bluuebunny/crossref_metadata_2025 huggingface dataset:
Inheritance of Vernalization Requirement in Carrot
Authors: Alessandro María S. , Galmarini Claudio R.
Published: January 2019

Carrot (Daucus carota L.) is a cool-season vegetable normally classified as a biennial or winter annual species, requiring vernalization to induce flowering. Nevertheless, some cultivars adapted to warmer climates require less vernalization and can be classified as early flowering or annual. The genetic control of this phenotypic difference has not been previously studied in carrot. The authors evaluated F1, F2, and BC1 progenies of an intercross between the early-flowering carrot (‘Criolla INTA’) and a late-flowering biennial carrot. F1 progenies were completely annual. Observed segregation ratios in the F2 and BC1 families were not significantly different from expected segregation ratios under the hypothesis of a single dominant gene conditioning the early-flowering habit. The authors conclude that annual habit is dominant over biennial and is a monogenic character.
Distribution of Rose Black Spot (Diplocarpon rosae) Genetic Diversity in Eastern North America Using Amplified Fragment Length Polymorphism and Implications for Resistance Screening
Authors: Whitaker Vance M. , Hokanson Stan C. , Bradeen James
Published: January 2019

Black spot, incited by the fungus Diplocarpon rosae Wolf, is the most significant disease problem of landscape roses (Rosa hybrida L.) worldwide. The documented presence of pathogenic races necessitates that rose breeders screen germplasm with isolates that represent the range of D. rosae diversity for their target region. The objectives of this study were to characterize the genetic diversity of single-spore isolates from eastern North America and to examine their distribution according to geographic origin, host of origin, and race. Fifty isolates of D. rosae were collected from roses representing multiple horticultural classes in disparate locations across eastern North America and analyzed by amplified fragment length polymorphism. Considerable marker diversity among isolates was discovered, although phenetic and cladistic analyses revealed no significant clustering according to host of origin or race. Some clustering within collection locations suggested short-distance dispersal through asexual conidia. Lack of clustering resulting from geographic origin was consistent with movement of D. rosae on vegetatively propagated roses. Results suggest that field screening for black spot resistance in multiple locations may not be necessary; however, controlled inoculations with single-spore isolates representing known races is desirable as a result of the inherent limitations of field screening.
Nitrogen and Phosphorus Uptake Efficiency and Partitioning of Container-grown Azalea During Spring Growth
Authors: Ristvey Andrew G. , Lea-Cox John D. , Ross David S.
Published: January 2019

The influence of fertilization rate on nitrogen (N) and phosphorus (P) nutrient partitioning and uptake efficiency of young, container-grown azalea (Rhododendron L. ‘Karen’) was determined under controlled greenhouse conditions during Spring 2001 and 2002. In 2001, fertilizer treatments included a factorial combination of two N (25 or 250 mg/week) and three P (0, 5, or 25 mg/week) rates; in 2002, an additional N rate (100 mg/week) was included in the experimental design. Five destructive harvests were performed during each study; plant tissues (root, stem, primary and secondary branches and leaves) from each harvest were analyzed to derive total N and P uptake. Leachates from containers were monitored and analyzed weekly to calculate nitrate (NO3-N), ammonium (NH4-N), and orthophosphate (PO4-P) loss. Fertilization rates of 5 mg P per week in 2001 and rates of 100 mg N per week and 5 mg P per week in 2002 maintained optimal growth compared with the highest fertilization rates (250 mg N and 25 mg P per week) in these studies. Increasing N fertilization rate largely promoted shoot growth, whereas decreasing N and P fertilization rates promoted root growth and increased uptake efficiency. In general, increasing N and P fertilization rates increased nutrient N and P leaching from the pine bark substrate. Reducing excess N and P fertilization to match plant growth requirements of young azalea increases nutrient uptake efficiency and reduces nutrient loss to the environment.
Deposition and Strain of the Cuticle of Developing European Plum Fruit
Authors: Knoche Moritz , Peschel Stefanie
Published: January 2019

Time courses of change in 1) fruit mass and surface area, 2) deposition of the cuticular membrane (CM), 3) strain of the CM, and 4) formation of microcracks in the CM of developing fruit of european plum (Prunus domestica L. ssp. domestica) were established. Fruit mass, fruit surface area, and CM mass per fruit increased between 50 and 133 days after full bloom (DAFB). Rates of CM deposition were higher during early stage III (50–71 DAFB) when amounts of wax and cutin per fruit increased, resulting in an increase in CM thickness from 3.1 to 5.9 g·m−2. Thereafter, cutin deposition ceased and CM thickness decreased to 4.7 g·m−2 at 133 DAFB. Percentage strain, determined on enzymatically isolated CM disks using image analysis, slightly decreased from 12.0% at 50 DAFB to 4.5% at 71 DAFB, but increased thereafter, averaging about 40% at 133 DAFB. The breakpoint in the time course of strain at 71 DAFB corresponded to the change in rate of cutin deposition. Frequency of microscopic cracks in the CM was closely related to strain of the CM across different developmental stages within a cultivar (pedicel end and cheek region) and across different cultivars at maturity. There was little change in microscopic cracking up to ≈20% strain. However, microcracks markedly increased when strain exceeded 20%. Most microcracks (91.0% ± 3.7% at 133 DAFB) were associated with stomata. These data indicate that a mismatch between surface area expansion of the growing fruit and cutin deposition caused strain and subsequent microcracking of the CM of developing plum.
Gas Exchange, Water Status, and Growth of Pepper Seedlings Exposed to Transient Water Deficit Stress are Differentially Altered by Antitranspirants
Authors: Goreta Smiljana , Leskovar Daniel I. , Jifon John L.
Published: January 2019

