bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth, Development, and Response of Peach Somaclones to the Root-knot Nematode, Meloidogyne incognita
Authors: Hashmi Ghazala P. , Hammerschlag F.A. , Huettel R.N. , Krusberg L.R.
Published: January 2019

Somaclonal variation has been reported in many plant species, and several phenotypic and genetic changes, including pathogen and pest resistance, have been described. This study was designed to evaluate somaclonal variation in peach [Prunus persica (L.) Batsch] regenerants in response to the root-knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood. Regenerants SH-156-1, SH-156-7, SH-156-11, and SH-156-12, derived from `Sunhigh' (susceptible) embryo no. 156, and regenerants RH-30-1, RH-30-2, RH-30-4, RH-30-6, RH-30-7, and RH-30-8, derived from `Redhaven' (moderately resistant) embryo no. 30, were screened in vitro for resistance to the root-knot nematode. Under in vitro conditions, fewest nematodes developed on regenerants SH-156-1 and SH-156-11, `Redhaven', and all `Redhaven' embryo no. 30 regenerants. The most nematodes developed on `Sunhigh', `Sunhigh' seedlings (SHS), and regenerant SH-156-7. Nematodes did not develop on `Nemaguard'. In greenhouse tests, fewer nematodes developed and reproduced on the no. 156-series regenerants than on `Sunhigh'. Under in vitro conditions, significant differences among uninfected (control) regenerants, cultivars, and rootstock `Nemaguard' were observed for shoot height and fresh root weights. Significant differences were also observed among infected regenerants, cultivars, and `Nemaguard' for these characteristics, but differences were not observed between control and infected regenerants. Different concentrations of α-naphthaleneacetic acid in half-strength Murashige and Skoog salt medium induced rooting of two peach cultivars, one rootstock, and four regenerants.
Light and Phytochrome Involvement in Rosa multiflora Seed Germination
Authors: Yambe Yoshiko , Takeno Kiyotoshi , Saito Takashi
Published: January 2019

Seed germination percentage of multiflora rose (Rosa multiflora Thunh.) was much higher under continuous white light than in complete darkness. Red light was the most effective in inducing germination, and far-red light was ineffective. Exposure to red light for 1 min increased germination; this effect was saturated at an exposure of2 min. The red-light effect was reversed by subsequent exposure to far-red light. The results indicate that rose seeds are positively photoblastic, and that the photoreceptor involved is most likely phytochrome.
Response of Forsythia × itermedia `Spectabilis' to Uniconazol. I. Growth; Dry-matter Distribution; and Mineral Nutrient Content, Concentration, and Partitioning
Authors: Thetford Mack , Warren Stuart L. , Blazich Frank A.
Published: January 2019

Uniconazole was applied as a foliar spray at 0, 90, 130, 170, or 210 mg·liter-1 to rooted stem cuttings of `Spectabilis' forsythia (Forsythia ×intermedia Zab.) potted in calcined clay. Plants were harvested 0, 40, 80, 120, and 369 days after treatment (DAT). Treatment with uniconazole at 90 to 210 mg·liter suppressed leaf area and dry weight an average of 16% and 18%, respectively, compared to the nontreated controls when averaged over all harvest periods. Stem and root dry weight suppression was greatest at 80 DAT, 47% and 37%, respectively. Uniconazole suppressed root length from 15% to 36% and root area from 15% to 33% depending on harvest date. Internode length and stem diameter of uniconazole-treated plants were suppressed at all harvests except 369 DAT. Uniconazole resulted in increased and decreased root: shoot ratios 40 and 80 DAT, respectively; while root: shoot ratios were not affected for the remainder of the study. Relative growth rates of leaves, stems, and roots decreased with increasing uniconazole concentration; however, no relative growth rates were suppressed beyond 80 DAT. Generally, mineral nutrient concentrations increased as a result of uniconazole application. The proportion of mineral nutrients allocated to leaves and roots was not affected while the proportion of nutrients allocated to stems decreased with uniconazole application compared to the controls. Chemical name used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazole).
Synthetic Cytokinin-1-(2=chloro=4=pyridyl)-3-phenylurea (CPPU)-Promotes Fruit Set and Induces Parthenocarpy in Watermelon
Authors: Hayata Yasuyoshi , Niimi Yoshiyuki , Iwasaki Naoto
Published: January 2019

Applying a 200 ppm solution of CPPU to pollinated ovaries of watermelon (Citrullus lunatus Matsum) at anthesis increased fruit set from 26.9% (control) to 95%. Applying CPPU solutions to nonpollinated ovaries at anthesis induced parthenocarpy, yielding 65% and 89.5% fruit set, respectively with 20 and 200 ppm applications. However, 64% of the 20 ppm CPPU-treated parthenocarpic fruit stopped growth 10 days after treatment. Growth of CPPU-treated, pollinated, and nonpollinated fruit increased significantly compared with growth of control fruit during the first 10 days after treatment, but, except for the 20 ppm CPPU parthenocarpic fruit, growth subsequently slowed, resulting in fruit equal in size to the control by harvest. CPPU application did not affect soluble solids content of pollinated fruit, but reduced content of parthenocarpic fruit treated with 20 ppm. Fructose content was generally higher than glucose and sucrose at harvest. However, in pollinated fruit treated with 20 ppm CPPU, sucrose levels were higher than glucose and fructose. These results suggest that CPPU is practical for promoting fruit set and seedless fruit without adversely affecting fruit quality and development.
Effects of Abscisic Acid on ex vitro Acclimatization of Aronia arbutifolia (L.) Pers.
Authors: Colón-Guasp Wilfredo , Nell Terril A. , Kane Michael E. , Barrett James E.
Published: January 2019

