intermediates during Onion Storage
Authors: Kopsell David E. , Randle William M. , Eiteman Mark A.
Published: January 2019

Onion (Allium cepa L.) pungency changes during storage. To better understand these flavor changes, seven onion cultivars representing different storage duration, photoperiodic requirement, and flavor intensity were greenhouse grown and the bulbs stored for 3 or 6 months at 5±3 °C, 0.8 to 1.1 kPa vapor pressure deficit. Bulbs were evaluated using high-pressure liquid chromatography quantification for changes in S-alk(en)yl cysteine sulfoxide (ACSO) flavor precursors and γ-glutamyl peptide (γ-GP) biosynthetic intermediates before storage and monthly thereafter. Before and during storage, cultivars differed in total ACSO, (+) S-methyl-L-cysteine sulfoxide (MCSO), trans-(+)-S-(1-propenyl)-L-cysteine sulfoxide (PRENCSO), (+) propyl-L-cysteine sulfoxide (PCSO), S-2 carboxypropyl glutathione (2-CARB), and γ-L-glutamyl-S-(1-propenyl)-L-cysteine sulfoxide (γGPECSO) concentration. During storage MCSO generally decreased while PRENCSO increased in concentration for most cultivars. The linear increase in PRENCSO concentration during storage was accompanied by a linear decrease in γGPECSO concentration. While not measured in this study, these trends indicate γ-glutamyl transpeptidase activity throughout bulb storage. γ-Glutamyl transpeptidase was previously reported to be active only in the later stages of bulb storage or during bulb sprouting. Changes in ACSO and γ-GP compounds during storage did not follow previously reported changes during storage for enzymatically formed pyruvic acid (EPY) for these cultivars. To better understand what causes flavor changes in onions during storage, future investigations should include analysis of the enzymes involved in flavor development and ACSO hydrolysis products.
Suppressing Green Mold Decay in Grapefruit with Postharvest Jasmonate Application
Authors: Droby Samir , Porat Ron , Cohen Lea , Weiss Batia , Shapiro Boris , Philosoph-Hadas Sonia , Meir Shimon
Published: January 2019

Jasmonic acid (JA) and methyl jasmonate (MJ), collectively referred to as jasmonates, are naturally occurring plant growth regulators involved in various aspects of plant development and responses to biotic and abiotic stresses. In this study, we found that postharvest application of jasmonates reduced decay caused by the green mold Penicillium digitatum (Pers.: Fr.) Sacc. after either natural or artificial inoculation of grapefruit (Citrus paradisi `Marsh Seedless'). These treatments also effectively reduced chilling injury incidence after cold storage. The most effective concentration of jasmonates for reducing decay in cold-stored fruit or after artificial inoculation of wounded fruit at 24 °C was 10 μmol·L-1. Higher and lower jasmonate concentrations were less effective at both temperatures. MJ at 10 μmol·L-1 also most effectively reduced the percentage of fruit displaying chilling injury symptoms after 6 weeks of storage at 2 °C and 4 additional d at 20 °C. When tested in vitro, neither JA nor MJ had any direct antifungal effect on P. digitatum spore germination or germ tube elongation. Therefore, it is suggested that jasmonates probably reduced green mold decay in grapefruit indirectly by enhancing the natural resistance of the fruit to P. digitatum at high and low temperatures.
Temperature Response of Whole-plant CO2 Exchange Rates of Three Magnolia Cultivars
Authors: van Iersel Marc W. , Lindstrom Orville M.
Published: January 2019

Temperature-response curves for photosynthesis and respiration are useful in predicting the ability of plants to perform under different environmental conditions. Whole crop CO2 exchange rates of three magnolia (Magnolia grandiflora L.) cultivars (`MGTIG', `Little Gem', and `Claudia Wannamaker') were measured over a 25 °C temperature range. Plants were exposed to cool temperatures (13 °C day, 3 °C night) temperatures before the measurements. Net photosynthesis (Pnet) of all three cultivars increased from 3 to 15 °C and decreased again at higher temperatures. `MGTIG' had the highest and `Little Gem' the lowest Pnet, irrespective of temperature. The Q10 (relative increase in the rate of a process with a 10 °C increase in temperature) for Pnet of all three cultivars decreased over the entire temperature range. `MGTIG' had the lowest Q10 at low temperatures (1.4 at 8 °C), while `Little Gem' had the lowest Q10 for Pnet at temperatures >17 °C and a negative Q10 > 23 °C. This indicates a rapid decline in Pnet of `Little Gem' at high temperatures. The decrease in Pnet of all three cultivars at temperatures >15 °C was caused mainly by an exponential increase in dark respiration (Rdark) with increasing temperature. `Little Gem' had a lower Rdark (per unit fresh mass) than `MGTIG' or `Claudia Wannamaker', but all three cultivars had a similar Q10 (2.46). Gross photosynthesis (Pgross) was less sensitive to temperature than Pnet and Rdark. The optimal temperature for Pgross of `MGTIG' was lower (19 °C) than those of `Little Gem' (21 °C) and `Claudia Wannamaker' (22 °C). The Q10 for Pgross decreased with increasing temperature, and was lower for `MGTIG' than for `Little Gem' and `Claudia Wannamaker'. All three cultivars had the same optimal temperature (11 °C) for net assimilation rate (NAR), and NAR was not very sensitive to temperature changes from 3 to 17 °C. This indicates that the plants were well-adapted to their environmental conditions. The results suggest that respiration rate may limit magnolia growth when temperatures get high in winter time.
Inhibition of Catalase by Antisense RNA Increases Susceptibility to Oxidative Stress and Chilling Injury in Transgenic Tomato Plants
Authors: Kerdnaimongkol Kanogwan , Woodson William R.
Published: January 2019