Successful field establishment of vegetable transplants often depends on the ability of young seedlings to tolerate various biotic and abiotic stresses after transplanting. Treatments that limit transpirational water loss could improve plant survival and stand establishment. In this study we evaluated growth and physiological responses of pepper (Capsicum annuum L.) seedlings to foliar application of chemical plant regulators [abscisic acid (ABA) and aminoethoxyvinylglycine (AVG)] or physical film-forming barriers [AntiStress (AS), Transfilm (TF), and Vapor Gard (VG)] during transient 4-day water deficit cycles. During two 4-day water deficit cycles, stomatal conductance (g
s) and net CO2 assimilation rate (ACO2) were unaffected by the application of physical materials, but differed for ABA and AVG. Compared with untreated control plants, ABA reduced g
s (47% to 69%) and ACO2 (37% to 57%) by the end of the second water deficit cycle, whereas AVG increased gs (27% to 60%) during the first desiccation cycle. Leaf (ψlf) and stem (ψst) xylem water potential of plants treated with film-forming materials generally decreased at the same rate as those of untreated plants, whereas application of AVG caused earlier and more pronounced decline of ψlf. Application of ABA enabled the maintenance of ψlf and ψst during two desiccation cycles, and thus prevented an increase of electrolyte leakage and leaf abscission. Growth rates of all plant components were reduced after ABA applications. However, allometric relationships showed similar patterns of dry matter allocation in leaves and shoots among ABA, TF, VG, and untreated control plants. Application of AS reduced allocation of dry matter to leaves, whereas AVG enhanced it at the expense of roots. These data indicate that water deficit tolerance of pepper seedlings only occurred with foliar application of ABA. This effect was associated with improved plant water relations, increased cell membrane stability, reduced leaf abscission, and a transient reduction in plant growth rates.
Assessing Nitrogen and Potassium Deficiencies in Olive Orchards through Discriminant Analysis of Hyperspectral Data
Authors: Gómez-Casero M. Teresa , López-Granados Francisca , Peña-Barragán José M. , Jurado-Expósito Montserrat , García-Torres Luis , Fernández-Escobar Ricardo
Published: January 2019

Hyperspectral reflectance curves of olive (Olea europaea L.) trees under different N or K treatments, and the best wavelengths or vegetation indices to discriminate between different N or K applications using discriminant analysis were investigated. Field hyperspectral studies were carried out in two olive orchards located at Cabra and Lucena (southern Spain) for N and K experiments, respectively, in 2004 and 2005. At Cabra, olive trees have been fertilized since 1993, and annual applications of N per tree consisted of 0 kg (N0), 0.5 kg [N1 (normal)], or 1 kg [N2 (high)]. At Lucena, olive trees were fertilized since 1997, with 0%, 2.5%, and 5% K2CO3. Hyperspectral measurements were collected for each N and K treatments using a handheld field spectroradiometer (spectral range, 400–900 nm) in July of both years. To determine the nutritional status, a leaf analysis was carried out in July 2004 and 2005 at both locations. At Cabra, leaf N concentrations under N0 treatment were below the critical threshold, indicating nutritional deficiencies. Reflectance curves corresponding to N1 and N2 showed higher reflectance values in the near-infrared (NIR) plateau than N0 treatments. Wavelengths within the NIR region (from 710–900 nm) were selected in both years for discriminating between N treatments, with an overall accuracy of up to 99.2%. At Lucena, when K was not applied, leaf K content was below the critical threshold, indicating that olive trees were under a nutritional deficiency. Wavelengths from 710 to 890 nm, and the normalized difference vegetation index {NDVI = [(R780 – R670)/(R780 + R670]} were selected for discriminating K treatments with an overall accuracy of up to 94.4%. Classification matrices for cross-validation classified and misclassified cases into the nearest category. The results suggest that the induction of N or K nutritional deficiency for more than 10 years in olive trees resulted in different leaf nutrient contents, and this consistently affected hyperspectral reflectance curves, mainly in the NIR region. These results are promising and could provide information for further work on the identification of N- or K-deficient olive trees using remote sensing.
Gene Expression in the Star Mutation of Petunia ×hybrida Vilm
Authors: Griesbach Robert J. , Beck Ronald M. , Hammond John , Stommel John R.
Published: January 2019

Gene silencing is one of the ways in which gene expression is controlled. The authors have developed a model system to study anthocyanin gene silencing using a recessive mutation in Petunia Juss. (Star mutation) and the ability of certain viruses to reverse the gene silencing mutation. In healthy plants, the star pattern was enhanced (increase in level of gene silencing) under high temperature or light growing conditions. Virus infection did not significantly influence the star pattern when plants were grown under either low-light or low-temperature conditions. Under high-light and -temperature conditions, virus infection reverses silencing, leading to a change in the star pattern. These changes in the star pattern corresponded to changes in gene expression. Viral infection had a greater affect on regulatory gene (Wd40, Myc, and Myb) expression than on structural gene expression (Chs and Ans).
The Contribution of Sucrose Metabolism Enzymes to Sucrose Accumulation in Cucumis melo
Authors: Burger Yosef , Schaffer Arthur A.
Published: January 2019