The use of abscisic acid (ABA) as an in vitro prehardening treatment to enhance ex vitro acclimatization of Stage III Aronia arbutifolia plantlets was explored. Effects of ABA (0-4 mg·liter-1) pretreatment on ex vitro shoot growth, leaf carbon assimilation (LCA) and nonstructural carbohydrate content were evaluated during plantlet acclimatization under two photosynthetic photon flux (PPF) levels (450 and 650 μmol·m-2·s-1). Stage III plantlets rooted in the presence of ABA exhibited both shoot growth inhibition and transient negative LCA rates at time of transfer ex vitro. Regardless of treatment, maximum LCA rates were achieved by day 20 post-transplant. Pretreatment with ABA had no effect on stem or leaf starch content at time of transplant, however, leaf and stem soluble sugar content was higher in ABA treated plantlets than controls. Further suppression of shoot growth and alteration in the pattern of stem starch utilization occurred at the higher irradiance level. These results indicate that ABA pretreatments provide no physiological advantage that would facilitate ex vitro acclimatization of Aronia plantlets.
Genetic Analysis of the Fused Vein Trait in Cucurbita pepo L.
Authors: Carle R. Bruce , Loy J. Brent
Published: January 2019

The expression and inheritance of the fused vein trait in Cucurbita pepo were investigated. The fused vein inbred, NH2405, was crossed to normal lines, NH614, and NHBP10. Reciprocal F1, F2, F3 and BC populations were generated and examined for leaf type segregation in field and greenhouse environments. Although the fused vein phenotype is stable in NH2405, it exhibited a continuum of expression in segregating populations. The onset of vein fusion ranged from the fourth to the tenth leaf stage and degree of fusion varied from slight (1-5 cm) to extreme (10-20 cm). Inheritance ratios varied with population, conditions of production, and direction of cross. Most segregating populations fit either a single or double recessive gene model, however, a quarter of the populations showed no or low fused vein recovery. A feasible explanation for the distorted inheritance is that the fused vein trait is a gametophytic subvital, governed by a single recessive gene, fv. Although less likely, a double recessive, subvital model cannot be ruled out.
Morphology and Anatomy of the Fused Vein Trait in Cucurbita pepo L.
Authors: Carle R. Bruce , Loy J. Brent
Published: January 2019

The morphology, growth rate and anatomy of the fused vein trait were characterized in Cucurbita pepo using the inbreds NH2405 (fused vein), NH7210 (moderately fused vein), and NH614 (normal). Morphological analysis showed that the trait is characterized by a partial fusion of the five primary leaf veins. Fusion begins at the distal point of the petiole and extends along the central vein. Branching of the veins is delayed and there is a reduction of the interveinal leaf blade. Consequently, the upper leaf surface appears puckered or wrinkled. Depending on genetic background, the onset of fused vein leaf production starts at the fourth to tenth leaf stage and continues throughout vegetative growth. The extent of fusion increases with leaf number but stabilizes by the twentieth leaf stage maximum extent of vein fusion also varies with genetic background (5-20 cm). Though fused vein and normal inbreds differed in the rate and pattern of leaf growth, examination of F2 and BC populations revealed no significant effect of the fused vein trait on leaf number, leaf size, and rate of leaf initiation. Anatomical examination revealed different vascular patterns in the transition zone between petiole and leaf blade for normal and fused vein leaves. In normal leaves, the vascular bundles of the petiole enlarge and coalesce to form a vascular crescent. The crescent reorganizes and diverges as large vascular columns and pairs of smaller flanking vascular bundles into each vein. In contrast, two cycles of enlargement, coalescence, and dispersal occur in fused vein leaves.
Micronutrient Toxicity in Seed Geranium (Pelargonium × hortorum Bailey)
Authors: Lee Chiwon W. , Choi Jong-Myung , Pak Chun-Ho
Published: January 2019

Seed geranium (Pelargonium × hortorum) micronutrient toxicity symptoms were induced by applying elevated levels of B, Cu, Fe, Mn, Mo, and Zn in fertilizer solution. Beginning at the 3-4 true leaf stage, seedling plants established in 11-cm (0.67-liter) pots containing peat-lite growing medium were fertilized at each irrigation for 5 weeks with solutions containing 0.25, 0.5, 1, 2, 3, 4, 5, and 6 mm plus the standard concentration of each micronutrient. The standard solution contained 20 μm B, 0.5 μm Cu, 10 μm Fe, 10 μm Mn, 0.5 μm Mo, and 4 μm Zn. All treatment solutions contained a fixed level of macronutrients. Visible foliar toxicity symptoms were produced when the nutrient solution contained 0.5 mm B, 0.5 mm Cu, 5 mm Fe, 1 mm Mn, 0.25 mm Mo, or 0.5 mm Zn. Reduction in dry matter yield was evident when 1 mm B, 2 mm Cu, 3 mm Fe, 2 mm Mn, 0.5 mm Mo, or 1 mm Zn was used in the fertilizer solution. Leaf chlorophyll contents decreased as Cu and Mn levels in the concentration range tested increased. Elevated levels of Fe increased tissue chlorophyll contents. The relationship between the nutrient solution and tissue concentrations of each of the six micronutrients was determined.
Identifying Genotypic Heterogeneity in `McFarlin' Cranberry: A Randomly-amplified Polymorphic DNA (RAPD) and Phenotypic Analysis
Authors: Novy R.G. , Vorsa N. , Patten K.
Published: January 2019

