bluuebunny/crossref_metadata_2025 huggingface dataset:
The Response of Nectarine Fruit Size and Midday Stem Water Potential to Irrigation Level in Stage III and Crop Load
Authors: Naor A. , Hupert H. , Greenblat Y. , Peres M. , Kaufman A. , Klein I.
Published: January 2019

The interactions between irrigation and crop level with respect to fruit size distribution and midday stem water potential were investigated for 3 years in a nectarine (Prunus persica L. `Fairlane') orchard located in a semi-arid zone. Wide ranges of crop loads and irrigation rates in stage III were employed, extending from practically nonlimiting to severely limiting levels. Irrigation during stage III of fruit growth ranged from 0.63 to 1.29 of potential evapotranspiration (ETp). Fruit were hand thinned to a wide range of fruit levels (300 to 2000) fruit/tree in the 555-tree/ha orchard. The yields and stem water potentials from 1996, 1997 and 1998 were combined together and the interrelations among yield, crop load and stem water potential were examined. Fruit <55 mm in diameter growing at 400 fruit per tree were the only ones not affected by irrigation level. The yield of fruit of 60 to 75 mm in diameter increased with irrigation level, but only a slight increase was observed when the irrigation rate rose above 1.01 ETp. A significant decrease in the yields of 60 to 65, 65 to 70, and 70 to 75-mm size grades occurred at crop levels greater than 1000, 800, and 400 fruit per tree, respectively. Midday stem water potential decreased with increasing crop level, and it is suggested that midday stem water potential responds to crop load rather than crop level. Relative yields of the various size grades were highly correlated with midday stem water potential. It was suggested that the midday stem water potential integrates the combined effects of water stress and crop load on nectarine fruit size.
Nitrogen Leaching in Sand-based Rootzones Amended with Inorganic Soil Amendments and Sphagnum Peat
Authors: Bigelow Cale A. , Bowman Daniel C. , Cassel D. Keith
Published: January 2019

sand-based rootzones are specified for golf course putting greens because they resist compaction and maintain drainage, even under heavy traffic. Although sands provide favorable physical properties, nutrient retention is generally poor and soluble nutrients like nitrogen (N) are prone to leaching. Laboratory experiments were conducted to evaluate several inorganic soil amendments (clinoptilolite zeolite (CZ), diatomaceous earth, and two porous ceramics), which varied in cation exchange capacity (CEC), and sphagnum peat for their ability to limit N leaching. Columns (35 cm tall × 7.6 cm diameter) were filled with 30 cm of sand-amendment mixtures (8:2 v/v) and NH4NO3 was applied in solution at a N rate of 50 kg·ha-1. Leaching was initiated immediately using 2.5 pore volumes of distilled water in a continuous pulse. Leachate was collected in 0.1 pore volume aliquots and analyzed for NH4+-N and NO3--N. All amendments significantly decreased NH4+ leaching from 27% to 88% which was directly proportional to the CEC of the amendments. By contrast, NO3- losses were consistently high, and no amendment effectively decreased loss compared to nonamended sand. Two amendments with the highest CECs, CZ and a porous ceramic, were selected to further study the effects of amendment incorporation rate, depth, and incubation time on N leaching. Ammonium but not NO3- leaching was decreased with increasing amendment rate of both products. At 10% amendment (v/v) addition, only 17% to 33% of applied NH4+ leached from the amended sands. Depth of amendment incorporation significantly affected NH4+ leaching, with uniform distribution through the entire 30 cm tall column being more effective than placement within the upper 2.5 or 15 cm. Allowing the NH4NO3 to incubate for 12 or 24 hours following application generally did not affect the amount leached. These results suggest NH4+-N leaching is inversely related to CEC of the root-zone mixture and that uniform distribution of these CEC enhancing amendments in the root-zone mixtures reduced N leaching to a greater extent than nonuniform distribution.
Association of Dark Opening of Stomata with Air Pollution Sensitivity of Irish Potatoes
Authors: Goknur Atilla B. , Tibbitts Theodore W.
Published: January 2019

The magnitude of dark opening of stomata on leaves of Irish potato (Solanum tuberosum L.) was studied to determine if this opening was related to the high sensitivity of these plants to air pollutants. Stomatal opening was studied over diurnal periods both in the field and in controlled environments. In both environments, stomatal conductance decreased rapidly at the initiation of dark to 0.1 cm·s-1 but then increased to 0.2 cm·s-1 over the dark period. However conductance was always less in the dark than in the light (0.3 to 0.9 cm·s-1). During the early part of the dark period, stomatal conductance in controlled environments was not as great as in the field, but conductance was similar in both environments over the latter part of the dark period. Cultivars Norchip and Kennebec had smaller conductances during the first hours of the dark than Haig or Katahdin, and all cultivars increased in conductance over the dark period. `Haig' showed slightly higher conductance than the other three during the last 4 hours of the dark period. Injury to `Haig' from 3-hour fumigations with sulfur dioxide (SO2) or ozone (O3) demonstrated that exposures during the day generally produced more injury than during the night, although exposures with SO2 during the last 3 hours of the light period produced similar injury to exposures at the end of the dark period. Thus, although partial opening during the dark may be permitting some pollution injury, it is concluded that previous published reports of similar opening of stomata on Irish potatoes during the light and dark periods, and equal or greater pollution injury during the dark compared with the light period, were not substantiated and apparently resulted from procedural artifacts.
Air Temperature, Humidity, and Leaf Age Affect Penetration of Urea Through Grapefruit Leaf Cuticles
Authors: Orbović Vladimir , Achor Diann , Petracek Peter , Syvertsen James P.
Published: January 2019