The relationship between sugar accumulation and sucrose metabolism enzyme activities was studied among seven genotypes of Cucumis melo L., covering the broad genetic range of sucrose accumulation found in the species. The primary determinant correlated with sucrose levels was the genetic variation for developmental loss of soluble acid invertase (AI) activity. Sucrose accumulation in the developing fruit began only when AI activity declined to less than an experimentally determined threshold value, and continued until removal of the fruit from the plant. In addition, the activities of sucrose phosphate synthase (SPS), sucrose synthase (SuSy), and neutral invertase (NI) were all positively correlated with sucrose accumulation among the genotypes. The low-sucrose-accumulating genotypes were characterized by low activities of each of the three enzymes, irrespective of their invertase activities. Final sucrose content was best predicted for each genotype by the number of days the fruit remained attached to the plant while characterized by “sucrose accumulation metabolism,” which was characterized primarily by AI activity less than threshold values, together with SPS, SuSy, and NI activities higher than threshold levels.
Carbon Dioxide-induced Flesh Browning in Pink Lady Apples
Authors: de Castro Elena , Biasi Bill , Mitcham Elizabeth , Tustin Stuart , Tanner David , Jobling Jennifer
Published: January 2019

To investigate a flesh browning (FB) disorder in Pink Lady apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. cv. Cripps Pink], fruit were harvested from the same orchard each year from 2002 to 2005, at two or three maturity stages each year. Fruit were kept in air or controlled atmosphere (CA) storage (1.5- to 2-kPa O2 in combination with 1-, 3-, or 5-kPa CO2) at 0.5 °C. Additional subsets of fruit were exposed to 1 μL·L−1 1-methylcyclopropane (1-MCP) for 24 hours and dipped in 2200 μL·L−1 diphenylamine (DPA) for 5 min or held in air at 0.5 °C for 2 or 4 weeks before CA storage. Flesh browning was not seen in air-stored fruit but appeared in CA-stored fruit as soon as 2 months after harvest. Flesh browning incidence did not increase after longer storage times. Flesh browning increased with increasing CO2 concentration and decreasing O2 concentration in storage. 1-MCP did not significantly affect FB incidence, while delaying CA by 2 or 4 weeks reduced it. Diphenylamine eliminated FB incidence. When similar storage atmospheres were compared for the four seasons, FB incidence was high in 2002 and 2004 and low in 2003 and 2005. Concentrations of B, Ca, and Mg in apple flesh and seasonal field temperatures during the growing and harvest periods were related to FB incidence in 2002, 2003, and 2004 but not in 2005. The relationship of these pre- and postharvest factors to FB susceptibility are discussed.
Quality Changes in Cantaloupe During Growth, Maturation, and in Stored Fresh-cut Cubes Prepared from Fruit Harvested at Various Maturities
Authors: Beaulieu John C. , Lea Jeanne M.
Published: January 2019

Cantaloupe (Cucumis melo L. var. reticulatus Naudin) were evaluated during development and then fresh-cut cubes were stored after preparation from various maturities to track quality changes during storage. Flowers were anthesis tagged one morning in two seasons (years) and developing fruit were harvested weekly at 13, 20, 27 to 28, and 34 to 35 days after anthesis (DAA). Mature fruit were harvested at 37 to 38 DAA with five distinct maturities: 1/4-, 1/2-, 3/4-slip, full-slip (FS), and overripe (OR). Hunter L* and a* color values indicated a change from pale green to light orange that occurred 28 DAA. There were significant decreases in L*, a*, and b* by day 9 in storage (4 °C) as fresh-cut cubes. After 28 DAA, sucrose dramatically increased, and this was positively correlated with increases in both total sugars (r = 0.882, P = 0.084) and percent soluble solids concentration (r = 0.939, P = 0.041). Gradual deterioration occurred during storage, as determined by a uniform subjective quality criterion, which was independent of maturity. There was a negative linear trend in hand-held and instrumental firmness over the length of storage for each maturity level, and the slopes decreased significantly with increasing maturity, indicating the effect of storage duration decreased as harvest maturity increased. There was a significant increasing trend in vitamin C (P = 0.042) during development from 12 through 35 DAA, then losses were greater in fresh-cut cubes prepared from full-slip fruit (65%) than less-mature fruit: 3/4-slip, 50%; 1/2-slip, 48%; 1/4-slip, 40%. The pH of mesocarp tissue dropped to the lowest value (5.25) just before physiological maturity at 27 to 28 DAA, then peaked after harvest (6.51–6.79), and declined somewhat by the end of storage as fresh-cut cubes. In sum, muskmelon fruit used to produce fresh-cut cubes should be harvested ≥1/2-slip to attain optimum physiological quality and consumer acceptability.
Mapping Fruit Susceptibility to Postharvest Physiological Disorders and Decay Using a Collection of Near-isogenic Lines of Melon
Authors: Fernández-Trujillo Juan Pablo , Obando Javier , Martínez Juan Antonio , Alarcón Antonio Luis , Eduardo Iban , Arús Pere , Monforte Antonio José
Published: January 2019

Melon (Cucumis melo L.) is a perishable fruit that requires refrigeration to extend its shelf life. Postharvest behavior differs substantially among melon varieties due to genetic differences. In this work, we use a collection of near-isogenic lines (NILs) derived from a cross between the Spanish cultivar Piel de Sapo (PS) and an exotic Korean accession ‘Shongwan Charmi’ [SC (PI161375)], each of them with a single introgressed region from SC into the PS background, to detect and map quantitative trait loci (QTLs) involved in postharvest life traits, such as total losses, water-soaking, necrosis of the placental tissue, chilling injury (CI), decay, fruit over-ripening, flesh browning, hollow flesh disorder, and flavor loss during storage. Fruit were examined at harvest and after 35 days at 8 °C. Three QTLs induced desirable quality traits: flv4.1 reduced the loss of fruit flavor after refrigeration, tl8.1 reduced total losses, and fus8.4 reduced the susceptibility to fusarium rot (Fusarium Link). Another 11 QTLs produced a detrimental effect on other quality traits. The NIL population was useful for dissecting complex, difficult-to-measure pre- and postharvest disorder traits of different degrees of development and for investigating flavor loss during storage. Further studies with the QTLs described herein will shed light on the genetic control of melon shelf life and help breeders who are interested in this fruit quality trait.
Recovery and Partitioning of Nitrogen from Early Spring and Midsummer Applications to Pecan Trees
Authors: Smith Michael W. , Wood Bruce W. , Raun William R.
Published: January 2019