Highly variable productivity among Vaccinium macrocarpon (Ait.) Pursh `McFarlin' bogs in Washington has been noted by growers. The fruiting habits of 12 Washington `McFarlin' bogs, ranging from 5.7-28.4 t/ha productivity were characterized. Uprights from each bog were characterized using RAPD markers, and then used in a greenhouse pollination experiment to determine if variation in fruiting and fertility phenotypes could be associated with RAPD profiles. Fifteen RAPD profiles were identified, and genetic heterogeneity was high among the 12 bogs. An association between RAPD profiles and reproduction characteristics was observed. The most frequent (30%) RAPD profile appeared to represent the `true' `McFarlin', since it was abundant in higher-yielding bogs and its profile was identical to `McFarlin' samples from other growing regions. A unique RAPD profile was also identified which exhibited high yield characteristics, but did not appear to be related to `McFarlin'. The Washington `McFarlin' bogs examined are composed of a diverse array of genotypes with variable fruiting phenotypes, indicating the variability in production has a genetic component.
Seasonal Changes in Cold Hardiness of Rhododendron L. `Catawbiense Boursault' Grown under Continuous and Periodic Water Stress
Authors: Anisko Tomasz , Lindstrom Orville M.
Published: January 2019

Water status is known to have an impact on cold hardiness of plants. Cold hardiness of `Catawbiense Boursault' rhododendron was examined under continuous and periodic water stress. Under continuous stress, water content of growing medium was maintained at 0.6 to 0.75, 0.45 to 0.6, or 0.3 to 0.45 m3·m-3. Under periodic stress, water content was either maintained between 0.6 to 0.8 m3·m-3 or plants were subjected to drought episodes at various times in late summer, autumn, and early winter. During a drought episode, watering was delayed until water content was below 0.4 m3·m-3. Watering then resumed and water content was maintained between 0.3 to 0.4 m3·m-3. Cold hardiness was evaluated on detached leaves and stem sections. The effect of continuous water stress depended on its severity and duration. Moderate stress did not increase cold hardiness compared to well watered plants during the first winter, but it did so when continued into the second winter. More severe stress increased cold hardiness during the first winter, but it decreased cold hardiness during the subsequent winter. The effect of periodic water stress depended on the timing of application. During initial and final stages of acclimation, cold hardiness increased in response to water stress less than during the intermediate stages. Water-stress-induced cold hardiness gradually decreased after rewatering.
Effects of the Production Environment on the Susceptibility of Rose Flowers to Postharvest Infection by Botrytis cinerea
Authors: Hammer Philip E. , Evensen Kathleen B.
Published: January 2019

We studied the effects of environmental conditions during production on susceptibility of roses to postharvest infection by B. cinerea. For flowers harvested from a commercial greenhouse, susceptibility was linearly correlated (r = 0.97) with mean air velocity during the 5-week periods before each harvest. Susceptibility was also correlated with mean leaf to air temperature gradient (r = 0.83) and inversely correlated with wetness measured on an electronic leaf (r = -0.92), but these correlations were interpreted as secondary effects of the correlation with air movement. Susceptibility was not correlated with temperature, relative humidity (RH), or the other factors measured. In growth chamber experiments, flowers grown under high wind speed (0.55 m·s-1) were significantly more susceptible to infection than flowers grown under low wind speed (0.18 m·s-1). High relative humidity during production increased background infection levels (i.e., those infections not caused by laboratory inoculation) but did not affect susceptibility.
Ten Cycles of Recurrent Selection for Fruit Yield, Earliness, and Quality in Three Slicing Cucumber Populations
Authors: Wehner Todd C. , Cramer Christopher S.
Published: January 2019

Fruit yield, earliness, and quality have low to moderate heritability, but are traits of major importance in cucumber (Cucumis sativus L.). The objective of this study was to determine the changes made in those traits using recurrent selection in three slicing cucumber populations (NCMBS, NCES1, and NCBA1). During population improvement, one or two replications of 200 to 335 half-sib families were evaluated in the spring season for five traits: total, early, and marketable fruit per plot, fruit shape rating, and a simple weighted index (SWI = 0.2(total yield)/2 + 0.3(early yield) + 0.2(% marketable)/10 + 0.3(fruit shape). Families from each population were intercrossed in an isolation block during the summer season using remnant seeds of the best 10% selected using the index. Response was evaluated using a split-plot treatment arrangement in a randomized complete block design with 32 replications in each of two seasons (spring and summer). Whole plots were the three populations, and subplots were the 11 cycles (cycles 0 to 9 plus checks). We measured improvement in performance of the populations in a selected (spring) and unselected environment (summer). Significant gains were made for all traits in all populations over the 9 to 10 cycles of recurrent selection. Greatest progress was made for the NCMBS population, with an average of 37% gain from cycle 0 to 9 over all five traits. The trait where most progress was made was early yield, with an average of 63% gain from cycle 0 to 9 over the three populations.
Performance Responses of Strawberry Seedlings to the Sublethal Effects of Nonfumigated Soils
Authors: Fort Sean B. , Shaw Douglas V. , Larson Kirk D.
Published: January 2019