Effects of air temperature, relative humidity (RH), and leaf age on penetration of urea through isolated leaf cuticles of `Marsh' grapefruit (Citrus×paradisi Macfad.) trees on `Carrizo' citrange (C. sinensis L. Osbeck × Poncirus trifoliata (L.) Raf. rootstock were examined. Intact cuticles were obtained from adaxial surfaces of `Marsh' grapefruit leaves of various ages. A finite dose diffusion system was used to follow movement of 14C-labeled urea from urea solution droplets across cuticles throughout a 4-day period. Within the first 4 to 6 hours after urea application, the rate of urea penetration increased as temperature increased from 19 to 28 °C, but there was no further increase at 38 °C. Increasing relative humidity increased urea penetration at 28 °C and 38 °C. Cuticle thickness, cuticle weight per area, and the contact angle of urea solution droplets increased as leaves aged. Cuticular permeability to urea decreased as leaf age increased from 3 to 7 weeks, but permeability increased in cuticles from leaves older than 9 weeks. Contact angles decreased with increased urea solution concentration on leaf surfaces that were 6 to 7 weeks old, but solution concentration had no effect on contact angle on cuticles from younger and older leaves. Changing urea solution pH from 8.0 to 4.0 could have an effect on the amount of urea penetrating the cuticle through the loss of urea from breakdown possibly due to hydrolysis. Results from this study define leaf age, environmental conditions, and formulation for maximum uptake of foliar-applied urea.
Heritability and Genetic Variance Estimates for Leaf and Stem Resistance to Gummy Stem Blight in Two Cucumber Populations
Authors: Amand Paul C. St. , Wehner Todd C.
Published: January 2019

Heritability of resistance to gummy stem blight (Didymella bryoniae (Auersw.) Rehm.) was measured in two diverse cucumber (Cucumis sativus L.) populations [North Carolina elite slicer 1 (NCES1) and North Carolina wide base pickle (NCWBP)]. Heritability was estimated using parent-offspring regression and half-sib family analysis in North Carolina field tests during 1991 and 1992. NCES1 is a slicing cucumber population with a narrow genetic base, and NCWBP is a pickling cucumber population with a wide genetic base. Heritability estimates were low to moderate ranging from 0.12 to 0.49 for the gummy stem blight leaf rating and from -0.03 to 0.12 for stem rating. Estimates of gain from selection were at least two times larger for selection based on half-sib families than for mass selection for all traits in both populations. Approximately three to five cycles of selection would be required to improve the NCES1 population mean for gummy stem blight leaf resistance by one rating scale unit, and three to four cycles of selection would be required to improve the NCWBP population mean for gummy stem blight leaf resistance by one rating scale unit, based on half-sib family selection. One rating scale unit decrease is equivalent to an 11% reduction in susceptibility. Gain would be slower if selecting for stem, or leaf and stem resistance. A moderate amount of additive genetic variation exists in both populations for gummy stem blight leaf resistance, but estimates for additive genetic variation for stem resistance indicate little to no additive genetic variation. Development of populations specifically for greater initial resistance and greater additive variance than found in these populations should aid in selection for resistance.
Generation Means Analysis of Leaf and Stem Resistance to Gummy Stem Blight in Cucumber
Authors: Amand Paul C. St. , Wehner Todd C.
Published: January 2019

Leaf and stem resistance to gummy stem blight [Didymella bryoniae (Auersw.) Rehm.] in five resistant by susceptible crosses of cucumber (Cucumis sativus L.) was investigated using generation means analysis. No single gene of major effect controls either leaf or stem resistance to gummy stem blight in these five crosses. The mean number of effective factors controlling leaf resistance in the cross `Slice' × `Wis. SMR 18' was estimated to be at least five. Estimates of broad- and narrow-sense heritabilities indicated that environmental effects were larger than genetic effects. In general, additive variance was the larger component of genetic variance. Epistasis was significant in most crosses, and dominance was present in several crosses. Additive gene effects contributed more to resistance than to susceptibility in contrast with dominance gene effects. Reciprocal differences for leaf rating were detected in the crosses M 17 × `Wis. SMR 18' and `Slice' × `Wis. SMR 18'. Phenotypic correlations between leaf and stem ratings were moderate (r = 0.52 to 0.72). Estimates of genetic gain for resistance to gummy stem blight ranged from low to moderate. Breeding methods that make best use of additive variance should be used because much of the variance for resistance is additive, and dominance effects, at least in these crosses, tended to contribute to susceptibility.
Sulfur Nutrition Affects Cellular Sulfur, Dry Weight Distribution, and Bulb Quality in Onion
Authors: Lancaster Jane E. , Farrant Julie , Shaw Martin L.
Published: January 2019