Effective nitrogen (N) management promotes consistent and abundant pecan [Carya illinoinensis (Wangenh.) C. Koch] production while minimizing waste. Recovery and partitioning characteristics of N potentially affects N management decisions; for this reason, we report certain N characteristics exhibited by trees in a bearing ‘Pawnee’ orchard. Nitrogen was applied prebudbreak (PBB) as a single 10 Mar. application at 1.689 g·cm−2 cross-sectional trunk area or a split application in Mar. (70%) followed by a midsummer application during rapid fruit development (RFD) on 28 July (30%) (i.e., PBB + RFD) using 15N-enriched fertilizer. Recovery of N by trees the first year was 7.2% from the PBB application and 11% from the RFD portion of the split application. Nitrogen application was 210% larger at PBB (Mar.) than at RFD (July), resulting in 118% more N absorbed. At harvest in November, fruit contained 41% and 36% of total N recovered during the first year from the PBB and RFD treatments, respectively. About 3% of the total fruit N was derived from fertilizer (NDF) absorption during the current year. Recovery was 12% for the PBB treatment and 19% for the RFD treatment by the end of the second growing season, with 93% more N absorbed from the PBB application. Nitrogen recovered from the PBB application increased ≈50% while trees were dormant, but there was little change in N recovery when applied during RFD. During the year of application, NDF was similar in shuck, shell, and kernel tissue when 15N-enriched fertilizer was applied PBB. When applied at RFD, more NDF was in the kernel than the shuck and shell, indicating rapid absorption and transport to the fruit, especially to the developing kernel. In both treatments, most fruit N was derived from tree storage reserves. In the second year, NDF was highest in shucks and lowest in kernels for the PBB application; thus, N enrichment from the previous year was being depleted. In contrast, NDF was higher in kernels than shucks and shells when 15N-enriched fertilizer was applied during RFD the previous year, indicating that N applied during RFD the previous July was being absorbed in the latter part of the subsequent growing season. This study demonstrates that pecan trees maintained with adequate N nutrition derived the majority of N used for annual parts from stored N pools, although applied N was also rapidly absorbed and transported to N sinks. Dependence on endogenous N pools explains why pecans usually require at least 2 years to respond when N is withheld from well-managed trees. These results emphasize the importance of maintaining an annual N fertility program for current and future production.
Histological Study of Expression of Seedlessness in Citrus kinokuni ‘Mukaku Kishu’ and Its Progenies
Authors: Yamasaki Atsu , Kitajima Akira , Ohara Norihiro , Tanaka Mitsutoshi , Hasegawa Kojiro
Published: January 2019

The factors of seedless expression in Citrus kinokuni hort. ex Tanaka ‘Mukaku Kishu’, ‘Southern Yellow’ {‘Tanikawa Buntan’ pummelo [an uncertain hybrid with C. maxima (Burm.) Merr.] × ‘Mukaku Kishu’}, and the hybrid seedling BSY lines of ‘Southern Yellow’ × Bu1-7 pummelo [chance seedling of ‘Suisho Buntan’ pummelo (C. maxima)] were investigated histologically. ‘Mukaku Kishu’, ‘Southern Yellow’, BSY18, and BSY21 are completely seedless, whereas others are seedy. The percentage of abnormal embryo sacs and fertilization in seedless cultivars and lines showed no differences from seedy ones, indicating that the seedlessness of ‘Mukaku Kishu’ and its progenies was not involved in abnormal embryo sacs and unfertilized ovules. In seedy cultivars and lines, embryos developed to the cotyledon stage by 14 weeks after pollination. In the seedless cultivars and lines, however, embryos only developed to the early stages of zygote or embryo development. These results indicate that the seedless expression of the seedless progenies of ‘Mukaku Kishu’ coincides with ‘Mukaku Kishu’ and is caused by an arrested seed development at the early stage.
Carbohydrate Content and Root Growth in Seeds Germinated Under Salt Stress
Authors: Leatherwood W. Roland , Pharr D. Mason , Dean Lisa O. , Williamson John D.
Published: January 2019