Nine selected strawberry genotypes (Fragaria ×ananassa Duch.) from the University of California, Davis, strawberry improvement program were intercrossed and their seedling offspring evaluated for five production traits. Plants were evaluated in annual hill culture, with and without preplant soil fumigation using a mixture of 67 methyl bromide: 33 chloropicrin (wt/wt, 392 kg/ha). Plant mortality was <1% for seedlings grown in either soil environment, indicating that the main effects of fumigation treatment in this experiment were due to the consequences of sublethal soil organisms. Plants grown in nonfumigated soils measured from 74% to 77% of the diameter of those grown in fumigated soils and yielded 59% as much fruit. Significant cross × fumigation interactions were not detected for fruit yield, fruit size, and weighted fruit appearance. Moreover, genetic correlations for these three traits calculated by comparing seedling performance in fumigated and nonfumigated soil environments were at or near unity, suggesting that the same genes condition genetic variability for these traits in both soil environments. Together, these findings demonstrate that strawberry fruit yield and vigor are increased substantially by fumigation, even in the absence of an identifiable major pathogen problem. Further, there may be little promise for developing cultivars with genetic adaptation specific to the sublethal effects of nonfumigated soils, as selection in either soil fumigation environment is likely to affect the same sets of genes.
Genetic Variation among and within United States Collard Cultivars and Landraces as Determined by Randomly Amplified Polymorphic DNA Markers
Authors: Farnham Mark W.
Published: January 2019

A collection of collard (Brassica oleracea L., Acephala group) germplasm, including 13 cultivars or breeding lines and 5 landraces, was evaluated using randomly amplified polymorphic DNA (RAPD) markers and compared to representatives of kale (Acephala group), cabbage (Capitata group), broccoli (Italica group), Brussels sprouts (Gemmifera group), and cauliflower (Botrytis group). Objectives were to assess genetic variation and relationships among collard and other crop entries, evaluate intrapopulation variation of open-pollinated (OP) collard lines, and determine the potential of collard landraces to provide new B. oleracea genes. Two hundred nine RAPD bands were scored from 18 oligonucleotide decamer primers when collard and other B. oleracea entries were compared. Of these, 147 (70%) were polymorphic and 29 were specific to collard. Similarity indices between collard entries were computed from RAPD data and these ranged from 0.75 to 0.99 with an average of 0.83. Collard entries were most closely related to cabbage (similarity index = 0.83) and Brussels sprouts entries (index = 0.80). Analysis of individuals of an OP cultivar and landrace indicated that intrapopulation genetic variance accounts for as much variation as that observed between populations. RAPD analysis identified collard landraces as unique genotypes and showed them to be sources of unique DNA markers. The systematic collection of collard landraces should enhance diversity of the B. oleracea germplasm pool and provide genes for future crop improvement.
Growth Regulatory Effects and Soil Concentration of Controlled-release Trifluralin Applied to Roots of Yellow poplar and Red Oak
Authors: Tworkoski Thomas J. , Engle Michael E. , Kujawski Peter T.
Published: January 2019

A polypropylene fabric containing control-release pellets of the herbicide, trifluralin, can be oriented in the soil to regulate the distribution of plant roots. In 1990, trenches were dug near 10-year-old red oak (Quercus rubra L.) and 10-year-old yellow poplar (Liriodendron tulipifera L.) and fabric containing trifluralin control-release pellets and polypropylene fabric alone were installed vertically to redirect root growth. Roots grew alongside trifluralin fabric and fabric alone and did not penetrate either fabric 38 months after installation. Shoot growth of yellow poplar was reduced about 47% each year by the trifluralin fabric treatment compared to control. Red oak shoot growth was not affected by trifluralin fabric. Leaf water potential was not affected by treatment in either species. Trifluralin residues in trifluralin fabric decreased from 23.3% to 22.0% from July 1990 to October 1993. During this time, trifluralin levels increased from 0.4 to 3.6 mg·kg-1 in soil sampled 0 to 15 cm below trifluralin fabric. These results suggest that controlled-release trifluralin will provide persistent inhibition of root and shoot growth of some species and will not migrate significantly in the soil. Chemical names used: α,α,α-trifluoro-2,6-dinitro-N-N-dipropyl-p-toluidine (trifluralin).
Carbon Supply Reduction has a Minimal Influence on Current Year's Red Raspberry (Rubus idaeus L.) Fruit Production
Authors: Fernandez Gina E. , Pritts Marvin P.
Published: January 2019

A 2-year study was conducted to investigate the influence of the light environment on source-sink relationships in `Titan' red raspberry. Treatments imposed included flower and cane removal in conjunction with partial or whole canopy shading. Raspberry plants were remarkably resistant to a reduction in carbon supply. Yields and primocane production were maintained even when canopies were shaded. Furthermore, if raspberry plants were prevented from producing a full crop in one year, yields the following year tended to be higher than normal. These data, and other studies demonstrating that raspberry roots are strong carbon sinks, suggest that raspberry plants may rely on stored carbohydrate to mature the current crop of fruits when current photosynthate is inadequate. This trait is characteristic of some perennial species adapted to progressively changing environments, but may not be optimal for horticultural situations where growing conditions are relatively constant from year to year. A large root storage capacity and excessive primocane production likely contribute to the relatively low yields that are typical of this species.
Effect of Night Temperature on Pollen Characteristics, Growth, and Fruit Set in Tomato
Authors: Peet Mary M. , Bartholemew Michael
Published: January 2019