Transgenic tomatoes (Lycopersicon esculentum Mill. `Ohio 8245') expressing an antisense catalase gene (ASTOMCAT1) were used to test the hypothesis that modification of the reactive oxygen species scavenging mechanism in plants can lead to changes in oxidative stress tolerance. A 2- to 8-fold reduction in total catalase activity was detected in the leaf extracts of transformants. A 2-fold increase in levels of H2O2 was observed in the transgenic plants with reduced catalase activity. Electrophoretic characterization of multiple catalase isoforms revealed the specific suppression of CAT1 in transgenic plants. Homozygous plants carrying the antisense catalase transgene were used to study the effect of alteration in the expression of catalase on stress tolerance. Transgenic plants treated with 3% H2O2 showed visible damage within 24 hours and subsequently died. In contrast, wild-type and azygous control plants recovered from the treatment. Transgenic plants did not survive 4 °C chilling stress compared to control wild-type and azygous lines. Physiological analysis of these plants indicated that suppression of catalase activity in transgenic tomato led to enhanced sensitivity to oxidative stress. Our data support a role for catalase in oxidative stress defense system in tomato.
Ethylene and Carbon Dioxide Production in Detached Fruit of Selected Pepper Cultivars
Authors: Villavicencio Lucia , Blankenship Sylvia M. , Sanders Douglas C. , Swallow William H.
Published: January 2019

Bell peppers (Capsicum annuum L.) are classified as nonclimacteric fruits while some hot peppers have been reported as climacteric. Responses of peppers to exogenously applied ethylene-releasing compounds suggest ethylene involvement in the ripening process. Ethylene production and respiration rates in 13 cultivars of pepper: `Camelot', `Cherry Bomb', `Chiltepin', `Cubanelle', `Banana Supreme', `Habanero', `Hungarian Wax', `Mesilla', `Mitla', `Savory', `Sure Fire', `Tabasco', and `King Arthur' were studied under greenhouse and field conditions. Fruit from each cultivar were harvested at different maturity stages determined by color, ranging from mature-green to full red-ripe. Carbon dioxide and ethylene production were measured by gas chromatography. Both variables were significantly different among maturity stages for all cultivars. Respiration rates were between 16.5 and 440.3 mg·kg-1·h-1 CO2. Ethylene production ranged from 0.002 to 1.1 μL·kg-1·h-1. Two patterns of CO2 production were identified: higher CO2 production for mature-green fruit with successive decreases for the rest of the maturity stages or lower respiration rates for mature-green fruit with an increase in CO2 production either when fruit were changing color or once fruit were almost totally red. A rise in CO2 production was present for most cultivars. Ethylene evolution increased significantly at maturity or before maturity in all cultivars except `Cubanelle' and `Hungarian Wax'. Respiration rates and ethylene production were significantly different among cultivars at the mature-green and red stages.
Comparison of Softening-related Changes during Storage of `Honeycrisp' Apple, Its Parents, and `Delicious'
Authors: Tong Cindy , Krueger Darryl , Vickers Zata , Bedford David , Luby James , El-Shiekh Ahmed , Shackel Kenneth , Ahmadi Hamid
Published: January 2019

Many studies of apple (Malus ×domestica Borkh.) softening have been done using cultivars that eventually become mealy. We wanted to determine whether observations in these studies would be seen in a cultivar that maintains its crispness. In this paper, we compared the texture, ultrastructure, and some physiological parameters of Honeycrisp, an apple cultivar introduced in 1991 by the Minnesota Agricultural Experiment Station, with its parents and Delicious. Sensory evaluations and instrumental texture measurements showed that `Honeycrisp' maintained a crisp texture from harvest through 6 months of cold storage, whereas its parents, `Macoun' and `Honeygold', softened over the same time period. Turgor potential, cell wall composition, and ultrastructural comparisons of the fruit were made. Cell turgor potentials of `Honeycrisp' and `Delicious' were similar and greater than those of `Macoun' and `Honeygold', and clearly correlated with firmness. There were no differences in cell wall neutral sugar composition, except for arabinose, which was not highly correlated with crispness. `Honeycrisp' fruit maintained cell wall integrity after 6 months of storage, while cell walls of `Macoun' and `Honeygold' deteriorated. These data show that it is important to compare more than one cultivar when studying crispness. Honeycrisp is a cultivar that maintains its crispness through long storage without controlled atmosphere conditions. After 6 months of storage, this crispness can be attributed to a maintenance of high turgor potential and cell wall integrity.
Inhibition of Pythium ultimum and Rhizoctonia solani by Shredded Leaves of Brassica Species
Authors: Charron Craig S. , Sams Carl E.
Published: January 2019