Sugars and sugar alcohols have well-documented roles in salt tolerance of whole plants and maturing seeds. Less is known, however, about possible effects of these compounds during germination. Seeds from mannitol-accumulating salt-tolerant celery [Apium graveolens L. var. dulce (P. Mill.) DC], non-mannitol-accumulating salt-tolerant cabbage (Brassica oleracea L. var. capitata L. ‘Golden Acre’), and salt-sensitive non-mannitol-accumulating tobacco (Nicotiana tabacum L.) and arabidopsis [Arabidopsis thaliana (L.) Heynh.] were placed on vertical Phytagel plates containing 0 to 300 mm NaCl. Germination percentage, root elongation, and carbohydrate content of seeds and seedlings were assessed. With the exception of cabbage, there was no positive relationship between ability to germinate in NaCl and the reported species salt tolerance of the mature plant. For instance, while cabbage seeds germinated in 300 mm NaCl, germination of two celery cultivars was inhibited completely by 150 mm NaCl. In contrast, seeds from salt-sensitive tobacco and arabidopsis germinated in 200 mm NaCl. There was also no obvious relationship between the observed salt tolerance and total soluble carbohydrates in either non-imbibed seeds or in seedlings germinated in salt. For example, the most-salt tolerant species in these studies, cabbage, had the third highest seed and seedling carbohydrate concentration, while the next most tolerant, arabidopsis, had the lowest. However, both species contained significant amounts of the osmoprotective oligosaccharides raffinose or stachyose. In addition, although celery seedling mannitol concentration initially increased at low NaCl concentrations (50 mm), germination and mannitol concentration decreased at higher NaCl concentrations (100 mm). Finally, the broadest response observed was a large increase in seedling sucrose at the lowest salt concentration that significantly inhibited germination. Although most seeds, with the notable exception of cabbage, did not germinate at 150 mm NaCl, they were still metabolically active because the sucrose content was two to eight times higher than in non-imbibed seeds, suggesting a possible role for sucrose in salt-stressed germinating seeds. These results not only suggest that mechanisms providing salt tolerance in mature plants are different from those in germinating seeds, but also that, even when the same mechanisms are employed, they may be less effective in seeds.
Drought Adaptation in Fuchsia magellanica and Its Effect on Freezing Tolerance
Authors: Pagter Majken , Petersen Karen K. , Liu Fulai , Jensen Christian R.
Published: January 2019

Fuchsia (Fuchsia L.) is a popular woody ornamental, but it is very susceptible to frost injury during winter. As drought stress may be used to enhance freezing tolerance in woody plants, the effects of different types of water deficit on growth, selected physiological traits, and freezing tolerance were examined in Fuchsia magellanica Lam. ‘Riccartonii’. Drought responses were investigated after 6 weeks of pretreatment, where individual plants grown in a greenhouse under conditions of unrestricted water supply were compared with plants subjected to cyclic or continuous water deficit. After an additional 4 weeks of treatment at short day (10 h) and low temperature (8 °C day/4 °C night), freezing tolerance was examined. Both continuous and cyclic water deficit plants reduced water loss by reducing aboveground biomass and by efficient stomatal regulation. Continuous water deficit plants tended to adjust osmotically, while cyclic water deficit induced significantly higher xylem sap abscisic acid [(ABA)xylem] and leaf proline concentrations and a lower leaf water potential (ψl) than continuous water deficit, indicating that F. magellanica responds differently to continuous water deficit and to fast drying associated with stress phases of cyclic water deficit. The root water potential (ψr) and (ABA)xylem were negatively linearly correlated, implying that increasing water deficiency stimulated formation of ABA in the roots. An inverse, curvilinear relation between (ABA)xylem and stomatal conductance (g
s) indicated that root-originated ABA might control g
s during mild water deficits. Neither cold-acclimating conditions alone nor combined with water deficit increased stem freezing tolerance, indicating that F. magellanica lacks cold-acclimation ability under the inductive conditions used in this study.
Identification of Melon Fruit Quality Quantitative Trait Loci Using Near-isogenic Lines
Authors: Obando Javier , Fernández-Trujillo Juan Pablo , Martínez Juan Antonio , Alarcón Antonio Luis , Eduardo Iban , Arús Pere , Monforte Antonio José
Published: January 2019

A collection of melon (Cucumis melo L.) near-isogenic lines (NILs) derived from the cross between the Spanish C. melo cultivar Piel de Sapo (PS) and the exotic Korean accession Shongwan Charmi [SC (PI161375)], was used to study the genetic control of a large number of melon fruit quality traits, including morphological, external appearance, texture, flavor, and the overall differences between NILs and PS that might be detected by consumers with a triangle test. Heritability was significant for all the traits, being >0.5 for the whole area of the longitudinal section of the fruit, flesh proportion, skin lightness color, hue angle coordinate of flesh color, and flesh-extractable juice. NILs were classified by principal-component analysis. The first principal component (22% of the variation) was affected mostly by morphological traits, the second component (10%) was influenced by internal and external morphology pattern and color, and the third component (9%) was controlled mainly by flavor traits. An average of 5.6 quantitative trait loci (QTL) per trait were identified (range, between 1 and 12 QTL; 134 QTL in total). In most cases, allele effects with opposite actions were detected. A substantial number of QTL may be good candidates to introduce new quality attributes in modern melon cultivars.
Differential Expression of Cell-wall–Modifying Genes and Novel cDNAs in Apple Fruit During Storage
Authors: Mann Harpartap S. , Alton Jennifer J. , Kim SooHee , Tong Cindy B.S.
Published: January 2019

During postharvest storage, apple [Malus pumila P. Mill.] fruit softens and its texture changes noticeably, with adverse effects on fruit quality. These changes are a result of degradation of the cell wall and middle lamella. Enzymes that cause changes in the cell walls have been characterized, but temporal distribution of their activities and their molecular regulation during storage is not well understood. ‘Honeycrisp’ fruit does not soften significantly during storage in contrast to fruit from ‘Macoun’, which softens significantly during storage. Contrasting phenotypes of ‘Honeycrisp’ and ‘Macoun’ were analyzed for changes in transcript levels of four cell-wall–modifying genes in fresh and 3-month-stored fruit from both cultivars. A suppression-subtractive hybridization experiment identified 15 cDNAs differentially expressed in fresh or 3-month-stored ‘Macoun’ fruit. Transcript levels of these 15 cDNAs were further quantified by quantitative real-time polymerase chain reaction (qRT-PCR) in fresh and 3-month-stored fruit from both ‘Macoun’ and ‘Honeycrisp’. The combination of a late increase in MdEXPA2 and decreased levels of MdPG and MdAFase1 transcript levels in ‘Honeycrisp’ fruit during storage may lead to its nonsoftening phenotype. Three cDNAs, potentially important for postharvest changes in apple fruit were also identified based on their different expression patterns in fresh and 3-month-stored ‘Macoun’ and ‘Honeycrisp’ fruit.
Drought Responses of Kentucky Bluegrass and Creeping Bentgrass as Affected by Abscisic Acid and Trinexapac-ethyl
Authors: McCann Stephen E. , Huang Bingru
Published: January 2019