Lycopersicon esculentum Mill. `Laura' plants were grown in the North Carolina State Univ. phytotron at 26C day temperature and 18, 22, 24, or 26C night temperatures to determine the effects of night temperature on pollen characteristics, growth, fruit set, and early fruit growth. Total and percentage normal pollen grains were higher in plants grown at night temperatures of 18 and 22C than at 24 and 26C, but germination was highest in pollen produced at 26C. Seed content was rated higher on the plants grown at 18C night temperatures than in any of the other treatments. Numbers of flowers and fruit on the first cluster were lower in the 26C night treatment than in the other night temperature treatments. Plant height was greatest but total shoot dry mass was lowest in the 22C night temperature treatments. Fruit fresh mass increased with night temperature, reflecting more rapid development, but the experiment was not continued to fruit maturity, so the effect of night temperature on final fruit size and total plant production could not be determined. Night temperatures of 26C reduced fruit number and percentage fruit set only slightly at a day temperature of 26C, even though these temperatures were above optimal for pollen production and seed formation. To separate temperature effects on pollen from direct or developmental effects on female reproductive structures, pollen was collected from plants in the four night temperature treatments and applied to stigmas of a male-sterile cultivar kept at 24-18C minimum temperatures in adjacent greenhouses. In the greenhouse-grown male sterile plants, no consistent effects of night temperature treatment given the pollen could be seen in fruit set, fruit mass, seed content (either on a rating or seed count basis), seedling germination, or seedling dry mass.
A Comparison of Four Processing Tomato Production Systems Differing in Cover Crop and Chemical Inputs
Authors: Creamer Nancy G. , Bennett Mark A. , Stinner Benjamin R. , Cardina John
Published: January 2019

Four tomato production systems were compared at Columbus and Fremont, Ohio: 1) a conventional system; 2) an integrated system [a fall-planted cover-crop mixture of hairy vetch (Vicia villosa Roth.), rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and barley (Hordeum vulgare L.) killed before tomato planting and left as mulch, and reduced chemical inputs]; 3) an organic system (with cover-crop mixture and no synthetic chemical inputs); and (4) a no-input system (with cover-crop mixture and no additional management or inputs). Nitrogen in the cover-crop mixture above-ground biomass was 220 kg·ha-1 in Columbus and 360 kg·ha-1 in Fremont. Mulch systems (with cover-crop mixture on the bed surface) had higher soil moisture levels and reduced soil maximum temperatures relative to the conventional system. Overall, the cover-crop mulch suppressed weeds as well as herbicide plots, and no additional weed control was needed during the season. There were no differences in the frequency of scouted insect pests or diseases among the treatments. The number of tomato fruit and flower clusters for the conventional system was higher early in the season. In Fremont, the plants in the conventional system had accumulated more dry matter 5 weeks after transplanting. Yield of red fruit was similar for all systems at Columbus, but the conventional system yielded higher than the other three systems in Fremont. In Columbus, there were no differences in economic return above variable costs among systems. In Fremont, the conventional systems had the highest return above variable costs.
Root Restriction and Potassium and Calcium Solution Concentrations Affect Dry-matter Production, Cation Uptake, and Blossom-end Rot in Greenhouse Tomato
Authors: Bar-Tal A. , Pressman E.
Published: January 2019

Root restriction has been reported to reduce fruit yield, the incidence of blossom end rot (BER) and K concentration in tomato (Lycopersicon esculentum L. `F121') plant organs. The objectives of the present work were to study the effect of root restriction, and combination of K and Ca solution concentrations, on greenhouse tomato fruit yield, quality and cation uptake. Root restriction reduced total yield but improved fruit quality by increasing the dry matter concentration and reducing the incidence of BER. Increasing the K concentration from 5.0 to 10 mmol·L-1 reduced the marketable yield, due to increased incidence of BER. Root restriction decreased K concentration and K/Ca ratio in tomato plant organs, but had no effect on K uptake rate per unit root fresh weight. Increasing K concentration from 2.5 to 10 mmol·L-1 increased the K concentration in plant organs and K uptake rate, but reduced that of Ca. In contrast, increasing Ca concentration in the solution had no effect on K concentration in plant organs and K uptake rate. The incidence of BER correlated well with K/Ca concentration ratio in the leaves, whereas a poor correlation was obtained with K/Ca concentration ratio in ripe fruit.
Influence of Whole-plant Net Calcium Influx and Partitioning on Calcium Concentration in Snap Bean Pods
Authors: Grusak Michael A. , Stephens Brian W. , Merhaut Donald J.
Published: January 2019

Snap beans (Phaseolus vulgaris L.) are a food source that can contribute to dietary Ca requirements in humans. Factors which might enhance the concentration of Ca in snap bean pods have been investigated by measuring whole-plant net Ca influx, whole-plant Ca partitioning, and various growth parameters in two snap bean cultivars—Hystyle and Labrador—that differ in pod Ca concentration. Plants were grown hydroponically under controlled environmental conditions while being provided adequate quantities of Ca. The concentration of Ca in pods (dry weight basis) was 52% higher in `Hystyle', relative to `Labrador', but net Ca influx throughout crop development or total plant Ca content at three stages of development were similar in both cultivars, demonstrating that pod Ca concentration differences were not due to differences in total plant Ca influx. However, `Hystyle' partitioned more total plant Ca to pods, relative to `Labrador'. Calcium flux analysis also revealed that daily rates of whole-plant net Ca influx gradually declined throughout the period of pod growth in both cultivars; this decline was not related to whole-plant water influx. These results suggest that enhancements in whole-plant net Ca influx during pod growth and/or enhancements in the xylem transport of absorbed Ca to developing pods could increase the Ca concentration of snap bean pods.
Nitrogen Fertigation Requirements of Drip-irrigated Strawberries
Authors: Hochmuth George J. , Albregts Earl E. , Chandler Craig C. , Cornell John , Harrison Jay
Published: January 2019