The U.S. Clean Air Act bans the use of methyl bromide after 2005. Consequently, the development of alternative methods for control of soilborne pathogens is imperative. One alternative is to exploit the pesticidal properties of Brassica L. species. Macerated leaves (10 g) from `Premium Crop' broccoli [B. oleracea L. (Botrytis Group)], `Charmant' cabbage [B. oleracea L. (Capitata Group)], `Michihili Jade Pagoda' Chinese cabbage [B. rapa L. (Pekinensis Group)], `Blue Scotch Curled' kale [B. oleracea L. (Acephala Group)], Indian mustard [B. juncea (L.) Czerniak, unknown cultivar] or `Florida Broadleaf' mustard [B. juncea (L.) Czerniak] were placed in 500-mL glass jars. Petri dishes with either Pythium ultimum Trow or Rhizoctonia solani Kühn plugs on potato-dextrose agar were placed over the jar mouths. Radial growth of both fungi was suppressed most by Indian mustard. Volatiles were collected by solid-phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry. Allyl isothiocyanate (AITC) comprised >90% of the volatiles measured from `Florida Broadleaf' mustard and Indian mustard whereas (Z)-3-hexenyl acetate was the predominant compound emitted by the other species. Isothiocyanates were not detected by SPME from `Premium Crop' broccoli and `Blue Scotch Curled' kale although glucosinolates were found in freeze-dried leaves of all species. When exposed to AITC standard, P. ultimum growth was partially suppressed by 1.1 μmol·L-1 (μmol AITC/headspace volume) and completely suppressed by 2.2 μmol·L-1 R. solani was partially suppressed by 1.1, 2.2, and 3.3 μmol·L-1 AITC. Use of Brassica species for control of fungal pathogens is promising; the presence of AITC in both lines of B. juncea suppressed P. ultimum and R. solani but some Brassicas were inhibitory even when isothiocyanates were not detected.
Postharvest Calcium Infiltration Alone and Combined with Surface Coating Treatments Influence Volatile Levels, Respiration, Ethylene Production, and Internal Atmospheres of `Golden Delicious' Apples
Authors: Saftner Robert A. , Conway William S. , Sams Carl E.
Published: January 2019

Effects of postharvest pressure infiltration of distilled water, CaCl2 solutions at 0.14 or 0.27 mol·L-1 without and with subsequent fruit coating treatments of preclimacteric `Golden Delicious' [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. `Golden Delicious'] apples on volatile levels, respiration, ethylene production, and internal atmospheres after storage at 0 °C for 1 to 6 months, and during subsequent shelf life at 20 °C were investigated. Over 30 volatiles were detected, most of the identified volatiles were esters; the rest were alcohols, aldehydes, ethers, a ketone, and a sesquiterpene. Pressure infiltration of water and increasing concentrations of CaCl2 resulted progressively in reduced total volatile levels, respiration, ethylene production, and internal O2 levels and increased CO2 levels in fruit following 2 to 4 months storage in air at 0 °C. Total volatile levels, respiration, ethylene production, and internal atmospheres of CaCl2-treated apples at 0.14 mol·L-1 gradually recovered to nontreated control levels following 2 weeks of shelf life at 20 °C and/or storage at 0 °C in air for more than 4 months. Following the calcium treatments with a shellac- or wax-based coating had similar but stronger and more persistent effects on volatile levels, respiration, ethylene production, and internal atmospheres than those found in fruit treated with CaCl2 alone. Calcium infiltration did not change the composition of volatile compounds found in fruit. Results suggest that pressure infiltration of `Golden Delicious' apples with CaCl2 solutions transiently inhibited volatile levels, respiration, and ethylene production, in part, by forming a more-or-less transient barrier to CO2 and O2 exchange between the fruit tissue and the surrounding atmosphere.
Dehydrator Onion Bulb Weight and Water-soluble Carbohydrates before and after Maturity
Authors: Wall Arthur D. , Wall Marisa M. , Corgan Joe N.
Published: January 2019

Onions (Allium cepa L.) with ≥18% bulb dry weight are dehydrated and used for spices and food ingredients. Bulb weight characteristics and water-soluble carbohydrates (WSC) of two commercial dehydrator cultivars, GS02 and GS04, and a breeding population, NM9335, were studied before and after maturity to observe phenotypic traits that may be useful for selection during breeding programs, and to study dehydrator onion carbohydrate physiology. At maturity, NM9335, GS02, and GS04 bulbs had 11.9 ± 0.33%, 18.6 ± 0.27%, and 19.4 ± 0.40% dry weight, respectively. Mature GS04 plants had 76.5 ± 0.01% of whole plant dry weight in bulbs, which is an extraordinarily high crop harvest index. NM9335 bulbs had higher fresh (hydrated) weight than bulbs of GS04 and GS02, but bulbs in all populations accumulated similar amounts of dry weight. Bulb percent dry weight before maturity did not indicate percent dry weight at maturity in the high-solids commercial onion cultivars. Bulb percent dry weight declined slightly after maturity in all populations. Glucose, fructose, and sucrose were relatively low, and fructans with degree of polymerization ≥6 were relatively high in GS04, but the converse was observed in NM9335. Relative amounts of GSO4 bulb fructan increased sequentially, in order of rank, from DP4 to DP6, but the converse was observed for NM9335.
Starch Degradation in Buttercup Squash (Cucurbita maxima)
Authors: Irving Donald E. , Shingleton Glen J. , Hurst Paul L.
Published: January 2019