The plant growth regulators abscisic acid (ABA) and trinexapac-ethyl (TE) may affect turfgrass responses to drought stress through regulating shoot growth and water relations. The objectives of this study were to investigate the effects of foliar application of TE and ABA on turf growth of two cool-season turfgrass species, Kentucky bluegrass (Poa pratensis L.) and creeping bentgrass (Agrostis stolonifera L.) exposed to drought stress, and to examine water relations associated with changes in drought tolerance due to TE or ABA treatment. ‘L-93’ creeping bentgrass and ‘Brilliant’ Kentucky bluegrass plants were foliar sprayed with 0.904 mL·ha−1 a.i. TE five times before exposure to drought or with 6.75 mL/week of ABA at 100 μm before and after exposure to drought in growth chambers. Drought stress was imposed by withholding irrigation until plants were permanently wilted. Foliar application of TE or ABA maintained higher soil volumetric water content, leaf relative water content, and turf quality for a longer period of time during 28 days of stress exposure for Kentucky bluegrass and creeping bentgrass compared with the untreated control. Leaves of TE-treated and ABA-treated plants in both species also had lower ψS at 28 days of drought stress than the untreated control. Creeping bentgrass treated with TE or ABA and Kentucky bluegrass treated with TE exhibited significantly lower shoot vertical growth rates at the initiation of drought stress, but maintained higher growth rates during prolonged drought compared with the untreated control. Turf treated with TE or ABA also showed higher levels of photochemical efficiency than the untreated control for both species. Our results suggest that TE or ABA application could prolong the survival of turfgrass under conditions of drought stress by suppressing shoot vertical growth and lowering water use during the early phase of drought and by sustaining growth and photosynthetic activity during prolonged periods of drought stress through osmotic adjustment for retaining cellular hydration.
Changes in Pigment Concentrations Associated with the Degree of Sunburn Browning of ‘Fuji’ Apple
Authors: Felicetti David A. , Schrader Larry E.
Published: January 2019

Significant changes in pigments were identified, quantified, and correlated to the changes in color associated with sunburn browning (SB) of ‘Fuji’ apples (Malus domestica Borkh.). Apples were sorted into five classes: NB, no sunburn; SB-1 to SB-4, increasing severity of sunburn browning. A decline in chlorophylls a and b and reduced anthocyanin accumulation with increased sunburn severity were observed. A significant increase in total quercetin glycosides was seen with slight sunburn (i.e., SB-1) with most of the increase resulting from increased quercetin 3-galactoside and quercetin 3-glucoside + quercetin 3-rutinoside. Quercetin glycosides increased modestly from SB-1 to SB-4, but few differences were statistically significant. β-carotene increased in sunburned apples both years, but changes in SB-3 and SB-4 were inconsistent between the 2 years. The xanthophylls were significantly higher (P < 0.05) in SB-1 than in NB, but no difference was detected from SB-1 to SB-4. Lutein, a xanthophyll, showed no change as a result of sunburn in either year. Hue angle was highly correlated (P < 0.05) to the concentrations of total chlorophylls, idaein, and total quercetin glycosides. Despite minor differences between growing seasons, the overall trends of decreased chlorophyll and idaein, and increased quercetin glycosides and carotenoids persisted. Lower chlorophyll and anthocyanin concentrations observed in the sunburned apples allowed the yellows from the carotenoids and quercetin glycosides to be more prominent. Additionally, the increases in carotenoid and quercetin glycoside concentrations of sunburned apples made the change in color more striking.
Growth and Physiological Responses to Drought Stress in Four Oleander Clones
Authors: Niu Genhua , Rodriguez Denise S. , Mackay Wayne
Published: January 2019

Oleander (Nerium oleander L.), native to southern Asia and the Mediterranean region, is a fast-growing evergreen shrub planted widely in the southern United States. A greenhouse study was conducted to quantify the growth and physiological responses of two cultivars, Hardy Pink and Hardy Red, and two breeding lines, EP1 and EP2, of oleander to a 12-week cyclic drought stress. Drought stress was imposed by irrigating the plants to near container capacity and then withholding irrigation until predetermined container weights were reached. Compared with the control where plants were well-irrigated throughout the experiment, shoot dry weight (DW) was reduced by 52%, 41%, 34%, and 11% in EP1, EP2, ‘Hardy Red’, and ‘Hardy Pink’, respectively. Root-to-shoot DW ratio was higher for the drought-treated plants than the control, regardless of cultivar or breeding line (hereafter, clone). The increase in root-to-shoot DW ratio from the drought treatment was highest in EP1, followed by EP2, ‘Hardy Pink’, and ‘Hardy Red.’ New shoot growth was greatest in ‘Hardy Pink’, followed by ‘Hardy Red’, EP1, and EP2. The number of newly developed shoots during the drought treatment period was 6.8, 3.0, 0.7, and 0.0 in ‘Hardy Pink’, ‘Hardy Red’, EP1, and EP2, respectively. As substrate volumetric moisture content decreased from 30%, leaf net photosynthetic rate (Pn), evapotranspiration rate (E), and stomatal conductance (gs) decreased in all clones. A curvilinear relationship between Pn and gs was found in all clones. EP1 had a lower maximum Pn (Pm) than those of ‘Hardy Pink’ and EP2 but was not different from that of ‘Hardy Red’. Predawn leaf water potential began to decrease rapidly when substrate moisture content dropped below 15% in all clones. During the dry-down, compared with the control, increases in minimal fluorescence (F0) or decreases in maximal fluorescence (Fm) and Fv/Fm (Fv = Fm – F0) in drought-stressed plants were observed in all clones, indicating some damage in photosystem II from the drought treatment. However, compared with growth parameters, the differences in physiological responses to drought stress among the clones were much smaller. ‘Hardy Pink’ was more tolerant to drought stress than ‘Hardy Red’ and the other two clones in terms of productivity because it maintained greatest growth during the drought-stress period. However, EP2 and EP1 may be more tolerant if survival is concerned because they had a higher root-to-shoot DW ratio with minimal new growth.
A Single Dominant Gene Ch for Chilling Resistance in Cucumber Seedlings
Authors: Kozik Elzbieta U. , Wehner Todd C.
Published: January 2019