Three onion (Allium cepa L.) cultivars, `Southport White Globe', `Grano', and `Pukekohe Longkeeper' were grown at low to high S (at 0.5, 1.8, 3.0 or 4.0 meq·L-1) in hydroponic culture. Differential solvent extractions of bulbs were used to isolate quantitatively cell contents, cell wall proteins, and cell wall residue. The weight of the cell fractions, their S content, and the S content of intact bulbs were determined. Bulb characteristics of fresh weight (FW), firmness, soluble solids concentration (SSC), and soluble sugars were also determined. For all three cultivars, bulb FW increased with S from 0.5 to 4.0 meq·L-1. Sulfur had a significant effect on bulb firmness. Onion bulbs grown with S at 0.5 meq·L-1, the lowest S concentration, were significantly softer than onion bulbs grown at the highest concentration of 4.0 meq·L-1. Varying the S supply had a major effect on dry weight (DW) allocation to the cell wall residue. Bulbs of all three cultivars grown at the lowest S had significantly less DW in the cell walls compared to S at 3.0 or 4.0 meq·L-1. In contrast to the effect of S supply on DW allocation, varying S supply had no effect on total bulb S, free SO4-2, and on the S content of the cell contents and the cell wall residue and only a minor effect on cell wall proteins. There was no significant effect of S supply on either SSC or soluble sugars. At low S nutrition, which is limiting to the growth of onion bulbs, cell wall deposition is reduced, with a consequent decrease in bulb firmness. The S composition of the cellular components is maintained at the expense of bulb growth.
Genotype of Apple Trees Affects Growth and Fruiting Responses to Shoot Bending at Various Times of Year
Authors: Lauri Pierre-Éric , Lespinasse Jean-Marie
Published: January 2019

Growing shoots of two apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] genotypes differing in shoot architecture, the preselection X.3318 and the cultivar `Chantecler', were bent on three dates during the summer and one in the winter to evaluate the interactive effects of shoot architecture and bending date on lateral shoot development and growth over 3 years. Bending X.3318, with a high proportion of vegetative lateral shoots on 1-year-old wood, on different dates did not change the percentage of lateral budbreak (62% to 65%). However, bending in June or July increased lateral growth on 1- and 2-year-old wood in a mesotonic position, whereas bending in winter reduced lateral growth and redistributed the shoots more basitonically. Both number and weight of fruits were reduced by bending. In `Chantecler', which forms many flower buds on 1-year-old wood, bending during flower bud formation (June-July) increased the percentage of lateral budbreak (60% vs. 45% for the control) and the number of flower buds. After 3 years of development, early summer treatments reduced the abortion of laterals as compared to the control. As a consequence, bending increased the number, as well as the weight of fruit. These results show that the effects of bending on the development and growth patterns of lateral shoots vary with genotype.
Genetic and Environmental Variation for Tomato Flesh Color in a Population of Modern Breeding Lines
Authors: Sacks Erik J. , Francis David M.
Published: January 2019

The genetic and environmental variation for flesh color of tomato (Lycopersicon esculentum Mill.) fruit was quantified using 41 red-fruited breeding lines, open-pollinated cultivars, and hybrids that are representative of the diversity of tomatoes grown for whole-peel processing in the midwestern and eastern United States and Ontario, Canada. Objective color measurements were made for 2 years from replicated experiments with 2 to 4 blocks per year. Genotypes differed significantly in lightness value (L*), saturation (chroma), and hue angle. Variation within fruit and among fruit in plots accounted for more than 75% of the environmental variation for the color traits. The crimson locus (ogc) accounted for less than one-third of the variation in fruit color among genotypic means, and explained 18% to 27% of the genotypic variation for L*, chroma, and hue. Estimates of variance components were used to develop sampling strategies for improving selection efficiency. Genotypes were identified that may be useful for studying genetic differences that lead to quantitative variation for fruit color in red-fruited populations of tomato.
Irrigation and Crop Load Influence Fruit Size and Water Relations in Field-grown `Spadona' Pear
Authors: Naor Amos
Published: January 2019

Interrelations between water potential and fruit size, crop load, and stomatal conductance were studied in drip-irrigated `Spadona' pear (Pyrus communis L) grafted on quince C (Cydonia oblonga L.) rootstock and growing in a semi-arid zone. Five irrigation rates were applied in the main fruit growth phase: rates of 0.25, 0.40, 0.60, 0.80, and 1.00 of “Class A” pan evaporation rate. The crop in each irrigation treatment was adjusted to four levels (200 to 1200 fruit per tree) by hand thinning at the beginning of June 1999. The crop was harvested on 1 Aug. 1999, and fruit size was determined by means of a commercial sorting machine. Soil, stem, and leaf water potentials and stomatal conductance were measured during the season. Crop yield was highly correlated with stem and soil water potentials. The highest midday stem water potential was lower than values commonly reported for nonstressed trees, and was accompanied by high soil water potential, indicating that the maximal water absorption rate of the root system under those particular soil conditions was limited. Stomatal conductance was highly correlated with leaf water potential (r2 = 0.54), but a much better correlation was found with stem water potential (r2 = 0.80). Stomatal conductance decreased at stem water potentials less than -2.1 MPa. Both stem water potential and stomatal conductance were unaffected by crop load under a wide range of irrigation rates.
Variation in Floral Induction Requirements of Hibiscus sp.
Authors: Warner Ryan M. , Erwin John E.
Published: January 2019