Strawberries (Fragaria ×ananassa Duch.) were grown in two seasons at Dover, Fla., with polyethylene mulch and drip irrigation. Nitrogen was injected weekly at 0.28 (50), 0.56 (100), 0.84 (150), 1.12 (200), and 1.40 (250) kg N/ha per day (kg·ha-1 for season) for `Oso Grande' and `Sweet Charlie' in 1991-92 season and for `Oso Grande' and `Seascape' in 1992-1993 season. Nitrogen fertilization in 1991-1992, over the range of 0.28 to 1.40 kg N/ha per day, had no significant effect on early (November to January) strawberry yields. March (the largest production month) yield and total-season yield increased with increasing N fertilization to 0.76 and 0.54 kg N/ha per day, respectively. Nitrogen fertilization did not affect yields of strawberry in 1992-93. Fruit firmness and average fruit weight were not affected by N fertilization from 0.28 to 1.40 kg N/ha per day. Nitrogen fertilization increased whole leaf N, leaf blade N, and petiole sap nitrate-N concentrations linearly for most sampling dates in both years. Early yields were greater for `Sweet Charlie' than `Oso Grande'. Yields were greater for `Oso Grande' during March, and total-season yields were similar for both cultivars in 1991-92. `Oso Grande' had greater early, March, and total yields than `Seascape' in 1992-93.
Sod Competition in Peach Production: I. Managing Sod Proximity
Authors: Glenn D.M. , Welker W.V. , Greene George M.
Published: January 2019

Mature peach trees were grown in six different-sized vegetation-free areas (VFAs) (0.36 to 13 m2) with and without stage 3 drip irrigation for 6 years. As VFA size increased, so did the trunk cross-sectional area, canopy diameter, total yield/tree, large fruit yield/tree, and pruning weight/tree. The yield efficiency of total fruit and large fruit initially increased with the increasing size of VFAs and then remained stable over the range of VFAs. Applying supplemental irrigation increased yield of large fruit and leaf N percentage in all VFAs. Cold hardiness was not affected by VFA size or irrigation treatment. The smaller VFAs resulted in smaller, equally efficient trees. Sod management was an effective, low-cost approach to controlling peach tree size, and, when combined with irrigated, high-density production, potentially increased productivity.
Quantifying the Relationship between Phases of Stem Elongation and Flower Initiation in Poinsettia
Authors: Fisher Paul R. , Heins Royal D. , Lieth J. Heinrich
Published: January 2019

Stem elongation of poinsettia (Euphorbia pulcherrima Klotz.) was quantified using an approach that explicitly modelled the three phases of a sigmoidal growth curve: 1) an initial lag phase characterized by an exponentially increasing stem length, 2) a phase in which elongation is nearly linear, and 3) a plateau phase in which elongation rate declines as stem length reaches an asymptotic maximum. For each growth phase, suitable mathematical functions were selected for smooth height and slope transitions between phases. The three growth phases were linked to developmental events, particularly flower initiation and the first observation of a visible flower bud. The model was fit to a data set of single-stemmed poinsettia grown with vegetative periods of 13, 26, or 54 days, resulting in excellent conformance (R2 = 0.99). The model was validated against two independent data sets, and the elongation pattern was similar to that predicted by the model, particularly during the linear and plateau phases. The model was formulated to allow dynamic simulation or adaptation in a graphical control chart. Model parameters in the three-phase function have clear biological meaning. The function is particularly suited to situations in which identification of growth phases in relation to developmental and horticultural variables is an important objective. Further validation under a range of conditions is required before the model can be applied to horticultural situations.
Natural Chilling and Limited Inductive Photoperiod Affect Flowering in Two Asteraceae Genera
Authors: Damann M. Peggy , Lyons Robert E.
Published: January 2019

To examine the effects of chilling and a limited inductive photoperiod (LIP) on flowering of Chrysanthemum superbum Bergmans ex J. Ingram `G. Marconi' and `Snow Lady', Coreopsis grandiflora Hogg `Sunray', and Coreopsis lanceolata L. `Early Sunrise', seeds were sown and plants were maintained in the greenhouse in short days (SDs) for 7 weeks, followed by 4 months of natural outdoor chilling for all plants except 10 of each cultivar, which remained in the greenhouse under SDs for the duration of the experiment. Upon return to greenhouse conditions, 10 plants of each cultivar were placed in SDs, all other chilled plants were placed in long-days (LDs) and subsequently transferred to SDs after receiving 6, 8, 10, 12, 14, 16, 18, 20, or 22 LD cycles. Ten chilled plants of each cultivar remained in LDs for the duration of the experiment. Continuous SDs without chilling resulted in 70%, 40%, 20%, and 10% flowering in `Snow Lady', `Early Sunrise', `Sunray,' and `G. Marconi', respectively. Chilling, followed by a return to continuous SDs, improved flowering in all cultivars compared to SDs without chilling. The number of LD cycles required for 100% flowering varied with cultivar. Ninety percent of the chilled `Early Sunrise' plants flowered with no LD cycles, and 100% flowering was produced by as few as six LD cycles. In `Snow Lady', 100% flowering occurred in chilled plants with no LD cycles and those receiving at least 10 LD cycles. With only six or eight LD cycles, 90% and 80% of these plants, respectively, still flowered. The percentage of `G. Marconi' and `Sunray' plants flowering ranged from 40% to 100% in the chilled treatments, with a general trend for more flowering with an increase in the number of LD inductive cycles. Continuous LDs following chilling resulted in as high or higher percent flowering than any other treatments (100% for `G. Marconi' and 90% for `Sunray'). The effects of LIP were evident in both Coreopsis cultivars but in neither Chrysanthemum superbum cultivar. There was a linear relationship between the number of LDs received and stem length at first flower in `Sunray' and `Early Sunrise'. In both cultivars, a reduction in stem elongation of about 10 cm occurred when plants received only 6 LDs compared to 22 LDs. The number of days from the start of LDs to first flower increased linearly as the number of LD cycles before the transfer back to SDs increased.
Differential Effects of Ethephon and Seniphos on Color Development of `Starking Delicious' Apple
Authors: Larrigaudiere C. , Pinto E. , Vendrell M.
Published: January 2019