Extractable activities of α-amylase, β-amylase, and starch phosphorylase were investigated in order to understand the mechanism of starch degradation in buttercup squash (Cucurbita maxima Duchesne ex Lam. `Delica') with the ultimate goal of improving the conversion of starch into sweet sugars. During rapid starch synthesis (0 to 30 days after flowering), extractable activities of α-amylase and β-amylase were low, but those of starch phosphorylase increased. After harvest, during ripening at 12 °C, or in fruit left in the field, activities of α-amylase and β-amylase increased. Starch contained 20% to 25% amylose soon after starch synthesis was initiated and until 49 days after harvest irrespective of whether the crop remained in the field or in storage at 12 °C. Maltose concentrations were low prior to harvest, but levels increased during fruit ripening. Data suggest starch breakdown is hydrolytic in buttercup squash, with α-amylase being the primary enzyme responsible for initiating starch breakdown.
Genetic Variation and Population Structure of Castanea pumila var. ozarkensis
Authors: Dane Fenny , Hawkins Leigh K. , Huang Hongwen
Published: January 2019

Genetic variation among nine populations of Ozark chinkapin [Castanea pumila (L.) Mill. var. ozarkensis (Ashe) Tucker], threatened by their susceptibility to chestnut blight (Cryphonectria parasitica (Murrill) Barr), was investigated. Population genetic parameters estimated from isozyme variation suggest the populations have a higher genetic diversity (He = 0.227) than populations of the other Castanea Mill. species on the North American continent, the American chestnut (C. dentata (Marsh.) Borkh.) High levels of heterozygosity were detected within the populations, but nonsignificant differences in genetic diversity were observed among the different populations. Principal component analysis based on isozyme allele frequencies or randomly amplified polymorphic DNA phenotype frequencies showed clustering of the same populations. Populations with high levels of genetic diversity and unusual alleles should be the focal point of conservation biologists for capturing much of the genetic variation of the species.
Scoparone and Scopoletin Accumulation and Ultraviolet-C Induced Resistance to Postharvest Decay in Oranges as Influenced by Harvest Date
Authors: D'hallewin Guy , Schirra Mario , Manueddu Enzo , Piga Antonio , Ben-Yehoshua Shimshon
Published: January 2019

`Washington Navel', `Biondo Comune', `Tarocco', and `Valencia Late' orange [Citrus sinensis (L.) Obsek] fruit, harvested at various periods of time, were subjected to ultraviolet-C (UV-C) irradiation at 0.5, 1.5, or 3.0 kJ·m-2 doses and then stored at 7 °C and 90% to 95% relative humidity (RH) for 4 weeks plus one additional week at 20 °C and 80% RH. Following UV-C treatment, there was varying amounts of rind browning and necrotic peel damage, depending on cultivar, treatment dose, and harvest date. `Tarocco' fruit were damaged more easily by UV-C treatment than the other cultivars. `Valencia L.' were the most resistant to UV-C irradiation, showing no adverse effects at the lowest dosage and having the lowest percentages of damaged fruit at higher dosages. `Washington Navel' and `Biondo Comune' oranges showed an intermediate susceptibility to UV-C treatment, with negligible differences between these cultivars. The percentage of damaged fruit after irradiation at the higher UV-C dosages decreased in most fruit samples as the season progressed. UV-C irradiation at 0.5 kJ·m-2 effectively reduced decay development compared with nontreated fruit. Irradiation with 1.5 kJ·m-2 was more effective compared with 0.5 kJ·m-2 only in early harvested fruit. In `Washington Navel' and `Biondo Comune' oranges in the later harvests, treatment with 3.0 kJ·m-2 improved decay control further, compared with 0.5 kJ·m-2. Following UV-C treatments the phytoalexins, scoparone and scopoletin, accumulated in flavedo tissue depending on the cultivar, fruit age, and UV-C treatment. Both phytoalexins displayed a similar accumulation pattern, however, the levels of scopoletin were very low compared with scoparone. Concentrations of phytoalexins rose as the irradiation dose increased. No scoparone and scopoletin could be detected in nontreated fruit. The highest concentration of phytoalexins among cultivars was recorded in `Valencia Late' oranges, the lowest in `Tarocco', with similar intermediate accumulations in `Washington Navel' and `Biondo Comune'. In `Washington Navel', `Biondo Comune', and `Tarocco' oranges, the rate of scoparone accumulation was significantly higher in fruit harvested earlier in the season while `Valencia late' oranges exhibited an opposite trend.
Optimizing Mineral Nutrition for Flower Production in Heliconia `Golden Torch' Using Response Surface Methodology
Authors: Clemens John , Morton R. Hugh
Published: January 2019