Thirty-six Hibiscus L. species were grown for 20 weeks under three lighting treatments at 15, 20, or 25 ± 1.5 °C air temperature to identify flowering requirements for each species. In addition, species were subjectively evaluated to identify those species with potential ornamental significance based on flower characteristics and plant form. Lighting treatments were 9 hour ambient light (St. Paul, Minn., November to May, 45 °N), ambient light plus a night interruption using incandescent lamps (2 μmol·m-2·s-1; 2200 to 0200 hr), or ambient light plus 24-hour supplemental lighting from high-pressure sodium lamps (100 μmol·m-2·s-1). Five day-neutral, six obligate short-day, six facultative short-day, three obligate long-day, and one facultative long-day species were identified. Fifteen species did not flower. Temperature and lighting treatments interacted to affect leaf number below the first flower and/or flower diameter on some species. Hibiscus acetosella Welw. ex Hiern, H. cisplatinus St.-Hil., H. radiatus Cav., and H. trionum L. were selected as potential new commercially significant ornamental species.
Growth and Development of Oenothera fruticosa Is Influenced by Vernalization Duration, Photoperiod, Forcing Temperature, and Plant Growth Regulators
Authors: Clough Emily A. , Cameron Arthur C. , Heins Royal D. , Carlson William H.
Published: January 2019

Influences of vernalization duration, photoperiod, forcing temperature, and plant growth regulators (PGRs) on growth and development of Oenothera fruticosa L. `Youngii-lapsley' (`Youngii-lapsley' sundrops) were determined. Young plants were vernalized at 5 °C for 0, 3, 6, 9, 12, or 15 weeks under a 9-hour photoperiod and subsequently forced in a 20 °C greenhouse under a 16-hour photoperiod. Only one plant in 2 years flowered without vernalization, while all plants flowered after receiving a vernalization treatment, regardless of its duration. Thus, O. fruticosa had a nearly obligate vernalization requirement. Time to visible bud and flower decreased by ≈1 week as vernalization duration increased from 3 to 15 weeks. All plants flowered under 10-, 12-, 13-, 14-, 16-, or 24-hour photoperiods or a 4-hour night interruption (NI) in a 20 °C greenhouse following 15-weeks vernalization at 5 °C. Time to flower decreased by ≈2 weeks, flower number decreased, and plant height increased as photoperiod increased from 10 to 16 hours. Days to flower, number of new nodes, and flower number under 24 hour and NI were similar to that of plants grown under a 16-hour photoperiod. In a separate study, plants were vernalized for 15 weeks and then forced under a 16-h photoperiod at 15.2, 18.2, 20.6, 23.8, 26.8, or 29.8 °C (average daily temperatures). Plants flowered 35 days faster at 29.8 °C but were 18 cm shorter than those grown at 15.2 °C. In addition, plants grown at 29.8 °C produced only one-sixth the number of flowers (with diameters that were 3.0 cm smaller) than plants grown at 15.2 °C. Days to visible bud and flowering were converted to rates, and base temperature (Tb) and thermal time to flowering (degree-days) were calculated as 4.4 °C and 606 °days, respectively. Effects of foliar applications of ancymidol (100 mg·L-1), chlormequat (1500 mg·L-1), paclobutrazol (30 mg·L-1), daminozide (5000 mg·L-1), and uniconazole (15 mg·L-1) were determined on plants vernalized for 19 weeks and then forced at 20 °C under a 16-h photoperiod. Three spray applications of uniconazole reduced plant height at first flower by 31% compared with that of nontreated controls. All other PGRs did not affect plant growth. Chemical names used: α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); (2-chloroethyl) trimethylammonium chloride (chlormequat); butanedioic acid mono-(2,2-dimethyl hydrazide) (daminozide); (2R,3R+2S,3S)-1-(4-chlorophenyl-4,4-dimethyl-2-[1,2,4-triazol-1-yl]) (paclobutrazol); (E)-(S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3-ol (uniconazole).
Influence of Irradiance and Period of Exposure on Fruit Set of French-American Hybrid Grapes
Authors: Ferree D.C. , McArtney S.J. , Scurlock D.M.
Published: January 2019

Vines of container grown `DeChaunac', `Vidal blanc', `Seyval blanc' and `Chambourcin' grapes were subjected to 5 days of 80% shade at prebloom, bloom or 2 and 4 weeks after bloom. Fruit set, cluster weight, berries per cluster and juice components [soluble solids concentration (SSC), pH and titratable acidity] of `DeChaunac' and `Vidal blanc' were not affected by a short period of intensive shade. `Chambourcin' was sensitive to a shade period near the time of bloom for most of the aforementioned factors, while `Seyval blanc' was intermediate in sensitivity. Shot (green, hard, and undersized) berries of `Chambourcin' and `Seyval blanc' were increased by a 5-day period of shade 2 or 4 weeks after bloom. In a second study, container-grown `Chambourcin' on 3309C (V. riparia × V. rupestris) with one or two clusters and `Vidal blanc' with one cluster were subjected to the following light regimes beginning at bloom for 5 weeks: supplemental light, ambient greenhouse light and 30%, 50% or 80% shade. Yield, fruit set, specific leaf weight (leaf dry weight/leaf area), saturation index, and total leaf chlorophyll increased linearly with increasing irradiance. `Chambourcin' juice pH, SSC, leaf chlorophyll a/b ratio, cluster color development and hue angle decreased as irradiance increased, likely related to crop reduction. Responses in `Vidal blanc' followed similar trends, but differences were not as great. Results demonstrate that light is an important determining factor in fruit set of French-American hybrid grapes and fruit set of some cultivars are sensitive to short periods of intense shade.
Transmission Ratio Distortion Due to the bl Gene in Table Beet
Authors: Austin Diane , Goldman I.L.
Published: January 2019