An experiment was conducted to determine the genetics of chilling resistance in cucumber (Cucumis sativus L.) inbred NC-76 that was developed from PI 246930, an accession from the U.S. Department of Agriculture germplasm collection. NC-76 was crossed with ‘Chipper’ and breeding line Gy 14 to produce F1, F1 reciprocal, F2, and BC1 generations for evaluation. Cucumber seedlings at the first true leaf stage were placed in growth chambers set at 4 °C for 7 h and a photosynthetic photon flux of 500 μmol·m−2·s−1. Segregation in the F2 fit a 3 : 1 inheritance pattern, with resistance being dominant. The backcross of the F1 to the susceptible parent produced a 1 : 1 ratio, confirming that chilling resistance was from a single gene. The single dominant gene controlling chilling resistance in NC-76 was given the symbol Ch.
Genetic Variation for Shelf-life of Salad-cut Lettuce in Modified-atmosphere Environments
Authors: Hayes Ryan J. , Liu Yong-Biao
Published: January 2019

Packaged salad-cut lettuce (Lactuca sativa L.) for food service and salad mixes is an increasingly important component of the lettuce industry. The product is highly perishable; cold storage and modified-atmosphere (MA) packaging are used to extend its shelf life. Given the importance of this market, lettuce cultivars, breeding lines, and populations should be selected for increased shelf life in MA environments. The objectives of this research were to determine the genetic variation in lettuce for shelf life in low-O2 MA environments and to develop rapid evaluation methods suitable for a lettuce breeding program. Lettuce was processed from field-grown plants of 33 romaine and three crisphead cultivars over 2 years. Shelf life was evaluated after storage in MA bags and in CO2-free controlled-atmosphere (CA) chambers with gas ratios of 0.2% O2:99.8% N2, 1.0% O2:99.0% N2, or 5.0% O2:95.0% N2. Deteriorated leaf blade tissue was water soaked and wilted with a dull to dark or black color, and midrib tissue and heart leaves were water soaked with a translucent to dark brown color. Genetic variation for shelf life was detected using MA bags or CA chambers, and the results from both years and testing methods were significantly correlated. Oxygen concentration did not affect shelf life in the CA chamber experiment, which indicated that the observed symptoms in the majority of cultivars were probably not from low O2 damage or CO2 injury, although multiple mechanisms of deterioration may be involved. Selection for lettuce cultivars, breeding lines, and populations with extended shelf life is possible using MA bags or CA chamber testing methods and could facilitate a consistent release of germplasm with stable shelf life in MA environments.
Fruit Yield and Quality as Related to Flushes of Bearing Shoots in Litchi
Authors: Chang Jer-Chia , Lin Tzong-Shyan
Published: January 2019

The goal of this study was to document the relationship between fruit growth patterns and flushing number in litchi (Litchi chinensis Sonn. cv. 73-S-20). The impact of flush number on fruit retention, fruit quality, and leaf efficiency (g fruit FW produced per unit of leaf area at harvest) was assessed in field-grown 6-year-old trees by adjusting the number of flushes per bearing shoot through girdling at two fruit developmental stages. The cumulative fruit growth was sigmoidal. The greatest fruit relative growth rate (RGR) occurred during 3 to 5 weeks after full bloom (AFB), peaking on week 3 at 0.39 g·g−1 dry weight (DW) per day. The greatest fruit absolute growth rate (AGR) occurred during weeks 8 to 11, peaking on week 11 at 0.16 g·d−1 DW. Fruit retention was sensitive to girdling applied during week 3. Most fruit dropped on branches with ≤ two flushes, whereas fruit continued to develop on branches with three flushes and on the controls. There was a gradual loss of fruit when the girdling was applied during week 8. The number of fruit retained on branches with two and three flushes was similar to the controls. At harvest, regardless of the time of branch girdling, fruit yield and quality increased with increasing number of flushes; shoots with three flushes were similar to ungirdled controls. Leaf efficiency on branches girdled during week 3 was inferior to that girdled during week 8. All treatments had similar leaf efficiency when branches were girdled during week 8. On the other hand, girdling treatment applied during week 3 resulted in variable leaf efficiency among treatment, indicating that fruit were utilizing reserves in bearing shoots. We concluded that bearing shoots of ‘73-S-20’ litchi trees require a minimum number of three flushes for adequate fruit production.
1-Methylcyclopropene Application and Modified Atmosphere Packaging Affect Ethylene Biosynthesis, Fruit Softening, and Quality of ‘Tegan Blue’ Japanese Plum During Cold Storage
Authors: Khan Ahmad Sattar , Singh Zora
Published: January 2019