Containerized plants of Heliconia psittacorum L.f. × H. spathocircinata Aristeguieta `Golden Torch' were grown in a greenhouse for 8 months from early summer to winter under selected combinations of N, P, and K. Fertilizer rates ranged from zero to rates that exceeded those reported in the literature by 50% to 100%. Biomass variables (vegetative and inflorescence dry weight, and leaf area) were predicted to be maximized at high N and high N to P, and N to K ratios corresponding to N-P-K application rates of 1.2, 0.5, and 0.6 kg·m-3, respectively (≈2:1:1). However, the number of shoots and flowers produced per rhizome were maximal at lower N to K ratios (1:1). Flower yield could therefore be optimized with appropriate fertilization, provided attention was paid to the N to K ratio so that the size of plants and their flowers was not compromised by efforts to increase shoot and flower number. The heavier the rhizome planted, the shorter the time for shoot emergence and flowering to occur, and the greater the number of flowers harvested. However, rhizome weight had no effect on number of shoots to emerge. The probability of shoots flowering declined markedly with order of shoot emergence, although this could be increased with appropriate mineral nutrition. The maximum number of leaves subtending the inflorescence (seven) was obtained at high N and P rates. Flower production was probably limited by declining solar radiation in autumn, and by within-plant competition for rooting space.
Growth and Nitrogen Partitioning, Recovery, and Losses in Bermudagrass Receiving Soluble Sources of Labeled 15Nitrogen
Authors: Picchioni G.A. , Quiroga-Garza Héctor M.
Published: January 2019

Two greenhouse studies were conducted to trace the fate of fertilizer N in hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy `Tifgreen'], and to estimate total plant N recovery and losses. The first experiment was performed during winter, with artificial light supplementing natural light to provide a photoperiod of 13.6 to 13.8 hours. The second experiment was conducted during summer and fall under only natural light conditions, with a progressively decreasing photoperiod of 13.7 to 11.1 hours. Urea (UR), ammonium sulfate (AS), and ammonium nitrate (AN) were labeled at 2 atom% 15N, and applied at N rates of 100 or 200 kg·ha-1 for 84 days (divided into six equal fractions and applied every 14 days). Fertilizer N source did not affect total dry matter (DM) accumulation by the plant components, but the high N rate increased clipping DM production under the longer photoperiod. Under the decreasing photoperiod, overall DM production was reduced, and clipping DM production was unaffected by increased N rate. Average N concentration of clippings varied between N sources, ranging from a high of 38.6 g·kg-1 DM with AS to a low of 34.7 g·kg-1 for UR. In Expt. 1, the greatest total plant N recovery [clippings, verdure (shoot material remaining after mowing), and thatch plus roots] occurred with AS (78.5%) and the lowest with UR (65.9%). In Expt. 2, these values declined to 53.0% and 38.0%, respectively. Urea fertilization resulted in the greatest N losses as a fraction of the N applied (33.6% to 61.5%) and AS fertilization the lowest (20.7% to 46.3%). In view of the greater N losses, UR may be a less suitable soluble N source for bermudagrass fertilization within the conditions of this study. In addition, late-season N fertilization may result in a significant waste of fertilizer N as bermudagrass progresses into autumnal dormancy when temperature, photoperiod, and irradiance decline and cause reduction in growth and N uptake.
Lovastatin Inhibits α-Farnesene Synthesis without Affecting Ethylene Production during Fruit Ripening in `Golden Supreme' Apples
Authors: Ju Zhiguo , Curry Eric A.
Published: January 2019

Lovastatin is a specific hydroxymethylglutaryl coenzyme-A reductase inhibitor in animals and as such, is a potent cholesterol lowering pharmaceutical for human use. Because it has also been shown to inhibit α-farnesene in certain plants, we investigated its effects on ethylene and α-farnesene biosynthesis, volatile production, and fruit color during ripening in `Golden Supreme' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. Immediately after harvest, fruit were dipped in Lovastatin solution for 2 min, allowed to dry, and stored in the dark at 20 °C for 30 days. Internal ethylene at harvest was low (< 0.1 mL·L-1) and α-farnesene was undetectable. Both internal ethylene and α-farnesene increased in nontreated fruit during 30 days storage. Prestorage Lovastatin treatment did not affect ethylene synthesis, but at 1.25 or 2.5 mmol·L-1 nearly eliminated α-farnesene production. At 0.25 mmol·L-1, Lovastatin delayed the increase in α-farnesene production about 12 days and reduced total α-farnesene production by the end of storage compared with controls. When applied to nontreated preclimacteric fruit, ethephon at 1.4 mmol·L-1 increased both internal ethylene concentration and α-farnesene production. In Lovastatin-treated preclimacteric fruit, however, ethephon increased internal ethylene concentration without promoting α-farnesene synthesis. In another trial, after 30 days storage at 0 °C, fruit were treated with 1.25 mmol·L-1 Lovastatin and stored at 20 °C with air circulation for 20 days. These fruit accumulated similar amounts of ethylene as nontreated controls, but α-farnesene production decreased rapidly and was not detectable after 5 days. Treating with ethephon at 1.4 mmol·L-1 increased α-farnesene production in control fruit but not in Lovastatin-treated fruit. Lovastatin treatment did not affect the change in fruit color. Chemical names used: [1S-[1α (R °), 3α, 7β, 8β (2S °, 4S °), 8ab]]-1,2,3,7,8,8α-hexahydro-3,7-dimethyl-8-[2-(tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1-naphthaienyl 2-methylbutanoate (Lovastatin); 2-chloroethylphosphonic acid (ethephon).
Remote Sensing of Fruit Textural Changes with a Laser Doppler Vibrometer
Authors: Muramatsu Noboru , Sakurai Naoki , Wada Naoki , Yamamoto Ryoichi , Tanaka Keiichi , Asakura Toshikazu , Ishikawa-Takano Yuko , Nevins Donald J.
Published: January 2019