The bl gene conditions a blotchy phenotype (irregular sectors of red and white root color) in table beet (Beta vulgaris ssp. vulgaris). Segregation of the bl gene was found to be consistent with a single recessive gene, however, some evidence for a departure from a single gene model was observed when blbl plants were used as females. In this report, segregation of the bl gene was examined in greater detail in 10 F2 populations derived from crosses of red blotchy-rooted females (genotype blbl, denoted blotchy) with red-rooted males (BlBl, denoted red,), and 10 F2 populations derived from the reciprocal cross. In blbl × BlBl crosses, the proportion of red-rooted progeny was greater than 0.75 in seven of the crosses, and was significantly greater (P = 0.005) in three crosses. A test for heterogeneity was significant, indicating that the proportion of red-rooted progeny differed significantly in these 10 crosses. In BlBl × blbl crosses, the proportion of red-rooted progeny was <0.75 in seven of the crosses and there were no significant departures from the expected 3:1 ratio in any of the individual crosses. However, a pooled estimate of the segregation ratio showed a significant (P < 0.01) departure from the 3:1 ratio (pooled estimate = 0.71). These data demonstrate transmission ratio distortion at the bl locus when blbl plants are used as both females and males in matings with wild type plants, but the degree of distortion is greater when blbl plants are used as females. Ratio distortion in such crosses may be due to a variety of factors, including increased transmission of the bl gene through female or male gametes depending on the direction of the cross, reduced fitness of maternally derived blbl progeny, epigenetic phenomena, increased fitness of paternally derived blbl progeny, or linkage of the bl gene to viability genes.
Sucrose Metabolism During Papaya (Carica papaya) Fruit Growth and Ripening
Authors: Zhou Lili , Paull Robert E.
Published: January 2019

Papaya (Carica papaya L.) fruit flesh and seed growth, fruit respiration, sugar accumulation, and the activities of sucrose phosphate synthase (SPS), sucrose synthase (SS), and acid invertase (AI) were determined from anthesis for ≈150 days after anthesis (DAA), the full ripe stage. Sugar began to accumulate in the fruit flesh between 100 and 140 DAA, after seed maturation had occurred. SPS activity remained low throughout fruit development. The activity of SS was high 14 DAA and decreased to less than one-fourth within 56 DAA, then remained constant during the remainder of fruit development. AI activity was low in young fruit and began to increase 90 DAA and reached a peak more than 10-fold higher, 125 DAA, as sugar accumulated in the flesh. Results suggest that SS and AI are two major enzymes that may determine papaya fruit sink strength in the early and late fruit development phases, respectively. AI activity paralleled sugar accumulation and may be involved in phloem sugar unloading.
Can We Approach Complete Dependence on Foliar-applied Urea Nitrogen in an Early-maturing Peach?
Authors: Johnson R. Scott , Rosecrance Rich , Weinbaum Steve , Andris Harry , Wang Jinzheng
Published: January 2019

The suspected contributory role of soil fertilization to nitrate pollution of groundwater has encouraged exploration of novel fertilizer management strategies. Foliar-applied urea has long been used to supplement soil N applications, but there have been no apparent attempts to replace soil N applications completely in deciduous orchard culture. Two experiments were conducted to study the effect of foliar-applied low biuret urea on productivity and fruit growth of the early maturing peach [Prunus persica L. Batsch (Peach Group)] cultivar, Early Maycrest. In a 3-year experiment, a total foliar urea regime was compared to an equivalent amount of N applied to the soil. The foliar treatment supplied adequate amounts of N to the various organs of the tree including the roots, shoots, and fruit buds, but mean fruit weights were lower than in the soil-fertilized treatment. In a 2-year experiment, a 50%-50% combination treatment of soil-applied N in late summer with foliar-applied N in October, maintained yields and fruit weight equal to the soil-fertilized control. Some soil-applied N appears necessary for optimum fruit growth. Soil N application may be needed to support root proliferation and associated processes, but we did not determine a threshold amount of soil-applied N needed. The combination treatment also reduced excessive vegetative growth which is characteristic of early maturing peach cultivars. Therefore, this combination treatment offers promise as a viable commercial practice for maintaining tree productivity and controlling excessive vegetative growth in peach trees.
Differences in Phenology and Reserve Carbohydrate Concentrations Between Dormant and Nondormant Production Systems in Southern Highbush Blueberry
Authors: Swain P.A.W. , Darnell R.L.
Published: January 2019

Two cultivars of southern highbush blueberry (Vaccinium corymbosum L. interspecific hybrid), `Sharpblue' and `Wannabe', were container-grown outside in either a dormant or nondormant production system to determine how the two production systems affected carbohydrate (CH2O) status, growth, and development. Plants were maintained in the nondormant condition by continuous N fertilization throughout winter (average maximum/minimum temperatures of 17/5 °C). Plants in the nondormant system retained their foliage longer into the winter compared with plants in the dormant system. Flower bud number, density, fruit number, and total fruit fresh weight (FW) per plant were greater in the nondormant compared with the dormant system plants for both cultivars. Mean fruit FW was greater in dormant compared with nondormant `Wannabe' plants, while in `Sharpblue', mean fruit FW was similar in both systems. Cane and root CH2O concentrations in nondormant system plants were generally similar to or lower than those measured in dormant system plants. Assuming that longer leaf retention in nondormant system plants increased CH2O synthesis compared with dormant system plants, the patterns of reproductive/vegetative development and root/shoot CH2O concentrations indicate that the increased CH2O in nondormant system plants was allocated to increased reproductive growth in lieu of CH2O reserve accumulation. It is probable that this increased CH2O availability, combined with longer perception of short days due to longer leaf retention, were major factors in increasing flower bud initiation and yield in the nondormant compared with the dormant system plants.
Biochemical Changes during Fruit Development of Four Strawberry Cultivars
Authors: Moing Annick , Renaud Christel , Gaudillère Monique , Raymond Philippe , Roudeillac Philippe , Denoyes-Rothan Béatrice
Published: January 2019