This research was carried out to extend the postharvest storage of japanese plum (Prunus salicina Lindl. cv. Tegan Blue), which has a short shelf life limiting its export potential. The effects of 1.0 μL·L−1 1-methylcyclopropene (1-MCP) and modified atmosphere packaging (MAP), alone or in combination, on quality of mature japanese plum fruit during storage (0 ± 1 °C and 90% ± 5% relative humidity) were investigated. The activities of enzymes of ethylene biosynthesis [1-aminocyclopropane-1-carboxylic acid synthase (ACS), 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), and 1-aminocyclopropane-1-carboxylic acid (ACC) content] and those of cell wall-associated enzymes [exo-polygalacturonase (exo-PG), endo-polygalacturonase (endo-PG), pectin esterase (PE), and endo-1,4-β-D-glucanase (EGase)] were also measured. 1-MCP-treated fruit stored in normal atmosphere or in MAP had lower ACC content and inhibited ethylene production with reduced ACS and ACO activities compared with fruit stored in MAP and in normal atmosphere. Similarly, 1-MCP-treated fruit, stored either in normal atmosphere or in MAP, were firmer with reduced exo-PG, endo-PG, PE, and EGase activities compared with fruit stored in MAP and in normal atmosphere. During storage as well as during ripening, fruit stored in MAP exhibited a higher rate of respiration compared with other treatments. MAP exacerbated the effect of 1-MCP in reduction of ethylene production and fruit softening. 1-MCP application in combination with MAP after 5 and 7 weeks of storage delayed the fruit ripening by 10 and 8 days in contrast with control fruit, respectively. During storage, and as well as in ripe fruit, weight loss was reduced in fruit stored in MAP either with or without 1-MCP application. Control fruit and 1-MCP-treated fruit, stored in a normal atmosphere or in MAP, had the same values for the following parameters: chromaticity value L*, C*, and hue angle, titratable acidity, and concentrations of soluble solids, ascorbic acid, and total antioxidants. In conclusion, 1-MCP application in combination with MAP can be used effectively to reduce the ethylene biosynthesis and fruit softening during cold storage and to extend the storage life up to 7 weeks followed by 8 d of ripening without any adverse effects on the quality of ripe fruit.
Structural Changes in Lettuce Seed During Germination at High Temperature Altered by Genotype, Seed Maturation Temperature, and Seed Priming
Authors: Sung Yu , Cantliffe Daniel J. , Nagata Russell T. , Nascimento Warley M.
Published: January 2019

To investigate thermotolerance in seeds of lettuce (Lactuca sativa L.), primed, nonprimed, or seeds matured at 20/10 and 30/20 °C (day/night on a 12-h photoperiod) were imbibed at 36 °C for various periods and then dissected. Structural changes in seed coverings in front of the radicle tip were observed during germination at high temperature. Thermotolerant genotypes, ‘Everglades’ and PI 251245, were compared with a thermosensitive cultivar, ‘Dark Green Boston’. In all seeds that germinated, regardless of seed maturation temperature or priming, a crack appeared on one side of the cap tissue (constriction of the endosperm membrane near the basal end of the seed) at the micropylar region and the endosperm separated from the integument in front of the radicle tip. Additional changes took place during imbibition in these seeds; the protein bodies in the vacuoles enlarged and gradually depleted, large empty vacuoles formed, the cytoplasm condensed, the endosperm shrank, the endosperm cell wall dissolved and ruptured, and then the radicle elongated toward this ruptured area. The findings suggested that the endosperm layer presented mechanical resistance to germination in seeds that could not germinate at 36 °C. Weakening of this layer was a prerequisite to radicle protrusion at high temperature. Seeds of ‘Dark Green Boston’, ‘Everglades’, and PI 251245 matured at 30/20 °C had greater thermotolerance than those matured at 20/10 °C. Results of the anatomical study indicated that the endosperm cell walls in front of the radicle of seeds matured at 30/20 °C were more readily disrupted and ruptured during imbibition than seeds matured at 20/10 °C, suggesting a reason why these seeds could germinate quickly at supraoptimal temperatures. Similar endosperm structural alterations also were observed in primed seeds. Priming led to rapid and uniform germination, circumventing the inhibitory effects of high temperatures. From anatomical studies conducted to identify and characterize thermotolerance in lettuce seed germination, we observed that genotype, seed maturation temperature, or seed priming had the ability to reduce physical resistance of the endosperm by weakening the cell wall and by depleting stored reserves leading to cell collapse.
Fruit Quality in Almond as Related to the Type of Pollination in Self-compatible Genotypes
Authors: Kodad Ossama , Socias i Company Rafel
Published: January 2019

Nut and kernel dimensions and sphericity, shelling percentage, oil content, and fatty acid composition were studied over 2 years in 15 advanced almond (Prunus amygdalus Batsch) selections. The aim was to test the effect of pollination type on these fruit traits for this group of new self-compatible selections of a mostly self-incompatible species as well as the yearly effect on these variables. Variability between selections was much higher than that between years, showing a moderate level of year-stability and a significant year effect only for some variables. The different pollination treatments affected all chemical components studied, as well as nut and kernel weight, but not the other physical traits. Self-pollination decreased kernel weight and volume as well as oil content and percentage of linoleic acid but increased the percentage of oleic acid. These variations in the fatty acid composition were in the trend of increasing kernel quality. Inbreeding depression could also negatively affect several aspects of nut and kernel quality. Thus, autogamous almond genotypes without apparent symptoms of inbreeding depression may yield kernels of increased nutritional and industrial quality.