Developmental changes in fruit texture during ripening were determined based on remote sensing of surface vibrations. The technique was evaluated with fruit having a range of firmness and textural characteristics including kiwifruit [Actinidia deliciosa (A. Chev.) Liang et Ferguson, `Hayward'] treated with ethylene, apple (Malus ×domestica Borkh. `Ourei') stored at 10 or 20 °C and persimmon (Diospyros kaki L. `Fuyu') stored at 10 °C. In each case fruit were placed on a stage capable of imparting sine wave vibrations with frequencies ranging from 5 to 2,000 Hz. The vibration transmitted through the fruit to the top surface was precisely measured without any direct contact with the Doppler laser vibrometer. The perceived fruit surface signal was corrected by subtraction of the stage vibration based on an accelerometer signal, hence the true vibrational signal of the fruit mass was determined. The phase shift at selected frequencies was based on the difference between the input and output vibration. The phase shift significantly increased in the range of 1,200 to 1,600 Hz in all three kinds of fruit analyzed as a function of maturation. The resonance frequency, peak height, and peak width of second resonance peak were also determined. The resonance frequency decreased in all fruit as a function of maturation. In apple, the peak height decreased as a function of storage duration, but in kiwifruit and persimmon the peak height fluctuated and a consistent pattern in this particular parameter was not observed. The amplitude of vibration decreased as a function of maturation when the imposed vibration exceeded 1,200 Hz. Data clearly showed that the Doppler laser vibrometer is capable of detecting the phase shift and vibration amplitude of fruit, and can be used as a versatile remote sensory tool for determining fruit firmness and for evaluations of maturity.
Seed Germination and Seedling Growth of Alnus maritima from Its Three Disjunct Populations
Authors: Schrader James A. , Graves William R.
Published: January 2019

Genotypic variation and horticultural potential of Alnus maritima [Marsh.] Nutt. (seaside alder), a large shrub or small tree found naturally in only three small, disjunct populations, have not been studied. We examined effects of population of origin and environment on seed germination and growth and morphology of seedlings. The first experiment showed that 6 weeks of cold stratification optimized germination of half-sibling seeds from Oklahoma at 73.2%. When this treatment was applied to multiple groups of half-siblings from all populations in a second experiment, seeds from Oklahoma had a higher germination percentage (55.0%) than seeds from Georgia (31.4%) and the Delmarva Peninsula (14.7%). In a third experiment, morphology and growth of multiple groups of half-siblings from all three populations were compared in one environment. Leaves of seedlings from Oklahoma were longer (12.8 cm) and more narrow (2.15 length to width ratio) than leaves of seedlings from Georgia (12.0 cm long; ratio = 1.76) and the Delmarva Peninsula (11.6 cm long; ratio = 1.86). Seedlings from Oklahoma and Georgia accumulated dry weight at higher rates (181 and 160 mg·d-1, respectively) than seedlings from Delmarva (130 mg·d-1), while seedlings from Oklahoma and Delmarva were more densely foliated (0.72 and 0.64 leaves and lateral shoots per centimeter of primary stem, respectively) than those from Georgia (0.46 per cm). These differences indicate genetic divergence among the three disjunct populations and the potential to exploit genetic variation to select horticulturally superior A. maritima for use in managed landscapes.
Exogenous Ethylene Enhances Formation of Embryogenic Callus and Inhibits Embryogenesis in Cultures of Explants of Spinach Roots
Authors: Ishizaki Takuma , Komai Fuminori , Msuda Kiyoshi , Megumi Chiaki
Published: January 2019

Effects of ethephon, AgNO3, and AVG on formation of embryogenic callus and somatic embryogenesis were examined in cultures of explants of spinach (Spinacia oleracea L. `Nippon') roots. At 10 μm, ethephon more than doubled the frequency of formation of embryogenic callus as compared to that in cultures without ethephon. Silver nitrate at 10 mm and AVG at 1 μm each inhibited formation of embryogenic callus but neither reduced the growth rate of established callus. When ethephon was applied at 10 μm during embryogenesis, it completely inhibited embryo development. By contrast, AgNO3 at 10 μm markedly increased the number of embryos. Results suggest that ethylene might be essential as a plant hormone for formation of embryogenic callus but inhibits somatic embryogenesis per se in cultures of explants of spinach roots. Chemical names used: 2-chloroethylphosphonic acid (ethephon), silver nitrate (AgNO3), aminoethoxyvinylglycine (AVG).
Use of GA3 to Manipulate Flowering and Yield of `Hass' Avocado
Authors: Salazar-García Samuel , Lovatt Carol J.
Published: January 2019