As genetic factors affect strawberry (Fragaria ×ananassa Duch.) fruit development and quality, changes in metabolite concentrations were studied during fruit development of four strawberry cultivars grown in the field: three commercial cultivars (Capitola, Elsanta and Dover) and a genotype from Centre Interrégional de Recherche et d'Expérimentation de la Fraise, France (`CF1116'). Major and minor metabolites changed with development. The two strawberry cultivars with the highest starch content at early stages, `Capitola' and `Elsanta', also had the highest fruit weight at harvest. There was no correlation between strawberry weight and osmolarity. At maturity, significant differences were observed among cultivars for most of the metabolites studied. `Capitola' and `Elsanta' responded similarly for most measured variables. `CF1116' was characterized by high juice osmolarity and high sucrose, inositol, glutamine, arginine and alanine concentrations, and low citrate and malate concentrations. `Dover' was characterized by a high galactose concentration and low asparagine and alanine concentrations. Organic acid differences among cultivars appeared early during development, while differences in soluble sugars appeared during maturation. The developmental pattern of each amino acid varied among cultivars. Timing of the biochemical differences observed among cultivars provides some information on their metabolic origin.
Physiological Factors Affecting Response of Mature `Valencia' Orange Fruit to CMN-Pyrazole. I. Effects of Young Fruit, Shoot, and Root Growth
Authors: Yuan Rongcai , Hartmond Ulrich , Grant Angela , Kender Walter J.
Published: January 2019

Influence of young fruit, shoot, and root growth on response of mature `Valencia' oranges [Citrus sinensis (L.) Osbeck] to the abscission chemical CMN-pyrazole was examined in 1999 and 2000. CMN-pyrazole dramatically increased ethylene production in mature fruit and reduced the fruit detachment force (FDF), except during a period of reduced response to CMN-pyrazole in early May when spring vegetative growth, young fruit of the following year's crop, and mature fruit were all on the trees. Removal of spring flushes, which included spring vegetative shoots and leafy and leafless inflorescences, prevented any young fruit and shoot growth, but did not inhibit root growth. However, trunk girdling in combination with removal of spring flushes not only prevented growth of young fruit and shoots but also inhibited root growth. During the responsive period, there were no differences in either ethylene production or FDF of CMN-pyrazole-treated mature oranges between 1) the nonmanipulated trees and those manipulated by either 2) removal of spring flushes alone, or 3) in combination with trunk girdling. However, during the less responsive period, ethylene production in CMN-pyrazole-treated mature oranges was significantly lower while the FDF was higher in nonmanipulated trees than in trees treated by either removal of spring flushes alone, or in combination with trunk girdling. There was no difference in either fruit ethylene production or FDF between trees manipulated by (2) removal of spring flushes alone, and (3) removal of spring flushes in combination with trunk girdling regardless of CMN-pyrazole application. Shoot growth terminated at least 2 weeks before the onset of the less responsive period. Removal of young fruit increased response of mature fruit to CMN-pyrazole during the less responsive period. This suggests that hormones from rapidly growing young fruit may be responsible for the occurrence of the less responsive period. Chemical name used: 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMN-pyrazole).
Inheritance and Linkage of Tomato Mottle Virus Resistance Genes Derived from Lycopersicon chilense Accession LA 1932
Authors: Griffiths P.D. , Scott J.W.
Published: January 2019

Tomato mottle virus (ToMoV) is a silverleaf whitefly (Bemisia argentifolii Bellows and Perring n. sp.) transmitted, bipartite geminivirus that infects tomatoes (Lycopersicon esculentum Mill.). Inbred lines resistant to ToMoV were derived from Lycopersicon chilense Dunal accession LA 1932. Inheritance was studied using a family developed from the crossing of a resistant inbred with a susceptible tomato inbred over two seasons. The F1 had resistance intermediate to the parents and generation means analysis of F1 and F2, backcross and parental populations suggested that the action of at least two additive genes with high heritability (h2n.s. = 0.87) controlled ToMoV resistance. When data from the two seasons were combined, an acceptable fit to an additive-dominance genetic model was obtained. Single plant comparisons, bulk comparisons, and tailends of F2 populations segregating for ToMoV resistance derived from LA 1932 identified randomly amplified polymorphic DNA (RAPD) markers using eight hundred 10-mer oligonucleotide primers. The F2 populations used for inheritance studies were screened for polymorphic markers, and 12 RAPD markers associated with the ToMoV resistant line were linked to the morphological markers self-pruning (sp) and potato leaf (c) on chromosome 6. RAPD markers that were associated with ToMoV resistance segregated into two linked regions flanking either side of the sp and c loci. The molecular studies suggested that the action of at least two additive regions controlled ToMoV resistance which supported the inheritance analysis.
Estimating Mean Fruit Weight and Mean Fruit Value for Apple Trees: Comparison of Two Sampling Methods with the True Mean
Authors: Marini Richard P.
Published: January 2019