The differential effects of two color improving products, ethephon an ethylene-releasing compound, and seniphos, a nonethylene-releasing product, were studied on `Starking Delicious' apples (Malus domestica Borkh L.). Ethephon and seniphos were applied 2 or 3 weeks before commercial harvest. Ethephon- and seniphos-treated fruit showed a significant improvement of peel color associated with a sharp increase in anthocyanin content and chromaticity values. Color improvement in ethephon-treated apples occurred during the preharvest period and cold storage. The seniphos-treated fruit stopped color development in cold conditions. In comparison to the ethephon-treated fruit, the seniphos-treated apples showed lower internal ethylene concentrations and a ripening delay. Both treatments sharply increased the activity of phenylalanine-ammonia-lyase enzyme, which seemed to be the determining factor of color enhancement. The seniphos-treated apples compared to ethephon had higher fruit firmness and lower soluble solids concentrations. Anthocyanin biosynthesis may be enhanced by seniphos treatment without inducing ethylene production or other ripening associated changes. As a consequence, fruit treated with seniphos can be held longer in storage.
Relative Performance of Strawberry Cultivars from California and other North American Sources in Fumigated and Nonfumigated Soils
Authors: Shaw Douglas V. , Larson Kirk D.
Published: January 2019

Performance characteristics for eighteen strawberry cultivars (Fragaria ×ananassa), nine from California and nine from other North American sources, were evaluated in annual hill culture, with and without preplant soil fumigation (2 methyl bromide : 1 chloropicrin, 392 kg·ha-1). Plants grown in nonfumigated soil yielded 57% and 46% of the fruit produced by plants on adjacent fumigated soil for cultivars from California and other North American origins, respectively. Plants in nonfumigated soils also developed fruit with lower berry weight (94% and 95% of fumigated trials) and smaller spring plant diameter (83% and 76%) for California and other sources, respectively. Trait values for exotic cultivars ranged from 39% to 80% of those for California cultivars, and the variance component due to germplasm sources explained 41% to 81% of the phenotypic variance of random effects in the experiment. Conversely, significant germplasm source × fumigation interactions were not detected for any of the growth or performance traits evaluated, and the proportion of variance attributable to these interactions was at most 2% of that due to germplasm source. These results demonstrate that strawberry growth and productivity for California and other North American germplasm sources are increased similarly by fumigation. Despite differing selection history, germplasm developed outside of California contains no obvious genetic diversity useful for developing cultivars specifically adapted to the sublethal effects of organisms in nonfumigated soils.
Founding Clones, Inbreeding, Coancestry, and Status Number of Modern Apple Cultivars
Authors: Noiton Dominique A.M. , Alspach Peter A.
Published: January 2019

Pedigrees of apple (Malus ×domestica Borkh.) cultivars were used to study worldwide genetic diversity among clones used in modern apple breeding. The most frequent founding clones were `Cox's Orange Pippin', `Golden Delicious', `Red Delicious', `Jonathan', and `McIntosh'. Coefficients of coancestry between 50 mainstream cultivars and these clones averaged 0.03, 0.12, 0.07, 0.06, and 0.02, respectively, but they were frequently as high as 0.25 with certain pairings. Among a group of 27 cultivars carrying the Vf gene for scab resistance, coefficients of coancestry with the five founding clones were of the same order. Although few of the cultivars sampled were substantially inbred, inbreeding could reach serious levels in their future offspring if current breeding practices are continued. The status effective number was 8 for the mainstream group and 7 for the Vf-carrier clones. This indicates clearly that apple breeders are operating with a population of greatly reduced genetic diversity. Careful consideration of pedigrees and increased size of the genetic base are needed in future apple breeding strategies.
Molecular Markers Associated with Plant Architecture and Resistance to Common Blight, Web Blight, and Rust in Common Beans
Authors: Jung Geunhwa , Coyne Dermot P. , Skroch Paul W. , Nienhuis James , Arnaud-Santana E. , Bokosi James , Ariyarathne H.M. , Steadman James R. , Beaver James S. , Kaeppler Shawn M.
Published: January 2019