Avocado trees (Persea americana Mill.) bearing a heavy crop produce a light “off” bloom the next spring. This results in a light crop and a subsequent intense “on” bloom the year after. The objective of the study was to quantify the effects of GA3 canopy sprays applied to `Hass' avocado trees during the months preceding an “off” or “on” bloom on inflorescence and vegetative shoot number and yield. The experiment was initiated approximately seven months before an anticipated “off” bloom in an attempt to increase flowering intensity and yield. GA3 (25 or 100 mg·L-1) was applied to separate sets of trees in September (early stage of inflorescence initiation), November (early stage of inflorescence development), January (initial development of the perianth of terminal flowers), March (cauliflower stage of inflorescence development; only 25 mg·L-1), or monthly from September through January (only 25 mg·L-1). Control trees did not receive any treatment. GA3 (100 mg·L-1) applied in September reduced inflorescence number in both years, but not yield. GA3 (25 or 100 mg·L-1) applied in November before the “on” bloom reduced inflorescence number with a concomitant increase in vegetative shoot number and 47% yield reduction compared to control trees. This treatment might provide avocado growers with a tool to break the alternate bearing cycle by reducing yield in an expected “on” crop year to achieve a higher yield the following year. GA3 (25 mg·L-1) applied in November or January stimulated early development of the vegetative shoot of indeterminate inflorescences. January and March applications did not affect the number of flowering or vegetative shoots produced either year. GA3 (25 mg·L-1) applied in March at the start of an “off” bloom increased 2-fold the production of commercially valuable fruit (213 to 269 g per fruit) compared to the control.
Floral Ontogeny of Pelargonium ×domesticum
Authors: Loehrlein Marietta , Craig Richard
Published: January 2019

Floral ontogeny of two cultivars of Pelargonium ×domesticum L.H. Bailey, (regal pelargonium) `Duchess' and `Jennifer', was examined. Plants of both cultivars were grown together in a growth chamber at 15.5 °C with a photosynthetic photon flux of 10 mol·m-2·d-1. Meristems were examined at 5-day intervals over an experimental period of 170 days. The initial vegetative meristem was convex with leaf primordia initiated on either side in an alternate pattern. Early floral initiation was characterized by formation of two clefts on either side of the meristem. Between the clefts new meristems developed. Proliferation of meristems continued until numerous meristems were organized in a cluster arrangement at the apex of the shoot. New meristems lacked leaf primordia and would develop into flowers. Floral organ primordia on a floral meristem were initiated in a succession of four whorls: sepals, petals, androecia, and gynoecium.
Inheritance of Yellow-flesh Intensity in Diploid Potatoes
Authors: Haynes Kathleen G.
Published: January 2019

Although potato (Solanum tuberosum L.) tuber yellow flesh per se is known to be controlled by a single gene, the intensity of yellow flesh varies widely in Solanum L. species. Many diploid species have very intense yellow flesh, as compared to the commercial tetraploid yellow-flesh cultivar `Yukon Gold'. Inheritance of yellow-flesh intensity at the diploid level was investigated in a hybrid population of S. phureja ssp. phureja (Juz. & Buk.)-S. stenotomum ssp. stenotomum (Juz. & Buk.) (PHU-STN). Six randomly chosen male parents were crossed to five randomly chosen female parents in a Design II mating scheme. In 1993, ≈12 progeny (clones) from each of the 30 families were planted in a randomized complete block design with two replications in Presque Isle, Maine, and evaluated for tuber yellow-flesh intensity as measured by a reflectance colorimeter. Twenty-five tubers from each plot were scored using the YI E-313 yellow intensity scale. An average YI E-313 score was obtained for each plot. Narrow-sense heritability on a plot mean basis was estimated as 0.99 with a SE of 0.65 to 0.72. There were significant differences among clones within a family. Results suggest that rapid progress can be made in breeding for intense yellow flesh in this diploid population. Clones from this population that produce 2n gametes represent an important source of germplasm for enhancing the intensity of the yellow-flesh trait in tetraploid potatoes.
Variability in the Rate of Cold Acclimation and Deacclimation among Tuber-bearing Solanum (Potato) Species
Authors: Vega Sandra E. , Palta Jiwan P. , Bamberg John B.
Published: January 2019

Two major components of frost resistance are freezing tolerance in the nonacclimated state (growing in normal condition) and capacity to cold acclimate (increase in freezing tolerance upon exposure to chilling temperatures). In addition to these two major components, numerous factors contribute to frost survival. Although the rate of cold acclimation and deacclimation have been recognized as important factors contributing to frost survival, very little information about them is available. Our objective was to determine if there is variability in the rate of cold acclimation and deacclimation among tuber-bearing wild potato species: S. acaule Bitter, S. commersonii Dunal, S. megistacrolobum Bitter, S. multidissectum Hawkes, S. polytrichon Rydb., S. sanctae-rosae Hawkes, and S. megistacrolobum subsp. toralapanum (Cárdenas & Hawkes) Giannattasio&Spooner. Relative freezing tolerance of these species was measured after 0, 3, 6, 9 and 12 days of cold acclimation and after 12 and 24 hours deacclimation. Our results showed there were differences in the rates of cold acclimation and deacclimation among these species. With respect to the rate of acclimation we found these species can be divided into four groups: (i) early; (ii) late acclimators; (iii) progressive acclimators, and (iv) nonacclimators. Likewise, a wide range of cold deacclimation behavior was found. Some species showed as low a loss of 20% of their freezing tolerance, others showed as much as >60% loss after 12 hours of deacclimation. Significant deacclimation was observed in all cold acclimating species after 1 day. These results demonstrate that the rates of cold acclimation and deacclimation were not necessarily related to the cold acclimation capacity of a species. Rapid acclimation in response to low temperatures preceding a frost episode and slow deacclimation in response to unseasonably warm daytime temperatures could be advantageous for plants to survive frost events. Thus, in addition to nonacclimated freezing tolerance and acclimation capacity, it would be very desirable to be able to select for rapid acclimation and slow deacclimation abilities. Results demonstrate that variability for these two traits exists in Solanum L. (potato) species.
Linking Hydraulic Conductivity to Anatomy in Plants that Vary in Specific Root Length
Authors: Huang Bingru , Eissenstat David M.
Published: January 2019