Data obtained over two years from chemical thinning experiments with `Redchief Delicious' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Manst.] on Malling 26 (M.26) rootstock were used to estimate mean fruit weight (MFW) and mean fruit value (MFV) using two sampling methods. The estimated values were compared with the true MFW and the true MFV calculated from the entire crop from a tree. Statistical techniques were used to assess agreement between the values obtained with estimation methods and the true values. Estimates of MFW obtained from a 20-fruit sample per tree may differ from the true value by ≈13% and estimates obtained from weighing all fruit on three limbs per tree may range from 11% to 19% of the true mean. Estimates of MFV obtained from packouts of a 20-fruit sample may differ from the true value by about $0.04 (U.S. dollars)/fruit and estimates from packing out all fruit on three limbs per tree may differ from the true mean by about $0.07/fruit. Analysis of variance was performed on each data set. The resulting P values differed for the three methods of calculating MFW and MFV. Therefore, erroneous conclusions may result from experiments where MFW and MFV are estimated from subsamples. Error associated with estimating fruit weight and fruit value from the sampling methods employed in this study may be larger than many pomologists can accept. Until protocols for sampling apple trees, which account for the important sources of within-tree variation, are developed, researchers should consider harvesting the entire crop to calculate MFW and MFV.
Decrease of Pollen Stainability of Green Bean at High Temperatures and Relationship to Heat Tolerance
Authors: Suzuki Katsumi , Tsukaguchi Tadashi , Takeda Hiroyuki , Egawa Yoshinobu
Published: January 2019

Pod yield of `Kentucky Wonder' green bean (Phaseolus vulgaris L.) decreased at high temperatures due to a reduction of pod set. A highly positive correlation was observed between pod set and pollen stainability in flowers that were affected by heat stress about 10 days before anthesis. Pollen stainability was decreased by heat stress applied 8 to 11 days before flowering under controlled environment conditions. When mean air temperature during this period exceeded 28 °C, pollen stainability decreased under field conditions. Low pollen stainability indicated sensitivity to high temperatures about 10 days before flowering. A heat-tolerant cultivar showed higher pollen stainability than did heat-sensitive cultivars under high temperatures. These results demonstrated that heat tolerance at an early reproductive stage could be evaluated by analyzing pollen stainability using flowers developed under high temperatures.
A Multistate Comparison of Native Octoploid Strawberries from North and South America
Authors: Hancock J.F. , Finn C.A. , Hokanson S.C. , Luby J.J. , Goulart B.L. , Demchak K. , Callow P.W. , Serçe S. , Schilder A.M.C. , Hummer Kim E.
Published: January 2019

An elite group of 38 strawberry accessions representing all subspecies of the beach strawberry [Fragaria chiloensis (L.) Miller] and the scarlet strawberry (F. virginiana Miller) was planted in a replicated design at five locations across the United States, and evaluated for plant vigor, flowering date, runner density, fruit set, fruit appearance, and foliar disease resistance. Considerable genotyp× location interaction was observed for many of these traits. However, a few genotypes were impressive at all locations including PI 551735 (FRA 368) with its unusually large, early fruit, and PIs 612486 (NC 95-19-1), 612493 (Frederick 9), and 612499 (RH 30), which were very vigorous and had unusually good fruit color. Genotypes that were superior at individual locations included PIs 551527 (FRA 110) and 551728 (Pigeon Pt.) in Maryland for their large fruit, and PI 612490 (Scotts Creek) in Oregon which had extremely large fruit, superior color, firmness, and flavor. The PIs 612495 (LH 50-4), 612498 (RH 23), and 612499 (RH 30) performed well as day neutrals at multiple sites.
Barriers for Introgression of Solanum ochranthum into Tomato via Somatic Hybrids
Authors: Stommel John R.
Published: January 2019

Solanum ochranthum Dunal is a nontuber bearing wild relative of the cultivated tomato (Lycopersicon esculentum Mill.), and a potential source of new genes for disease and pest resistance. Because S. ochranthum is sexually isolated from tomato, somatic hybrids between tomato (PI 367942; L. esculentum Mill. var. cerasiforme (Dunal) A. Gray VFNT cherry × L. peruvianum (L.) Mill. backcrossed to VFNT cherry) and S. ochranthum (LA2117) were developed previously to overcome these crossing barriers. Attempts to backcross these hybrids to tomato have been unsuccessful. Pollen fertility and mitotic and meiotic studies in tomato + S. ochranthum somatic hybrids determined the cause of the sterility of the somatic hybrids and identified hybrids with moderate fertility. Chromosome counts of dividing root tip cells delineated tetraploid (2n = 4x = 48) and hexaploid (2n = 6x = 72) genotypes and aneuploidy in these hybrids. Meiotic analysis of developing microspores confirmed the presence of precocious division and laggard chromosomes at anaphase in both hexaploid and tetraploid hybrids. Bridges were observed in hexaploids at anaphase I and II and multivalent configurations were observed at diakinesis. Multivalents and univalents were evident in nearly all cells examined, proving that the two genomes are homoeologous. Aberrant microsporocytes with five to six developing microspores were noted in hexaploid hybrids. The occurrence of homoeologous pairing between chromosomes of both fusion parents is advantageous to effect recombination between these isolated species. However, the negative effects of multivalent formation and univalents likely contributed to observed sterility in these first generation fusion hybrids. Low to moderate levels of pollen fertility (0% to 52%) were found in tetraploid hybrids, while little or no viable pollen (0% to 4%) was observed in hexaploid somatic hybrids.
Metabolic Contributors to Drought-enhanced Accumulation of Sugars and Acids in Oranges
Authors: Hockema Brandon R. , Etxeberria Ed
Published: January 2019