Random amplified polymorphic DNA (RAPD) markers were used to construct a partial linkage map in a recombinant inbred population derived from the common bean (Phaseolus vulgaris L.) cross BAC 6 × HT 7719 for studying the genetics of disease resistance in common bean. The linkage map spanned 545 cM and included 75 of 84 markers used in this study. The population of 128 recombinant inbred lines was evaluated for resistance to common bacterial blight, foliar resistance to web blight [WB; Thanatephorus cucumeris (Frank) Donk], and resistance to rust [Uromyces appendiculatus var. appendiculatus (Pers.:Pers) Unger]. Common bacterial blight [CBB; Xanthomonas campestris pv. phaseoli (Smith) Dye] resistance was evaluated for CBB strain Epif-IV in later-developed trifoliolate leaves and for CBB strain EK-11 in seeds, first trifoliolate leaves, later-developed trifoliolate leaves, and pods. In addition, lines were rated for plant uprightness and branch density. Two to six markers accounted for 14% to 34% of the phenotypic variation for each trait. Significant marker locustrait associations were found for 14 mapped loci and 7 of the 9 unmapped markers. The distribution of detected QTL appeared to be nonrandom with most significant markers associated with more than one trait or closely linked to markers significantly associated with variation for a different trait. One marker, BC4091250, was significantly associated with WB resistance, resistance for CBB strain Epif-IV in later-developed trifoliolate leaves, and resistance for CBB strain EK-11 in first trifoliolate leaves, later-developed trifoliolate leaves, and pods. A rust resistance gene was mapped in an interval 14.6 cM from RAPD marker H191050 and 12.5 cM from marker AJ16250.
Nitrogen Nutrition of New Guinea Impatiens `Barbados' and Spathiphyllum `Petite' in a Subirrigation System
Authors: Kent Matthew W. , Reed David Wm.
Published: January 2019

Greenhouse cultural methods must minimize runoff to keep pace with environmental regulation aimed at protecting water resources. Two experiments were designed to investigate the effect of N fertilization rate on New Guinea impatiens (Impatiens ×hawkeri) and peace lily (Spathiphyllum Schott) in an ebb-and-flow subirrigation system. Maximum growth response for impatiens was centered around 8 mm N levels as measured by root and shoot fresh and dry weight, height, leaf number, leaf area, and chlorophyll concentration. For peace lily, growth peaked at about 10 mm N. Growing medium was divided into three equal layers: top, middle, and bottom. Root distribution favored the middle and bottom layers, and the relative distribution of roots was consistent as N level increased. EC remained low in middle and bottom layers at N concentrations below 10 mm, but increased significantly for all layers at levels above 10 mm. The EC for the top layer was 2 to 5 times higher than in the middle or bottom layers at all N levels. Increased nitrate concentration paralleled increased EC, while pH decreased as N concentration increased for impatiens and peace lily.
Mechanical Conditioning for Controlling Excessive Elongation in Tomato Transplants: Sensitivity to Dose, Frequency, and Timing of Brushing
Authors: Garner Lauren C. , Björkman Thomas
Published: January 2019

During production of plug transplants, the high plant density results in rapid stem elongation as plants compete for light. The resulting tall, weak-stemmed plants are difficult to transplant and are easily damaged. One technique that can prevent excessive elongation is mechanical stimulation by brushing. Wide adoption of brushing is limited by a lack of information on how plants respond to variations in applying the technique. Our investigation examined how tomato (Lycopersicon esculentum cv. Oh8245) seedling growth responded to varying doses of mechanical stimulation, varying intervals between brush strokes during stimulation, time of day that stimulation was applied, and growth stage at which application started. Seedlings were grown in 288-cell flats at 2100 plants/m2. Daily doses from 0 to 40 brush strokes were applied from canopy closure until the nontreated plants reached a canopy height of 15 cm. The final height was reduced by ≈20% for all brushed treatments, with little further effect with >10 strokes/d. Intervals between strokes as long as 10 minutes resulted in the same reduction in the rate of stem elongation as the same daily dose applied in one continuous treatment. Treatments were similarly effective whether applied in the morning or late afternoon. Treatments begun at a canopy height of 6 (canopy closure), 8, or 10 cm gave similar reductions in the rate of stem elongation. Plants grew 6 mm·d-1 when they were not treated and 3 mm·d-1 when treated. Therefore, the final height was directly related to the number of treatment days. Stimulation appears to be sensed and integrated over at least half an hour and the reduction in the rate of stem elongation expressed over the subsequent daily cycle of growth. All results indicate that there is substantial flexibility in applying brushing for controlling elongation in tomato transplants.
A Climatic Model for Pecan Production under Humid Conditions
Authors: Sparks Darrell
Published: January 2019

A multiple regression model was developed from historical data, 1945-92, to predict pecan [Carya illinoensis (Wangenh.) C. Koch] production in a humid climate. Variables were production trend (year of production), previous year's production, and climatic indices for the previous and current year. Production trend was used to measure change in production with time. Previous year's production was the index of alternate bearing. Variables for previous year's climate were heating degree-days for April-October and cumulative rainfall during May-July and 1-15 Sept. Variables for current year's climate were cumulative rainfall during April-August and 1-15 Sept. The indicator used for scab [Cladosporium caryigenum (Ell. & Langl.) Gottwald] infection was the highest cumulative sum of 2 or more days of consecutive rain occurring in May, June, or 1-15 July. The R2 for the model was 0.908. Production trend was the most important factor influencing production during the 1945-92 study period. Importance of the other variables in decreasing order were previous year's rainfall in May-July, consecutive rainy days, previous year's production, current year's 1-15 Sept. rainfall, previous year's heating degree-days, previous year's rainfall for 1-15 Sept., and current year's rainfall during April-August. Previous year's conditions had a greater effect on production than current year's. The recent decline in pecan production in the southeastern United States is due to an unfavorable change in climate.