In Citrus L. sp., specific root length of whole root systems has been correlated positively with root hydraulic conductivity, but there is little mechanistic understanding of the causes for this association. The hydraulic conductivity of individual roots in relation to root anatomical characteristics in seedlings of three citrus rootstocks [sour orange (SO) (Citrus aurantium L.), trifoliate orange (TO) (Poncirus trifoliate (L.) Raf.), and Swingle citrumelo (SC) (C. paradisi Macf. × P. trifoliata)] that vary widely in specific root length (SRL) was measured. Among fibrous roots, first-order and secondorder laterals were examined. Relative differences among rootstocks in the overall hydraulic conductivity (LP) and radial conductivity (LR) for individual 1-month-old and 6-month-old second- and first-order roots generally were consistent with hydraulic conductivity determined previously for entire root systems. There were no significant differences in axial conductance per unit pressure (Kh) in either first- or second-order roots among the rootstocks. This was consistent with the similarity in number and diameter of xylem vessels. One-month-old second-order roots had no suberized exodermis but varied in cortical radius. Six-month-old second-order roots of TO, however, had more nonsuberized cells (passage cells) in the exodermis than roots of SC and SO, although the cortical radius of SC and SO roots were not different. Compared to 6-month-old second-order roots, 1-month-old second-order roots had much higher LP and LR but lower Kh. Differences in overall root hydraulic conductivity among the citrus rootstocks were mainly related to structural differences in the radial pathway for water movement, suggesting that radial hydraulic conductivity was the primary determining factor of water uptake in citrus rootstocks.
Reproduction and Horticultural Performance of Transgenic Ethylene-insensitive Petunias
Authors: Gubrium Erika K. , Clevenger Donna J. , Clark David G. , Barrett James E. , Nell Terril A.
Published: January 2019

A series of experiments on ethylene-insensitive (EI) petunia plants (Petunia ×hybrida Hort. Vilm.-Andr.) generated in two genetic backgrounds were conducted to determine the involvement of ethylene in horticultural performance. Experiments examined various aspects of horticultural performance: days to flower, flower senescence after pollination and without pollination, fruit set and ripening, and adventitious root formation on vegetative stem cuttings. The development of EI plants was altered in several ways. Time from seed sowing to first flower anthesis was decreased by a week for EI plants grown at 26/21 °C. Flower senescence in nonpollinated and self-pollinated flowers was delayed in all EI plants compared to wild-type plants. Fruit set percentage on EI plants was slightly lower than on wild-type plants and fruit ripening on EI plants was delayed by up to 7 days. EI plants produced fewer commercially acceptable rooted cuttings than wild-type plants. There was a basic difference in the horticultural performance of the two EI lines examined due to a difference in the genetic backgrounds used to generate the lines. EI plants displayed better horticultural performance when grown with day/night temperatures of 26/21 °C than 30/24 °C. These results suggest that tissue-specific ethylene insensitivity as well as careful consideration of the genetic background used in transformation procedures and growth conditions of etr1-1 plants will be required to produce commercially viable transgenic floriculture crops. EI petunias provide an ideal model system for studying the role of ethylene in regulating various aspects of plant reproduction.
Drought Response of Three Ornamental Herbaceous Perennials
Authors: Prevete Kelly J. , Fernandez R. Thomas , Miller William B.
Published: January 2019

Boltonia asteroides L. `Snowbank' (Snowbank boltonia), Eupatorium rugosum L. (eastern white snakeroot), and Rudbeckia triloba L. (three-lobed coneflower) were subjected to drought for 2, 4, and 6 days during the fall and spring. Leaf gas exchange, leaf water potential, growth, and carbohydrate partitioning were measured during drought and throughout the following growing season. Leaf gas exchange of B. asteroides was not affected by drought treatment in the fall, not until day 6 of spring drought, and there were no long-term effects on growth. Transpiration and stomatal conductance of R. triloba decreased when substrate moisture decreased to 21% after drought treatment during both seasons. Assimilation of drought-treated R. triloba decreased when substrate moisture content decreased to 12% during spring but was not affected by drought in the fall. There was a decrease in the root-to-shoot ratio of R. triloba that had been treated for 4 days, which was attributed to an increase in the shoot dry weight (DW) of treated plants. Reductions in spring growth of E. rugosum were observed only after fall drought of 6 days, and there were no differences in final DWs of plants subjected to any of the drought durations. Spring drought had no effect on growth index or DW of any of the perennials. Boltonia asteroides and R. triloba had increases in low-molecular-weight sugars on day 4 of drought, but E. rugosum did not have an increase in sugars of low molecular weight until day 6 of drought. Differences in drought response of B. asteroides, E. rugosum, and R. triloba were attributed to differences in water use rates.