The nature of sink strength in orange fruit and changes occurring during drought stress were investigated. Potted trees of `Hamlin' orange [Citrus sinensis (L.) Osbeck] grafted on Troyer citrange [Citrus sinensis × Poncirus trifoliata (L.) Raf.] were irrigated using a microsprinkler system creating either well-watered or water-stressed conditions, as determined by stem water potentials. Fruit were harvested every other week from trees of both well-watered and drought-stressed treatments during the final stage of fruit development when sugars accumulate rapidly. Fruit quality indices and activities of sucrose synthase (SuSy), invertase, sucrose-P synthase, sucrose-P phosphatase, V-ATPase, and V-PPase were measured. Acids and soluble sugar concentrations were elevated in drought-stressed fruit, whereas juice pH decreased in those same fruit. Results indicate that increased sink strength in fruit from stressed trees was accompanied by an increase in SuSy activity and lowered juice pH. The remaining enzymes examined in this experiment showed no changes in activity between control and treated fruit, as was the case for plasmalemma and tonoplast sucrose carriers. Based on the present data, we conclude that SuSy and vacuolar pH are the predominant factors controlling photoassimilate accumulation in orange fruit under enhanced sink conditions brought about by imposition of a mild drought stress.
Harvest Maturity, Storage Temperature, and 1-MCP Application Frequency Alter Firmness Retention and Chlorophyll Fluorescence of `Redchief Delicious' Apples
Authors: Mir Nazir A. , Curell Erin , Khan Najma , Whitaker Melissa , Beaudry Randolph M.
Published: January 2019

Fruit of `Redchief Delicious' apple [Malus sylvestris (L) Mill. var. domestica (Borkh.) Mansf.] were harvested 1 week before the climacteric (harvest 1), at the onset of the climacteric (harvest 2), and 1 week after the onset of the climacteric (harvest 3). Fruit were stored at 0, 5, 10, 15, or 20 °C and were treated with 0.7 μL·L-1 1-MCP on a once-per-week, once-per-2-week, once-per-month, and once-per-year basis or were left nontreated. The initial 1-MCP treatment was at 20 °C and subsequent applications were at storage temperatures. The compound slowed softening at all temperatures relative to nontreated fruit, however as temperature decreased, the benefits of 1-MCP application became less pronounced. Effectiveness of 1-MCP declined slightly as harvest maturity increased. Efficacy of 1-MCP treatment increased with greater frequency of application at 5, 10, 15, and 20 °C, but not at 0 °C. Fruit stored without refrigeration (20 °C) for more than 100 days did not soften significantly when treated once per week with 1-MCP. However, decay was a significant problem for treated and nontreated fruit stored at temperatures >5 °C; 1-MCP application reduced, but did not prevent decay. Rate of decline in titratable acidity increased with storage temperature and 1-MCP had no significant effect on retarding the decline in acid content. Minimal (Fo) and maximal (Fm) chlorophyll fluorescence was altered markedly by 1-MCP application, but the ratio of (Fm-Fo)/Fm was only slightly affected. The most effective 1-MCP treatment frequency was once per week and, at all elevated temperatures (5, 10, 15, and 20 °C), slowed loss of firmness to a greater extent than refrigeration (0 °C) alone. Application of 1-MCP resulted in greater retention of firmness than controlled atmosphere (CA) with O2 and CO2 at 1.5 kPa and 3 kPa, respectively. Data suggest that 1-MCP application, has the potential to reduce reliance on refrigeration and CA storage for maintaining firmness of `Redchief Delicious' apple, especially for relatively short storage durations (<50 days) when fruit are harvested within a week of the ethylene climacteric. Chemical name used: 1-methylcyclopropene (1-MCP).
Effectiveness of Fall versus Spring Soil Fertilization of Field-grown Peach Trees
Authors: Niederholzer F.J.A. , DeJong T.M. , Saenz J.-L. , Muraoka T.T. , Weinbaum S.A.
Published: January 2019

Marginally nitrogen (N)-deficient, field-grown peach trees [Prunus persica (L.) Batsch (Peach Group) 'O' Henry'] were used to evaluate seasonal patterns of tree N uptake, vegetative growth, and yield following fall or spring fertilization. Sequential tree excavations and determinations of tree biomass and N contents in Feb. and Aug. allowed estimation of N uptake by fall-fertilized trees between September 1993 and mid-February 1994. Total N uptake (by difference) by spring- fertilized trees as well as additional N uptake by fall-fertilized trees over the spring.summer period was also determined. In fall-fertilized trees, only 24% of tree N accumulation between September 1993 and August 1994 occurred during the fall/dormancy period. Spring- and fall-fertilized trees exhibited comparable vegetative growth, fruit size, and yield despite lower dormant tree N contents and tissue N concentrations in the spring-fertilized trees. Fifty percent of tree leaf N content was available for resorption from leaves for storage in woody tree parts. This amount (N at ~30.kghhhhhhha-1) was calculated to represent more than 80% of the N storage capacity in perennial tree parts of fertilized peach trees. Our data suggest that leaf N resorption, even without fall soil N application, can provide sufficient N from storage to initiate normal growth until plant-available soil N is accessed in spring.